digital cctv
DIGITAL CCTV
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DIGITAL CCTV
A Security Professional’s
Guide
Emily Harwood
AMSTERDAM • BOSTON • HEIDELBERG • LONDON
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Library of Congress Cataloging-in-Publication Data
Harwood, Emily.
Digital CCTV / Emily Harwood.
p. cm.
Includes bibliographical references and index.
ISBN-13: 978-0-7506-7745-5 (alk. paper)
ISBN-10: 0-7506-7745-7 (alk. paper)
1. Closed-circuit television. 2. Digital video. I. Title. II. Title: Digital closed
circuit television.
TK6680.H356 2007
384.55′6—dc22
2007004218
British Library Cataloguing in Publication Data
A catalogue record for this book is available from the British Library
ISBN 13: 978-0-7506-7745-5
ISBN 10: 0-7506-7745-7
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1
Table of Contents
About the Book
Introduction
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
We Live in an Analog World
What Exactly is Digital Video?
In the Beginning
Compression—The Simple Version
More on Digital Video Compression
Internet Transmission, Networked Video, and Storage
Guided Video Transmission
Wireless Video Transmission
Examples of Digital Video for Security
Pieces and Parts
Integrating Digital Video with Other Technologies
More Digital Video Applications
From VTRs to VCRs, DVRs, and NVRs
Central Station Monitoring and Video
More Digital Video Applications
New Roles of Digital Video
vii
ix
1
19
39
57
75
93
111
129
147
163
179
189
197
205
211
219
Glossary
225
Index
233
v
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About the Book
WHO IS THIS BOOK FOR?
CEOs
Security Managers
Directors of Security
Loss Prevention Managers
CCTV Product Manufacturers
Electronic Security Sales
Personnel
Electronic Security
Manufacturers
Representatives
IT Managers
Security Systems Integrators
Electronic Security Installers
Security Dealers
Security Consultants
Architects and Engineers
Specifiers
WHAT IS THE PURPOSE OF THIS BOOK?
The purpose of this book is to provide you, the reader, with the
information you need to interpret what is behind all of the technology smoke and acronym mirrors surrounding digital video technology enabling you to better understand today’s new digital
products. At last you will be able to answer puzzling questions
about digital technology like how much storage space and bandwidth are necessary to handle digital video at specific quality
levels and image rates.
vii
viii
About the Book
This book provides practical information about how digital
video works, how digital video is stored and transmitted, what
digital systems can and cannot accomplish, and what to expect
from digital video equipment in modern CCTV systems.
An explanation of digital video and compressed digital video
is provided, and the distinction between raw digital and compressed digital video is explained. After a basic understanding of
how these differences affect the video image is reached by the
reader, things like picture quality, resolution, and evidentiary use
of digital video will be easier to comprehend. Compression variables such as lossless and lossy will be explained by reviewing
Huffman and Run Length Encoding (RLE). A review of JPEG,
motion JPEG, MPEG, and wavelet compression schemes, among
others, will also be provided.
Introduction
Growth naturally stimulates change, and CCTV technology has
been no exception. A system that once merely required cameras,
cabling, and video monitors has now become a complex electronic
configuration of equipment intertwined with both computer and
telecommunications technologies. This dramatic change is directly
related to the introduction of digital technology. Why do we need
to understand how digital technology works, and what does it
have to do with the future of security? It’s simple—the newest
revolution in technology is pervasive computing. Computers
are or soon will be everywhere, linked to everything, and everything will be connected by the Internet—including security
systems.
Upheavals within the electronics industry have been persistent and are well known. For example, most everyone remembers
how eight track players were relegated to the trash heap without
so much as a backward glance. Phonograph records were shut out
by compact discs and the consumer VCR has virtually been
replaced by the DVD player. In the security industry, the revolution from analog to digital is similar to these earlier advancements
and will probably be looked at with the same amount of disdain
regarding archaic processes of the past. Digital technology is
exploding around us, yet a large amount of industry professionals
ix
x
Introduction
are still looking for a comprehensive explanation of digital video
as a security technology.
Security professionals today understand how the components of a CCTV system work. They know the applications, limits,
strengths, weaknesses, and relative costs of lenses, cameras, camera
mounts, pan/tilt units, and housings. Such knowledge enables
professionals to design systems and to select from a myriad of
products just the right components, resulting in a CCTV system
that will meet customer performance requirements and budgets.
There is, however, a concern that digital CCTV equipment
concepts have not been adequately explained. The reality is that
digital technology is much more than a trend and requires a rather
extensive learning process if one can intelligently buy, sell, install,
or recommend digital video products. In today’s environment, it
is essential for the security professional to know how the Internet
works and how LANs and WANs function in relation to the World
Wide Web.
WHY SWITCH TO DIGITAL?
There are many reasons to make the switch to digital for security
surveillance and recording applications. Probably the strongest
reason is that digital information can be stored and retrieved with
virtually no degradation, meaning that with digital images, copies
are as good as the originals. When a digital recording is copied, it
is a clone, not a replica.
Digital information is not subject to the noise problems that
degrade analog information as quickly as it is stored, retrieved,
and duplicated. There are no amplifiers to introduce distortions
and noise to a digital signal. When transmitting images, a digital
system reduces noise over successive transmissions because small
variations in the signal are rounded off to the nearest level. Analog
transmission systems must filter out the noise, but the filter itself
can sometimes be a source of noise.
In some ways, digital information outperforms analog information. For example, digital music from a CD has a much wider
dynamic range (very quiet to very loud) than analog music from
Introduction
xi
a tape or a record. With all of the advancements available in digital
technology, it is not as “perfect” as analog video and does present
a variety of new problems in transmission and storage. Because
digital video consists of large amounts of data, it must be compressed, in most cases, to be useful. Compression discards a significant amount of the original information and results in a new
kind of degradation called “artifacts”. This discarding of information by compression techniques has raised questions about
whether digital video or compressed digital video can be used as
evidence in a court case.
WHAT ELSE CAN DIGITAL DO FOR VIDEO?
As an added bonus, most digital video systems permit the manipulation of devices from a location off-site. Pan/tilt/zoom
features on cameras can be controlled allowing an enhanced portrayal of events as they occur; motorized gates, electric door locks,
lights, and environmental controls can be remotely activated as
well. With these features, approved access can be controlled offsite and the expensive misuse of utilities can be monitored and
corrected instantly.
Digital images of a crime or a hazardous situation of some
type can be transmitted over a wireless local area network to first
responders for evaluation. The use of an IP network to transmit
these images can allow access to the system from any device with
an Internet connection and proper authorization for access.
The benefits of digital video transmission technology in the
security arena are limitless. Intelligence can be programmed into
a digital system so that it will “look” for specific analogies and
respond in some manner. Digital video systems can automatically
zoom in on individual faces to improve or verify identification.
Video verification of events is immediate—intruders can be positively identified, false alarms eliminated, and facility management
improved—all with one system.
Many other intelligent operations can be integrated with
a digital system to expand its functionality. Networked video
systems permit remote surveillance via WAN/LAN and Internet
xii
Introduction
infrastructures. With an open-architecture design, networked
digital systems can provide easy integration with other technologies including access control, facial recognition, points of sale, and
database systems.
There are significant economic considerations for using
digital technology. Digital circuits can be manufactured for less
money than analog circuits due to the fact that analog circuits
require resistors, capacitors, diodes, chokes, transformers, and
other discreet components to make things work. Digital circuits
also use many of these components but they are typically much
smaller, surface mount components and not as many are needed
since IC (Integrated Circuit) chips replace many of them. The
largest portions of digital circuits are simple on/off transistor
switches that can easily be applied to integrated circuits in large
quantities. Also, integrated circuits can be mass-produced, which
drives down costs.
In most cases you will obtain more performance per dollar
spent with digital than with analog video. Once video has been
digitized, it can be used virtually anywhere in the world and with
the aid of communications links like telephone, Internet, and
various wireless technologies, it can be transmitted anywhere in
the world as well. TCP/IP transmittal of surveillance video is now
a viable and economical mode of remote monitoring of multiple
locations.
Unlike digital signals, which are composed of ones and zeros
and can pass through a wire or be recorded to tape with absolutely
no change, analog signals are composed of information, which will
change slightly every time it goes through a wire or gets recorded
to tape. The ultimate quality of an analog process is not inherently
inferior; it is very difficult to keep the original quality through the
entire production pipeline.
DIGITAL TECHNOLOGY REDUCES
MANPOWER REQUIREMENTS
Until recently, video surveillance technology has relied on human
operators for detecting breaches and facilitating appropriate
Introduction
xiii
responses, making the surveillance only as effective as the operator. Because advances in technology have made it possible to integrate more cameras and send images virtually anywhere in the
world, there is a growing potential for an overload of information
resulting in operational inefficiency. For a large surveillance system
with hundreds of cameras, the fatigue factor is extreme. These
adverse conditions can be overcome by utilizing new advancements in the technology of video surveillance.
Software that intelligently monitors images and automatically detects potential security threats changes the dynamics of
video monitoring for security. Today’s digital video surveillance
systems are much more than camera eyes that view and record
the scenes around them. Surveillance systems now analyze and
make decisions about the images they are viewing based on the
confirmation or violation of preset protocols. The system immediately relays information to human operators (or in some cases to
other security or operational systems) for immediate action. The
resulting investigation of suspicious incidents help operators
makes the right decision, on time.
How does it work? Analytics transform video into security
information. Software programs that utilize complex mathematical algorithms to analyze scenes in a camera view are designed to
detect predetermined behaviors such as someone lying on the
floor, erratic movements, people or cars converging on each other,
a person or vehicle staying in one place for an extended period, a
person or vehicle traveling against the normal flow, objects newly
appearing on the scene—the list continues to grow. These types of
programs tremendously increase a security officer’s efficiency.
THE ENIGMA OF DIGITAL VIDEO
Over the last few years, there has been more and more news media
coverage on the subject of video for security in the US. The use of
CCTV for surveillance is by no means new, but from some news
clips, you might think it is the latest invention in crime detection
and investigation. The community inside of the security industry
knows how prevalent the use of video is and that the new benefits
xiv
Introduction
arriving with digital advancements are almost exponential. For
outsiders, the news is not as common. In fact CCTV, digital video
surveillance and intelligent video solutions cover such a wide
range of relevance that these subjects almost always have to be
covered from the very beginning to the present.
The adage “time waits for no man” could not be more applicable than in the world of digital technology. Even as these words
are being written, new developments are underway all over the
world, which will continue to contribute additional cost effective,
efficient alternatives for the compression and transmission of
video, audio, and data.
1
We Live in an
Analog World
The security world is well acquainted with the term Closed Circuit
Television (CCTV), which is a visual surveillance technology
designed for monitoring a variety of environments and activities.
CCTV systems are used in applications such as monitoring public
areas for violent actions, vandalism, theft, and unlawful entry,
both indoors and out. CCTV recordings are used to obtain and
provide evidence for criminal and other investigations; they are
sometimes disclosed to the media in the hopes of gaining information about images of a suspect or suspects caught in or near a crime
scene.
The term Closed Circuit Television can be misleading, as the
word television actually means to see at a distance, which implies
broadcast. If public broadcast is not the intent, CCTV is the correct
terminology, as it is not a system for broadcast to the public in
general. Unlike television that is used for public entertainment, a
CCTV system is closed and all its elements are directly connected
either by hardwire methods or wireless technologies.
1
2
Digital CCTV
Wireless analog devices typically use line of sight radio frequency that can usually only be transmitted for short distances.
Some newer technologies, however, can transmit for several miles.
This means that the transmitted video can only be viewed with
the proper equipment set to the proper frequency. While the signal
could be intercepted, it is still considered a closed circuit since it
is not used for a multi-point broadcast such as cable TV.
It is important to review some of the key concepts related to
analog video in order to have an understanding of how these
concepts play a role in digital video. The word video comes from
the Latin verb videre, “to see”, and is commonly used when referring to devices such as video monitors or video recorders. In this
book, video will also refer to the actual product of the technology,
that is to say, the image produced. The purpose of this first chapter
is to acquaint the reader with the basics of analog video as it is
normally used in a security function. For some readers, this chapter
will merely be a review of basic analog video theory. For others,
it may introduce or explain various concepts in enhanced detail.
For a number of readers, it will be a primer of video concepts.
HOW AN ANALOG VIDEO IMAGE IS GENERATED
We live in an analog world, and vision is an analog function.
Waves and electromagnetic fields are analog, meaning they are
continuous signals capable of smooth fluctuation. Electric current,
characterized by its flowing current, is also analog. Electricity is a
current of electrons with either a direct flow or current called DC
or an alternating flow or current called AC. In an analog CCTV
system, an analog camera “sees” an event, which it turns into an
electronic signal. It then transmits the signal over some type of
medium and the signal terminates at a display or recording mechanism. In the United States, a video image is made up of 525
horizontal lines, according to the NTSC standard. NTSC stands for
National Television System Committee, which devised the NTSC
television broadcast system in 1953. One still picture or frame of
video consists of two scans containing 525 alternate horizontal
lines that are produced by a ray of electrons. The camera and
picture tube first scan 262.5 odd numbered lines, and then the
We Live in an Analog World
3
picture is scanned again to form 262.5 even numbered lines. Each
half of the frame or 262.5 lines is one “field” of video. After the
ray or beam of electrons writes the lines one at a time onto a
picture tube, one frame of video is created.
This operation of assimilating a picture, translating that
picture for transmission, and then scanning that same picture at
the receiving location results in the successful transmission of one
full frame of video. The time involved in this operation from
beginning to end is the “update” or “refresh” rate. After the process
is repeated thirty times, the illusion of motion is created. This is
the same principle used for creating flipbooks—you quickly flip
through to see a moving picture. Cartoons that are drawn and
rapidly displayed one picture at a time use the same technique to
create perceived motion. Each of the 30 frames is a still image of
a scene, and by slightly changing something in each scene, the
viewer will perceive a progressively changing or moving image.
Analog video is comprised of continuously varying voltage
levels that are proportional to (analogous to or the same as) the
continuously varying light levels in the real world. When we refer
to electronics in relation to video, we are referring to the use of
current and voltage to carry electric signals modified to represent
information. If we can convert picture information into electronic
or radio signals, we can send it virtually anywhere in the world
with the right transmission system.
A very simple explanation of video transfer goes something
like this: imagine that the camera is the eye of the system and its
function is to make its view (the image) available in an electronic
format of impulses. These impulses are then propelled along wires,
cables, or microwaves via voltage, which is the pressure or electromotive force that compels electrical charges to move from negative to positive. The result is the transfer of video information from
the camera to its ultimate destination. See Figure 1-1.
Wires and certain other parts of circuits are made of materials
called conductors. These conduits carry the electric currents. Wireless transmission technology will be discussed in a later chapter.
For now, let’s just acknowledge that video signals can be transmitted without the benefit of wires as conductors. Electromagnetic
waves are unique forms of energy, known as radiant energy. They
4
Digital CCTV
Figure 1-1
Video Transfer
are created when electrically charged particles, such as electrons,
are made to move. As the charged particles move, they generate
fields of electrical and magnetic energy. These two forms of energy
radiate from the particles as electromagnetic waves.
Energy is a property of many substances and is associated with
heat, light, electricity, mechanical motion, and sound. Energy is
transferred in many ways. In physics, the transfer of energy by some
form of regular vibration or oscillatory movement, like an electromotive force, is called a wave. An electromagnetic wave consists of
two primary components—an electric field and a magnetic field.
The electric field results from the force of voltage, and the magnetic
field results from the flow of current. Although electromagnetic
fields that are radiated are commonly considered to be waves, under
certain circumstances their behavior makes them appear to have
some of the properties of particles. In general, however, it is easier
to picture electromagnetic radiation in space as horizontal and vertical lines of force oriented at right angles to each other.
Frequency is the measure of the number of waves that pass
through a fixed point in a specified period of time—often measured as cycles per second. One cycle per second is called a Hertz
(Hz), one thousand is called a kiloHertz (KHz), and one million is
called a megaHertz (MHz). The amplitude of a wave is defined as
the measurement from its crest to its trough. The distance between
consecutive crests or troughs is the wavelength. The frequency of
a wave is equal to the number of crests (or troughs) that pass a
fixed point per unit of time. The smaller the wavelength is, the
greater the frequency is. See Figure 1-2.
Properly terminated video signals have amplitude of one volt
peak-to-peak. This means the total voltage produced is one volt from
We Live in an Analog World
5
A
M
P
L
I
T
U
D
E
Point in time
Point in time
Frequency
Figure 1-2
Wavelength and Frequency
the bottom of the sync pulse to the top of the white level, hence one
volt peak-to-peak (p/p). And there you have it—video signals.
WHEN EVERYTHING IS BLACK AND WHITE
Two things are necessary for a camera to produce a monochrome
(black-and-white) video signal: the scanning control information
called synchronizing pulses and the black-and-white picture intensity information called luma. Luma is the monochrome or blackand-white portion of a video signal. This term is sometimes
incorrectly called “luminance”, which refers to the actual displayed brightness. Luminance ranges from pure black to pure
white. Black level is the level of brightness at the darkest (black)
part of a visual image—the level of brightness at which no light is
emitted from a screen, resulting in pure black. Black level varies
from video display to video display with better displays having a
better black level. White level is the brightness of the lightest portions of an image (white areas). There are many levels of gray
within the overall grayscale, ranging from slightly gray and almost
white to very dark charcoal colors that are nearly black. The level
of gray, white, or black in a video signal is derived from the luminance portion of the signal.
Inside the camera there are various support circuitries and
an imager that converts light to an electronic signal. On the front
6
Digital CCTV
of the camera, a lens causes light to be focused onto the imager.
An easy way to grasp this may be to think of holding a magnifying
glass between the sun’s rays and a piece of paper. When light rays
pass through the magnifying glass, the lens, they can be focused
onto a specific point on the paper and start a fire. In a camera, the
light travels through the lens and is focused onto the imager
(minus the fire of course!). The imager converts the focused light
to an electronic signal with a voltage level proportional to the
brightness level of the focused image. The black-and-white portion
of a video signal, which carries the information for brightness and
darkness and contrast, is luminance.
The camera sends out this electronic signal similar to the way
we read a book, from left to right, line after line, top to bottom,
and page after page. This is called horizontal and vertical retrace.
The scan lines are the portion that are visible in the image, while
the retrace, or return to the start of the next line, is not. Take a
moment to look at Figure 1-3, which illustrates horizontal and
vertical retrace. Notice that at the end of each horizontal line, your
eye retraces back to the beginning of the next line, providing the
horizontal retrace. At the end of the page, your eye retraces vertically to the top of the next page, which is the vertical retrace.
The camera’s support circuitry, mentioned earlier, now comes
into play by adding a horizontal synchronizing (horizontal retrace)
pulse at the end of each scanned line. Before each line is scanned,
horizontal sync pulses set the electron beam to a locked position
Figure 1-3
Horizontal and Vertical Retrace
We Live in an Analog World
7
so that each line of picture information starts at the same position
during scanning. There is also a horizontal blanking interval,
which occurs between the end of one scan line and the beginning
of the next. This blanking interval is controlled by the horizontal
sync pulse. When all the lines of a page have been scanned, the
camera adds a vertical synchronizing (vertical retrace) pulse to the
video signal and begins the next page of scanning. The vertical
sync pulse controls the length of time of the vertical blanking
interval. This is the period when the TV screen goes blank between
the end of one field and the beginning of the second field. The
combination of these two is known as composite sync.
Figure 1-4 shows the composite video signal that results from
one horizontal scan line of a grayscale chart. Notice that the bars
Figure 1-4
Composite Video Signal
8
Digital CCTV
of the grayscale chart are black on the left and white on the right,
with shades of gray in the middle. Now, notice the horizontal
white lines in the analog video signal waveform. You can see that
each of these lines is the same width as the gray bar it represents.
The white line’s height above black level represents its voltage
level, or how bright (what shade of gray) the bar is. The grayscale
video waveform is often called a stair-step because the video signal
waveform looks like a series of steps.
CREATING MOTION
Motion pictures originally set the frame rate at 16 frames per
second. This was found to be unacceptable and the frame rate was
increased to 24 frames per second. In Europe, this was changed to
25 frames per second, as the European power line frequency is
50 Hz.
Because video technology evolved after motion picture technology, many of the terms used in video are borrowed from the
motion picture vocabulary. The concept of frames and fields is
rooted in motion picture technology. For example, motion picture
film is exposed at a rate of 24 images, or frames, per second. The
rather low frame rate is a compromise between the amount of time
needed to expose the film with enough light to make a good image
and the number of frames per second necessary to provide the
illusion of continuous motion. The human eye sees continuous
motion, but with a very noticeable flicker in the brightness of the
image. By projecting each frame twice, the flicker disappears and
the human eye perceives only continuous motion.
A motion picture projector is equipped with a rotating shutter
that alternately reveals and blocks the light from a bright light
source. The shutter is synchronized with the mechanism that
moves the film past the light source so that one frame is flashed
two times onto the projection screen. See Figure 1-5. The result is
that 24 frames per second are projected onto the screen two times
each, or 48 fields per second.
We Live in an Analog World
Figure 1-5
9
Motion Picture Projection
INTERLACE—FRAMES AND FIELDS
Like motion pictures, each frame of video is made up of two fields;
therefore, there are 60 fields per second in a video stream. However,
unlike motion pictures where one single frame is projected twice,
each video field is generated within the camera. Two fields, field
1 and field 2, together, make one frame. Figure 1-6 illustrates how
field 1 is the scan of all the odd numbered lines (1, 3, 5, 7 and so
on) and field 2 is the scan of all the even numbered lines (2, 4, 6,
8 and so on). The fields are interlaced. The same process takes
place in PAL cameras, except there are 50 fields, 25 frames per
second.
10
Digital CCTV
Figure 1-6
Interlaced Fields
HOW A VIDEO IMAGE IS DISPLAYED
Video is usually displayed on an analog video monitor that is
comprised of a picture tube or cathode ray tube (CRT) and various
support circuitries. Figure 1-7 illustrates how the composite video
signal is disassembled inside the analog video monitor by a sync
separator. The synchronizing pulses are converted to horizontal
drive and vertical drive signals that are connected to an
electromagnet.
The deflection yoke, made up of coils of wire wound around
the neck of the cathode ray tube (the small end opposite the screen),
generates a magnetic field and uses it to direct the electron beam
in the CRT. The electromagnetic fields generated by the deflection
yoke cause an electron beam inside the picture tube to reproduce
the scanning pattern generated by the camera, left to right, top to
bottom.
The video is applied to a control grid inside the tube to vary
the intensity of the electron beam in proportion to the brightness
or darkness of the original image. The more intense the beam is
when it strikes the phosphor at the front of the picture tube, the
brighter the phosphor glows. The less intense the beam is, the less
the phosphor glows. As the electron beam scans the phosphor, left
to right, top to bottom, the original image made by the camera is
reproduced in the glowing phosphor, and a viewer sees a good
reproduction of the camera’s image.
We Live in an Analog World
Figure 1-7
11
Composite Video Signal
GAMMA
Gamma is basically explained as the relationship between the
brightness of a pixel as it appears on the screen and the numerical
value of that pixel. Gamma correction controls the overall brightness of an image. Images that are not properly corrected can look
either bleached out or too dark. Cathode-ray tubes have a peculiar
relationship between the voltage applied to them and the amount
of light emitted. An inverse gamma function, called gamma
correction, takes place at the camera so that the video signal is
non-linear for most of its journey. In other words, the transmitted
signal is deliberately distorted so that, after it has been distorted
again by the display device, the viewer sees the correct brightness.
Figure 1-8 illustrates a video signal before and after gamma
correction.
Notice the grayscale steps in the “before” video signal
form a straight diagonal line as they increase in brightness
voltage from left to right. The grayscale steps in the “after” video
signal form a curved diagonal. The curved (non-linear) brightness
steps inversely match the non-linearity of black and white
picture tubes and closely match the non-linearity of color picture
tubes.
12
Digital CCTV
Figure 1-8
Gamma Correction
COMPONENTS OF A VIDEO SIGNAL—LUMINANCE,
HUE, AND SATURATION
Analog video is an electrical signal that represents luminance, hue,
saturation, and synchronizing pulses. For simplicity we have considered video as a black-and-white image up to this point. Luminance is the term that describes dark and light values in the picture
we see when we view a black-and-white image. In other words,
We Live in an Analog World
13
luminance is the black-and-white portion of a video signal that
carries the information for brightness, darkness, and contrast.
Luminance ranges from pure black to pure white. The darkest
luminance level is black and the brightest luminance level is white.
Most of the resolution or detail that the human eye perceives is
contained in the luminance portion of an image.
When looking at a color image, two more concepts are added
to the luminance of the image: hue and saturation. Hue is the term
that describes the color values we see when we view a color image.
We have given names to these hues or colors such as green, blue,
red, purple, or yellow. Hues are actually light of differing frequencies that cause our eyes and brain to perceive different colors.
Hues range from blue at the low end of the spectrum to red at the
high end of the spectrum and include all of the colors we can see
through green and violet and orange and yellow. Hue is the term
used to state what color an object is. For example, a ripe tomato is
red and the leaves on trees are green. Red and green are the hues.
Saturation is a property of hue that describes how rich or intense
the color is. A tomato that is just beginning to ripen is a pale red
and a ripe tomato is deep red. A leaf in the spring is a light green
when it first emerges and a dark green in the summer. A very
intense green color is said to be rich or saturated. A very weak
green color is said to be pale or pastel. A color image adds hue
and saturation information to the luminance to make a complete
image.
NOISE
Noise is what we call unwanted electrical signals that can be
caused by the interference of electronic components in the camera
and transmission lines. It can also be caused by interference from
other equipment or signals that are not a part of the intended
video signal. Electronic noise is present to some extent in all video
signals. Broadband random noise gives the picture a snowy
appearance and looks like snow or graininess over an entire image.
Sources of noise include poor circuit design, excess heat, overamplification, external influences, automatic gain control, and
14
Digital CCTV
transmission systems. In analog and digital communications,
signal-to-noise ratio, written S/N or SNR, is a measure of signal
strength relative to background noise. The amount of picture
information compared to the amount of noise is usually expressed
in decibels (dB). Measuring SNR can be a good way of comparing
the quality of video equipment.
THE ANALOG IMAGE
Once a camera has converted light into a video signal, the signal
must travel outside the camera to another device such as a monitor,
a VCR, or other storage device. The medium most often used for
transmission is coaxial cable with a characteristic impedance of 75
Ohms (Ω). An RG-59 type coaxial cable, about 1/4 inch in diameter,
can carry a video signal of one volt peak-to-peak up to 1,000 feet
(304.8 m) without any significant degradation of the signal. A
twisted pair of wires with impedance matching transformers can
carry a video signal for hundreds of feet, depending on the environment where the twisted pair wire is installed. A twisted pair
of wires with active electronic amplifiers for balanced line transmission at each end can carry a video signal 3,000 feet (914 m).
A fiber optic cable, similar in size or smaller than RG-59 cable,
can carry a video signal several miles, depending on a
variety of factors. Fiber optic cables can be used to transmit video
and control signals further with no interference from common
hazards such as ground loops, lightning, or man-made noise. For
this reason, fiber optic cabling is often used in traffic monitoring
applications.
The amount of information that can be carried in a given time
period by these transmission means is called bandwidth. Bandwidth plays a very important role in the digital process, and it will
be covered extensively later in the book.
One camera connected to one monitor makes up a simple
system. As a camera scans each line and adds a synchronizing
pulse, a monitor tracks the camera’s scan by interpreting the synchronizing pulses and sprays an electron beam onto the phosphor
face of the picture tube, reproducing the image. When more than
We Live in an Analog World
Figure 1-9
15
Switching
one camera needs to be displayed on a single monitor, a switch
can be used to connect first one camera, then the next, and so on
to the monitor. Figure 1-9 illustrates multiple cameras connected
to a single monitor via a simple rotary switch.
THE IMPORTANCE OF SYNCHRONIZING
When a camera is turned on, its synchronizing (sync) generator
begins to make horizontal and vertical retrace pulses, or sync
pulses. As several cameras are turned on, even if they are all
turned on at the same time, each camera’s sync pulse generator
runs to its own beat. This means that the horizontal and vertical
sync pulses for each camera are occurring at different times.
As camera 1 is connected to the monitor, the monitor’s deflection yoke begins to deflect the picture tube’s electron beam according to the sync from camera 1. When the switch is moved to select
camera 2, deflection circuits must begin to deflect the picture tube’s
electron beam according to the sync from camera 2. As the switch
is moved to select cameras 3 and 4 in turn, the monitor’s deflection
yoke must again begin to deflect the picture tube’s electron beam
according to the new sync. When the sync timing is different for
each camera, the deflection yoke has to make sudden, large adjust-
16
Digital CCTV
Figure 1-10
Sync
ments to track the new sync from the next camera. Figure 1-10
illustrates the video stream as it might flow from four cameras.
Notice that while the horizontal scan lines and horizontal
sync pulses are fairly close to each other in time from one camera
to the next, the vertical sync pulses are considerably different in
time. An analog video tape recorder makes a timing signal called
a control track. The function of the control track is similar to the
sprocket holes in motion picture film. Control track pulses keep
the tape moving from the supply reel to the take up reel at a constant speed. Control track pulses are recorded on the tape along
with the video and the audio.
During playback, the control track pulses are read and compared to a reference 60-cycle signal to keep the tape motion constant. The control track signal is often generated from the vertical
sync of the video being recorded. When video to tape is switched
between cameras and the vertical sync pulses are not aligned in
time, the control track pulse that is generated by the incoming
video’s vertical sync is not continuous. As a result, during playback, the picture often tears or distorts badly when the video
recorder is playing between one camera and the next.
Most video cameras provide a solution for synchronization,
which allows the sync pulses to line up in time either by using a
We Live in an Analog World
17
synchronizing generator or by a circuit in the camera. A synchronizing generator produces horizontal and vertical synchronizing
pulses that are supplied to a number of cameras. The cameras
use the sync signal from the synchronizing generator to time
their horizontal and vertical scans. As a result, all the cameras
connected to the sync generator are reading their pictures at the
same time and all the video signals arriving at the switch are
synchronous.
Unfortunately, synchronizing generators can add substantial
cost to a video system. The sync generator itself is a cost and each
camera in a system requires at least one coaxial cable, sometimes
two, from the sync generator in addition to the coaxial cable that
carries the composite video back to the switcher. For this reason,
sync generators are seldom used in CCTV systems. Since almost
all of the cameras in a CCTV system use either primary Alternating Current (AC) power or low voltage AC power, and since both
primary AC and low voltage AC have a 60-cycle alternating
current, the AC itself can be used as a cheap synchronizing
source.
As the AC power crosses zero on its excursion from plus to
minus and back, as seen in Figure 1-11, a circuit inside the camera
causes the imager to begin scanning, or reading, its next frame at
the zero crossing point.
Since all the cameras in a system are connected to AC power,
all of the cameras begin their scans at the same time and are subsequently synchronized vertically. This method sounds simple in
theory but in practice there are some issues. Most buildings are
Figure 1-11
Zero Crossing Point
18
Digital CCTV
Figure 1-12
Vertical Sync
wired with 220 volt, three-phase power. Therefore, any given
camera can be out of phase with another camera by 120 degrees.
In a perfect world, when video streams from synchronized
cameras reach a switch or a VCR, the only thing that changes is
the video itself. All the synchronizing pulses are lined up in time,
and no vertical jump or roll is created when switching between
cameras. Figure 1-12 illustrates video signals that are synchronized vertically.
2
What Exactly is
Digital Video?
There are several technologies behind the growth of digital video
for security surveillance applications. Once the personal computer
gained popularity and became affordable, companies began creating security and surveillance applications for it—developing frame
grabbers that convert analog video into digital images. When
Ethernet and TCP/IP standards were developed, network-based
applications became viable. Next, advances in wireless communications provided unprecedented mobility to surveillance applications. All of these advances in technology are possible because of
video digitalization.
One of the important things to grasp about digital video is
that it is simply an alternative way of carrying the same video
information as an analog system. Digital video is a series or string
of numbers that represent the voltage levels of an analog video
signal. An ideal digital system has the same characteristics as an
ideal analog system; both are completely transparent and reproduce the original applied waveform without error.
19
20
Digital CCTV
Remember the waves from chapter one? That information is
now being translated into a digital language, so to speak. In fact,
a very good way to understand analog and digital video technologies is to consider them as two different languages. Everyone must
learn a language as a child and some people even grow up learning more than one language. We may later choose to learn more
languages, which require a certain amount of time and concentration because it is not what we are used to. In the electronic industry most of us learned analog as our basic language. Now in order
to understand and communicate with the digital language, we
must take the time to learn it.
THE SIMPLE BREAKDOWN OF DIGITAL
The numbers used in a digital video string are called binary
numbers. Binary means that there are only two possible states or
conditions. It is quite simple to remember if you associate the
word binary with other “bi” words such as bifocal, biplane, and
bicentennial, which all refer to two of something. When referring
to binary numbers, on and off or high and low are represented as
one (1 = on or high) and zero (0 = off or low).
To the computer, binary digits are not really 1s and 0s. They
are actually electrical impulses. Since you only have two possible
switch combinations or electrical possibilities, the computer only
needs various combinations of two digits to represent numbers,
letters, or pixels. These two digits are visually represented by 1s
and 0s. In the digital world we call these electrical impulse representations bits, or binary digits. We also have bytes, which are
made up of eight bits. See Figure 2-1.
Figure 2-1
Eight Bits Make One Byte
What Exactly is Digital Video?
21
The easiest way to understand bits is to compare them to
something you are already familiar with, such as digits. A digit is
a single place that can hold numerical values between 0 and 9.
Digits are normally combined together in groups to create larger
numbers. For example, 6357 has 4 digits. It is understood that in
the number 6357 the seven is filling the “ones place”, while the
five is filling the “tens place”, the three is filling the “hundreds
place” and the six is filling the “thousands place”. We all work
with this type of decimal (base-10) digit system every day as a
matter of course.
Computers happen to operate using the base-2 number
system, known as the binary number system (just like the base-10
number system is known as the decimal number system). Where
decimal digits have ten possible values ranging from 0 to 9, bits
have only two possible values: 0 and 1. Therefore, a binary number
is composed of only 0s and 1s like this: 1011. How do you figure
out what the value of the binary number 1011 is? You do it in the
same way we did it above for 6357, but using a base of two instead
of a base of ten.
In the decimal counting system that we use every day there
are placeholders defined by commas, which tell us how many
units we are describing with a given number. See Table 2-1.
For example, the number 1000 consists of one thousands,
zero hundreds, zero tens and zero units (ones). What if the placeholders had a different meaning? What if the placeholders meant
this? See Table 2-2.
Table 2-1
Tens of
Millions
Base of Ten
Millions
Table 2-2
Hundreds of
Thousands
Tens of
Thousands
Thousands
Hundreds
Tens
Units
1
0
0
0
Base of Two
Decimal number
Binary number
128
64
32
16
8
1
4
0
2
0
1
0
22
Digital CCTV
Table 2-3
Binary Counting
Decimal Number
0
1
2
3
4
5
6
7
8
9
10
Binary Number
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
Notice that as you read from right to left, the decimal value
of the placeholder doubles. In this case, 1000 would mean eight
because the column representing eight has an “on” value and the
remaining numbers all have an “off” value. One (8), plus zero (4),
plus zero (2), plus zero (1). Using this reasoning, the binary number
1001 would represent the number nine. One (8), plus zero (4), plus
zero (2), plus one (1). 1010 would represent the number ten. One
(8), plus zero (4), plus one (2), plus zero (1) or eight plus two equals
ten.
You should begin to see that when using binary numbers,
each bit holds the value of increasing powers of two. This makes
counting in binary pretty simple. Table 2-3 provides a different
view of how binary counting works. This view may make it easier
to see how decimal and binary numbers are related.
When you look at the binary numbers as they increment from
0 to 10, you will see a pattern. The bit on the extreme right toggles
off, on, off, on, and so on. The second bit from the right, the second
bit, toggles every second increment, off, off, on, on, off, off, on, on,
and so on. Because there are eight bits in a byte, we can represent
256 values ranging from 0 to 255. See Table 2-4.
For example, the numbers 00011000 represent the decimal
number 24. Zero (128), plus zero (64), plus zero (32), plus one (16),
What Exactly is Digital Video?
Table 2-4
128
0
64
0
23
Counting Bits
32
0
16
1
8
1
4
0
2
0
1
0
plus one (8), plus zero (4), plus zero (2), plus zero (1) add up to
24 or 16 + 8 = 24. It may sound a bit confusing at first, but once
you catch on it is really very simple. 256 values ranging from 0 to
255 are shown here:
0 = 00000000 1 = 00000001 2 = 00000010
254 = 11111110 255 = 11111111
As previously mentioned, a group of eight bits is called a byte.
This convention has evolved over the history of binary numbers.
It is important to note that some devices provide digital performance information in bits, and some in bytes. Data speed is rarely
expressed in bytes per second, and rarely is data storage or memory
expressed in bits. If you are not careful, you can misunderstand
the meaning of the information you are evaluating. For example,
the bandwidth provided by telephone carriers is commonly
expressed in multiples of bits per second (bps), and the size of a
file you may want to send or receive over the phone line is
expressed in multiples of bytes.
The most common convention for abbreviating bits and bytes
is to use the lower case “b” for bits and the upper case “B” for
bytes. A voice grade telephone line might provide a capacity or
bandwidth of 64 Kbps or 64 kilobits per second, and the size of the
file to be sent may be 64 KB or 64 kilobytes. 64 Kbps involves 64,000
bits, while 64 KB is describing 512,000 bits. That is a difference of
448,000 bits, which could result in a colossal misunderstanding.
Kilo or k represents 1,024 bits rounded to 1,000 for convenience. Larger amounts of bytes are described with the prefixes
Mega, Giga, Terra, Peta, Exa, Zetta and Yotta, which sounds a lot
like something out of a Star Wars movie! These become Megabyte,
Gigabyte, and so on. Even shorter descriptives are derived from
using singles letters as in K, M and G, written Kbytes, Mbytes, and
Gbytes or KB, MB, and GB. See Table 2-5.
24
Digital CCTV
Table 2-5
Numeric Abbreviations
Name
Abbreviation
Kilo
Mega
Giga
Terra
Peta
Exa
Zetta
Yotta
K
M
G
T
P
E
Z
Y
Size
2∧10
2∧20
2∧30
2∧40
2∧50
2∧60
2∧70
2∧80
=
=
=
=
=
=
=
=
1,024
1,048,576
1,073,741,824
1,099,511,627,776
1,125,899,906,842,624
1,152,921,504,606,846,976
1,180,591,620,717,411,303,424
1,208,925,819,614,629,174,706,176
You can see from this chart that Kilo is about a thousand,
Mega is about a million, and Giga is about a billion, and so on. So
when someone says, “this computer has a 2 gig hard drive”, what
he/she means is “2 gigabytes”, meaning approximately 2 billion
bytes and exactly 2,147,483,648 bytes.
HOW DOES ANALOG VIDEO BECOME
DIGITAL VIDEO?
There are a number of ways that video can be represented digitally. One way is by using Pulse Code Modulation (PCM), in
which an analog waveform at the source (transmitter end) of a
communications circuit is sampled (measured) at regular time
intervals. In digital technology, the analog wave is sampled at
some interval and then turned into numbers that are stored in the
digital device. This process is called sampling. The frequency at
which samples are taken is called the sampling rate or sampling
frequency.
There is a general theory in engineering that you need
to sample at a rate that is at least twice the fastest frequency
component of the signal you are measuring. This is called the
Nyquest theory. The sampling rate or number of samples per
second is several times the maximum frequency of the analog
waveform in hertz (Hz). In the United States, common household
electrical supply is at 60 hertz. Broadcast transmission is at
What Exactly is Digital Video?
25
much higher frequency rates, usually expressed in kilohertz (KHz)
or megahertz (MHz).
The result of sampling a video signal is digital video. There
are many ways to accomplish sampling. The standard that has
emerged for digital video sampling is the ITU-R BT.601, more
commonly known as CCIR 601. ITU stands for the International
Telecommunications Union, an organization established by the
United Nations with members from virtually every government
in the world. The ITU’s mission is to set telecommunications
standards and allocate frequencies for various uses around the
world.
CCIR 601 is based on multiples of a fundamental 3.375 MHz
sample rate. This sampling rate has been carefully chosen because
of its relationship to both NTSC and PAL. Component digital
video signals are sometimes referred to as 4 : 2 : 2, meaning that for
every four bits that are dedicated to the Y component, two bits
each are dedicated to the U & V components on both even (second
2) and odd lines (third 2) of the image. The luminance or Y channel
carries most of the image detail and is, therefore, assigned more
bits. The luminance signal is sampled at 13.5 MHz, four times the
fundamental sampling rate. Each of the color difference signals is
sampled at 6.75 MHz, two times the fundamental sampling rate.
To complete the conversion, each sample is represented by a discrete number in a process known as quantizing.
A discrete unit has no part; in other words, if it is divided the
result is no longer a unit. For example, there is no such thing as
half a person, so people are counted in discrete numbers. Ten
people can be divided only in half, fifths, and tenths, but if you
try to divide them into thirds you will receive loud complaints!
See Figure 2-2.
Distance is not made up of discrete units but is continuous.
Consider the distance between point A and point B in Figure 2-3.
Not only can we take half of the distance from A to B, we can
take any part of the distance that we like; a third, a tenth, or a
hundredth. See Figure 2-4.
This is true because AB is not composed of units. Every part,
however small, still has a discernable length demonstrating that
which is continuous is not limited by size. A discrete number, on
the other hand, will always have a limit; namely, one unit. The
26
Digital CCTV
Figure 2-2
A Discrete Unit Has No Part
Figure 2-3
Distance is Continuous
A
Figure 2-4
B
Distance is Discrete
analog waveform is continuous and therefore must be changed
into a discrete form in order to be received as digital data.
Getting back to the subject of sampling rates, examine Figure
2-5. The numbers on the left side of the scales represent voltage
amplitude. To keep it simple, the values range from zero to 100
units. You also need to know that time runs from left to right. If a
sine wave is one cycle of a one kHz tone, the amount of time on
the grid is 1/1000 or 1 millisecond. 1 millisecond equals 1,000
microseconds (μsec.).
The small circles represent sample points. Sample points are
the points at which the voltage is measured and converted into a
binary number that represents the voltage level of the signal at
that point. Notice that each of the samples is taken at equal time
intervals. The stepped, straight-line figure in black is the digital
equivalent of the sine wave reconstructed from the measurements
taken at the sample points.
When you look at Figure 2-5A, you can see that the digital
equivalent of the sine wave is a square wave that suggests an
What Exactly is Digital Video?
27
Sampling Rates
Figure 2-5
28
Digital CCTV
analog sine wave. The sample rate is five times the sine wave
frequency, or 5,000 Hz. Increasing the sample rate to 17,000 Hz or
17 sample points as in Figure 2-5B reveals a symmetrical waveform, but the digital equivalent of the sine wave is rough. Doubling the sample rate to 34,000 Hz as in Figure 2-5C yields 34
sample points. Now the digital equivalent of the sine wave looks
very much like a sine wave but it is still a little rough. Double the
sample rate again to 68 Hz or 68 sample points as in Figure 2-5D
and the digital equivalent looks the most like a sine wave.
Sampling could be compared with surveying the entire
country for specific data. The information you receive would
depend on the amount of areas sampled. In the United States, if you
collect regional samples by dividing the country into the cardinal
directions, you would gain four samples or four pieces of data. If
you were to sample by state, you would receive fifty samples or
pieces of data. Should you decide to sample by county or parish,
you would gain a much larger amount of samples and consequently, you would have a very large amount of data. Obviously,
it would be much easier to handle the data from the regional sampling, but how accurate are your results from the smaller sample
group? On the other hand, by taking the numerous county samples,
you gain a superior result at the expense of handling much larger
amounts of data. Are you beginning to see the tradeoff?
It should be becoming obvious that taking more samples
results in a higher resolution. The downside is that more samples
also result in more data, therefore requiring more bandwidth and
consequently more storage space. It is important to understand
that you can convert an analog signal to representative numbers
and then convert it back again to an analog signal that is an accurate representation of the original signal.
QUANTIZATION
The process of converting the sample amplitude into “bits” of data
is called quantization. Quantization can occur either before or after
the signal has been sampled, but usually after. Quantization is a
process of approximating the continuous set of values in the image
What Exactly is Digital Video?
29
data with a finite (preferably small) set of values. It is how many
levels (bits per sample) the analog signal will have to force itself
into. The input to a quantizer is the original data, and the output
is always one among a finite number of levels. A good quantizer
ultimately represents the original signal with a minimum of loss
or distortion. There are two types of quantization, scalar quantization and vector quantization. In scalar quantization, each input
symbol is treated separately when producing the output. In vector
quantization input symbols are organized in groups called vectors
and then processed to produce output.
CREATING THE IMAGE
A computer-created image consists of many points of color called
picture elements, or pixels. A pixel is the smallest element of a
picture or image. Graphics monitors display pictures by dividing
the display screen into thousands (or millions) of pixels, arranged
in rows and columns. Pixels are so close together that they appear
to be connected. To help understand this, consider the make up
of a tapestry. One of the earliest forms of depicting scenes, it is
actually very similar to the method of creating digital pictures. A
tapestry is nothing more than fabric woven from threads of different colors that form a picture or design. The scene on a tapestry
consists of vertical and horizontal threads of varying shades and
sizes, which form the finished image. A digital image consists of
pixels of varying shades and sizes that, when put together in a
specific order, form a picture. In both cases, the detail of the image
depends on the quantity of information—increasing the number
of threads or pixels will produce a finer, more detailed image.
The number of bits used to represent each pixel determines
how many colors or shades of gray can be displayed. For example,
in 8-bit color mode, the color monitor uses 8 bits for each pixel,
making it possible to display 2 to the 8th power (256) different
colors or shades of gray. With 8 bits in a byte, you can represent
256 values ranging from 0 to 255, as shown here:
0 = 00000000 1 = 00000001 2 = 00000010
254 = 11111110 255 = 11111111
30
Digital CCTV
HOW MANY BITS DOES IT TAKE TO MAKE
A BLACK-AND-WHITE PICTURE?
If there is only black-and-white information in a picture, one bit
for each dot or bit per pixel (bpp) in the picture is all that is
required. A dot is either black or white. The 1-bpp format is for
simple black-and-white displays. 0 represents black and 1 represents white. Think of each dot in a picture as a light bulb with
black representing off and white representing on. How many dots
does it take to make a picture? This question leads to an understanding of resolution. Figure 2-6 illustrates a simple sketch of a
face with a cook’s hat on a black background.
The image here is clear and crisp. The line where the hat
meets the head is smooth and straight with no jagged edges. The
curves are smooth as well. This sketch was created at 300 dots per
inch (dpi) resolution on a PC. Since this book is printed in a highresolution format of 300 dpi or more, the clear, crisp lines show no
jagged edges.
Figure 2-7 is the same artwork as Figure 2-6, but at a
much lower resolution of 6 dpi. Without the original highresolution image as a reference, it would be difficult to determine
what this illustration is. The resolution is so low that it makes it
difficult to see the mouth or the line where the chef’s hat joins the
head.
Figure 2-6 High Resolution
What Exactly is Digital Video?
31
Figure 2-7 Six Dots Per Inch
Figure 2-8 Twelve Dots Per
Inch
Figure 2-8 is the same image again at twice the resolution as
Figure 2-7 or 12 dpi. It is a little easier to see that the picture is of
a face with some sort of hat on it. The mouth is now visible but
the line where the hat meets the head is still not clear. It looks as
if there are ears on the head but this is just an aberration or an
artifact of the low-resolution image.
Figure 2-9 is double the resolution of Figure 2-8, or 24 dpi.
Now the hat looks a little like a chef’s hat and the line where the
hat meets the head is visible. The smile has more detail and the
nose and eyes have begun to show some shape.
A resolution of 24 dpi is about 1/3 to 1/4 of the resolution of
a computer graphics display monitor. Imagine how much better
32
Digital CCTV
Figure 2-9 Twenty-Four Dots
Per Inch
the image in Figure 2-9 would become if the resolution were
doubled and then doubled again.
How many dpi does it take to achieve acceptable resolution?
Of course, the answer is subjective. Beauty is in the eye of the
beholder and so is resolution. As a rule of thumb, 150 dpi provides
“good” results. Printed images look really good at 300 dpi, which
is the resolution digital photographers use when printing on photo
paper. Most desktop laser printers and many ink jet printers
have a resolution of 600 dpi. This is considered “excellent” quality.
Professional image setter printers and premium ink jet printers
have a resolution of 1200 dpi or better, but few of us can see any
difference in quality between 600 dpi and 1200 dpi.
The relationship between the number of pixels in an image
and the image’s printed size is important to understand. Most
readers can relate to the size of an image on paper, and most
readers can judge the quality of what they see on paper.
The larger the pixel dimensions, the larger the number of
pixels in the image and the larger the printed image size at a given
resolution. Bit depth is the number of bits used to store information about each pixel. You might ask at this point, why not use the
best bit depth for all images to obtain the best possible resolution?
The simple answer is that the higher the bit depth, the more bits
per pixel used in an image, and the more pixels used in an image,
the larger the actual file is going to be. Once again, this leads to
the issue of bandwidth needed to move digital information.
What Exactly is Digital Video?
33
WHAT ABOUT GRAY?
Images made by a black-and-white video camera contain more
than simple black or white dots. Black-and-white video images are
comprised of black, white, and many shades of gray—as seen in
Figure 2-10.
In order to convert shades of gray into numerical values for
digitizing an image, we must define the shades of gray between
black and white. Earlier in chapter one, Figure 1-6 portrayed a
10-step grayscale chart and the video waveform that results from
one scan line of the chart by a video camera. It should be clear that
Figure 2-10
Shades of Gray
34
Digital CCTV
Figure 2-11
Table 2-6
Shades of Gray in Steps
Number of Bits Needed To Make Each Picture
Dots per row
Number of rows
Total dots
Number of bits
Fig. 3-2
6 dpi
Fig. 3-3
12 dpi
Fig. 3-4
24 dpi
Fig. 3-1
300 dpi
16
16
256
256
32
32
1024
1024
64
64
4096
4096
800
800
639,997
639,997
10 shades of gray are not enough to reproduce the many shades
of gray in an image like the one in Figure 2-10. How many shades
are enough? Figure 2-11 illustrates the answer to this question.
64 steps of gray look almost good enough to represent continuous shading from white to black. 128 steps looks like what we
need to produce continuous shading. Any more steps would
probably be wasted. 256 steps are far more than what is needed
to represent all of the shades of gray that the human eye can
perceive.
The important piece of information about the number of
shades necessary to make acceptable continuous shading is the
number of bits needed to define the number of shades of gray.
Table 2-6 illustrates the number of bits (and bytes) needed for 64
shade, 128 shade, and 256 shade grayscale choices.
After the digital images reach their final destination, the
digital signal often has to be reverted back to an analog signal.
This is achieved with a digital-to-analog converter (DAC).
Basically, digital-to-analog conversion is the opposite of analogto-digital conversion.
What Exactly is Digital Video?
Table 2-7
35
Continuous Shading
Pixels per row
Number of rows
Total pixels
# of Bits/Pixel
64 shades—6 bits
128 shades—7 bits
256 shades—8 bits
640
480
307,200
Total Bits
1,843,200
2,150,400
2,457,600
Total Bytes
230,400
268,800
307,200
When you digitize video, you decide:
1. Frame rate—how many frames per second to capture.
2. Frame size—what size the frames should be.
Even though the NTSC standard dictates 29.97 frames per second
to achieve an acceptable video image, you can actually slow that
rate down to 15 or 16 frames per second without diminishing the
illusion of movement. The level of video resolution is also directly
related to the size of the screen and the viewing distance.
Although it is possible to capture video at a size that will fill
your screen—typically 640 pixels by 480 pixels—it is advisable to
specify a smaller frame size in your video capture software. For
example, on a monitor displaying 640 × 480 screen resolution a
frame size of 160 pixels by 120 pixels would fill 1/16 of the screen.
Frame sizes always maintain an aspect ratio of 4 : 3 to reflect the
resolution of computer monitors and televisions.
A video image the size of an average 640 × 480 frame size
with a resolution of 24 bits per pixel (thousands of colors) and a
standard NTSC frame rate of 30 frames per second represents a
little over 26 MB of data per second of video, not counting audio.
This means a 1 GB hard disk could only hold about 38 seconds of
video. By reducing frame size, frames per second, and bits per
pixel you can make the video more manageable (i.e., make changes
that would reduce the amount of information to store or transmit)
at the expense of the image quality.
To calculate storage needs for digital video from black-andwhite cameras, multiply the horizontal camera resolution by the
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Digital CCTV
vertical camera resolution. Next, divide this number by the
compression factor (if compression is 10 : 1 use the number 10).
Multiply the result by the frame-capture rate (30 frames per
second multiply by 30). The final number equals the amount of
bytes you will need the capacity to store per second. 720 times 480
= 345600 divided by 10 = 34560 times 30 = 1,036,800 Bytes per
second (Bps) needed storage capacity per second.
Speeds at which images can be transmitted are significantly
increased by digital compression, but many variables still affect
the update rates. These variables include such factors as image
color, movement within the image, and bandwidth of the transmission medium.
THE ELECTROMAGNETIC SPECTRUM
In order for us to see, there must be light. What we perceive as
color is really a reflection from the surface of what we are looking
at. The colors we perceive are actually electromagnetic radiation
of various frequencies. The visible light spectrum is part of a total
electromagnetic spectrum that ranges from low frequencies like
radio waves in thousands of cycles per second to high frequencies
like gamma rays in multi-trillions of cycles per second.
The electromagnetic spectrum is comprised of the complete
range of electromagnetic frequencies from 3 kHz to beyond
300,000 THz. The electromagnetic spectrum includes, from longest
wavelength to shortest: radio waves, microwaves, infrared, optical,
ultraviolet, X-rays, and gamma rays. See Figure 2-12. The visible
spectrum contains all the colors between infrared and ultraviolet.
Infrared and ultra violet are invisible to the human eye.
Figure 2-12
Electromagnetic Spectrum
What Exactly is Digital Video?
37
NTSC standards have not changed significantly since their
establishment, except for the addition of new strictures for color
signals. NTSC signals are not directly compatible with computer
systems. The NTSC standard for television defines a composite
video signal with a refresh rate of 60 half-frames per second. Each
frame contains 525 lines and can contain 16 million different colors.
Composite video is the format of an analog television signal before
it is modulated onto an RF carrier. It is a composite of three source
signals called Y, U, and V (together referred to as YUV). Composite video is sometimes called CVBS for color, video, blanking, and
sync, or composite video baseband signal.
When NTSC television standards were introduced the frame
rate was set at 30 Hz (1/2 the 60 Hz line frequency). Then, the rate
was moved to 29.97 Hz to maintain 4.5 MHz between the visual
and audio carriers. Movies filmed at 24 frames per second are
simply converted to 29.97 frames per second on television
broadcasting.
There are three dominating video standards in use around
the world, NTSC, PAL, and SECAM. These three formats have
developed in different parts of the world for historic reasons. The
PAL standard involves the scanning of 625 lines per frame and
utilizes a wider channel bandwidth than NTSC. PAL, which stands
for Phase Alternating Line, was introduced in the early 1960’s and
was implemented in most European countries except for France
where the standard is SECAM (Sequential Couleur Avec Memoire
or Sequential Color with Memory), also introduced in the 1960’s.
SECAM uses the same bandwidth as PAL but transmits color
information sequentially. American engineers have been known
to jokingly explain that SECAM stands for “System Essentially
Contrary to the American Method.” Generally these formats are
not compatible with each other because they differ in aspects like
specific scanning frequencies, number of scan lines, and color
modulation techniques.
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3
In the Beginning
Since the beginning of time, humanity has had an insatiable desire
to communicate distances that are beyond the range of unaided
hearing or sight. One of the earliest devices used in an attempt to
transmit video was the Nipkow disk named for its inventor, Paul
Nipkow. The Nipkow disk consisted of a circular disk with a spiral
of holes cut into it. These holes were positioned so that they could
scan every part of an image as it spun around. Light coming
through the disk was translated to an electrical current that caused
a second light to appear at the opposite end of a wire. This light
passed through a second disk, which was spinning at the same
speed as the original, causing a picture to be projected onto a
screen. The Nipkow disk may seem very primitive now, but in its
day it truly seemed like magic!
The desire to reach across distances became a reality with the
development of technologies like the telegraph, telephone, and
radio transmitters. As communication techniques allowed people
to actually speak to each other over long distances, the wish for
39
40
Digital CCTV
Figure 3-1
Copthorne Macdonald
visual communication grew. This wish was granted in the late
1950’s when an amateur radio ham developed a system of sending
video signals over extensive distances that allowed him to “see”
the people with whom he was speaking.
Copthorne (Cop) Macdonald (Figure 3-1) received his ham
license at the age of fifteen, and his love and curiosity of the
ham radio world stayed with him throughout his life. While
Macdonald was working his way through the University of Kentucky’s engineering school, he began looking into the feasibility
of a practical SSTV (Slow Scan TV) system for ham radio operators.
After addressing problems such as what sort of display tubes to
use and how to get frequency response down, Macdonald gained
permission from the University of Kentucky’s Electrical Engineering Department to build a working model as a course project. Not
only was the project a success, but his paper describing the system
In the Beginning
41
won first prize in the American Institute of Electrical Engineers’
national competition in 1958. By developing a system of sending
video signals to distant locations via radio frequency, Copthorne
Macdonald charted a course in communication techniques whose
benefits are still multiplying today.
In the 1960s NASA, the United States space agency, took up
the challenge and improved video transmission technology for use
in the space program. Though the scenes were somewhat choppy
and fuzzy, the world was able to actually see early astronauts at
work in their capsules as they circled the earth. The security industry has roots in the history of Slow Scan Television (SSTV) in the
following lineage: A number of engineers from the NASA design
team continued to research and modify remote transmission
techniques and founded Robot Inc., a slow scan manufacturing
company. Robot Research founded in the late 1960s in southern
California and American Dynamics started in the early 1970s in
upstate New York were acquired by Sensormatic Electronics
Corporation, followed by Tyco International Ltd., who purchased
Sensormatic in 2001.
Several well-known companies began to work on the development of video transmission products in the 60s, 70s and 80s.
AT&T demonstrated its Picturephone at the World’s Fair in 1964.
Sony and Mitsubishi introduced monochrome versions of the
videophone in the late 1980s. Unfortunately, low resolution and
slow frame rates (not to mention high costs) caused these products to take a back seat to other priorities, specifically those
that were more profitable.
Bringing people together from around the world and across
the country for business meetings can be quite costly, both in time
and money. The search for a solution to this expensive necessity
guided business leaders to the advantages of teleconferencing as
a communications alternative, and this growing market for remote
video products stimulated further research.
Manufacturers who realized a potential market for remote
video as a security surveillance product began adding their
resources to the mix, along with visionaries from the world of
medicine who understood the possible advantages of rapidly
sending images long distances. The race was on!
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Digital CCTV
THE OPTICAL ILLUSION
The process of transmitting a moving picture is dependent upon
an optical illusion that makes a series of still pictures seen in rapid
succession appear to be in motion. The first step in creating this
illusion is to transmit one still picture or one frame of video. As
discussed in chapter one, a still picture or frame of video consists of
two scans containing 525 alternate horizontal lines. The camera and
picture tube first scan 262.5 odd numbered lines. The picture is then
scanned again to form 262.5 even numbered lines. Each half of the
frame or 262.5 lines is one “field” of video. The European PAL standard involves the scanning of 625 lines per frame.
This operation of assimilating a picture, translating that
picture for transmission, and then scanning that same picture at
the receiving location results in the successful transmission of one
full frame of video. The time involved for this process from beginning to end was initially called the “update” or “refresh” rate.
Now it is commonly known as frames per second or fps.
Image updates achieved in the late 60s and early 70s were at
an approximate rate of one frame every 35 seconds. Because the
human brain assimilates 25 to 30 frames a second as full motion,
the early technology of sending one picture each 35 seconds was
far too slow to create the needed illusion.
The challenge of transmitting video evolved into a compulsion to send information at speeds that would imply full motion
or “real time” to the human eye. The problem behind transmitting
video information at a speed that simulates motion is in the amount
of information that must be sent. This is where the value of compression comes into play. By compressing much of the information
to make it smaller, it can be transmitted more efficiently.
LOSSLESS AND LOSSY COMPRESSION
Compression techniques or algorithms can be divided into two
basic categories: lossless and lossy. Lossless techniques compress
an image in such a manner that the final decompressed image is
an exact copy of the original image. Applications such as the
In the Beginning
43
compression of medical X-rays or other diagnostic scans require
the lossless technique to ensure that the original image is not
distorted.
Lossless compression: The size of the data in its compressed
form (C) in relation to the original size (O) is known as the
compression ratio (R = C/O). If the inverse of the process,
which is decompression, produces an exact replica of the
original, the compression is known as lossless.
In this formula, you see that the lossless technique compresses
information in such a manner that the final decompressed image
is an exact replica of the original. This form of compression is
required if you are transferring a program file or data file to be
used in an application like Word or Excel as well as when transmitting information over a phone line to a facsimile machine.
Initially, none of the lossless compression techniques could
achieve the necessary update rates to create the illusion of full
motion. For that reason, the industry turned to the lossy technique
of compression for audio and video transmission, where accurate
approximation is suitable.
Lossy compression: A compression scheme that intentionally
loses some information in order to provide the highest compression ratio possible. Lossy compression allows only an
approximation of the original to be generated. Used where the
loss of information will not produce a significant degradation
of information.
Unlike lossless compression, lossy techniques do not restore the
original information to 100 percent of the original. The most basic
lossy compression techniques simply reduce the number of bits
transmitted. In lossy compression, information is analyzed and a
determination is made about what loss of information will not
noticeably affect the decompressed version. After concluding
that the loss will not noticeably affect the image, the selected
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Digital CCTV
information is literally thrown away. Once this compression has
been completed, it is not possible to put back the information that
was removed. The missing information accounts for the differences, called artifacts, between the original and the decompressed
images.
The success of video compression depends largely on the
information itself. Generally some elements within the information are more common than others and most compression algorithms utilize this property, known as redundancy. The greater the
redundancy the more successful the lossy compression is likely
to be. Fortunately, digital video often contains a great deal of
information that is redundant. Certain characteristics of the
way in which humans perceive information can also be
exploited to achieve higher lossy compression ratios. For example,
our visual system is less sensitive to certain color information.
With this eye response information, lossy compression could conceivably remove some of this color and it would not be readily
perceived. The discarded information can produce minimal to
drastic differences.
To obtain a better understanding of why the lossy method of
compression is more suitable for video transmission, we can
review the events involved in producing a moving picture. As
stated, the process of creating a moving picture is dependent upon
an optical illusion; specifically, a series of still pictures seen in
rapid succession by the human eye appears to be in motion. Each
still picture involved in the illusion is referred to as one frame of
video. In order for motion to be perceived, these frames of video
must pass before our eyes at a rate of approximately 25 to 30 per
second. The difficulty involved in creating this optical illusion
arises in transferring enough frames at a fast enough rate to perceive not just motion but fluid motion.
Here is a simplified explanation of how the speed of still
frames influence the illusion of motion: Let’s assume we are
viewing a dog on one side of a large fence. See Figure 3-2. Presuming our frame rate is too slow to achieve the illusion of fluid
motion, our next picture might show the dog on the other side of
the fence. See Figure 3-2. With this information we know two
things: we know the dog was originally at point A and that he
In the Beginning
Figure 3-2
45
Slow Update Rate
somehow arrived at point B. Unfortunately, we don’t know what
events took place between these two scenes. The reason we did
not see how the dog got to the other side of the fence is that the
update rate is too slow. If the name of the dog is Houdini this
might not be considered a problem, but in many cases, especially
in a security application, this missing information could be vital.
In order to ensure that important information is not missed,
we must speed up the procedure of assimilating information,
process the information for transfer (i.e. compress the information
to a size which can be most quickly transmitted), decompress
(return the picture to its original form) the picture, and project the
picture onto a display device.
The transference of video information is achieved by a variety
of processes. Pulse modulation is a system of modulation involving pulses being altered and controlled to represent a message for
communication. The amplitude, duration, and timing of a series
of pulses are controlled in pulse-code modulation. Morse code is
a very simple example of pulse-code modulation. Different modulation techniques like AM, FM, etc. represent different ways to
shape or form electromagnetic radio waves. See Figure 3-3.
Amplitude Modulation—Both AM radio stations and the
picture portion of a TV signal use amplitude modulation to encode
information. In amplitude modulation, the amplitude of the sine
wave (its peak-to-peak voltage) changes. See Figure 3-4.
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Digital CCTV
Figure 3-3
Pulse Modulation
Figure 3-4
Amplitude Modulation
Figure 3-5
Frequency Modulation
Frequency Modulation—FM radio stations and hundreds of
other wireless technologies (including the sound portion of a TV
signal, cordless phones, and cell phones) use frequency modulation. In FM, the transmitter’s sine wave frequency changes very
slightly based on the information signal. See Figure 3-5.
High frequency radio waves can carry a lot of information.
Very High Frequency (VHF) waves are used to carry FM radio
broadcasts and Ultra High Frequency (UHF) waves are used to
carry television broadcasts.
Radio Waves
A radio wave is an electromagnetic wave sometimes referred to
as a Hertzian wave after Heinrich Hertz, who was the first to send
and receive radio waves. James Clerk Maxwell had mathemati-
In the Beginning
Figure 3-6
47
High and Low Frequency Radio Waves
cally predicted their existence in 1864, and as a professor of physics,
he produced electromagnetic waves in the laboratory and measured their wavelength and velocity. Radio waves are the electromagnetic waves with the longest wavelengths and the lowest
frequencies. See Figure 3-6.
Microwaves
Microwaves are very short waves of electromagnetic energy that
travel at the speed of light. Microwaves are good for transmitting
information from one place to another because microwave energy
can penetrate haze, light rain and snow, clouds, and smoke. Radar
uses microwave radiation to detect range, speed, and other
characteristics of remote objects. Microwaves, used for radar, are
just a few inches long. Cable TV and Internet access on coax cable
as well as broadcast television use some of the lower microwave
frequencies. Wireless LAN communication protocols such as
IEEE 802.11 and Bluetooth also use microwaves in the 2.4 GHz
ISM band, although some variants use a 5 GHz band for
communication.
The Institute of Electrical and Electronics Engineers Standards
Association (IEEE-SA) is the leading developer of global industry
standards in a broad range of industries. The 802.11 standard
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Digital CCTV
covers wireless networks. The a, b and g notations identify variations of the 802.11 standard. 802.11b was the first version to reach
the marketplace. It is the slowest and least expensive of the three.
802.11a was second to arrive, and 802.11g is a mix of both.
Infrared
Infrared radiation has a wavelength longer than visible light but
shorter than microwave radiation. Its name means “below red”
(from the Latin infra, “below”) because if it were visible to the
human eye, we would see infrared directly below “red” in the
visible light portion of the spectrum. “Near infrared” light is
closest in wavelength to visible light and “far infrared” is closer
to the microwave region of the spectrum.
Infrared transmission refers to energy in the region of the
electromagnetic radiation spectrum at wavelengths longer than
those of visible light and shorter than radio waves. Infrared frequencies are higher than microwaves but lower than visible light.
Even though infrared radiation is not visible, we can feel it in the
form of heat. The longer, far infrared wavelengths are thermal.
The shorter, near infrared waves are the ones used by a TV’s
remote control.
Visible Light Waves
Visible light waves make up only a small part of the electromagnetic spectrum and are the only electromagnetic waves we can
actually see with our eyes. Visible light waves appear as the colors
of the rainbow, with each color having a different wavelength.
Dispersion of visible light produces the colors red (R), orange (O),
yellow (Y), green (G), blue (B), indigo (I), and violet (V). It is
because of this that visible light is sometimes jokingly referred to
as ROY G. BIV. Red has the longest wavelength and violet has the
shortest wavelength, and if all of the waves are seen together, they
make white light.
In the Beginning
49
Ultraviolet
Ultraviolet (UV) light has shorter wavelengths than visible light.
Though these waves are invisible to the human eye, some insects,
like bumblebees, can see them!
X-ray
As the wavelengths of light decrease, their energy increases.
Because X-rays have small wavelengths we usually talk about
them in terms of their energy rather than wavelength. Konrad
Rontgen discovered X-rays in 1895 during an experiment with a
fluorescent plate and a beam of fast electrons in a tube. He discovered that the fluorescent plate glowed even when it was a long
way from the electron tube and by placing his hand in front of the
fluorescent plate he created the first X-ray picture. Today, X-rays
are produced in an X-ray tube by firing a beam of electrons into a
Tungsten metal target.
Gamma ray
Gamma rays have the smallest wavelengths and the most energy
of any other wave in the electromagnetic spectrum. These waves
are generated by radioactive atoms and in nuclear explosions.
Gamma rays can kill living cells and are sometimes used by physicians to kill cancerous cells.
WHAT DOES COLOR HAVE TO DO WITH IT?
Color is a complex phenomenon that has whole books dedicated
to it. The objective here is to gain a very small bit of insight into
what color is and what is involved in portraying color in a video
situation. The significance of color is that the process of transmitting color video involves a great deal of information that will also
50
Digital CCTV
have to be compressed in order to transmit with any useable
speed. In order to transmit color video, the video signal has to
provide extra color information, which consists of a synchronization signal, a luminance signal, and a chrominance signal. Monochrome images are concerned only with the first two signals that
provide information about the brightness and coordination of each
line that makes up the frame. These signals are called composite
video because the synchronizing and luminance information are
combined into a lone signal.
The color signal is called a chroma-burst and must be accurately transmitted to the receiving end with no loss of information.
The chrominance portion of the signal tells a video display what
color to reveal. The luminance value adjusts the color to light or
dark, bright or shadowed in order to provide the correct contrast
and color depth. Chrominance is abbreviated with the letter C, and
we already know that luminance is abbreviated with the letter Y.
A chrominance signal requires the transmission of extra data,
which accounts for the larger data file related to color.
We have talked about sampling rates and pixels and how
these affect the file size, but how is transmission speed affected by
color? Many of the color images we see are not what they seem.
What may appear to be pink, yellow, or black is actually another
optical illusion. Instead of being composed of all the colors that
we perceive, they are made of three primary colors (red, blue, and
green) mixed together. Everything absorbs some of the light that
falls on it, making it appear to be a certain color because it absorbs
all of the light waves except those whose frequency corresponds
to that particular color. Those waves are reflected back and cause
the eye to see a particular color. The color of an object therefore
depends on the frequency of the electromagnetic wave reflected.
What we perceive as color is a function of the colors contained in the source of the light that is illuminating what we see
and the colors absorbed and reflected by the objects upon which
the light falls. Light is focused on a sensitive part within our eyes
containing two kinds of receptors: rods and cones. There are about
100 million rods and about seven million cones. Rods are sensitive
to luminance or black-and-white information. Cones are sensitive
to both luminance and to red, green, or blue color information.
In the Beginning
51
The cones are made up of three types: one is sensitive to redorange light, the second to green light, and the third to blue-violet
light. When a single cone is stimulated, the brain perceives the
corresponding color. If our green cones are stimulated, we see
green; if our red-orange cones are stimulated, we see red. If both
our green and red-orange cones are simultaneously stimulated,
we see yellow.
The human eye cannot tell the difference between spectral
yellow and some combination of red and green. Because of this
physiological response, the eye can be fooled into seeing the full
range of visible colors through a proportionate adjustment of just
three colors: red, green, and blue. Colors are represented by bits
and the more bits that are available, the more precise the color
definition is portrayed. Digital video uses a non-linear variation
of RGB called YCbCr. Cb represents luminance and Cr represents
chrominance.
Subtractive Color
Subtractive color is the basis for printing. It is called subtractive
because white, its base color, reflects all spectral wavelengths and
any color added to white absorbs or “subtracts” different wavelengths. The longer wavelengths of the visible spectrum, which
are normally perceived as red, are absorbed by cyan. Magenta
Figure
3-7 Primary
Colors in Subtractive Color
System
52
Digital CCTV
absorbs the middle wavelengths (green), and yellow absorbs the
shorter wavelengths of the visible spectrum (blue-violet). Mixing
cyan, magenta, and yellow together “subtracts” all wavelengths
of visible light and, as a result, we see black.
Printing inks comprised of the colors cyan, magenta, and
yellow combine to absorb some of the colors from white light and
reflect others. Figure 3-7 illustrates how cyan, magenta, and yellow,
when printed as three overlapping circles, work to produce black
as well as red, green, and blue. In practice, the black produced by
combining cyan, magenta, and yellow is often not black enough
to provide a large contrast range, so printers often add black ink
(K) to the mix, resulting in the four color printing process sometimes known as CMYK. Cyan, magenta, and yellow are the primary
colors in the subtractive color system. Red, green, and blue are the
primary colors in the additive color system.
Additive Mixing
Video systems deal with subtractive color when a camera captures
the light reflected from objects the same way as our eyes. But,
when a video system needs to display a color image, it has to deal
with a whole new way of working with color. Images that are
sources of light, such as the television screen or monitor, produce
color images by a process known as additive mixing. To create a
color, the wavelengths of the colors are added to each other. Before
any colors have been added, there is only black, which is the
absence of light. On the flip side, adding all three additive primary
colors in equal amounts creates white. All other colors are produced by mixing the three primary wavelengths of light in different combinations. When the three primary colors of light are
mixed, intensities of the colored light are being added. This can
be seen where the primary color illumination overlaps. Yellow is
formed when red light added to green light is equal to the illumination of the red and green combined.
In a video signal, the color white is comprised of 30% Red,
59% Green, and 11% Blue. Since green is dominant, it is used for
In the Beginning
53
the luminance or black-and-white information in the picture. Note
that the common symbol for luminance is the letter Y. The luminance equation is usually expressed to only 2 decimal places as
Y = 0.3R + 0.59G + 0.11B. The letter R is of course representing
red, B representing blue, and G representing green.
Instead of sending luminance (Y) and three full color signals
red, green, and blue, color difference signals are made to conserve
analog bandwidth. The value of green (also Y) is subtracted from
the value of Red (R-Y). The value of green is also subtracted from
the value of blue (B-Y). The result is a color video signal comprised
of luminance Y and two color difference signals, R-Y and B-Y.
Since Y (the luminance signal) is sent whole, it can be recombined
with the color difference signals R-Y and B-Y to get the original
red and blue signals back for display.
PICTURE QUALITY
One of the most important things to a security professional is
picture quality. The effort and expense of capturing video images
will be of little value if, when viewed, the image is unrecognizable.
The fact is that the science of removing redundant information to
reduce the amount of bits that need to be transferred would not
even be necessary if we lived in a world of unlimited bandwidth.
For the present, at least, this is not the case. So we must learn how
to use bandwidth to its fullest advantage. Choices for high quality
or high image rate result in high bandwidth requirements. Choices
for lower bandwidth result in reduced image quality or reduced
update rate or both. You can trade off image rate for quality within
the same bandwidth.
THE BANDWIDTH WAGON
The term bandwidth is used for both analog and digital systems
and means similar things but is used in very different ways. In a
digital system, bandwidth is used as an alternative term to bit rate,
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Digital CCTV
which is the number of bits per second, usually displayed as kilobits per second. Technically, bandwidth is the amount of electromagnetic spectrum allocated to a telecommunications transmitter
to send out information. Obviously, the larger the bandwidth, the
more information a transmitter can send out. Consequently, bandwidth is what determines the speed and, in some cases, the clarity
of the information transferred. Bandwidth is restricted by the laws
of physics regardless of the media utilized. For example, there
are bandwidth limitations due to the physical properties of the
twisted-pair phone wires that service many homes. The bandwidth of the electromagnetic spectrum also has limits because
there are only so many frequencies in the radio wave, microwave,
and infrared spectrum. In order to make a wise decision about the
Figure 3-8
Traffic. Courtesy of WRI Features.
In the Beginning
55
path we choose, we need to know how much information can
move along the path and at what speeds. Available bandwidth is
what determines how fast our compressed information can be
transferred from one location to another.
Visualize digital video as water and bandwidth as a garden
hose. The more water you want to flow through the hose, the
bigger around the hose must be. Another example can be found
in comparing driving home in rush hour traffic with transmitting
video signals. If there are 500 cars, all proceeding to the same
destination, how can they make the trip more expediently? A
larger highway would be the obvious answer. See Figure 3-8.
If those 500 cars were traveling over four lanes as opposed
to two lanes, they could move with greater speed and accuracy.
Now imagine those 500 cars on an eight-lane highway. The four
and eight lane highways simply represent larger bandwidths.
Conversely, if there is very little traffic, a two-lane highway will
be adequate. The same is true for transmitting digital data. The
bandwidth requirements are dictated by the amount of data to be
transferred.
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4
Compression—The
Simple Version
It can be difficult to get a simple answer to questions concerning
the compression of video, especially when faced with making
purchasing decisions. Manufacturers of video compression systems
can choose from a variety of compression techniques, including
proprietary technologies, and they each feel that certain attributes
are more important than others. It can be easy to feel overloaded
with information but at the same time feel like you are not getting
any answers. The next few chapters will attempt to explain some
of the common video compression idiosyncrasies so that better
decisions can be made.
Compression
1. An increase in the density of something.
2. The process or result of becoming smaller or pressed together.
3. Encoding information while reducing the bandwidth or bits
required.
Merriam-Webster Online Dictionary
57
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Digital CCTV
Image compression is the same as data compression—the process
of encoding information using fewer bits. Various software and
hardware techniques are available to condense information by
removing unnecessary data or what are commonly called redundancies. This reduction of information in turn reduces the transmission bandwidth requirements and storage requirements for
audio, image, and full-motion video signals. The art or science of
compression only works when both the sender and receiver of the
information use the same encoding scheme.
The roots of compression lie with the work of the mathematician Claude Shannon, whose primary work was in the context of
communication engineering. Claude Elwood Shannon is known
as the founding father of the electronic communications age.
Shannon investigated the mathematics of how information is sent
from one location to another as well as how information is altered
from one format to another. Working for Bell Telephone Laboratories on transmitting information, he uncovered the similarity
between Boolean algebra and telephone switching circuits. He
theorized that the fundamental unit of information is a yes-no situation in which something is or is not. Using Boolean two-value
binary algebra as a code, one means “on” when the switch is
closed and the power is on, and zero means “off” when the switch
is open and power is off.
One of the most important features of Shannon’s theory was
the concept of entropy. The basic concept of entropy in information theory has to do with how much randomness is in a single
or in a random event. He is also credited with the introduction
of the Sampling Theory, which is concerned with representing a
continuous-time signal from a (uniform) discrete set of samples.
These concepts are deeply rooted in the mechanics of digital
compression.
COMPRESSION IN THE 1800’s
The compression of data is an idea that is not necessarily new. A
compression algorithm is the mathematical process for converting
data into smaller packages. An early example of a compression
Compression—The Simple Version
59
method is the communication system developed by Samuel Morse,
known as Morse code. In 1836, Samuel Morse demonstrated the
ability of a telegraph system to transmit information over wires.
The idea was to use short code words for the most commonly
occurring letters and longer code words for less frequent letters.
This is what is known as a variable length code. Using a variable
length code, information was compressed into a series of electrical
signals and transmitted to remote locations.
Morse code is a system of sending messages that uses short and
long sounds combined in various ways to represent letters,
numbers and other characters such as punctuation marks. A
short sound is called a dit; a long sound, a dah. Written code
uses dots and dashes to represent dits and dahs.
“Morse code” World Book Online Reference Center. 2004. World
Book, Inc.
In the past, telegraph companies used American Morse Code to
transmit telegrams by wire. An operator tapped out a message on
a telegraph key, a switch that opened and closed an electric circuit.
A receiving device at the other end of the circuit made clicking
sounds and wrote dots and dashes on a paper tape. See Table 4-1.
Today, the telegraph and American Morse Code are rarely
used.
Compression techniques have played an important role in
the evolution of telecommunication and multimedia systems from
their beginnings. As mentioned in Chapter 3, pioneers of slow scan
transmission of video signals have roots in the 1950s and 60s. In
the 1970s, interest in video conferencing as a business tool peaked,
resulting in a stimulation of research that improved picture quality
and digital coding.
Early 1980s compression based on Differential Pulse Code
Modulation (DPCM) was standardized under the H.120 standard.
During the late 1980s, the Joint Photographic Experts Group
became interested in compression of static images and they chose
Discrete Cosine Transfer (DCT) as the basic unit of compression,
mainly due to the possibility of progressive image transmission.
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Digital CCTV
Table 4-1
A .B -. . .
C -.-.
D -. .
E.
F . .-.
G --.
H....
I..
J .--K -.L .-. .
M --
Morse Code
N -.
O --P .--.
Q --.R .-.
S...
TU . .V . . .W .-X -. .Y -.-Z --. .
1 .---2 . .--3 . . .-4 . . . .5.....
6 -. . . .
7 --. . .
8 ---. .
9 ----.
0 ----/ -. .-.
+ .-.-.
= -. . .-
. .-.-., --. .-? . .--. .
( -.--.
) -.--.- -. . . .” .-. .-.
_ . .--.’ .----.
: ---. . .
; -.-.-.
$ . . .-. .-
This codec showed great improvement over H.120. The standard
definition was completed in late 1989 and is officially called the
H.261 standard.
Compression, or the process of reducing the size of data
for transmission or storage, is typically achieved by the use of
encoding techniques such as these just mentioned because video
sequences contain a significant amount of statistical and subjective
redundancy (recurring information) within frames. The ultimate
goal of video compression is to reduce this information for storage
and transmission by examining and discarding these redundancies and encoding a minimum amount of information. The performance of a video compression technique is significantly influenced
by the amount of redundancy in the image as well as on the actual
compression method used for coding.
CODECS
One second of uncompressed NTSC video requires approximately
27 MB of disk space and must definitely be compressed in order to
store efficiently. Playing the video would then require decompression. Codecs were devised to handle the compression of video for
storage and transmission and the decompression when it is played.
Compression—The Simple Version
61
The system that compresses data is called an encoder or coder,
and the decompressor is known as a decoder. The term codec comes
from the “co” in “compressor” and the “dec” in “decompressor.”
When we talk about video format, we’re referencing the manner
in which information is stored on disks. Formats include things
like AVI and QuickTime. A format does not necessarily mean
anything about the video quality; it only dictates the underlying
structure of a file. We’ll talk more about formats in the chapter
about personal computers and the Internet.
The compression of video, graphics, and audio files is
accomplished by removing redundant information, thereby
reducing file size. In reverse order, decompression recreates the
video, graphics, and audio files. A codec is typically used when
opening a video file for playback or editing, as the frames must
be decompressed before they can be used. Similarly, the compressor must be used when creating a video file to reduce the
size of the source video frames to keep the size of the video file
to a minimum. Many codecs use both spatial and temporal
compression techniques. Choosing a codec depends on the video
source. For temporal compression, video that changes very little
from frame to frame will compress better than video with lots
of motion. With spatial compression, less detail means better
compression.
Hardware codecs provide an efficient way to compress and
decompress video files to make them faster and require fewer
central processing unit (CPU) resources than corresponding software codecs. Using a hardware compression device can supply
high-quality video images but requires viewers to have the same
decompression device in order to watch it. Software codecs are
less expensive, and freeware versions are often available. Viewing
images compressed by software usually only require a copy of the
software at the viewers end. The drawback to software codecs is
that they can be CPU intensive.
Compression coder-decoders (codecs) are based upon one of
four techniques for accomplishing lossy compression: (1) vector
quantization, (2) fractals, (3) discrete cosine transform (DCT),
and (4) wavelets. Each of these four compression techniques has
advantages and disadvantages.
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Digital CCTV
1. Vector quantization is a lossy compression that looks at an
array of data and generalizes what it sees. Redundant data is
compressed, preserving enough information to recreate the
original intent.
2. Fractal compression, also a lossy compression, detects similarities within sections of an image and uses a fractal algorithm to
generate the sections. Fractals and vector quantization require
significant computing resources for compression but are quick
at decompression.
3. DCT samples an image, analyzes the frequency components,
and discards those that do not affect the image. Like DCT,
discrete wavelet transform (DWT) mathematically transforms
an image into frequency components. DCT is the basis of standards such as JPEG, MPEG, H.261, and H.263.
4. Wavelet mathematically transforms an entire image into frequency components that work on smaller pieces of data, resulting in a hierarchical representation of an image, where each
layer represents a frequency band.
COMPRESSION SCHEMES
The principle behind compression is a simple one—convert data
(using a recipe or algorithm) into a format requiring fewer bits
than the original for transmission and storage. The data must be
able to be returned to a good approximation of its original state.
There are many popular general-purpose lossless compression
techniques that can be applied to any type of data. We will examine
a few here. Please do not expect to fully understand the intricacies
of these techniques from the very brief explanations and examples;
rather take from them the concept of various types of coding
methods. In the future, when you see these or other terms relating
to compression formats, you will understand the theories if not
the specific complexities.
Run-length Encoding
Run-length encoding (RLE) is a simple
form of data compression where strings of data occur consecu-
Compression—The Simple Version
63
tively and are stored as single data values rather than as the
original string. This compression technique works by replacing
consecutive incidences of a character with the character coming
first and followed by the number of times the character is repeated
consecutively. For example, the string 2222211111000000 is represented by 251506. The character or symbol 2 is followed by a 5
indicating the 2 appears 5 times, the 1 is followed by 5 for the 5
times it appears, and the 0 is followed by 6 for 6 times.
Clearly this compression technique is most useful where
symbols appear in long runs. RLE replaces consecutive occurrences of a symbol with the symbol, followed by the number of
times it is repeated. This system uses the idea that when a very
long string of identical symbols appear, one can replace this long
string by saying X appears 10 times. Stated another way, it replaces
multiple occurrences of one value by one occurrence and the
number of repetitions.
RLE takes advantage of the fact that data streams contain
long strings of ones and long strings of zeros. RLE compresses the
data by sending a pre-arranged code for string of ones or string of
zeros followed by a number for the length of the string. The space
indicated by the arrow in the following string of code represents
the amount of compression achieved:
Original: 0001 0000 1111 1111 1111 1111 1111 1111 1111 1111
>
1111 1111 0001 0000 0001 <
Compressed: 0 × 3, 1, 0 × 4, 1 × 40, 0 × 3, 1, 0 × 7, 1
This compression technique is most useful where symbols appear
in long runs. RLE would not be as efficient if the symbols were
not repetitious as in the following example, which shows the
coded version as longer than the original version.
>
Original: 0 11 0 0 01 1 111 1 0 0 00 101 00 <
Compressed: 0, 1 × 2, 0, 0, 01, 1, 1 × 3, 1, 0, 0, 0 × 2, 101, 0 × 2
Relative Encoding
Relative encoding is a transmission technique that improves efficiency by transmitting the difference
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Digital CCTV
between each value and its predecessor, in place of the value itself.
Simply put, each value is relative to the value before it. For example,
if you had to compress the number string 15106433003, it would
be transmitted as 1 + 4-4-1 + 6-2-1 + 0-3 + 0 + 3. In other words,
the value of the number one is transmitted and the next value is
conveyed by adding four to the first value of one, which equals
five. The next value, which is one, is represented by subtracting
four from the five we have just achieved in the previous calculation. This method of coding results in a reduction of one-third the
number of bits. Differential Pulse Code Modulation (DPCM) is an
example of relative encoding. By using DPCM, an analog signal is
sampled and the difference between its actual value and its predicted value, which is determined from a previous sample or
samples, is then converted to a digital signal.
Variable Length Codes
It is sometimes advantageous to use variable length codes (VLC),
in which different symbols may be represented by different
numbers of bits. For example, Morse code does not use the same
number of dots and dashes for each letter of the alphabet. In particular, E, the most frequent letter, is represented by a single dot.
In general, if our messages are such that some symbols appear
very frequently and some very rarely, we can encode data more
efficiently (using fewer bits per message) if we assign shorter
codes to the frequent symbols. Consider the alternative code for
the letters A through H:
A = 0, C = 1010, E = 1100, G = 1110, B = 100,
D = 1011, F = 1101, H = 1111.
Using this code, the same message as above is encoded as
follows:
100010100101101100011010100100000111001111.
This string contains 42 bits and saves more than 20 percent in
space compared to the three bit per character, fixed-length code
Compression—The Simple Version
65
shown above. An inconvenience associated with using variable
length codes is that of not always knowing when you have reached
the end of a symbol in a sequence of zeros and ones. In other
words, how do you know when the zeros and ones have left off
of representing one piece of data and begun representing another?
Morse code solves this problem by using a special separator code
after the sequence of dots and dashes for each letter. Another solution is to design the code in such a way that no complete code for
any symbol is the beginning (or prefix) of the code for another
symbol. This kind of code is called a prefix code. In the example
above, the letter A is encoded by 0 and the letter B is encoded by
100, so no other symbol can have a code that begins with 0 or with
100.
In general, we can attain significant savings if we use variable
length prefix codes that take advantage of the relative frequencies
of the symbols in the messages to be encoded. One particular
scheme for doing this is called the Huffman encoding method,
which is a form of lossless compression.
Huffman Encoding
The Huffman compression algorithm is named for its inventor,
David Huffman. In computer science, Huffman coding is an
entropy encoding algorithm used for data compression that finds
the best possible system of encoding strings based on the comparative frequency of each character. Entropy coding refers to a variety
of methods that seek to compress digital data by representing frequently reoccurring patterns with minimal bits and rarely occurring patterns with many bits. Examples of entropy include run
length encoding, Huffman coding, and arithmetic coding. Entropy
coding, exampled by Morse code, is one of the oldest data compression techniques around. Entropy encoding assigns codes to
symbols in order to match code lengths with the probabilities of
the symbols appearing, resulting in the most common symbols
having the shortest codes.
Huffman is a statistical data compression technique
whose symbols are reassigned their original fixed length codes on
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Digital CCTV
decompression. Huffman’s idea is very simple as long as you
know the relative frequencies to put it to use. A colorful example
is shown here using the word abracadabra where the letter A is
the most frequently used symbol, so it is given the shortest code
representation, a single 0. If you observe that the coded length of
symbols is longer than the original, you are right, but remember
that the goal is to reproduce the information using the shortest
possible digital code.
A=0
B = 100
C = 1010
D = 1011
R = 11
ABRACADABRA = 01001101010010110100110
A Huffman compressor computes the probability at which certain
data values will occur and then assigns the shortest codes to those
with the highest probability of occurring, and longer codes to the
ones that don’t show up as often. This method produces a variable
length code where the total number of bits required to transmit
data can be made considerably less than the number required if a
fixed length representation is used.
Adaptive or Conditional Compression
Adaptive compression is really just what it sounds like. It dynamically adjusts the algorithm used based on the content of the data
being compressed. In other words, it adapts to its environment.
Adaptations of Huffman’s method, known as dynamic Huffman
codes or adaptive Huffman codes, were eventually developed to
overcome very specific problems. Adaptive or conditional compression has achieved impressive increases in update speed by
compressing and transmitting frame-to-frame motion. This system
of compression sends an initial picture to a receiver and after the
first full frame is sent, only those portions of the picture that have
changed are compressed and transmitted.
Compression—The Simple Version
Figure 4-1
67
Talking Heads
A reduction in image update is the result of only small portions of the picture changing. Unfortunately, if there is a significant change to the original picture such as several persons entering
the camera view, the update time will increase in direct proportion
to the amount of picture changes. Conditional compression was
originally very popular in the video conferencing arena where
only the small movements of a person’s mouth were necessary to
transmit. See Figure 4-1.
UNCONDITIONAL COMPRESSION
An alternative approach commonly referred to as “unconditional”
video transmission involves full frame compression. This method
grabs each frame of video independently, and the entire picture is
compressed and transmitted to the receiver regardless of changes
within the monitored area. Because this method of compression
transmits every picture in its entirety, there can be no arguments
as to its integrity.
There are two criteria by which each of the compression
techniques discussed here can be measured: the algorithm complexity and amount of compression achieved. When data compression is used in a data transmission application, the goal is
speed. The speed of the transmission relies on number of bits sent,
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Digital CCTV
the time it takes the encoder to generate the coded message, and
the time it takes for the decoder to recover the original data.
Intraframe or Spatial Compression
Compression is achieved by taking advantage of spatial and
temporal redundancies elementary to video. In plain English,
spatial compression reduces the amount of information within the
space of one image by removing repetitive pieces of information.
Spatial compression is used to compress the pixels of one frame
by itself or one frame within a sequence to eliminate unneeded
information within each frame.
Spatial redundancy takes advantage of the similarity in color
values shared by bordering pixels. Spatial compression, sometimes referred to as intraframe compression, takes advantage of
similarities within a video frame. Intraframe compression exploits
the redundancy within the image, known as spatial redundancy.
Intraframe compression techniques can be applied to individual
frames of a video sequence. For example, a large area of blue sky
generally does not change much from pixel to pixel.
The same number of bits is not necessary for such an area as
for an area with large amounts of detail, for example if the sky
was filled with multi-colored hot air balloons. Spatial compression
deletes information that is common to the entire file or an entire
sequence within the file. It also looks for redundant information,
but instead of logging every pixel in a frame, it defines the area
using coordinates.
Interframe or Temporal Compression
Some compressors employ temporal compression, which makes
the assumption that frames that are next to each other look very
similar. Therefore, it is used only on sequences of images. Temporal compression, sometimes referred to as frame differencing or
interframe compression, compares a frame of video with the one
Compression—The Simple Version
69
before it and eliminates unneeded information. Temporal or interframe compression makes use of the similarities between consecutive video frames.
When it can be assumed that relatively little changes from
one video frame to the next, interframe compression reduces the
volume of data required to express the run of data. For example,
if two consecutive frames have the same background, it does not
need to be stored two times. Only the differences between the two
frames need to be stored. The first frame is spatially digitized in
its entirety. For the next frame, only the information that has
changed is digitized. Interframe compression involves an entire
sequence of video frames and the similarities between frames,
known as temporal redundancy. There are several interframe
compression techniques that reuse parts of frames to create new
frames.
Sub-sampling can also be applied to video as an interframe
compression technique, by transmitting only some of the frames.
Sub-sampled digital video might, for example, contain only every
second frame. Either the viewer’s brain or the decoder would be
required to interpolate the missing frames at the receiving end.
Difference coding is a simple interframe process that only updates
pixels, which have changed.
A simpler way to describe temporal compression is by understanding that it looks for information that is not necessary to the
human eye. Temporal compression is accomplished by comparing
images on a frame-by-frame basis for changes between frames.
This compression algorithm compares the first frame with the next
frame to find anything that’s changed. After the initial frame, it
only keeps the information that does change, allowing for the
removal of a large portion of the file. It does this for each frame
until it reaches the end of the file.
When there is a scene change, the new frame is tagged as the
key frame and becomes the comparison image for the next frames.
The comparison continues until another change occurs and the
cycle begins again. The file size increases with every addition of a
new key frame. This means that the fewer changes in the camera
view, the smaller the data to be stored or transferred.
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Digital CCTV
There are several temporal or interframe compression techniques of various degrees of complexity, most of which attempt
to compress data by reusing parts of frames the receiver already
has to construct new frames. Both spatial and temporal compression methods reduce the overall file size, which is of course the
main goal of compression. If this does not sufficiently decrease the
amount of data, one can make a larger reduction in file size by
reducing colors, frame rate, and finally quality.
PREDICTIVE VS. TRANSFORM CODING
In predictive coding, information is used to predict future values.
With this technique, one removes the correlation between neighboring pixels and quantizes only the difference between the value
of a sample and a predicted value; then the difference is coded.
Differential Pulse Code Modulation, discussed earlier, is an
example of predictive coding. Transform coding transforms the
image from its spatial domain representation using some wellknown transform and then codes the transformed values. The
image is divided into blocks and the transform is calculated for
each block. After the transform is calculated, the transform coefficients are quantized and coded. The transform method affords
greater data compression compared to predictive methods, in
exchange for more complex computation.
Some codecs incorporate motion prediction because moving
objects are reasonably predictable. The first frame in a sequence is
coded in the normal way for a still image, and in subsequent
frames the input is the difference between the input frame and the
prediction frame. The difference frame is called the prediction
error frame.
In MPEG (Motion Picture Experts Group) compression,
where picture elements are processed in blocks, bits are saved by
predicting how a given block of pixels will move from one frame
to the next. Only the motion vector information is sent. With
motion prediction, several frames of the video are being processed
within the compressor at any given time, which produces a
delay.
Compression—The Simple Version
71
Rather than simply comparing two successive frames, this
technique notices moving objects in a frame and predicts where
they will be in the next frame so only the difference between the
prediction and the actual location needs to be stored. For common
video sequences, areas of pictures in successive frames are highly
correlated. Motion prediction exploits such correlations to attain
better quality and lower bandwidth requirements.
When video compression made the leap from intra-frame to
inter-frame techniques, the gains were minimal. As inter-frame
compression became more advanced, appreciably lower bit rates
were achieved meeting memory and computational requirements,
but this was still costly.
Fixed Length Codes
Let’s examine this example of a fixed length code. If we use
the eight symbols A, B, C, D, E, F, G, and H to create all of our
messages, we could choose a code with three bits per character,
for example: A = 000, C = 010, E = 100, G = 110, B = 001, D = 011,
F = 101, and H = 111.
With this code, the message BACADAEAFABBAAAGAH
(which contains eighteen characters) is encoded as the following
string of 54 bits:
001000010000011000100000101000001001000000000110000111.
We know there will be 54 bits in the string because 18 characters
times three bits equals 57. The American Standard Code for Information Interchange (ASCII) is a 7-bit code that was proposed by
the American National Standards Institute (ANSI) in 1963 and
finalized in 1968. The ASCII coding system contains 256 combinations of 7-bit or 8-bit binary numbers to represent every possible
keystroke. Codes such as ASCII and the sample A-through-H code
above are known as fixed-length codes because they represent
each symbol in the message with the same number of bits: ASCII
with seven bits per symbol and the A-through-H code having
three bits per symbol.
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Digital CCTV
COMPRESSION RATIO
Even though you will hear the term compression ratio used quite
frequently in connection with digital video, you do not necessarily
want to be sold or sell digital video systems based upon compression ratios. A compression ratio is simply a figure that describes the
difference between information in and information out. It describes
a numerical representation of the original video information compared to the compressed version of the same information.
For example, a compression ratio of 200 : 1 describes the
original video with the numeric value of 200. In comparison, the
compressed video is represented by the lower number. As more
compression occurs, the numerical difference between the two
numbers increases. The compression ratio is equal to the size of
the original image divided by the size of the compressed image.
Remember the formula (R = C/O) from chapter three? A 10 MB
file that compresses to 2 MB would have a 5 : 1 compression ratio.
Another way to look at it is that MPEG4 video compressed to a
30 : 1 ratio allows the storage of 30 compressed frames in the same
space as a single uncompressed frame.
In most cases, the video quality decreases as the compression
ratio increases. This is the obvious result of throwing away more
and more information to achieve compression. Think of it in terms
of making orange juice from fresh oranges. See Figure 4-2. Six
Figure 4-2
Six To One Ratio
Compression—The Simple Version
73
oranges may be squeezed down to make one cup of orange juice;
thus the compression ration is six to one or 6 : 1. First you have six
whole oranges. In order to receive the benefit of the oranges (the
juice) you may discard the skin, seeds, and most of the pulp. The
juice that remains is still identifiable as orange, and it takes about
one sixth of the space to store one glass of juice as opposed to six
oranges.
In terms of video data, a high compression ratio is not necessarily a good thing. The greater the amount of compression, the
more data that has been discarded, and the more the original
picture degraded. The type of compression technique used can
also affect the results. A video stream that is compressed using
MPEG at 100 : 1 may look better than the same video stream compressed using JPEG at 100 : 1. It is of the utmost importance that a
video system is considered on the merits of its performance in the
actual environment where it will be used, not how well it does
somewhere else.
The compression technique in use and camera placement are
usually the two major influencing factors when determining the
evidentiary value of a video image. When it comes to digital video
for security purposes, you want sharp images from the best angle
possible. Everything else is secondary.
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5
More on Digital
Video Compression
In a perfect world, video could be transmitted without any changes
or adjustments to the data whatsoever. The reality is that storing
and transmitting uncompressed raw video is not a good idea
because it requires too much storage space to store and bandwidth
to transmit. Therefore the need for compression exists. The actual
compression of video is achieved by a collection of mathematical
processes that manipulate the content of an image. There are
several different processes to achieve compression; in each case,
the aim is to decrease the amount of data required to represent the
image in a recognizable facsimile of the original. The type of video
compression used for security surveillance varies between manufacturers and by products. Some types of video compression are
proprietary and not compatible with other systems.
Standards ensure interoperability and increase utility and
ease of use by enabling products to work together and communicate with each other. This means that products that comply with
standards, no matter who develops them, are able to work with
75
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Digital CCTV
other products that comply with the same standards. There are
several organizations responsible for defining standards, including the American National Standards Institute, the International
Organization for Standardization, and the International Electrotechnical Commission.
The definition of a standard by the American National Standards Institute (ANSI) is “a set of characteristics or qualities that
describes the features of a product, process or service.” ANSI is a
private, non-profit organization that administers and coordinates
the U.S. voluntary standardization and conformity assessment
system. The Institute’s mission is to enhance both the global competitiveness of U.S. business and the U.S. quality of life by promoting and facilitating voluntary consensus standards and conformity
assessment systems and safeguarding their integrity.
The International Organization for Standardization (ISO) in
Geneva is the head organization for many national standardization bodies, including:
●
●
●
●
●
●
●
●
●
DIN—Deutsches Institut fuer Normung, Germany
BSI—British Standards Institution, United Kingdom
AFNOR—Association francaise de normalisation, France
UNI—Ente Nazionale Italiano di Unificatione, Italy
NNI—Nederlands Normalisatie-instituut, Netherlands
SAI—Standards Australia International
SANZ—Standards Association of New Zealand, New
Zealand
NSF—Norges Standardiseringsforbund, Norway
DS—Dansk Standard, Denmark
The ISO is the world’s largest developer of standards: a nongovernmental organization that works to promote the development of standardization to facilitate the international exchange of
goods and services and spur worldwide intellectual, scientific, technological, and economic activity. The ISO is the source of ISO 9000,
ISO 14000, and more than 14,000 International Standards for business, government, and society. The ISO is made up of a network of
national standards institutes from 146 countries working in
partnership with international organizations, governments, and
industry, including business and consumer representatives.
More on Digital Video Compression
77
International Electrotechnical Commission (IEC) is an international standards and assessment body for the fields of electrotechnology. Established in 1988, the IEC prepares and publishes
international standards for all electrical, electronic, and related
technologies. These serve as a basis for national standardization
and as references when drafting international tenders and
contracts.
DO YOU HAVE ALGORITHM?
Before we look at individual compression standards, let’s clear up
the commonly used term algorithm, which is used similarly as the
term standard. An algorithm, which can be implemented either in
software or hardware, refers to the process for doing a task or
specific function. Standards are documented agreements between
groups that set rules for the development of products and services.
A standard may include a specific algorithm that is used as part
of the function of the product itself.
In mathematics and computer science, algorithm usually
refers to a process that solves a recurrent problem. An algorithm
will have a well-defined set of rules and a specific stopping point.
A computer program can, in fact, be viewed as an elaborate algorithm. The word algorithm comes from the name of the mathematician Mohammed ibn-Musa al-Khwarizmi, who was part of the
royal court in Baghdad and lived from about 780 to 850.
Algorithms often have repetitive steps and may require that
decisions be made to complete the desired task. Different algorithms may complete the same task with difference in time, space,
effort, etc. An algorithm could be compared with a recipe in that
different algorithms may complete the same task utilizing a different set of instructions concerning time, space, and effort. For
example, one might have a recipe for chicken soup that calls for
boning the chicken first, while another recipe may suggest boning
after the chicken has been boiled. Either recipe will eventually
result in chicken soup when completed.
We use algorithms every day for things like baking cookies
or putting together a bicycle, by following a recipe or a set of
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directions. So, when a seller begins talking about algorithms pertaining to his or her digital video system, they are merely referring
to the particular recipe the system follows to achieve compression
and other functions. Unfortunately, an algorithm cannot complete
its task if it is flawed in some way, just as the recipe will not turn
out as chicken soup if pork is used in place of chicken even if all
the other directions are performed perfectly.
There can be a lot of confusion surrounding the terminology
involved with video compression. For example, the codec should
not to be confused with the video file format used to store information after it has been encoded. Codec refers to the compression/
decompression procedure used by encoding tools and players. File
formats are shared by encoding tools and servers to generically
store encoded streams. A video codec is an algorithm that provides a lossy compression technique for video.
Architectures allow information to be traded in a standard
format. Architectures in digital video allow you to specify which
codecs are used and provide the overall structure and synchronization for media delivery. Codecs are the smaller encoding components that fit within an architecture. For example, QuickTime
and Windows Media are architectures; Sorenson Video and MPEG4 are video codecs. Many different codecs are available and more
are being developed every day.
COMPRESSION AND TRANSMISSION STANDARDS
In recent years, a number of video compression and transmission
standards have been proposed and approved by international
standardization committees like the Society of Motion Picture and
Television Engineers (SMPTE) and the Institute of Electrical and
Electronics Engineers (IEEE). The IEEE is the largest technical
professional organization in the world (in number of members),
with more than 360,000 members in 150 countries (as of 2004) They
are a non-profit organization, formed in 1963 by the merger of the
Institute of Radio Engineers and the American Institute of Electrical Engineers. The IEEE promotes the engineering process of creating, developing, integrating, sharing, and applying knowledge
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about electro and information technologies and sciences for the
benefit of humanity and the profession.
MPEG
The Moving Picture Experts Groups, known collectively as MPEG,
is a working group responsible for developing and maintaining
digital video and audio encoding standards for compressed video.
MPEG has put together and uses specific procedures for the development, adoption, testing, and review of digital multimedia standards. Having these MPEG standards as international standards
insures that video encoding systems will produce files that can be
opened and played with any standards-compliant decoder. The
major advantage of MPEG compared to other video and audio
coding formats is that MPEG files are much smaller for the same
quality.
Moving objects tend to be predictable and in MPEG compression, picture elements are processed in blocks. Space is saved by
predicting how a block of pixels might move from frame to frame.
After analyzing the video information, only the motion vector
information is sent. MPEG compression utilizes three types of
frame development:
●
I-frame: (Intra-frame)
Key frames are compressed using the JPEG standard. These are
frames with no past history, typically the first frame that is encoded.
The I-frame is a reference point for the following B and P
frames.
●
P-frame: (Predicted frame)
Predicted frames are constructed by comparing redundancies
from preceding frames.
●
B-frame: (Bi-directional frame)
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Figure 5-1
A Sequence of Frames
Bi-directional frames are generated by referencing redundancies
in either the preceding or succeeding frames. By looking for
matches in the before and after frames, the B-frame can be constructed by only encoding the difference. If no good match is
found, a new I-frame may be generated. A typical sequence of
frames may look like this: IBBPBBPBBPBBIBBPBBPB . . . See
Figure 5-1.
The prediction technique used in MPEG video is based on
motion estimation. The basic premise of motion estimation is that,
in most cases, consecutive video frames will be similar except for
changes induced by objects moving within the frames. The result
of full MPEG compression is called Group of Pictures (GOP),
which must be taken as a whole in order to decompress and
display them properly. A GOP describes a sequence of coded pictures bounded by I-frames (reference frames), in which Predictive
(P-frames) and Bidirectional-predictive (B-frames) techniques
have been used. Once coded, a GOP does not come apart into
component frames easily. Full MPEG is a challenge for CCTV
applications because of the industry’s need for still frame picture
evaluation and frame-by-frame playback.
Motion compensation is used as part of the predictive process
because when an image sequence shows moving objects their
motion can be measured. The information is used to predict the
content of frames later in the sequence. In the MPEG standard,
each picture is divided into blocks of 16 × 16 pixels, called a macroblock. Each macroblock is predicted from a previous or future
frame, by estimating the amount of the motion in the macro block
during the frame time interval. For each block in the current frame,
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a matching block is found in the past frame and if suitable, its
motion vector is substituted for the block during transmission.
Each macroblock is divided into four blocks, which are divided
into eight scan lines by eight pixels. A discrete cosine transform
(DCT), which is a lossy compression algorithm that regularly
samples an image to get rid of information that does not affect it,
is then applied to each block. DCT samples the image at regular
intervals and analyzes the frequency components present in the
sample. This is the basis for standards such as JPEG, MPEG, H.261,
and H.263.
For an elementary look at this process let’s take another
glimpse at “Houdini the dog”, who we introduced in chapter
three. Our first picture shows a doghouse located in a garden. The
entire scene is made up of the doghouse itself, grass, a few trees
in the background, and a patch of blue sky. The compression
process that is the same for both JPEG and the Intra-frame portion
of MPEG will include an analysis of the entire scene. After this
analysis is made, it may be determined that much of the green
color of the grass can be discarded with minimal effect to the
outcome. The same may be true for the blue sky portion of the
picture. By contrast, the trees may have too many variations of
color to allow for much information to be removed without distorting the final picture.
The result of this process is called the reference frame or Iframe. Now we will assume that Houdini has entered the yard
and taken a sitting position in front of his house, but nothing else
has changed within the scene. The P-frame is now built with only
the information concerning Houdini being compressed. The information regarding the grass, sky, and trees need not be addressed
as it is identical to the preceding I-frame. If Houdini takes a nap
and nothing else changes within the scene for some time, the
frames between the I-frame and P-frame may be filled in by Bframes that have taken information from both.
Assume that a freak blizzard blows through the garden. The
sky turns dark gray and all of the leaves are blown from the trees.
The grass is covered with white snow and Houdini is driven into
his house. A search will be made but as none of the previous
frames contain information about this new scene, an I-frame will
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have to be generated, beginning the process of compression over
again. As you can see, the longer the scene remains the same or at
least has similar components, the amount of information needed
to supply frames is minimal. As dramatic differences occur within
the scene, the compression process becomes more complicated,
requiring more storage space and more time for transfer of data.
This is certainly an oversimplified example, but hopefully the
MPEG compression process can be better understood by this
imaginary representation. The obvious advantage of the MPEG
standard of compression is the fact that the greatest redundancy
does not reside within a single frame but within a sequence of
frames.
MJPEG or Motion JPEG
MJPEG is a quasi-standard consisting of chronological JPEG
frames. It does not take advantage of frame-to-frame redundancies
like MPEG does. With MJPEG, each frame is separately compressed into a JPEG image. The downside to MJPEG video is that
the acquired information processed on equipment from one manufacturer may not be compatible with MJPEG from another manufacturer. This is partly because some proprietary systems may use
key frame and difference frames to achieve results similar to interframe compression. The addition of JPEG compression means that
the compressed information retains its frame integrity, but the
combinations of methods used are varied.
MPEG-1
The first digital video and audio encoding standard, MPEG-1, was
adopted as an international standard in 1992. This standard was
designed to store and distribute audio and motion video emphasizing video quality. MPEG-1 is a common standard used for
video on the Internet. MPEG-1 relies heavily on the substantial
amount of redundancy within and between frames. These are
spatial, spectral, and temporal redundancies, which can be compressed without significantly changing the output.
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Correlation between neighboring pixel values—Spatial
redundancy, as explained earlier, removes repetitive
information composed of adjoining pixels.
Correlation between different color planes or spectral bands—
Spectral redundancy consists of color spectra or “brightness”
due to the fact that the human eye distinguishes differences
in brightness more readily than it sees differences in pure
color values.
Correlation between different frames in a video sequence—
Temporal redundancy is the similarity of motion between
frames. If motion redundancy did not exist between
frames, there would be no perception of realistic motion.
Level 3 of MPEG-1 is the most popular standard for digital
compression of audio, commonly known as MP3.
MPEG-2
MPEG-2, published as a standard in 1994, is a high bandwidthencoding standard based on MPEG-1 that was designed for the
compression and transmission of digital broadcast television. This
is the standard used by DVD players. MPEG-2 will decode MPEG1 bit-streams. MPEG-2 was designed for high bit rate applications,
and like MPEG-1, it does not work well at low bandwidths. The
main difference between MPEG-1 and MPEG-2 is the encoding of
interlaced frames for broadcast TV. MPEG-1 supports only progressive frame encoding and MPEG-2 provides both progressive
frame and interlaced frame encoding.
MPEG-4
MPEG-4, an open standard, was released in October 1998 and
introduced the concept of Video Object Planes (VOP). The result
is an extremely efficient compression that is scalable from low bit
rates to very high bit rates. MPEG-4 is advanced audio and video
compression that is backward compatible with MPEG-1 and 2,
H.261, and H.263.
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MPEG-4 is designed to deliver video over a much narrower
bandwidth. It uses a fundamentally different compression technology to reduce file sizes than other MPEG standards and is more
wavelet based. Object encoding provides great potential for object
or visual recognition indexing, based on discrete objects within a
frame, and allows access to individual objects in a video sequence.
For example, if you need to track particular vehicles in series of
images taken from a parking garage, a properly set up MPEG-4
based system would be a good choice.
MPEG-7
MPEG-7, also called Multimedia Content Description Interface,
started officially in 1997. One of main features of MPEG-7 is to
provide a framework for multimedia content that will include
information on content manipulation, filtering, and personalization, as well as the integrity and security of the content. Contrary
to the previous MPEG standards, which described actual content,
MPEG-7 will represent information about the content allowing for
faster searches of video information. Visual descriptors are used
to measure similarities in images or videos. These descriptors
search and filter images and videos based on features such as
color, object shape, object motion, and texture. High-level descriptors are used for applications like face-recognition.
MPEG-21
MPEG-21, the newest of the standards produced by the Moving
Picture Experts Group, is also called the Multimedia Framework.
MPEG-21 will attempt to describe the elements needed to build an
infrastructure for the delivery and consumption of multimedia
content. A comprehensive standard framework for networked
digital multimedia, MPEG-21 includes a Rights Expression Language (REL) and a Rights Data Dictionary. Unlike other MPEG
standards that describe compression coding methods, MPEG-21
describes a standard that defines the description of content and
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also processes for accessing, searching, storing, and protecting the
copyrights of content. The goal of MPEG-21 is to define the technology needed to support users to exchange, access, consume,
trade, and otherwise manipulate digital information in an efficient, transparent, and interoperable way.
JPEG
Joint Photographic Expert Group (JPEG) is a committee of the
International Standards Organization (ISO), which was established
to generate standards for the compression of still images. The goal
of the JPEG standard was to agree upon an efficient method of
image compression for both full color and grayscale images. The
ISO had begun work on this standard in April 1983 in an attempt
to find methods to add photo quality graphics to the text terminals. The “Joint” in JPEG stands for refers to the merger of several
groupings in an attempt to share and develop their experience.
JPEG achieves much of its compression by exploiting known
limitations of human sight. With JPEG compression, an image is
transformed by converting the values of the image to the YUV
color space (Y = luminance signal, U and V = chrominance signals),
allowing access to color components of the image that are the least
sensitive to the human eye. The down sampling process takes
fewer samples from the chrominance portions of the images than
from the luminance portions. A down sampling ratio of 4 : 1 : 1
means that for every 4 samples of luminance information, each of
the chrominance values is sampled once, allowing 24 bits of information to be stored as 12 bits. Due to the physiological circumstances involving sensitivity levels of color and luminance, this
reduction of information should not be noticeable to the human
eye.
JPEG does not work well on non-photographic images such
as cartoons or line drawings, nor does it handle compression of
black-and-white (1 bit-per-pixel) images or moving pictures. It
does allow for compressed image size to image quality trade-off.
In other words, the operator can reduce compression to achieve
better resolution at the price of a slower frame rate. Compared
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with commercially pervasive formats, such as GIF and TIFF, JPEG
images typically require anywhere from one third to one tenth the
bandwidth and storage capacity.
The Central Imagery Office has chosen JPEG as the still
imagery compression standard for the United States Imagery
System architecture because the wide commercial acceptance of
the ISO standard, coupled with its good imagery quality, will
enhance interoperability. The Intelligence Community, DOD, and
other agencies have a large installed base of JPEG capable
systems.
JPEG 2000
JPEG 2000, which uses wavelet technology, represents the latest
series of standards from the JPEG committee. Several of the fundamental differences between the common JPEG and JPEG 2000
include the option of lossless compression in JPEG 2000, the
smoothness of highly compressed JPEG 2000 images, and the
additional display functionality, including zooming, offered by
JPEG 2000.
Two things make JPEG 2000 desirable in bandwidth-limited
applications—error resilience and rate control. Error resilience is
the ability of the decoder to recover from dropped packets or noise
in the bit stream during file transmission. Rate control is the ability
to compress an image to a specified rate.
Four modes of operation were formulated within the JPEG
standard:
●
●
●
●
Sequential Mode
Progressive Mode
Hierarchical Mode
Lossless Mode
Sequential
With sequential, each image component is encoded in a single
left-to-right, top-to-bottom scan. The information is than passed to
an encoder, normally DCT based. This mode is the simplest and
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most widely implemented. The sequential JPEG image compression standard provides relatively high compression ratios while
maintaining good image quality. The downside of the JPEG technique image transmission is that it may take long time to receive
and display the image.
Progressive
A refinement of the basic JPEG is broken down into several passes,
which are sequentially sent to a monitor. First, highly compressed,
low quality data is sent to the screen and the image quality
improves as more passes are completed. The first pass takes little
time to execute. In the successive passes more data is sent, gradually improving the image quality.
Several methods for producing series of partial images are
supported by JPEG. In this mode, the image is scanned in sections
so that users can watch the image building in segments and reject
images that are not of interest as they are being delivered. The progressive JPEG mode still requires long transmission times for highresolution, complex images, or bandwidth at the receiver’s end.
Hierarchical
The image is encoded at various resolutions, allowing lower resolution versions to be decoded without decoding the higher resolution versions. The advantage here is that a trade off can be made
between file size and output image quality. This capability allows
the image quality to be adjusted to an acceptable condition as the
application requires.
Lossless
The image is encoded in a manner that allows an exact replication
to be decoded after transfer. The lossless mode of JPEG does not
use DCT because it would not result in a true lossless image (an
image with no losses). The lossless mode codes the difference
between each pixel and the predicted value for the pixel. Lossless
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JPEG with the Huffman back end is not the best choice for a true
lossless compression scheme because exact replication cannot be
guaranteed. Although the JPEG standard covers lossless compression it is rarely, if ever, used within the security industry for video
transmission.
H.261
H.261 is the video compression portion of compression standards
jointly known as ITU-T H.320. ITU comes from International Telecommunications Union. The ITU Telecommunication Standardization Sector (ITU-T) is one of three Sectors of the International
Telecommunication Union. ITU-T’s mission is to ensure efficient
and on-time production of high quality standards (recommendations) covering all fields of telecommunications. ITU-T was created
on March 1, 1993 and replaced the former International Telegraph
and Telephone Consultative Committee (CCITT) whose origins go
back to 1865. Both public and the private sectors cooperate within
ITU-T for the development of standards that benefit telecommunication users worldwide.
The ITU-T H.320 family was developed to ensure worldwide
compatibility among videoconferencing and video phone systems
using ISDN telephone services. H.261 is a DCT based algorithm
using both intra- and inter-frame compression designed to work
at data rates that are multiples of 64 K bits per second. H.261 supports CIF and QCIF resolutions.
H.261 compression is similar to the process for MPEG compression with some differences in the sampling of color information. Color accuracy is reduced, but the results are acceptable for
small images. At a rate of less than 500 K bits per second, H.261
quality is better than MPEG-1.
H.263
H.263 is also a DCT based compression scheme designed with
enhancements enabling better video quality over modems. H.263
is part of the ITU H.324 suite of standards, which were designed
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for multimedia communication over telephone lines by modem.
H.263 is approximately twice as efficient as H.261 and is supported
by MPEG-4.
The H.263 standard specifies the requirements for a video
encoder and decoder. It does not describe the encoder or decoder
itself, but it specifies the format and content of the encoded (compressed) stream. H.263 supports five resolutions. In addition to
QCIF and CIF that were supported by H.261, there are SQCIF, 4CIF,
and 16CIF. SQCIF is approximately half the resolution of QCIF. 4CIF
and 16CIF are 4 and 16 times the resolution of CIF, respectively.
H.263.v2/H.263+
H.263.v2, also known as H.263+, is a low-bit rate compression that
was designed to take the place of H.263 by adding several annexes
that substantially improve encoding efficiency.
H.264
H.264 is a high compression digital video standard written by the
ITU-T Video Coding Experts Group (VCEG) together with the
ISO/IEC Moving Picture Experts Group (MPEG) as the product
of a collective effort known as the Joint Video Team (JVT). This
standard is identical to ISO MPEG-4 part 10, also known as AVC,
for Advanced Video Coding. H.264 accomplishes motion estimation by searching for a match for a block from the current frame
in a previously y coded frame. MPEG-2 uses only 16 × 16-pixel
motion-compensated blocks, or macroblocks. H.264 provides the
option of motion compensating 16 × 16-, 16 × 8-, 8 × 16-, 8 × 8-,
8 × 4-, 4 × 8-, or 4 × 4-pixel blocks within each macroblock. The
resulting coded picture is a P-frame.
WAVELET COMPRESSION
Wavelets have been utilized in many fields including mathematics, quantum physics, electrical engineering, and seismic geology.
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Recent years have seen wavelet applications like earthquake prediction and image compression. Wavelet compression, also known
as Discrete Wavelet Transform (DWT), treats an image as a
signal or wave, giving it the name. Wavelet algorithms process
data at different scales or resolutions—they analyze according to
scale.
Basically, wavelet compression uses patterns in data to
achieve compression. The image information is organized into a
continuous wave that has peaks and valleys and is centered on
zero. After centering the wave, the transform records the distances
from zero to points along the wave (these distances are known as
coefficients). An average is then used to produce a simplified
version of the wave, reducing the image’s resolution or detail by
half. The averages are averaged again, and again, resulting in
progressively simpler waves.
Images compressed using wavelets are smaller than JPEG
images, meaning they are faster to transfer and download. The FBI
uses wavelet compression to store and retrieve more than 25
million cards, each containing 10 fingerprint impressions. 250 terabytes of space would be required to store this data before compression. Without compression, the sorting, archiving, and searching
for data in these files would be nearly impossible.
The FBI tried a Discrete Cosine Transform (DCT) initially. It
did not perform well at high compression ratios because blocking
effects made it impossible to follow the ridge lines in the
fingerprints after reconstruction. This did not happen with
Wavelet Transform because it retains the details present in data.
Wavelet Transforms are used in the JPEG 2000 compression
standard.
Wavelet images used in forensic applications have the advantage of being frame-based, assuring authenticity of video evidence.
Images are viewed from their original compressed state, including
a frame-by-frame time code. There are no standards for wavelet
video compression, which means that wavelet-based images
from one manufacturer’s system might not be able to be decompressed properly on a wavelet-based device from another
manufacturer.
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Wavelets and Multi-Resolution Analysis
Multi-resolution analysis (MRA) approximates several resolution
levels to obtain a multi-scale decomposition. In other words, as the
wavelet transform takes place, it generates progressively lower
resolution versions of the wave by approximating the general
shape and color of the image. In addition to this, it has all the
information necessary to reconstruct the wave in finer detail. The
idea behind MRA is that the signal is looked at very closely at first,
then slightly farther away and then farther still. See Figure 5-2.
Products of a wavelet transform can be used to enhance the
delivery of an image, such as providing improved quality and
more efficient compression. The wavelet transform results in simplified versions of the image along with all of the information
necessary to reconstruct the original because the decomposition
process produces a series of increasingly simplified versions of the
image. If these are played back in reverse as the image is reconstructed and displayed, the result is a picture that literally grows
in size or in detail.
There are many algorithms for video compression and more
are under development each day. Work continues in developing
advanced codecs for various applications with different requirements, and the power of processors keeps going up as the costs
come down. There may eventually be one or two standards more
readily accepted, but we are still a long way from determining
what those standards will be.
Two major features to look for today for a successful deployment of new digital video equipment are software programmabil-
Figure 5-2
Example of MRA
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ity and system flexibility. Programmability will allow you to
download different video codec formats directly onto end products, and system flexibility will enable you to switch from one
digital media standard to another or even run several simultaneously. Most importantly, when considering which compression
standard or combination of standards is right for you, believe
what you see with your own eyes, because quality is subjective.
Despite all of the advances, remember that video quality in
any given compression system is highly dependent upon the
source material. Make sure that the demonstrations you receive
are comparable to the real life situations you expect in your daily
operation. Take a good look at the system you are considering and
make sure you actually see it do everything it claims to do.
6
Internet Transmission,
Networked Video,
and Storage
By now, we have all been hearing new terminologies like IP-based
video, web-based video, or networked video. Then there are
IP-cameras and video servers, and a host of other web-based
technology. If you are feeling a bit confused, you’re not alone.
These terms are open to interpretation in many cases because there
is no genuine consensus on what they all mean.
This brings us around to the question “How digital is it?” It
is possible to have analog cameras and monitors, use coaxial cable,
and have a DVR, and call that a digital surveillance system. In
truth, you have a digital video recorder that is converting analog
signals to digital signals. A fully digital system includes CCD
cameras with signal processing that send packetized video streams
via Ethernet over a cat 5 LAN cable (or wireless method) to a LAN
switch and into a video server, which manages and manipulates
the video signal.
Not every video system claiming to be digital is the same. In
many cases, existing analog cameras are kept in place to reduce
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Digital CCTV
the costs. Also, digital systems do not necessarily operate through
a computer but may utilize a proprietary box commonly referred
to as a DVR. We will talk in length about these anomalies in
upcoming chapters. For now, we can unravel some of the history,
terminology, and actual application of digital surveillance, starting with the computer.
The first electronic computer weighed 30 tons, used 18,000
vacuum tubes, and drained electricity from the entire West Philadelphia area when it was turned on. The first microprocessor had
the same capacity and measured just 1/8″ by 1/16″. A microprocessor, or CPU, is an extremely small (in comparison) but powerful high speed electronic brain etched on a semiconductor chip.
The microprocessor receives incoming communications from
devices like keyboards and disks for processing and contains the
basic logic, storage, and arithmetic functions of a computer.
Gordon Moore was employed at Fairchild Semiconductor,
prior to becoming a cofounder of Intel, when he made the prediction that the amount of data that can be stored on an electronic
chip would double about every 18 months. If his theory, now
called Moore’s Law, were to hold true, the approximate year of
2030 will find the circuits on a microprocessor measured on an
atomic scale. Next will come quantum computers that will use
molecular and atomic energy to perform memory and processing
tasks billions of times faster than any silicon-based computer.
Why do we care about the progression of micro-processing
and computers? Electronic security and especially digital video
systems have become entwined with computer software and hardware to such an extent that their futures will almost certainly
evolve in tandem, not to mention the capabilities that have been
added by the introduction of the Internet.
THE DIFFERENCE BETWEEN INTERNET AND INTRANET
Intranet refers to any network of interconnected computers belonging to one group. It operates almost the same as the Internet and
uses the same protocols and software that are used on the Internet,
but is separate from the Internet. Some businesses have special
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95
intranet web sites that can only be viewed by employees in their
offices, or when connected to their Virtual Private Network (VPN).
Internet, on the other hand, refers to the worldwide network of
interconnected computers, all of which use a common protocol
known as TCP/IP to communicate with each other.
On October 24, 1995, the Federal Networking Council (FNC)
unanimously passed a resolution defining the term Internet.
This definition was developed in consultation with members of
the Internet and intellectual property rights communities.
RESOLUTION: The Federal Networking Council (FNC) agrees
that the following language reflects our definition of the term “Internet”. “Internet” refers to the global information system that—(i) is
logically linked together by a globally unique address space based on
the Internet Protocol (IP) or its subsequent extensions/follow-ons;
(ii) is able to support communications using the Transmission Control Protocol/Internet Protocol (TCP/IP) suite or its subsequent
extensions/follow-ons, and/or other IP-compatible protocols; and (iii)
provides, uses or makes accessible, either publicly or privately, high
level services layered on the communications and related infrastructure described herein.
The migration from analog to digital video does not mean the end
for existing analog equipment. Video servers convert images from
existing analog CCTV cameras into digital video for network
transmission.
NETWORKING
When you connect individual PCs together allowing them to
access each other’s information and/or resources, you have created
a network. Networks are made up of hardware, network software,
connecting cables, and network interface cards connected to a
network server, which is the central manager of the system.
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There are several kinds of networks:
●
●
●
●
●
Local area networks (LANs) consist of computers that are geographically close together.
Wide area networks (WANs) are set up with computers farther
apart that are connected by communication lines or radio
waves.
Campus area networks (CANs) refer to a network of computers
within a limited geographic area, like a campus or military
base.
Metropolitan area networks (MANs) implies a data network
designed for a town or city.
Home area networks (HANs) are networks restricted to a user’s
home that connects digital devices.
Topology is the term used for the geometric arrangement of computer systems that are networked. Topologies are either physical
due to the way workstations are connected to the network or
logical—referring to the arrangement of devices on a network or
their method of communicating with each other. Familiar topologies include star, ring, bus, and mesh. See Figure 6-1.
When in the star format, devices connect to a central hub via
nodes that communicate by passing data through the hub. Each
device has its own cable connecting it to the central point much
like a phone system and a central switching station. Messages go
through the central computer or network server that controls the
flow of data. The administrator of a star topology can give certain
nodes higher priority status than others. The central computer
looks for signals from these higher priority workstations before
recognizing other nodes.
Ring topology is just what it sounds like: all nodes connected
to a main cable in the shape of a ring through which messages are
routed in one direction only. Failure of one node on the network
stops data from proceeding around the ring, making it tricky to
add new workstations while the network is in operation.
A bus topology connects all devices to a central cable, which
is called the bus or the backbone. Since all nodes share the bus, all
messages must pass through the other workstations on the way to
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Figure 6-1
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Network Designs
their destinations, but bus topologies do allow individual nodes
to be out of service without disrupting service to the remaining
nodes.
Mesh topology refers to devices connected with redundant
interconnections between network nodes. In a true mesh topology,
every node has a connection to every other node in the network.
Network video technology utilizes and extends this same infrastructure for local and remote monitoring.
The network has various common parts such as hubs,
switches, and routers. The hub is a common connection point that
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allows several pieces of equipment to share a single Ethernet connection as it forwards data packets throughout the network. A
switch allows different computers or devices on a network to communicate directly with one another by filtering and forwarding
packets between LAN segments. A switch can transmit data
packets from different sources simultaneously. Switches can interface between 10, 100, and 1,000 Mbps. A switch may include the
function of the router, determining what adjacent network point
the data should be sent to. Finally, the router connects networks
together and to the Internet by forwarding network packets according to their IP address.
Wireless Networks
Wireless data networks exist in a large number and variety. Some
run over wireless voice networks, such as mobile telephone networks. Others run on their own physical layer networks, utilizing
anything from antennas built into handheld devices to large antennas mounted on towers. A few wireless networks, like Bluetooth,
are intended only to connect small devices over short distances.
NETWORKED VIDEO
When digital video systems are connected to a network, the video
can be viewed by authorized parties at any other point on the
network, provided they have the proper network rights and
viewing software. Typically the user would enter the network
address of the digital video recorder and be prompted to enter a
user name and password. They could also open the user interface
software, which would be preconfigured with the proper network
addresses. Just as with the administrative rights of each computer
and user on the network, access to the digital video can and should
be restricted by user name and password, controlled by the system
administrator and/or the security manager.
Within the network, Digital Video Recorders (DVRs) and
Digital Video Network Servers (DVNs) perform in a similar
manner to standard computer servers. Each unit will have a
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network address and the data on that server can be accessed
through that address. DVRs and DVNs allow access to stored and
live video and allow users to archive video data as needed.
While they are used solely for the function of video, they are no
different than any other network server in functionality and
accessibility.
VIDEO DISTRIBUTION VIA THE INTERNET
Telephone lines can be used to provide the lifeline of security
systems by transmitting various types of data—whether alarm
information, video, or voice. Expanding telephone connectivity
and increasing bandwidth have made inroads, but the real vascular system of the future is comprised of Internet connections with
the PC as the heart and digital data as the blood. Advancements
in digital video compression make it possible for video to be
carried over typical network circuits both on the LAN and across
the WAN, as well as over the Internet.
Internet Beginnings
The Defense Advanced Research Projects Agency (DARPA), which
is the central research and development organization for the
Department of Defense, initiated a research program pertaining to
interlinking packet networks of various kinds. This was called the
Internetting Project, and the resulting system of networks that
emerged is what we today know as the Internet.
In 1973, development began on the protocol by a group
headed by Vinton Cerf from Stanford and Bob Kahn from DARPA.
The system of protocols they developed over the course of this
research effort became known as the TCP/IP Protocol Suite, after
two initial protocols: Transmission Control Protocol (TCP) and
Internet Protocol (IP). These standards have been adopted as the
standard protocols for Internetworking. Today’s Internet is
the result of wide area networks created in the US and the rest of
the world becoming interconnected using the IP stack of protocols.
TCP/IP has become the standard for networking. The open architecture allows for multiple systems to share network space and
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take advantage of new technology aimed at improving the capacity, reliability, scalability, and accessibility of network resources.
The resulting advantage of IP to the video surveillance world
is the ability to conduct video surveillance while taking advantage
of networks already in place or that will be installed for multiple
purposes within a facility. Many manpower hours and dollars are
saved by not having to completely rewire a facility, campus, or
even a city for a new system to communicate. Video over IP is the
ultimate two-for-one deal.
IP handles the actual delivery of data, while TCP is used for
coordinating and organizing the data to be sent between computers via the Internet. In order for video or any other data to be
transmitted via the Internet, you will need a delivery address, just
as in any mail system. An IP address is a 32-bit binary number
with two parts, a network address and a local address. The network
address identifies the network to which the address is attached,
and the local address is the specific device within that network.
TCP is the tracking system that monitors individual units of data,
called packets, the form in which information is efficiently routed
over the Internet. TCP makes sure no packets are lost by assigning
sequence numbers, which are also used to make sure that the data
is delivered in the correct order.
You might compare it to sending boxes of puzzle pieces
through the mail. At destination A, the puzzle is disassembled and
the pieces put into various boxes. The boxes are numbered and
sent on their way to destination B. Even though the boxes will
travel separately, they should arrive at the same location at approximately the same time, allowing all of the pieces to be put back
together to reform the original. Sending video over the Internet
works in the same manner. Currently, there are two basic methods
of transmitting video over the Web: streaming and downloadable
video.
STREAMING VIDEO AND DOWNLOADABLE VIDEO
Streaming technologies were developed to overcome the bandwidth limitations of the Web. These are techniques for transferring
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steady and continuous streams of data, making it possible to transmit and receive live video from any computer, anywhere, with
Internet access. Of course, there are protocols to be used when
transmitting data over the Internet. Hypertext Transfer Protocol
(HTTP) is the most commonly used at this time. You will recognize
the acronym from using addresses like this one: http.www.
videoonttheweb.com. The Real Time Streaming Protocol (RTSP)
handles streaming video content. Both HTTP and RTSP can be
used to deliver streaming video data, but RTSP serves as a control
protocol and as a jumping off point for negotiating transports,
such as Real-Time Protocol (RTP), over multicast or unicast
network services.
Streaming technology sends data to the receiver continuously but does not download the entire file. This means the recipient does not have to wait to download a large file before seeing
the video because it is played as it arrives. Streaming services have
a variety of applications including online video presentations,
product demonstrations, video archive and retrieval, video broadcasting, remote monitoring, and high quality video surveillance.
The choice between streaming and downloadable video is mainly
one of duration. Since downloaded video files must be stored
somewhere (in most security applications the video will definitely
need to be stored somewhere) long files may put too much demand
on the client CPU. Downloadable video, such as QuickTime, is
stored either in memory or on disk.
As discussed in an earlier chapter, a codec is an algorithm,
which is a recipe or list of instructions that identifies the method
used to compress data into smaller byte sizes. Codecs determine
the size of a file, the bit rate of a stream, and the way encoded
video and audio content looks and sounds. They do this by compressing an audio or video source during encoding and then
decompressing the audio or video during playback.
When using temporal compression, where the video changes
little from frame to frame, data will compress better than video with
lots of motion. For spatial compression, the less detail in the image,
the better it can be compressed. There are many codecs available,
and many more in the pipeline. In fact, there are so many being
developed every day that it would be impossible to attempt to cover
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and compare them here. We will review some popular codecs just
to get a feel for what they are and what they do.
DivX Compression
A trademark of DivXNetworks, Inc., the DivX codec is a digital video
compression format based on the MPEG-4 compression standard.
DivX files can be downloaded over high-speed lines in a relatively
short time without reducing visual quality. According to DivXNetworks, this codec is so advanced that it can reduce an MPEG-2 video
(the same format used for DVD or Pay-Per-View) to ten percent of its
original size and reduce video on regular VHS tapes to about one
hundredth of their original size. DivX is not related to and should not
be confused with DIVX (Digital Video Express), which was an attempt
by Circuit City and an entertainment law firm to create an alternative
to video rental in the United States.
RealVideo
As RealNetworks’ cross-platform, multimedia software architecture, RealSystem is used to publish video, sound, graphics, text,
music, SMIL, or Flash files over the Internet with an RTSP true
streaming server. RealMedia was designed specifically for Internet
multimedia. RealVideo is a streaming technology developed by
RealNetworks for transmitting live video over the Internet.
RealVideo works with normal IP connections and IP Multicast
connections. RealVideo differs from conventional video codecs in
that it has been optimized for streaming via the proprietary PNA
protocol or the newer standardized Real Time Streaming Protocol.
It can be used for download and play (dubbed on-demand) or for
live streaming.
RealVideo was first released in 1997 as a proprietary video
codec from RealNetworks. The main desktop media player for
RealMedia content is the RealNetworks’ RealPlayer, currently at
version 10. RealNetworks claims a 30% improvement over previous generation RealVideo 9 codec with dramatically improved
compression at any bit rate, on any device.
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QuickTime
QuickTime is Apple’s multi-platform, industry-standard, multimedia software architecture. QuickTime supports a number of
compression standards including MPEG, JPEG, H.263, Microsoft
Video 1, and AVI by providing software codecs that transform
RAM into a compressor/decompressor for each compression type.
The QuickTime architecture synchronizes video, sound, text,
graphics, and music. QuickTime is a cross-platform standard, with
versions running on Windows-based PCs, NT-based PCs, and
UNIX-based workstations in addition to its native Apple Macintosh environment. It has an open architecture supporting many
file formats and codecs, including Cinepak, Indeo, Motion JPEG,
and MPEG-1. A “fast-start” feature allows users to start playing
video and audio before the file is completely downloaded.
ZyGoVideo
ZyGoVideo is a QuickTime video codec especially adept at
streaming video and compressing video with detailed content.
ZyGoVideo works well for low bandwidth applications, especially
wireless and Internet connections. ZyGoVideo allows for full
screen, full frame rate video streaming using high power G5 and
Pentium computers and also has a mode for streaming video to
handheld and smart cell phones using processors from ARM. New
product additions include handheld security solutions for commercial firms—a direct outgrowth of the Tracker and Seeker school
ID security solutions.
Video for Window/Audio Video Interleaving
Video for Windows (VfW), sometimes called AVI (Audio Video
Interleaving), was the first video capture and display system
developed by Microsoft for the Windows operating system with
a format for encoding pictures and sound for digital transmission.
In this file format, blocks of audio data are woven into a stream
of video frames. These files have an AVI extension.
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Common Intermediate Format (CIF)
CIF is a video display standard for Internet videoconferencing that
was developed by the International Telecommunication Union
Telecommunication Standardization Sector (ITU-T’s) as the H.261
and H.263 standards, supporting both NTSC and PAL signals.
These standards are commonly used by the security industry to
transmit video over the Internet.
QCIF (Quarter CIF) transfers one fourth the amount of data
and is suitable for transmission systems that use telephone lines.
The Q or Quarter indicates that these frames contain one quarter
of the pixels as the CIF frame. This of course means that less bandwidth is needed for transmission of QCIF frames. Video quality
can be broken down into three segments:
●
●
●
Low quality/small image (SQCIF, QCIF)
Medium quality/medium-sized image (CIF)
High quality/large image (4CIF, 16CIF, SDTV)
STORING DIGITAL VIDEO
The compression of video is essential to viewing, managing, and
transmitting video. The resulting reduction of data not only reduces
the bandwidth needed for transmission but also reduces the space
required to store it. One of the most significant factors in the growth
of digital video technology in security is the ability to store larger
amounts of video using less storage space and the ability to retrieve
video information quickly. The terms memory and storage are
often confusing, especially when describing amount. Memory
refers to the amount of RAM installed in the computer, and storage
refers to the capacity of the computer’s hard disk.
Random Access Memory (RAM)
The computer industry commonly uses the term memory for
Random Access Memory (RAM). RAM is the most common form
of computer memory and is considered “random access” because
you can access any memory cell directly if you know the row and
column that intersect at that cell.
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Read–Only Memory (ROM)
Read-only memory (ROM), also known as firmware, is an
integrated circuit (IC) programmed with specific data when it is
manufactured. Data stored in these chips is nonvolatile and
cannot be lost when power is removed. Data stored in these chips
is either unchangeable or requires a special operation to change.
Recording can be done mechanically, magnetically, or optically. Storage options are categorized as primary or secondary,
volatile or non-volatile, read-only memory, Write Once, Read
Many (WORM), or read-write. Each type of storage is best suited
for different applications:
●
●
●
Primary storage contains data actively being used.
Secondary storage, also known as peripheral storage—the
computer stores information that is not necessarily in
current use.
Volatile storage loses its contents when it loses power,
non-volatile storage does not.
The good news is that the physical size of storage media
keeps getting smaller while the storage capacity keeps getting
larger.
Sometimes, confusion can result when referring to telecom,
network, and data storage with the term Meg by itself. Mb refers
to megabits and MB refers to megabytes, but the term Meg is
noncommittal. Be sure to clarify. When data is transmitted in a
local or wide area network, it is normally specified in megabits
per second or Mbps. Data streams from digital video cameras are
also specified in megabits per second. When referring to data
storage, the correct term is megabytes.
HARD DISC STORAGE
In the 1950s when hard discs were first invented, they started as
large disks up to twenty inches in diameter, held just a few megabytes, and were called fixed discs. The name later changed to hard
disks to distinguish them from floppy disks. A hard disk drive is
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a machine that reads data from a hard disc and writes data onto
a hard disk. They store changing digital information in a relatively
permanent form. A floppy drive does the same with floppy disks,
a magnetic disk drive reads magnetic disks, and an optical drive
reads optical disks.
Disk drives can be either internal (within the computer) or
external (outside the computer) and their performance is measured in two ways: data rate and seek time. Data rate is the number
of bytes per second that the drive can deliver to the CPU, and seek
time is the amount of time that passes between the time a file is
requested and when the first byte of the file is sent to the CPU.
Another important aspect of the capacity of the drive is the number
of bytes it can hold.
In some ways, a hard disk is not that different from a cassette
tape—both use the same magnetic recording techniques and both
share the benefits of magnetic storage. It makes sense to use hard
disks for video storage because they can store large amounts of
digital data.
Techniques for guarding against hard disk failure, such as
the redundant array of independent disks (RAID), were developed as precautionary measures. With this method, information
is spread across several disks using techniques called disk striping
(RAID Level 0), disk mirroring (RAID level 1), and disk striping
with parity (RAID Level 5) to achieve redundancy and maximize
the ability to recover from hard disk crashes. These are a category
of disk drives that employ two or more drives in combination for
fault tolerance and performance. RAID technology allows for the
immediate availability of data and, depending on the RAID level,
the recovery of lost data.
REMOVABLE STORAGE
Storage devices that are removable can store megabytes and even
gigabytes of data on a single disk, cassette, card or cartridge. These
devices fall into one of three categories: magnetic storage, optical
storage, and solid state storage.
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Magnetic Storage
Magnetic storage, the most common, refers to the storage of data
on a magnetized medium. In most cases, removable magnetic
storage consists of a mechanical device called a drive that connects
to the computer. Magnetic storage is taking to paths in capacity,
with some types using small cartridges with volume measured in
megabytes and portable hard drives that range in the gigabytes.
Optical Storage
Basically, optical drives work by bouncing a laser beam off of the
recording layer of an optical disk and registering differences in
how the light is reflected back. The read-write head contains a
laser, mirrors, and lenses to send and receive the reflected light.
All optical drives read data in a similar way, with different technologies using different methods to record data.
Three kinds of drives record data by putting marks on a
disk’s recording layer: compact-disc recordable (CD-R), compact
disc rewritable (CD-RW), and compact-disc read-only-memory
(CD-ROM). A finished disk contains non-marked areas, indicated
by marks and spaces. Each mark or space represents one bit of
data. Marks are non-reflective, and spaces are reflective. Since they
reflect light differently, the laser can read the recording surface
and translate recorded data into 1s and 0s.
Compact Disc Recordable (CD-R)
CD-R works by replacing
the aluminum layer in a normal CD with an organic dye compound. This compound is normally reflective, but when the laser
focuses on a spot and heats it to a certain temperature, it “burns”
the dye, causing it to darken. The problem with this approach is
that you can only write data to a CD-R once. After the dye has
been burned in a spot, it cannot be changed back.
Compact Disc Rewritable (CD-RW)
Rewritable optical drives
read and write to optical disks and can be erased and rewritten
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many times, just like a hard disk. Some manufacturers have
included Compact Disc Rewritable (CD-RW) drives on their DVR.
This is NOT a good idea. With this scenario, you are allowing for
the possibility that data may be altered or overwritten, destroying
its evidentiary value. Some systems come with robbery buttons,
which automatically download pertinent images in seconds or, in
some cases, images can be range locked on the hard drive, preserving them indefinitely.
Write-Once-Read-Many
(WORM) Write-Once-Read-Many
(WORM) drives can write data to an optical disk, and then
read the data over and over again. Each sector on a WORM disk
can be written just once, and cannot be erased, overwritten or
altered.
Solid State Storage
Solid state storage is a non-volatile, removable storage medium
that employs integrated circuits rather than magnetic or optical
media. It is the equivalent of large-capacity, non-volatile memory.
Examples include flash memory Universal Serial Bus (USB) devices
and various proprietary removable packages intended to replace
external hard drives.
The main advantage of solid state storage is the fact that
it contains no mechanical parts. Everything is done electronically. As a result, data transfer to and from solid state storage
media takes place at a much higher speed than is possible
with electromechanical disk drives. The absence of moving parts
may translate into longer operating life, provided the devices are
reasonably cared for and are not exposed to electrostatic
discharge.
Solid state storage media lags behind electromechanical
drives in terms of storage capacity. Data storage has seen a significant decrease in price with the emergence of Network Attached
Storage (NAS) and SAN (Storage Area Networks), another attribute of digital technology.
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Network Attached Storage (NAS)
109
A network attached storage
(NAS) device is a server that is dedicated to file sharing. NAS does
not provide any of the activities that a regular server typically
provides, such as e-mail, authentication, or file management. It
does allow for more hard disk storage space to be added to a
network that already utilizes servers without shutting them down
for maintenance and upgrades. A NAS device does not need to be
located within the server but can exist anywhere in a LAN and
can be made up of multiple networked NAS devices.
The Information Storage Industry Consortium (INSIC) is
the research consortium for the worldwide information storage
industry. INSIC membership consists of more than 65 corporations, universities, and government organizations with common
interests in the field of digital information storage. Corporate
membership includes major information about storage product
manufacturers and companies from the storage industry infrastructure. The Storage Performance Council and the Computer
Measurement Group are two members who may provide more
information about storage options and advancements.
The Storage Performance Council (SPC) is a vendor-neutral
standards body focused on the storage industry. It has created the
first industry-standard performance benchmark targeted at the
needs and concerns of the storage industry. From component-level
evaluation to the measurement of complete distributed storage
systems, SPC benchmarks will provide a rigorous, audited, and
reliable measure of performance.
The Computer Measurement Group, commonly called
CMG®, is a worldwide organization of data processing professionals committed to the measurement and management of computer systems. CMG members are primarily concerned with
performance evaluation of existing systems to maximize performance and with capacity management where planned enhancements to existing systems or the design of new systems are
evaluated to find the necessary resources required to provide adequate performance at a reasonable cost. Professionals charged
with the measurement and management of computer systems and
networks from a performance, capacity, and cost recovery standpoint may benefit from membership in CMG.
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7
Guided Video
Transmission
Now that we have made the video, sampled it, and possibly compressed it, how do we get the digital video or the compressed
digital video from point A to point B? And what do we need to
know about the transmission medium we choose?
The quality of a data transmission is determined by the
medium used for transmission and the signal itself. For guided
transmission, which uses wires or cables, the medium is more
important. For unguided or wireless transmission, the signal is
more important. The advantage of a hardwired system is that you
can usually rely on having a strong, clear signal at your destination,
assuming that you are using a reasonably high quality cable and
not running an unreasonable length. The disadvantage of a hardwired system is the necessity of having to run the cable between
your source and destination. This can become cumbersome and
costly in situations where you have to run between walls, streets,
and buildings. This section deals with the three categories of guided
transmission mediums available for video transmission today,
which are Twisted Pair, Coaxial Cable, and Optical Fiber.
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Twisted Pair
All cables, regardless of their length or quality, represent some
problems when used for the transmission of video signals. The
biggest problem is the need for large amounts of bandwidth. There
are two main types of cable used for transmitting video signals:
unbalanced (coaxial) and balanced (twisted pair). A twisted pair
consists of two insulated copper wires twisted together, just as the
name implies. Twisted pair includes two copper conductors, each
insulated by a low-smoke, fire resistant substance. Both wires
transmit and receive signal data. Because each pair carries similar
electric signals, twisted pair is considered (in electrical terms) to
be balanced. Balanced cable or twisted pair has been in use for
many years. It is frequently used where there would be an unacceptable loss due to a long run of coaxial cable. Some of its advantages include its ability to reject unwanted interference, smaller
size, and lower cost.
The twisting of wires allows each wire to have approximately
the same noise level and reduces crosstalk, which is a disturbance
caused by the electric or magnetic fields of one telecommunication
signal affecting a signal in an adjacent circuit. When crosstalk
occurs, you can hear the conversation of someone whom you did
not call. You might hear half or both sides of the conversation. The
occurrence of crosstalk is known as electromagnetic interference
(EMI) and can be the result of things like wire placement or shielding and transmission techniques. EMI can be any electromagnetic
disturbance that interrupts, blocks, or otherwise breaks down the
performance of electronics or electrical equipment. Crosstalk
Attenuation refers to the extent that a system resists crosstalk,
bringing us back to twisted pair. It is the twisting that decreases
the crosstalk interference between neighboring pairs within a
cable, by using different twist lengths.
UTP and STP
There are two kinds of twisted pair used for transmission. They are unshielded (UTP) and shielded (STP) twisted
pairs. Unshielded twist pair, which is subject to external electromagnetic interference, is commonly used for ordinary telephone
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wire. A shielded twisted pair is shielded with a metallic braid or
sheath that reduces interference. Shielded twisted pair provides
better performance at higher data rates for most applications, but
can be more expensive and difficult to work with compared to
untwisted pair. STP is not typically used for video transmission.
When twisted pair cabling is used for video transmission, UTP is
typically used.
Using STP cabling reduces the transmission distances, and
manufacturers of the transmission and receiving components
design their devices to work exclusively with unshielded cables.
There are three more common types of UTP. They include Cat 3,
which provides for up to 16 MHz and 16 Mbps, Cat 4 providing
up to 20 MHz, and Cat 5 up to 100 MHz and 100 Mbps. More
recently, Cat 5e (enhanced) and Cat 6 have been introduced and
are becoming more widespread. Both provide even greater bandwidth and transmission speeds.
Cat 5
Cat 5, short for Category 5, is part of an EIA Category Specification
developed to specify transmission wire used in data communications. Category 5 is specified for Ethernet 100 Base-T and 10 Base-T
(100 Mbps and 10 Mbps) two conductor LANs. Cat 5 wire has a
capacity of 100 Mbps and is usually terminated with an RJ 45 plug.
The specification carefully controls the twist in the wire to achieve
certain electrical performance levels.
Coaxial Cable
Coaxial cable was invented in 1929 and first used commercially in
1941. It is used primary by the cable television industry and is
widely used for computer networks, such as Ethernet. Although
more expensive than standard telephone wire, it is less susceptible
to interference and can carry more data. A coax cable consists of
a center conductor, a metallic outer conductor (shield), which
serves as ground, an insulator covering the center conductor, and
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Figure 7-1
Makeup
Coaxial Cable
a plastic jacket. See Figure 7-1. It is used to transmit both analog
and digital signals and has superior frequency characteristics compared to twisted pair. Its shielded concentric construction makes
it less susceptible to interference and cross talk.
The commonly used terms for the two kinds of coax are
Thinnet and Thicknet, sometimes called ThinWire and ThickWire.
These terms refer to the larger and smaller size of coaxial cable
used in Ethernet local area networks. Thicknet is 0.4 inches in
diameter and has 50 ohms of electromagnetic impedance. Thinnet
is 0.2 inches in diameter with the same impedance as Thicknet.
Thicknet was the original Ethernet wiring, but Thinnet, which is
cheaper and easier to install, is the more commonly used.
Coax is made up of two conductors that allow it to operate
over a wider range of frequencies compared to twisted pair and
is made in several impedances. In coaxial, impedance is measured
between the inner conductor and the outer sheath. Impedance is
determined by the physical construction of the cable, including the
thickness of the conductors and the spacing between them. Materials used as insulators within the cable also affect impedance.
Coaxial cables may be rigid with a solid sheath or flexible with a
braided sheath. The inner insulator, or dielectric, has a considerable effect on the cable’s properties, such as its characteristic
impedance and its attenuation. The dielectric may be solid or perforated with air spaces.
The type of coaxial cable used will determine the distance that
video signals can travel. These cables are categorized according to
size and distance-carrying capabilities. For example, the most
common coaxial cable used today is RG59/U, which carries signals
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for distances of approximately up to 750 or 1,000 feet, depending on
which manufacturer you ask. It will be necessary to choose the
correct coaxial cable for the job at hand. 75 ohm impedance cable is
the standard used in CCTV systems. RG is the cable specification
for use as a radio guide, and the numerical value distinguishes the
specifications of each individual cable. Even though each cable has
its own number, characteristics, and size, there is no difference in
the way these different numbered cables work.
Coaxial cable is used primarily for the transmission of analog
video. The most common place it will be seen, even with digital
video systems, is from the camera to the control equipment. Since
many DVRs still require an analog video input, they are still
equipped with BNC connectors for the connection of coaxial cables.
Some new DVRs will allow for inputs from analog and digital
cameras, so until analog cameras are replaced completely with
digital output cameras, coaxial cable will still be very common.
Optical Fiber
Optical fiber is a thin, flexible material used to guide optical rays.
Fiber optic transmission was designed to transmit digital signals
in the form of pulses of light. A fiber optic cable contains one or
more hair-thin strands of glass fiber, each wrapped within a plastic
tube and an external coating, and capable of transmitting messages modulated onto light waves. See Figure 7-2.
Figure 7-2
Optical Fiber With Cladding
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Digital CCTV
Optical fiber is made up of a cylindrical cross-section with
three concentric links:
●
●
●
Core—the innermost section containing one or more very
thin strands or fibers
Cladding—a plastic or glass coating with optical properties that surrounds each strand
Jacket—the outermost layer made of plastic and other
materials that surrounds one or more claddings and protects them from environmental elements like moisture,
cuts, and crushing.
Fiber optic cables are much thinner and lighter than metal wires
and can carry far more information than copper wire. For longer
distance, fiber optic cables can be used to transmit video signals
without interference from ground loops, lightning hazards, and
man made noise. Optical fibers are not affected by interference
from electromagnetic sources.
FDDI
Fiber Distributed Data Interface (FDDI) refers to a set of
ANSI protocols for sending digital data over fiber optic cable.
These networks can support data rates of up to 100 Mbps and are
often used as the basis for wide-area networks.
FDDI-2 FDDI-2 supports the transmission of voice, video, and
data.
Another variation of FDDI called FDDI Full Duplex Technology (FFDT) can potentially support data rates up to 200 Mbps.
FTTP
Fiber to the Premises (FTTP) is a set of standards defining
common technical requirements for extending fiber optic cabling
and equipment to homes and businesses, which was begun in the
U.S. in 2004 by the RBOCs. These industry standards facilitate the
deployment of broadband services such as voice, video, and highspeed Internet to homes and businesses.
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SONET
Synchronous Optical Network (SONET) is a standard
for optical telecommunications transport. The standard defines a
ranking of interface rates that allow data streams at different rates
to be transmitted over a single line or media.
With a networked security installation, video can normally be
viewed from any point on the network locally, as well as remotely
from around the world. Access to the video information is controlled through user names and passwords, rather than restricting
physical access to a monitor and/or operator keyboard. As long as
you can connect to the network, there’s an excellent possibility to
view and manage the information coming from the cameras.
TRANSMISSION AND CONNECTION TYPES
When the transmission of digital video first became feasible, Public
Switched Telephone Service (PSTN) was restricted to twisted pair
telephone links with a capability of around 30 Hz to 3.4 KHz bandwidth—adequate for voice transmission but very limiting when
trying to transmit video signals. The broad accessibility of PSTN
service was certainly an advantage, but unfortunately, PSTN has
limited bandwidth due to its employment of analog signals. These
must be converted from digital and back again, greatly slowing
the transmission process. The differences between analog and
digital information could be compared to two different spoken
languages. If you only speak Latin and you must communicate
with someone who only speaks Greek you will need a translator;
hence the modem.
A modem is the modulator/demodulator that translates
digital signals so that they can be sent over analog lines. The
receiver will also require a modem in order to translate the analog
information back to a digital format. It is fairly easy to comprehend why the necessity for a translator will slow down the communication process. The speed of the translator (modem) will also
be a factor. Today, modems not only run faster, they contain features like error control and data compression. Modems can also
monitor and regulate information flow. These modems select the
appropriate speed according to the current line conditions.
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Much like the multitude of highways available for travel by
car, many paths for video transmission now exist, including
various modes of phone line transmission. Similar to taking a car
from point A to point B, you will have decisions to make about
the best route to take. Should it be the fastest, the straightest, the
one with the most restaurants, or the least stop lights? There are
many things to take into consideration when choosing a transmission medium for your video data as well.
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Availability
Cost
Speed
Number of Users
Reason for Connection
Costs can vary widely depending on the location, and some options
are not available in all areas. In large cities, there may be a variety
of options available in varying price ranges, whereas rural areas
may only have a few expensive options. Certain options may only
offer a specific speed while others have additional speed abilities,
for an additional fee. An office with two employees may only need
an ISDN connection or an ADSL connection, whereas an office
with fifty employees may require a T1, Frame Relay, or ATM connection to handle the load. Of course, the reason for connection
has a significant bearing on the choice of service.
The subject of data transmission involves a tremendous
amount of acronyms, which will be identified throughout the
chapter. Let’s start with the most basic and most familiar of our
choices for video transmission, the phone line. Composite video
cannot be transmitted down a telephone line. It must be converted
to a digital signal via a modem. The modem converts the digital
signal to a series of tones, which pass down the phone lines.
POTS
The standard telephone service that most homes use is affectionately called POTS, for Plain Old Telephone Service. POTS is a
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standard, single line telephone service with access to the Public
Switched Telephone Network (PSTN). In order to use a conventional modem for transmitting digital data and a telephone for
transmitting voice at the same time on a POTS system, two lines
are needed.
PSTN
Public Switched Telephone Network usually refers to the international telephone system, which is based on copper wires carrying
analog voice data. It is a normal voice grade telephone line with
a slow transmission speed but worldwide availability. Modern
networks are not connected, and rout packets contain digitized
audio voice information as it is produced.
In some countries, there is only one telephone company. In
countries with many competitive phone services like the United
States, telephone company refers to the entire interconnected
network of phone companies. Regular modems are needed to send
digital data over a PSTN line. The speed of transmission is restricted
by the bandwidth of the PSTN, and the maximum amount of data
that you can receive using ordinary modems is about 56 Kbps.
ISDN
The abbreviation for Integrated Services Digital Network is ISDN.
This is an international communications standard for sending
voice, video, and data over digital telephone lines or normal telephone wires. ISDN protocols are used worldwide for connections
to public ISDN networks or to attach ISDN devices to ISDNcapable PBX systems. ISDN is a telephone company service that
is supported by the ITU H.320 suite of standards and supports
data transfer rates of 64 Kbps.
ISDN builds on groups of standard transmission channels.
Bearer channels or B channels transmit information at comparatively high speeds. Separate Data channels or D channels
carry the set-up, signaling and other user data. B channels are
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clear-channel pipes and D channels are packet-switched links.
Packets are routed to their destination through the most expedient
path. Packet switching is a communications standard in which
messages or fragments of messages are individually routed
between nodes, with no previously determined communication
route. Each packet is transmitted individually and can follow different routes to its destination. Once all the packets forming a
message arrive at the destination, they are assembled into the
original message.
There are two versions of ISDN, Basic Rate Interface (BRI)
and Primary Rate Interface (PRI).
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Basic Rate Interface is made up of two 64-Kbps B-channels and
one D-channel for transmitting control information. Each of the
two B channels is treated independently by the network, permitting simultaneous voice and data or data only connections.
With specialized hardware and software, multiple B channel
connections can be combined to attain rates of several Megabytes of data per minute or more. This version is referred to as
ISDN 2 in Britain and ISDN 2e in Europe.
Primary Rate Interface consists of 23 B-channels and one Dchannel in the United States or 30 B-channels and one D-channel
in Europe, which was designed for larger organizations. PRI
service is generally transmitted through a T-1 line or an E1 line
in Europe. It is also possible to support multiple PRI lines with
one 64 kb/s D channel using Non-Facility Associated Signaling
(NFAS), a special case of ISDN signaling in which two or more
T1 PRI lines use the same D channel, and you can add a backup
D channel. The NFAS option extends D-channel control to Bchannels not resident on the same interface.
B-channel is the main data channel in an ISDN connection.
D-channel is the ISDN channel that carries control and signal
information. ISDN originally used baseband transmission but
another version known as B-ISDN uses broadband transmission
and is able to support transmission rates of 1.5 Mbps. This version requires fiber optics and is not readily available in many
locations.
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DSL
Digital Subscriber Line (DSL) is a general term for any local
network loop that is digital in nature. It is a very high-speed connection that uses the same wires as a regular telephone line. The
copper wires that make up regular phone lines have plenty of
room to transmit more than just voice conversations. DSL takes
advantage of this extra bandwidth without disturbing the voice
conversations. To interconnect multiple DSL users to a high-speed
network, the telephone company uses a Digital Subscriber Line
Access Multiplexer (DSLAM). At the other end of each transmission, a DSLAM demultiplexes signals and sends them to individual DSL connections. On average with DSL, data is downloaded
at rates up to 1.544 Mbps and you can send data at 128 Kbps. DSL
service requires a special modem and a network card in your
computer.
Current information on DSL technology advancements can
be obtained from the DSL Forum, which is an international industry consortium of approximately 200 service providers, equipment
manufacturers, and other interested parties who are focused on
developing the full potential of broadband DSL. DSL Forum’s
Web site dedicated to providing information to end-users can be
found at www.dsllife.com
ADSL
Most homes and small business users are connected to an
Asymmetric Digital Subscriber Line (ADSL) that was designed to
transmit digital information at a high bandwidth over existing
phone lines. ADSL is different from regular phone service in that
it provides a continuous or always on connection. It is called asymmetric because of the way it divides up a channel, on the assumption that most Internet users download or receive much more
information than they upload or send. ADSL uses most of the
available channel for receiving. ADSL supports data rates of from
1.5 to 9 Mbps when receiving data and from 16 to 640 Kbps when
sending data.
An ADSL circuit connects an ADSL modem on each end of
a twisted-pair telephone line, creating three information channels.
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These include a high speed downstream channel, a medium speed
duplex channel, and a POTS channel. The POTS channel is split
off from the digital modems by filters to guarantee uninterrupted
phone service. Most DSL technologies call for a signal splitter
requiring a phone company visit, although it is possible to manage
the splitting remotely. This is known as splitterless DSL, DSL Lite,
G.Lite, or Universal ADSL and has recently been made a standard.
Various forms of DSL are allowing phone companies to compete
with cable modem services.
xDSL
Usually referred to as simply DSL, it is sometimes called
xDSL with the “x” denoting “any” for DSL variations. It is a
generic term for DSL services in that the x can be replaced with
any of the letters that represent the various types of DSL technology such as these:
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Very high bit-rate DSL (VDSL), a fast connection that only
works over short distances.
Symmetric DSL (SDSL), often used by small businesses, does
not allow dual use. Incoming and outgoing data-rates are the
same.
Rate-adaptive DSL (RADSL), a variation of ADSL where a
modem can adjust the speed of the connection depending on the
length and quality of the line. Using modified ADSL software,
RADSL makes it possible for modems to automatically adjust
transmission speeds, sometimes providing better data rates for
customers located at greater distances from the central offices.
High bit-rate Digital Subscriber Line (HDSL) is used for wideband digital transmission within a site and between the telephone company and a customer. HDSL is symmetrical (an
equal amount of bandwidth is available in both directions) and
HDSL can carry as much on a single wire of twisted-pair cable
as can be carried on a T1 line (up to 1.544 Mbps) in North
America or an E1 line (up to 2.048 Mbps) in Europe. The oldest
of the DSL technologies, HDSL continues to be used by telephone companies deploying T1 Services at 1.5 Mbps and
requires two twisted pairs.
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ISDN DSL (ISDL) is primarily geared toward existing users of
ISDN. ISDL is slower than most other forms of DSL, operating
at fixed rate of 144 Kbps in both directions. The advantage
for ISDN customers is that they can use their existing
equipment, but the actual speed gain is typically only 16 Kbps
(ISDN runs at 128 Kbps). IDSL provides up to 144 Kbps transfer
rates in each direction and can be provisioned on any ISDN
capable phone line. Compared to ADSL and other DSL technologies, IDSL can be used at further distances from the
central offices, and by users who are not served directly from
the central office but through digital loop carriers and other
technologies.
Multirate Symmetric DSL (MSDSL) is Symmetric DSL that is
capable of more than one transfer rate. The transfer rate is set
by the service provider. Voice-over DSL (VoDSL) allows
multiple phone lines to be combined into a single phone line
with data-transmission capabilities.
SW56
Switched 56 (SW56) is a dial-up digital service provided by local
and long distance telephone companies, which requires a DSU/
CSU for connection rather than a modem. A Digital (or Data)
Service Unit/Channel Service Unit (DSU/CSU) is a pair of communications devices that connect an inside line to an external
digital circuit. The DSU sends and receives signals while the CSU
terminates the external line at the customer. A CSU may not be
required in certain T1 ready communication devices. SW56 is the
traditional data network in the United States using an analog
signal with 56K bandwidth.
T1
T1 is a digital transmission link with a capacity of 1.54 Mbps over
two twisted pairs of wires. One pair is used to transmit, the
other to receive. T1 service accommodates 24 voice signals or any
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combination of voice and data signals up to 1.54 Mbps. A T1 line
is plugged into the phone system for voice and into the network’s
router for data transmission. The 64 Kbps channels can be divided
into any combination of voice and data transmission duties when
a T1 link is configured. Initially designed for voice, T1 and T3 lines
are now widely used to create point-to-point private data networks. Cost is generally based on the length of the circuit. E1 is
the European version of T1.
T3
A T3 line is a dedicated phone/data connection supporting data
rates of about 43 Mbps. T3 consists of 672 channels that each
support a 64 Kbps data link. Each 64 Kbps link can traditionally
support one voice conversation. T-3 lines are used mainly by Internet service providers (ISPs) and are sometimes referred to as DS3
lines.
ATM
Asynchronous Transfer Mode (ATM) is a form of data transmission
that allows voice, video, and data to be sent along the same network.
ATM is a key component of broadband ISDN having a high bandwidth, low delay, packet-like switching, and multiplexing technique. Information is divided among short, fixed-length packets
called cells for transport, transmitted, and then re-assembled at
their final destination. It is asynchronous because cells are not transferred periodically but are given time slots on demand.
Since ATM provides “bandwidth on demand”, customers
can be charged only for the data they send. It is best known for its
ease of integration with other technologies and its sophisticated
management features. ATM service works for applications that
require bandwidth at speeds of 1.5 Mbps and higher. Because
ATM divides data for transport into fixed-length, 53-byte cells, it
supports high speed plus low delay, which means voice and video
can run on the same infrastructure as data with no loss of quality.
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Interoperability between the ATM equipment of different manufacturers and gateways to existing LAN/WAN standards mean
maximum performance.
Cable Transmission
Cable Internet works by using TV channel space for data transmission. It can make your Internet access many times faster than with
a conventional dialup system. Cable Internet works over the same
hybrid fiber coax (HFC) networks that provide cable television
service. In the case of HFC networks, coax cable is used within
neighborhoods, and optical fiber often connects neighborhoods to
central facilities. A cable modem is needed to access the Internet
in this manner.
A cable modem has two connections: one to the cable wall
outlet and the other to a PC or to a set-top box for a TV set. More
complex than the telephone modem, the cable modem attaches to
a standard 10 BASE-T Ethernet card in the computer. The wall
outlet leads to a company cable line that connects with a Cable
Modem Termination System (CMTS) at the local cable TV company
office and can only send and receive signals to and from the CMTS.
Cable modems cannot communicate with each other. In a business
or commercial environment, the cable modem interfaces with a
local area network (LAN) through an Ethernet hub, switch, or
router and provides access to numerous users through a single
cable modem.
Many cable operators are beginning to deploy high-capacity
packet transport solutions over fiber rings connecting the CMTS
units in their distribution hubs, such as Packet over SONET (POS),
at up to 622 Mbps. In addition to the faster data rate, an advantage
of cable transmission over telephone for Internet access is that it
is a continuous connection.
Ethernet is the most common Local Area Network used by
PCs. Ethernet is a specification for a LAN that is intended to carry
10 Mbps of data for use in the same building over high quality
twisted pair wires or coaxial cable. There are 4 versions of Ethernet
LANs:
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10 Base-2 thinnet—coaxial cable and BNC connectors—180
meters max—30 nodes
10 Base-5 thick Ethernet—thick coaxial cable—500 meters max–
100 nodes
10 Base-T twisted pair cable—RJ 45 connector—100 meters
max—2 nodes
10 Base-F fiber optic cable—2000 meters max—2 nodes
Fast Ethernet is IEEE standard 802.3 u. Fast Ethernet raises the
communications bandwidth from 10 Mbps to 100 Mbps with only
minimal changes to existing Ethernet cable structures:
100 Base-TX for use with Category 5 cable—RJ 45 connector
100 Base-FX for use with fiber optic cable
100 Base-T4 for use with Category 3 cable—two extra wires
Other LANs include token Ring, Fiber Distributed Data Interface
(FDDI), and LocalTalk.
Frame Relay
Frame relay is an extremely efficient form of data transmission
frequently used to transmit digital information over local area
network (LAN) and wide area network (WAN) with variable connection speeds of 128 k up to 1.5 Mbps. Frame relay was originally
designed for use across ISDN interfaces using packets referred to
as frames. Today, it is used over a variety of other network interfaces as well. The technology was intended to be an intermediate
solution for the demand for high bandwidth networking. It is a
packet switching technology, which relies on low error rate digital
transmission links and high performance processors.
Frame relay is provided on fractional T-1 or full T-carrier
system carriers. Frame relay complements and provides a midrange service between ISDN, which offers bandwidth at 128 Kbps,
and ATM, which operates in somewhat similar fashion to frame
relay but at speeds from 155.520 Mbps or 622.080 Mbps. A Frame
relay requires a circuit to be installed by the phone company.
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Fast Ethernet
Fast Ethernet is a local area network (LAN) transmission standard
that provides a data rate of 100 megabits per second. It is commonly referred to as 100BASE-T. Workstations with existing 10
megabit per second or a 10BASE-T Ethernet card can be connected
to a Fast Ethernet network using three types of physical wiring:
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00BASE-T4 (four pairs of telephone twisted pair wire)
100BASE-TX (two pairs of data grade twisted-pair wire)
100BASE-FX (a two-strand optical fiber cable)
There is a vast scope of applications, and the various methods are
mutating and evolving at a rapid pace.
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8
Wireless Video
Transmission
Wireless may be an old-fashioned term for a radio receiver, but
there is nothing old-fashioned about wireless video transmission.
Communicating digital images without the benefit of cables, cords,
or wires is now almost commonplace. Today, the term is practically universal for the transmission of data between devices via
radio frequency, microwave, or infrared signals.
ELECTROMAGNETIC RADIATION
An energy wave called a radio wave, which is generated by a
transmitter, is a complex form of energy containing both electric
and magnetic fields. This combination of fields cause radio waves
to also be called electromagnetic radiation. All wireless data is
carried by some form of electromagnetic radiation, and the most
commonly used for wireless data communication include radio
waves, microwaves, and infrared. Many remote video transmission systems used in security applications today are equipped
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to operate wirelessly via radio frequency, microwave, or satellite
link-ups in the case of a system interruption. These features are
considered as backup or redundant systems that automatically
take the place of the wired transmission systems should they terminate for some reason. Natural disasters such as wind storms,
earthquakes, or floods provide an excellent example of the necessity of backup systems when land based communications are
interrupted. In cases where traditional phone and cable communications systems are inoperable or unavailable, wireless communication capabilities are critical.
The electromagnetic field is used to transfer energy from
point to point with an antenna as the source of these electromagnetic waves. Antennas are simply electronic components designed
to send or receive radio waves. Energy is sent into space by a
transmitting antenna, and the signal is then picked up from space
by a receiving antenna. The design of the antenna is important
because it determines the efficiency with which energy is transmitted. An efficient transmitting antenna must have exact dimensions. Characteristics are essentially the same for sending and
receiving electromagnetic energy. This interchangeability is known
as antenna reciprocity.
Antenna systems are required for all broadband wireless networks to operate. There are four basic styles or types of antennas
used for broadband wireless systems: the sector (hub) antennas,
flat-panel antennas, parabolic (dish) antennas, and dual-band
antennas. A complete antenna system consists of a coupling device
that connects the transmitter to the feeder and the feeder, a transmission line that carries energy to the antenna, and the antenna
itself, which radiates energy into space. Factors determining the
kind of the antenna used are the frequency of operation of the
transmitter, the amount of power to be radiated, and the general
direction of the receiving system.
The majority of antennas have evolved from two basic types,
the Hertz and the Marconi. The basic Hertz antenna is 1/2 wavelength long at the operating frequency and is insulated from
ground. The basic Marconi antenna is 1/4 wavelength long and is
either grounded at one end or connected to a network of wires
called a counterpoise.
Wireless Video Transmission
Table 8-1
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Frequency Levels
Extremely low frequency
Voice frequency
Very low frequency
Low frequency
Medium frequency
High frequency
Very high frequency
Ultra high frequency
Super high frequency
Extremely high frequency
(ELF, ITU band 2)
(VF, ITU band 3)
(VLF, ITU band 4)
(LF, ITU band 5)
(MF, ITU band 6)
(HF, ITU band 7)
(VHF, ITU band 8)
(UHF, ITU band 9)
(SHF, ITU band 10)
(EHF, ITU band 11)
Below 300 Hz
300–3000 Hz
3–30 kHz
30–300 kHz
300–3000 kHz
3–30 MHz
30–300 MHz
300–3000 MHz
3–30 GHz
30–300 GHz
Radio Waves
Radio waves carry information bearing signals that are either
encoded directly on the wave by periodically disrupting its transmission (similar to telegraph), or the information is impressed on
the carrier frequency by a process called modulation. Modulation
is achieved by varying some characteristic of the wave. Amplitude
modulation, known as AM, is achieved by manipulating the intensity or amplitude, and frequency modulation or FM is achieved
by manipulating the frequency of the wave. See Table 8-1.
Infrared Transmission
Infrared data communications systems use infrared beams to carry
data with light pulses. Another term for infrared transmission is
beaming. With this type of system, video is superimposed onto an
infrared beam by a transmitter and aligned to strike a receiver
where the signal is output as a conventional composite video
signal. The performance of infrared beams can be affected by
weather and environmental conditions.
A wavelength ranging from 750 to 1,000,000 nanometers
places infrared between microwaves and visible light in the spectrum. Infrared beams can quickly transmit data between two locations in the same room but it cannot carry information through or
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around walls or other obstacles. Most infrared communications
systems are used to connect local workstations, PCs, and
printers.
Microwave Transmission
Microwaves are commonly used in communications links spanning short distances, such as cellular telephone systems. These
high frequency electromagnetic waves fall in a range between
radio and infrared, with an approximate wavelength of one
millimeter to one meter. Microwave links are capable of much
farther transmission distances than infrared, and they are largely
unaffected by weather conditions.
CELLULAR TRANSMISSION
Normally, a geographic region served by a cellular system via
microwave is divided into areas called cells. Each cell has a central
base station and two sets of assigned transmission frequencies—
one set is used by the base station and the other by mobile telephones. This is where the name cellular comes from. To prevent
radio interference, each cell uses frequencies different from those
used by its surrounding cells. When a mobile telephone leaves one
cell and enters another, the call is transferred from one base station
and set of transmission frequencies to another by a computerized
switching system.
A cellular telecommunications system consists of a portable
or mobile radio transmitter and receiver, or cell phone, linked by
radio frequencies to base stations. MTSO stands for the Mobile
Telephone Switching Office that connects all of the individual cell
towers, controls the cell sites, and manages all of the mobiles via
a control channel. It is the link between the Public Switched Telephone Network (PSTN) and the cell sites providing the cellular
customers connectivity to the standard phone network.
With cellular transmission, each cell phone identifies itself to
the cellular system every time it places or receives a call. A cell
phone’s identity includes two unique values—the phone number
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that is assigned by the service provider, called a Mobile Identification Number (MIN), and an Electronic Serial Number (ESN). The
ESN is a 32-bit binary number that cannot be changed.
Originally, American cellular telecommunications relied on
an analog transmission system known as Advanced Mobile Phone
Service (AMPS). These first generation cellular services essentially
transmit voices as FM radio signals. Although AMPS is still in
place, it is rapidly being replaced by digital technology. The most
common of these are Time Division Multiple Access (TDMA),
Code Division Multiple Access (CDMA), and Personal Communication System (PCS), a version of the European Global System for
Mobile Communications (GSM). Frequency Division Multiple
Access (FDMA) is used mainly for analog transmission. While it
is certainly capable of carrying digital information, FDMA is not
considered to be an efficient method for digital transmission.
TDMA assigns each call a certain portion of time on a designated
frequency. CDMA gives a unique code to each call and spreads it
over the available frequencies, and FDMA places each call on a
separate frequency.
The total number of mobile subscribers worldwide exceeds
one billion and is growing. Many experts predict that number will
double before the year 2010. Mobile wireless networks are continuously evolving and will be increasingly important enablers of
new business and consumer applications including the transmission of digital video for the near future.
TDMA: Time Division Multiple Access
TDMA systems build upon the AMPS framework. TDMA may also
be referred to as DAMPS, Digital AMPS, or US Digital. When the
wireless industry first began to explore converting the existing
analog network to digital, the Cellular Telecommunications Industry Association (CTIA) chose TDMA, in which three time slots are
assigned to a single carrier frequency, allowing one channel to
support multiple phone calls. In other words, several users can
access a single radio-frequency (RF) channel without interference.
Both analog and digital data can be transmitted with TDMA
systems because it is a dual mode wireless transmission method
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with bandwidth divided into common intervals for different data
streams. The time slots used in each channel increase the amount
of data that can be transferred over analog cellular systems. TDMA
is also the access technique used in the European digital standard
(GSM) and the Japanese digital standard, personal digital cellular.
GSM systems use encryption to make phone calls more secure.
GSM operates in the 900-MHz and 1800-MHz bands in Europe and
Asia, and in the 1900-MHz band in the United States.
CDMA: Code Division Multiple Access
CDMA is a form of wireless multiplexing that is used to send data
over multiple frequencies at once making it possible for many
conversations to occur on a single channel. The technology is used
in cellular telephone systems in the 800-MHz and 1.9-GHz bands.
CDMA codes each digital packet (data) with a unique key that a
CDMA receiver responds to. CDMA phones consume less power
than analog phones because they are idle between bursts.
Variations of CDMA include B-CDMA, W-CDMA, and
composite CDMA/TDMA. Developed originally by Qualcomm,
CDMA is characterized by high capacity and small cell radius,
employing spread-spectrum technology and a special coding
scheme.
GSM-PCS Cellular System
The Personal Communication System, sometimes referred to as
GSM-PCS Cellular System, is a TDMA digital system that changes
voice and access information into digital data. GSM-PCS uses
radio frequencies with approximately three times the efficiency of
TDMA.
EDGE: Enhanced Data Rate for GSM Evolution
EDGE is a faster version of the GSM wireless service, designed to
deliver wireless multimedia IP-based services and applications at
theoretical maximum speeds of 384 Kbps with a bit-rate of 48 Kbps
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per timeslot and up to 69.2 Kbps per timeslot in good radio conditions. This enables the delivery of multimedia and other broadband applications to mobile phone and computer users. The EDGE
standard is built on the existing GSM standard, using the same
time-division multiple access frame structure and existing cell
arrangements.
2 G and 2.5 G
Wide-area wireless technologies are commonly referred to by their
generation of technology. As mentioned earlier, 1 G refers to the
original analog systems in America (AMPS). Second generation or
2 G represents digital circuit switched networks. 2.5 G is the evolution of the digital network to include packet-switched data.
3 G Wireless
3 G Wireless is an International Telecommunications Union (ITU)
specification for cellular communications technology, also known
as 3 G, IMT-2000, International Mobile Telecommunications 2000,
and Third Generation Wireless.
WIRELESS BROADBAND ACCESS TECHNOLOGIES
Wireless broadband access technology refers to high-speed wireless access services that provide bandwidths that exceed DSL and
cable network technologies. Wireless Wide Area Networks, Wireless Local Area Networks, and Wireless Personal Area Networks
all utilize complex communication techniques enabled by the
increasing capabilities of digital signal processing.
There are several bits of jargon that would be useful to identify at this point to avoid confusion. For example, some services
are considered to be fixed wireless. This means even though the
data transmission is wireless, the stations are fixed rather than
moving or mobile wireless. The term local refers to the signal’s
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range limit. Point-to-point refers to a long-range wireless network
between two points. A wireless network in which one point (the
access point) serves multiple other points around it is known as
point-to-multipoint. Indoor wireless networks are all point-tomultipoint.
Local Multipoint Distribution Service
Local Multipoint Distribution Service (LMDS) provides two-way
Internet access using radio waves. It is a broadband point-tomultipoint communication system, developed as a wireless local
loop, to be used in areas where installing physical cable is either
impossible or cost prohibitive. LMDS uses a point-to-multipoint
radio topology where a base station broadcasts to subscriber antennas. A transmission speed of several billion bits per second (gigabits) is possible along line of sight distances of several miles.
JPWL
Wireless communications offers its own particular set of problems
that can make transmitting video data a challenge. To address this
issue, the JPEG committee has established a new work item, JPEG
2000 Wireless (JPWL), as Part 11 of JPEG 2000 to standardize tools
and methods to achieve the efficient transmission of video data
over wireless networks. The JPWL system supports the functions
of protection of the code stream against transmission errors,
the description of the degree of sensitivity of different parts
of the code stream to transmission errors, and the description
of the locations of residual errors in the code-stream. JPWL has
made JPEG 2000 very resistant to transmission errors, rendering
it a good choice for wireless applications.
Wireless LAN (WLAN)
Wireless LANs provide high-speed data within a small region,
such as a campus or small building. The standard, IEEE 802.11,
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specifies the technologies for wireless LANs. The standard includes
an encryption method—the Wired Equivalent Privacy (WEP)
algorithm. Most wireless LANs in the US frequency bands are
located at 900 MHz, 2.4 GHz, and 5.8 GHz because an FCC license
is not required to operate in these bands. The downside of this is
that many other systems operate in these bands, causing interference between systems. There are two modes of WLAN.
Wireless Fidelity (Wi-Fi)
Wi-Fi wireless networking, also known as 802.11 networking, is a
set of standards for wireless local area networks (WLAN) based
on the IEEE 802.11 specifications. The IEEE 802.11 specifications
are standards that specify an over-the-air interface between a wireless client and a base station or access point, as well as between
wireless clients. The 802.11 standards can be compared to the IEEE
802.3 standard for Ethernet for wired LANs. Wi-Fi was originally
intended to be used for wireless devices and LANs, but is now
often used for Internet access. It enables a person with a wirelessenabled computer or personal digital assistant to connect to the
Internet when in proximity of an access point called a hotspot.
Wireless mobile devices including portable computers, PDAs,
and a variety of small wireless communication devices increasingly need to connect to corporate networks, perform database
queries, exchange messages, transfer files, and even participate in
collaborative computing. These wireless systems are achieving
higher data rates to support Internet and other data-related applications, including the transmission of digital video.
Worldwide Interoperability for Microwave
Access (WiMAX)
WiMAX is a more robust standard for high-speed broadband
wireless delivery to laptops and desktops. The 802.16 standards
are still being ironed out and products are not yet readily available
as current development is concentrating on cost and power
reduction.
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WiMAX is the IEEE 802.16 technology that provides MAN
(Metropolitan Area Network) broadband technology to connects
IEEE 802.11 (Wi-Fi) hotspots. A hotspot is a connection point for
a Wi-Fi network consisting of a small box hardwired into the
Internet. The box contains an 802.11 radio that can simultaneously
talk to up to 100 or so 802.11 cards. There are many Wi-Fi hotspots
now available in public places like restaurants, hotels, libraries,
and airports.
Metropolitan area networks are large computer networks
usually spanning a campus or a city. They typically use optical fiber connections to link their sites.WiMAX provides highthroughput broadband connections over long distances at speeds
of up to 75 Mb/sec. Signals can be transmitted up to 30 miles.
Wi-Fi and WiMAX are complementary technologies.
802.11 is a family of specifications developed and maintained
by the Institute of Electrical and Electronics Engineers. Most users
know that the letters appearing after the reference denote speed,
but they also define the distance the network can operate over, its
security capabilities, and the frequency over which the networks
operate. See Table 8-2.
Ultra-Wide Band (UWB)
UWB is a short-range radio technology that complements other
longer range radio technologies like Wi-Fi and WiMAX and
cellular wide area communications. It is a wireless technology that
can transmit data up to 60 megabits per second and eventually up
to one gigabit per second, used to relay data from a host device to
other devices in the immediate area (up to 30 feet). UWB transmits
ultra-low power radio signals with very short electrical pulses
across all frequencies at once. UWB receivers translate short bursts
of noise into data by listening for a familiar pulse sequence sent
by the transmitter. Early UWB systems were developed mainly as
military surveillance tools because they could “see through” trees
and beneath ground surfaces. The greatest attribute of UWB
devices is spectrum efficiency evidenced by its ability to operate
Wireless Video Transmission
Table 8-2
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802.11 is a Family of Specifications
802.11a
Applies to wireless ATM systems
Enhanced data speed
Frequency range 5.725 GHz to 5.850 GHz
802.11b
High data speed
Low susceptibility to multipath-propagation
interference
Frequency range 2.400 GHz to 2.4835 GHz
802.11d
Allows for global roaming
Particulars can be set at Media Access Control (MAC)
layer
802.11e
Includes Quality of Service (QoS) features
Facilitates prioritization of data, voice, and video
transmissions
802.11g
Offers wireless transmission over relatively short
distances
Operates at up to 54 megabits per second (Mbps)
802.11h
Resolves interference issues
Dynamic frequency selection (DFS)
Transmit power control (TPC)
802.11i
Offers additional security for WLAN applications
802.11j
Japanese regulatory extensions to 802.11a specification
Frequency range 4.9 GHz to 5.0 GHz
802.11k
Radio resource measurements for networks using
802.11 family specifications
802.11m Maintenance of 802.11 family specifications
Corrections and amendments to existing
documentation
802.11x
Generic term for 802.11 family specifications under
development
General term for all 802.11 family specifications
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Table 8-2
Continued
Wi-Fi
Originally created to ensure compatibility among
802.11b products
Can run under any 802.11 standard
Indicates interoperability certification by Wi-Fi
Alliance
802.15
A communications specification for wireless personal
area networks (WPANS)
802.16
A group of broadband wireless communications
standards for metropolitan area networks (MANS)
802.16a
Enhancement to 802.16 for non-line-of-sight extensions
in the 2–11 GHz spectrum
Delivers up to 70 Mbps at distances up to 31 miles
802.16e
Enhancement to 802.16 that enables connections for
mobile devices
802.1X
Designed to enhance the security of wireless local area
networks (WLANs) that follow the IEEE 802.11
standard
Provides an authentication framework for wireless
LANs
The algorithm that determines user authenticity is left
open
Multiple algorithms are possible
802.3
A standard specification for Ethernet
Specifies the physical media and the working
characteristics of the network
802.5
Standard specification for Token Ring networks
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in an already overloaded spectrum without producing harmful
interference.
WUSB
The universal serial bus (USB) technology is a popular connection
type for computers and consumer electronic and mobile devices
that can now provide the same functions of wired USB without
the cables. The Wireless USB Promoter Group defines the specifications that provide standards for the technology.
Wireless Wide Area Network (WWAN)
A wide area network is a collection of local area networks connected by a variety of physical means. The Internet is the largest
and most well known wide area network. Wide area wireless networks provide access to within a 20 mile radius with line of sight
to an antenna, which is the limiting feature. Weather can interfere
with traffic transmission.
Satellite Transmission
At the other end of the spectrum, so to speak, are satellite communication systems. Satellites in low earth orbit (LEO) circle the
Earth at an altitude of 1242 miles. These low orbiting satellites
obtain much clearer surveillance images and require less power to
transmit data. The first communications satellite was NASA’s
Echo 1, an inflatable sphere that passively reflected radio signals
back to Earth. The sphere successfully redirected transcontinental
and intercontinental telephone, radio, and television signals. The
success of this project proved that microwave transmission to and
from satellites in space could be understood, exhibiting the potential promise of communications satellites.
Today’s communications satellites relay information from
one point to another via transponders. The transponder receives
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data at one frequency, amplifies it, and retransmits it back to Earth
on another frequency. Communications satellites are usually geosynchronous (GEO), which means they circle the Earth once every
day at the exact same speed as the Earth rotates on its axis, making
the satellite stationary to its position with the Earth.
Artificial satellites orbit the Earth from a vantage point that
avoids the curvature-of-the-Earth limitations formerly placed on
communications between ground-based facilities. By transmitting
radio signals at high frequencies through the Earth’s atmosphere,
satellites can provide communications over great distances. Satellites are also beneficial as backup systems. In the event of natural
disasters, a satellite may be able to receive and transmit information when traditional point-to-point methods are not functional.
Internet service via satellite is achieved by using a satellite
dish for two-way communications. Upload speed is about onetenth of its average 500 Kbps download speed. A key installation
planning requirement is a clear view to the south, since satellites
orbit over the equator area. Two-way satellite Internet uses Internet Protocol (IP) multicasting technology, which means up to 5,000
channels can simultaneously be served by a single satellite.
GLOBAL POSITIONING SYSTEMS (GPS)
Wireless data communication via satellites should not be confused
with using satellites with GPS technology. GPS receivers use satellites to triangulate and calculate the device’s longitude, latitude,
and elevation, but they do not transmit signals. Inmarsat, the satellite company that provides roaming communications services to
maritime vessels, military units, and aircraft, has launched a new
generation of satellites that provide a wider range of global highspeed voice and data offerings. I-4 is the fourth-generation of
Inmarsat satellites and will be the backbone of the company’s
Broadband Global Area Network, offering at least 10 times the
communications capacity of the current network. The new satellites allow the company to offer data speeds of up to 432 K bits per
second for uses such as video-on-demand, video conferencing,
phone, e-mail, LAN, Internet, and intranet services.
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Inmarsat satellites are used for peaceful communications,
such as offering links between military units, but still require a
high level of security. The company has its headquarters and satellite control room in downtown London, but has a mirrored site at
an undisclosed location in the north of the city, which offers complete redundancy.
There are no limits to the uses for satellite transmission and
no lack of imagination either. A new lightweight “communications suit” combines Inmarsat’s latest Regional Broadband Global
Area Network (BGAN) technology with state-of-the-art video
monitoring tools. BGAN is an Inmarsat network comprising satellites and land earth stations that permits data speeds up to
432 Kbps. The suit, made by German and US companies, features
a built-in still and video camera, personal computer, and a keyboard that is attached to the user’s arm. Software developed by a
Russian company send images, text, and video from the camera
to the PC, and a wireless Bluetooth link provides the connection
between the computer and the Regional BGAN satellite IP modem.
Providing continuous coverage within the satellite footprint, it
offers a secure 144 Kilobits per second shared channel, “always
on” access to the Internet, and other IP-based networks across a
large portion of the Americas, Europe, the Middle East, and India.
Currently, billing is managed according to the amounts of data
sent rather than time spent on line.
Terrestrial Microwave (TMW)
Microwaves are a form of electromagnetic radiation with frequencies ranging from several hundred MHz to several hundred GHz
and wavelengths ranging from approximately 1 to 20 centimeters.
Because of their high frequencies, microwaves are able to carry
more information than ordinary radio waves and can be beamed
directly from one point to another. On the other hand, these advantages make them more expensive than infrared links. There must
be a clear “line of sight” between the transmitter and receiver of
the microwave signal. For this reason, antennas are placed high so
that the curve of the earth does not interfere with transmission.
Microwave signals are largely unaffected by weather conditions.
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WIRELESS SECURITY
Security vulnerabilities within 802.11 networks are well documented, and standards groups are moving quickly to solve these
issues. 802.1x authentications, WEP, WPA, AES encryption,
TKIP, MIC, and EAP-TLS are just some of the security fixes
available.
802.1x
Standard 802.1x was approved by both the IEEE and ANSI in 2001.
802.1x is very scalable and supports a variety of authentication
types. The IEEE 802.1x standard defines a port-based network
access control to authenticate and authorize devices interconnected by various IEEE 802 LANs. IEEE 802.11i also incorporates
802.1x as its authentication solution for 802.11 wireless LANs.
Based on industry standards from the IEEE, 802.1X authentication
provide dynamic, per user, per session encryption keys instead of
the static keys used in WEP or WPA. It enables centralized policy
control, and a session timeout triggers re-authentication and new
WEP key.
Wired Equivalent Privacy: WEP
Wired Equivalent Privacy (WEP) is a security protocol, specified
in the IEEE Wireless Fidelity (Wi-Fi) standard 802.11b, designed
to provide a level of security and privacy comparable to what is
usually expected of a wired LAN. Wired LANs are generally protected by physical security mechanisms. WEP encrypts data transmitted over the WLAN.
Wi-Fi Protected Access: WPA
Wi-Fi Protected Access (WPA) is a standards-based, interoperable
security enhancement that strongly increases the level of data
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protection and access control for wireless LAN systems. The technical components of WPA include Extensible Authentication Protocol (EAP), Temporal Key Integrity Protocol (TKIP), and 802.1X
for authentication and dynamic key exchange.
Wi-Fi Protected Access 2 (WPA2)
WPA2 is the second generation of WPA security providing enterprise and consumer Wi-Fi users with a high level of assurance that
only authorized users can access their wireless networks. It is
based on the final IEEE 802.11i amendment to the 802.11 standard
and essentially mandates the use of the AES encryption standard
as an option alongside WPA’s Temporal Key Integrity Protocol.
WPA2 provides government grade security by implementing the
National Institute of Standards and Technology FIPS 140-2 compliant AES encryption algorithm. WPA2 is backwards compatible
with WPA.
AES: Advanced Encryption Standard
AES is a symmetric key encryption technique resulting from a
worldwide call for submissions of encryption algorithms by the
National Institute of Standards and Technology (NIST) in 1997 and
completed in 2000. AES was selected by NIST as a Federal Information Processing Standard in 2001. The U.S. Government (NSA)
announced in 2003 that AES was secure enough to protect classified information up to the top secret level.
EAP-TLS: Extensible Authentication
Protocol—Transport Layer Security
EAP-TLS was created by Microsoft and accepted as RFC 2716: PPP
EAP TLS Authentication Protocol. It is the de facto EAP used in
802.11i.
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TKIP: Temporal Key Integrity Protocol
TKIP (Temporal Key Integrity Protocol) is part of a draft standard
from the IEEE 802.11i working group. TKIP is an enhancement to
WEP security, which adds a per-packet key mixing function to
de-correlate the public initialization vectors from weak keys.
There are many advantages to using these types of wireless
systems, including ease of setup and increased flexibility. The
main disadvantage of wireless systems is their susceptibility to
interference problems due to the fact that when using wireless
transmission methods, a video signal is no longer on a dedicated
run. This may lead to signal problems that can decrease video
quality. However, the number of frequencies (channels) available
reduce the probability of this happening, making wireless a
popular mode for video transmission.
9
Examples of Digital
Video for Security
The very word “security” can be ambiguous, meaning different
things to different people. This is the definition given by Webster:
security n., 1. Feeling secure, freedom from fear, doubt, etc. 2. Protection;
safeguard. Providing “protection” and “safeguard” have been a tall
order for those in the security industry. Over the years many forms
of security have evolved from those as simple as on-site guards
to more complicated methods such as biometrics identification
systems.
With the capabilities of digital video, security providers are
now able to offer a more substantial version of the “protection”
and “safeguard” referred to by Webster. The uses and benefits of
remote digital video technology within the security industry have
grown exponentially. Functions as diverse as border control, safeguarding employees, and monitoring hazardous materials make
the applications of digital video immeasurable. Military, government, commercial, and private citizens all make up the spectrum
of users of this technology. Following are examples of some
common uses of the technology today.
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CRITICAL INFRASTRUCTURE PROTECTION
Since September 11th, 2001 virtually everything is considered to be
at risk, including energy supplies, water resources, bridges and
tunnels, waterways, and airports. Improving the security at these
and other potential targets has become a priority for our nation.
Protecting our county’s critical infrastructures and key assets
involves a multitude of physical protection challenges due to the
complex nature of the infrastructures and assets involved. Potential targets consist of a highly varied, mutually dependent mix of
facilities, systems, and functions. Failure in one could conceivably
begin a domino effect of consequences that could, in turn, negatively affect public health and safety, national security, the
economy, and public confidence.
Scores of US dams are key components of other critical infrastructure systems, which provide water and electricity. There are
approximately 80,000 dam facilities identified in the National
Inventory of Dams. The federal government is responsible for
roughly 10 percent of the dams whose failure could cause significant property damage or have public health and safety consequences. The remaining critical dams belong to state or local
governments, utilities, and corporate or private owners. Current
policies make dam owners principally responsible for the safety
and security of their own facilities.
Idaho Power, an investor-owned, electric utility company
headquartered in Boise, is taking positive action to prevent their
facilities from becoming a target. That action includes the installation of digital video security equipment used to monitor three
dams, power plants, and associated project facilities. The system
is also used by Idaho Power’s plant operators to view the areas
below the dams prior to operating spill gates.
SCHOOL AND CAMPUS SECURITY
Schools and campuses have been implementing surveillance
systems for years now, but digital technology has enhanced the
abilities of these systems tremendously. For example, a school
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system in Washington State recently installed a digital video surveillance system that is linked with the local police and fire departments. When activated, the system gives police and fire department
personnel visual access to most school areas from cameras placed
at each entrance, facing the playing fields, in the library, and in
each hallway. Live visuals of the hallways and outside are transmitted to responding individuals who may be outfitted with portable devices (both in vehicles and hand-held) able to receive the
feeds. Response time is about the same, but knowledge of the situation, whether it is a fire or hostage situation, is immediately discernable. If a fire breaks out in one part of the school, firefighters
are better prepared to know where and how to approach it.
The program is planned to tie in with the county’s Amber
Alert program, which deals with missing and exploited children.
With this system in place, if a child is abducted from the school
area, law enforcement officials can study outside camera feeds to
track suspects or suspicious vehicles.
Vanderbilt University takes campus security very seriously
and is committed to maintaining a safe, secure environment for
students, faculty, staff, and visitors. Twenty-four hour foot and
vehicle patrols, night transport/escort service, twenty-four-hour
emergency telephones, lighted pathways/sidewalks, student
patrols, digital surveillance systems, and controlled dormitory
access (key or security card) work together to create a safe campus
environment. The digital video system allows university officials
to easily perform video searches and to e-mail digital video footage
to the appropriate authorities when necessary. The university has
saved time and reduced labor costs and incident response time as
a result of upgrading to a digital closed-circuit television system.
School Coverage Areas
School security has developed extensively since so many incidents
have gained large amounts of publicity in recent years. New
schools are even being designed differently. For example, administrative offices are located so that the primary entrance can easily
be seen at all times. Since many older schools cannot simply
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relocate the administrative offices, technology must be used to
achieve the same result. By installing a camera at the primary
entrance and a large wall-mounted monitor in the administrative
office, the staff can easily see the entrance at all times.
An advantage of digital video systems for schools is the
ability to access the system remotely in the event of a major incident. This means first responders can gain access to the camera
system to view what is going on inside of the building, allowing
them to direct their response to the appropriate areas and not
waste efforts in areas where there is no immediate concern.
AIRPORT SECURITY
Airport security increasingly includes the electronic eyes of video
surveillance technologies, which complement and support
security personnel. Managing digital video surveillance over a
computer network allows for the addition of thousands of cameras
without the addition of staff to monitor the video data captured.
A networked digital video management system is a perfect
example of how to add camera “eyes” to an airport, or any facility,
and automate the alarm triggers on the data captured so that
security personnel are monitoring more of the facility without
adding staff. Potential digital video tools will provide a return on
investment not seen with previous surveillance systems while
adding a greater sense of security at airports.
One of the most significant problems facing airports today
are breaches at checkpoints and screening areas, even though
these breaches are not necessarily caused by anyone with malicious intent. Unfortunately, when there are large numbers of
people moving through a fast paced environment like an airport,
someone may go through a checkpoint before they have presented
proper ID or may gain entry through a screening area before they
or their carry-on baggage have been properly screened. Such a
security breach can create delays both for passengers as well as
the air traffic network, which in turn can be responsible for tremendous economical loss to both the airport and airlines. A digital
video surveillance system can be of tremendous value in reducing
the problems associated with these types of breaches.
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Another important surveillance challenge faced today is
timely and accurate detection of potential threats from unattended
baggage and other objects. There are many digital video systems
on the market with features that detect non-moving objects,
working opposite of the better known motion detection
features.
A digital video system can offer more than additional security and surveillance to an airport; it can also provide some of the
due diligence necessary in detaining suspects. With the right video
system, the chain of events following a breach is expedited. Many
different people may need to be involved in deciding a course of
action. With a digital system, everyone concerned can instantly
and positively identify an offender by viewing the same video
recording of the event from predetermined locations around the
airport. A physical description is immediately available and tracking of the offender can be viewed from said locations. This could
allow airport officials to close off and search a very specific area,
saving both time and money.
With digital video in place, airport security has the option of
interfacing digital video data with other data sources, making the
system more efficient, and more importantly, more effective. By
converting video to a computer network, the door is open to
activate software tools to recognize changes captured by the
video data. With a networked digital video management system,
advanced software tools have the capability to detect traffic patterns throughout the airport, ensuring that unscreened travelers
are not entering secure areas. Key factors in an airport’s decision
to implement digital video should be high frame rate, open architecture for ease of integration, wide range of storage options, and
user friendly system management.
NATIONAL MONUMENTS
Current global and political climates have increased the need for
all public facilities to place a more concentrated emphasis on
public safety and asset protection. As part of this trend, the National
Park Service determined that an evaluation of Mt. Rushmore’s
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security systems was necessary. The evaluation concluded that the
original system installed was inadequate and should be expanded
and modernized. Emphasis was placed on visitor safety and protection of the memorial as a whole.
A basic monitoring system with limited CCTV coverage was
already in place and was incorporated into the new digital system.
The new system provides a wide variety of security monitoring,
using numerous types of technology, card access, and CCTV. All
components are integrated together to make one seamless system.
The foundation of the system is an NT server that communicates
to remote control panels, workstations, and CCTV via fiber optic
technology.
Every facet of building security—including access control,
intrusion detection, video badging, and closed circuit television—
is linked to a common database and controlled from a single
operating platform. Security personnel monitor various input
devices such as readers, keypads, door contacts, and request to
exit switches, as well as control door locks, alarms, and other
output devices. Special benefits of the new system include the
ability to communicate to all buildings and sites via fiber optic
cable for both monitoring and CCTV. Fiber optic lines were
required due to the high incidence of lightning strikes in the area.
The fiber optical lines, by nature, provide electrical isolation
between system components around the site.
The CCTV system is integrated with the intrusion detection
and duress alarms to provide instantaneous camera call-ups upon
alarm, and the system allows National Park Service staff the ability
to visually monitor areas more efficiently. Additional duress and
intrusion detection alarms allow instantaneous notification of the
Resource Management and Visitor Protection staff in case of
trouble. Vehicular traffic is limited by the new system such that
only authorized vehicles can reach sensitive areas of the memorial.
Access to non-public facilities is controlled by proximity cards and
PINs to exclude the general public from these areas. Perhaps the
biggest concern at national monuments is the threat of someone
leaving behind an explosive device. Proper video coverage of
public areas within or around a monument can be used to watch
for suspicious activity.
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SURFACE TRANSPORTATION
The Federal Transit Administration National Transit Database
reported a total of 132,293 criminal incidents related to surface
transport in the year 2000, including 12 homicides. Data reported
included approximately 450 of the largest transit agencies and
only included incidents where arrests were made. The crimes
reported included forcible rape, robbery, aggravated assault,
larceny/theft, and motor vehicle theft. Public transportation such
as buses, light rail, subway systems, and platforms not only require
monitoring but also greater intelligence for preventative efforts.
Escalation of an event can become acute in these environments
because of the vast amounts of people that may be involved. Making
public transportation safer and more secure for riders and reducing
exposure of municipalities to liabilities is a goal shared by many.
Transit agencies have scrambled to beef up passenger security by
looking to new technology, including mobile video surveillance
systems. These systems can monitor and record onboard events,
collect footage from inside and outside, store operational data, and
generally improve the quality and safety of public transportation.
The Santa Clara Valley Transportation Authority (VTA) of
San Jose, CA has cameras on up to 630 light rail vehicles and buses
throughout the Santa Clara County area. The Charlotte Area
Transportation System (CATS) Authority project includes systems
on 285 buses. Each bus is fitted with a six-camera system that
captures both video and audio data. CATS uses the system for
three main functions: accident investigation, driver training, and
enhancing security on the fleet. Two cameras tape the exterior of
the vehicle—one views the area in front of the bus and the other
down the passenger boarding side. Inside the bus, cameras are
positioned to see boarding, fare payment, and areas down the bus
and toward the rear of the bus. San Francisco Municipal’s system
includes coverage that helps deal with issues such as vagrants
using buses as shelter, vandalism, unauthorized access to buses
while in the depot area, and flagging of specific incidents and/or
passenger counts for insurance review.
During a testing phase on VTA vehicles in California,
over 200 arrests were made for vandalism alone. The system
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continuously records and holds approximately 80 hours of video.
When an incident occurs, drivers are able to indicate that a recording should not be overwritten and security personnel can pull
video nightly or go on site to an incident and view video for fast
analysis.
THE HEALTH CARE INDUSTRY
Many security professionals have horror stories such as stolen
cars, employee attacks, vandalism, and expensive equipment
being stolen. Babies missing from the maternity ward is one that
most security managers do not have to worry about. University
Health Care expanded their existing security system and integrated it into a PC based system that allows them to monitor the
entire hospital. Not a moment goes by that vulnerable spots in the
facility aren’t being monitored and recorded. In addition, the new
camera system does more than just watch, it reacts. When the
camera senses motion in an area where there shouldn’t be any, it
alerts the appropriate personnel.
The original job, completed in August 1999, consisted of a
closed circuit surveillance and panic alarm system. Since then, an
extra parking deck with nine additional pan/tilt/zoom cameras
and several panic alarms has been added to the system. Since the
installation of the parking deck cameras, University was able to
record a car theft and reduce loitering instances. Also, employees
of University Health Services have a higher sense of safety while
at work. University now has the option to replace their aging
access control system and integrate it with the new closed circuit
surveillance and panic alarm system. This will allow University to
have one completely integrated security management system.
FAR AWAY PLACES
A new digital system has been set up at the Caribe Hilton Hotel
and Casino of Puerto Rico primarily to monitor access/egress
to and from hotel facilities. All major entrances and exits are
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monitored, and secondary stages of surveillance include access
points to ballrooms, meeting rooms, the main driveway, and all
public areas of the lobby, including guest elevators at the lobby
level. “Back of the house” sensitive area surveillance includes the
loading dock, service corridors, accounting office, general cashier,
general storeroom, and drop safe room. Finally, the system covers
the inside of all service elevators.
Full 24 hour surveillance of the above areas serves as a deterrent for criminal activity throughout the property, simultaneously
providing guests and associates with the feeling of being in a safe
and secure environment. It also provides the security department
with a powerful crime prevention tool and the ability to record
accidents and/or incidents that may occur throughout the property. Damage to cargo and service elevators, in most cases done
by delivery persons and outside contractors, has been eliminated.
Since the cameras’ installation, the hotel has only experienced two
incidents of this nature. In each case, the events were caught on
video and the hotel was able to identify those responsible and
collect payments for the damages.
SECURITY AT THE SECURITY CONVENTION
The folks who attended the 2002 ASIS seminars and exposition at
the Pennsylvania Convention Center were lucky enough to enjoy
the award winning blend of classic style and modern technology
brought together within the 1.3 million square foot facility. What
they may not have known was that a new digital video system was
installed at the Pennsylvania Convention Center as part of a security upgrade. The primary reason for the system is to ensure the
safety of the staff, convention center attendees, and clients as well
as to combat typical convention center thefts: laptops, bags, and
purses. Spokesman for the Center said that almost all incidents
prior to installation of the new system went unresolved by local
authorities and/or convention center security personnel. The cataloging of tapes was highly ineffective and investigation was difficult. Using the old recording system, there was no indication that
the analog recorders were ever used or useful for post-incident
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investigations. Once the new digital system was installed, all incidents that occurred within camera view have been resolved, including five major incidents. Major incidents would involve items
valued in excess of $50,000 per incident. In fact, the Convention
Center has received several letters from the Philadelphia Police
Department commenting on the usefulness in providing evidence
for prosecution of suspects involved in criminal activity in and
around the facility. The system has also proven to be a highly successful liability mitigation tool.
RETAIL SECURITY
As part of Home Depot’s growth philosophy, the Atlanta based
retailer recently launched a $250 million store remodeling program
with the intention of streamlining store operations and redeploying gained efficiencies to improve customer service. Included in
the overhaul is the rollout of a new digital video surveillance
system that will provide a safe environment for customers and
associates, aid in combating identity theft and credit card fraud,
reduce in-house shrinkage, cut down on cash register errors and
other fraudulent actions, and work to eliminate shoplifting.
The new digital surveillance technology integrated with
Home Depot’s POS system enables the retailer to view individual
transactions as well as provide real-time, remote monitoring of
store operations from the company’s district offices or its headquarters in Atlanta. The platform is a software-based tool that
stores, organizes, and delivers digital images collected by surveillance cameras.
Approximately 100 cameras per store will monitor checkout
stands, receiving docks, store aisles, and various other parts of its
operations, including parking lots. With the new system, Home
Depot can actually e-mail law enforcement agencies with digital
photos or action sequences or evidence can be downloaded onto
a CD for transport or storage. While Home Depot is certainly not
the first retailer to use digital video surveillance, it is one of the
first of its kind to use a coordinated digital system throughout all
store operations. The end result will be approximately 40,000
Examples of Digital Video for Security
Figure 9-1
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Dome Camera In Retail Facility
video cameras in use to better monitor stores, reduce shoplifting,
and deter fraud.
It is an unfortunate fact that the “convenience” of convenience stores often accommodates both the consumer and the
criminal. For the consumer, convenience stores provide easy access
to groceries, prepared foods, gasoline, and other services. From
the perspective of the criminal, these stores offer easy access to
money. Convenience stores, like other establishments that deal
with merchandise and money, also offer the occasional temptation
for theft to employees. Digital video systems are making this kind
of crime much harder to conceal.
The use of digital video is not limited to security purposes.
With continuous digital recording, important marketing information can be gathered and disbursed to appropriate management
personnel or even consultants. In the case of a retail application,
pertinent data can be gleaned such as peak business hours, customer profiles, the attractiveness and attention getting quality of
displays or product arrangement. Inventory levels can be assessed
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and addressed from off-site and general facility appearances
appraised. Improved processes, marketing strategies, customer
satisfaction and retention, and improved sales are just a few
benefits possible.
With networked digital video, site management takes on a
new dimension. Not only can a store manager remotely inspect
the appearance of stores, displays, and inventory but the behavior
and presence of staff can also be monitored. If a store manager
suspects a cash register has been tampered with after closing, he
or she can retrieve and review video images of that cashier station
between certain hours and only when the register was opened. In
another example, a truck entering an off-limits loading area can
deliver an alert message containing video images.
Evaluations can more easily be made about the effectiveness
of the site layout as well as the efficiency of the staff to customer
ratios. Situations such as unsecured doors, wasted utilities, low
stock levels, erroneous product shipments, and inefficient workflows can all be documented and corrected. Improvements in personnel conduct and store appearance are immediate, and savings
related to improved site management alone should result in a
significant return on investment. Surveillance cameras have been
around for a long time in the retail industry, but digital technology
has increased its business benefits. Many liability suits can be won
with the evidence provided by a continuously recording digital
system if you have the ability to hand over authentic video
information.
CARS ON VIDEO
A provider of some of the world’s finest automobiles, located in
the heart of Coral Gables, Florida is home to a collection of cars,
ranging in price from $30K to more than $200K. A state-of-the-art,
three-story, 350,000 square-foot facility called The Collection
houses seven world-class auto franchises under one roof including
Maserati, Aston Martin, Ferrari, Porsche, Jaguar, Audi and Lotus.
The building is secured by an extensive access control system,
including biometric readers and integrated digital CCTV and
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communications systems. The CCTV portion contains 105 color
cameras plus five integrated PTZ color dome cameras, with five
monitoring and control locations. The entire system is networked
with five workstations that control all access points to the facility,
lock and unlock showroom doors on schedule, as well as control
the building elevators.
CITYWIDE SECURITY
City of London, Ontario turned to digital video technology as a
means of crime prevention and as a means to verify and respond
to criminal activities or other emergencies.
The plan officially began when a committee of elected public
officials, members of the city police department, and chairman of
a citizens committee initiated the “London Downtown CCTV
Project” to deter future crime in the downtown location. After
two and a half years of preparation, the cameras went live on
November 9, 2001.
The project is currently comprised of cameras equipped with
pan, tilt, and zoom capabilities installed at major intersections in
the downtown core of the city. The cameras are monitored 24
hours a day, 7 days a week at city hall, and can also be viewed
and controlled from police headquarters. The main function of the
cameras is to improve community safety, crime prevention, and
the desirability of the city as a place for shopping, business, and
leisure.
This system is unique in the fact that all controls and video
images are transmitted to the control station via wireless links.
This was necessary due to the lack of fiber optic or copper wire
available at the camera locations. Cameras are suspended from
traffic light poles on steel arms that also hold omni directional
antenna transmitters. These transmitters send the video and control
signal to a receiver atop a centrally located high-rise office tower
from which the signals are re-transmitted to city hall. At the camera
location, the video signal is converted to a digital signal so that it
can be transmitted over a wireless network. All cameras are being
digitally recorded to provide visual evidence if required.
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Preprogrammed tours are set up to view desired areas of the
streets. When an incident occurs or suspicious activity is noticed,
the operator will assume manual control and track the occurrence.
The cameras are able to scan 360 degrees in less than a second,
reading license plates at hundreds of feet and zooming in on a
designer logo on a shirt or a tattoo on an arm. If police intervention
is required, headquarters is alerted to view the camera and/or
respond with officers. In one case, three men suspected of beating
another man were identified and charged because they walked by
security cameras outside police headquarters minutes after an
assault a few blocks to the east.
A gas station robber was caught on video. The video was
released to The Free Press and New PL TV and within 24 hours, a
suspect was identified and charged with six robberies. Over all,
this system leaves the City of London with a greater feeling of
security and the police with an instant picture of incidents such as
fights, demonstrations, vandalism, and robberies.
GAMING SECURITY
Gaming has become a multi-billion dollar industry and it is inevitable that wherever there is an exchange of large amounts of
money, there is a need for security measures. Digital video systems
provide more than just security and surveillance to casino, hotel,
and resort management; they also provide some of the intelligence
necessary to making business decisions about how the facilities
are run. In a casino environment, surveillance is typically a reactive endeavor. Changing from a reactive to a proactive system
allows casino security to be alarmed on an event, and gives them
access to video data in seconds.
These tools can help to deter criminal activity such as card
counting while simultaneously monitoring all areas of the casino.
A small but growing number of casinos across the nation are
utilizing even a more sophisticated surveillance tool: facialrecognition software and databases. With this software in place, a
casino can look for known offenders automatically, record a
problem guest’s face for future reference, and even track high-
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161
roller guests throughout the facility, providing them with exceptional customer service. Gaming establishments all across the
nation are realizing that the latest digital surveillance technology
can better protect them against customer fraud, employee misconduct, and fraudulent claims.
FINANCIAL INSTITUTIONS
Financial institutions usually require an open architecture digital
video solution that can be installed on a network and also provide
a method to quickly send video data to law enforcement agencies.
Another requirement is a system that marries into existing teller
environments and the ATMs. Digital video technology provides a
perfect solution.
Networked digital video can provide on-site capture and offsite retrieval of video and security and remote accessibility allows
retrieval and administration over LAN/WAN, local, or modem
connectivity. In addition, networked digital video systems can
provide instant access for live monitoring of ATM atriums or in
cash counting areas, as well as quick access to stored video data.
It can also be configured to send alarm messages triggered by
specific events such as video motion detection, digital inputs, and
camera faults. When an event occurs, a message is sent with the
time of occurrence and a brief description.
SECURITY IN THE BAYOUS
At the mouth of the Mississippi River on the southernmost tip of
Louisiana lies some of the best fresh water, salt water, and offshore
fishing in the world. Cypress Cove Lodge and Marina is located
in this fisherman’s paradise. Not only will you find fishing,
hunting, occasional alligators, and scenic beauty at Cypress Cove,
but also state of the art security. The Cypress Cove complex consists of not only the lodge but also a full service marina and marina
store. The facility also provides 196 dry boat storage spots and 140
wet slips. The boat storage buildings, the store, and lodge all
require security surveillance.
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A remote digital video surveillance system was installed as
an adjunct to the 24 hour guards in place. A system with seven
cameras and one DVR is currently in place at Cypress Cove, which
the owners use to keep a close eye on employees and the general
management of the facility. There is a camera view of the fuel
pump area so that they can be alerted to chemical spills and assign
responsibility if they occur.
SECURING BUILDING SITES WITH SPECIALTY
SURVEILLANCE EQUIPMENT
Construction sites are often isolated and devoid of inhabitants on
holidays, weekends, and evenings, making them good targets for
thieves who want to pick up building supplies unnoticed and
unpaid for. In recent years, contractors nationwide have reported a
wave of thefts of everything from standard building materials,
tools, and appliances to heavy equipment and vehicles. These construction site thefts are resulting in millions of dollars in losses. The
upsurge in thefts is blamed on a building boom and the rising price
of materials. In Southern California, a unique digital video system
with night vision and license plate recognition technology is used
by one builder to assure that acts of material or equipment theft are
likely to be captured on video. By producing clear digital images of
the culprit in either day or night time, the theft is documented. By
retrieving the license plate number of the vehicle involved, the thief
is captured. After an incident of theft or vandalism, personnel who
are trained in finding evidence of the incident as quickly as possible
retrieve the stored digital data. Copies of the pertinent digital information are given to the customer along with a formal report of the
incident and still shots from the video images obtained. In most
cases, the information is given to local authorities who, with a clear
license plate number as evidence, usually have no problem locating
and convicting the perpetrators.
As is so often the case, the advantages of digital technology
are its multitude of uses. Several customers have some form of
broadband transmission, which makes images available for view
from various locations on site or off.
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Pieces and Parts
We know that digital compression is a method of converting information to a format that requires fewer bits and can be reversed to
a close approximation of its original state once transferred to a new
location. In the case of CCTV, this means that video can be digitized to a smaller form and therefore transmitted at a quicker
speed. An important fact to remember when considering cameras
for CCTV applications is that the final resolution quality will only
be as good as the weakest link in the system. In other words, if
you have high resolution capability from the camera but your
monitor provides a lower resolution, the monitor will determine
the resolution you receive. Do not make the mistake of assuming
that because you have high resolution capable cameras, you will
automatically receive high resolution images. Just like an automobile, all parts of the CCTV system must provide equal or similar
performance levels to achieve the overall goal. A superior motor
on a car with bad tires will not get you very far.
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CAMERAS
Traditional analog cameras convert light intensities into images on
light-sensitive film or tape. Digital cameras convert light intensities into discrete numbers for storage on an electronic medium,
such as a hard disk or flash disk. Like their analog counterparts,
a digital video camera captures a continuous stream of information, and a digital still camera captures a snapshot.
The job of the camera is to provide information from the site
via electronic signal, cable, or phone line to the viewer. The two
basic camera types are tube and chip. The use of the tube camera
has gradually decreased despite its lower cost and higher
resolution.
Advantages of the chip camera include fewer maintenance
requirements, better durability, longer life, resistance to lag and
bloom, and smaller size. The chip camera also produces a digital
signal that allows for freeze of action and digital motion
detection.
The camera location and environment will play an important
role in deciding on the type of camera you use. Placement of the
camera is also a determining factor, especially when it comes to
the evidentiary value of the images captured. Variations such as
whether the camera is located inside or outside, temperature
extremes, light levels and how the light levels may change are all
factors whether you are using analog or digital systems.
Charged Couple Device (CCD)
Tube cameras used to be the most commonly used type because
they are relatively inexpensive and well suited to most indoor
uses. They can be susceptible to damage from very bright lights,
making them less desirable for outdoor use. The Charged Couple
Device (CCD) cameras, sometimes called chip cameras, have
moved up in popularity as prices have come down.
A chip camera works as light passes through the lens and
forms an image on the CCD. The CCD is a semiconductor grid of
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thousands of pixels that produce an electric charge according to
the color and brightness of light passing through it. It is an integrated circuit containing an array of linked, or coupled, capacitors.
Under the control of an external circuit, each capacitor can transfer
its electric charge to an adjoining capacitor.
Light hitting the surface of the CCD causes it to free electrons
to move around and accumulate in the capacitors, providing a
black-and-white image from the light that falls on each pixel.
Repeating this process converts the entire contents of the array to
a varying voltage that is sampled and stored. Stored images can
then be transferred to a printer, storage device, or video display.
Advantages of the chip camera include fewer maintenance requirements, longer life, resistance to lag and bloom and resilience to
shock or vibration. They are also smaller and require less power
to operate. The chip camera also produces a digital signal that
allows for freeze of action and digital motion detection. CCDs are
characteristically sensitive to infrared light.
Infrared Cameras
Though technology has not yet achieved X-ray vision, infrared and
advanced thermal imaging runs a close second. The ability to see
in the dark, through smoke, fog, and certain natural obstacles such
as foliage brings infinite advantages for security, military, and fire
fighters. Infrared cameras are not dependent upon digital technology, but the advances in digital transmission and storage increase
their value tenfold.
Adding infrared capabilities to a video surveillance infrastructure provides both early detection and full visibility irrespective of the prevailing light levels or weather conditions. Infrared
radiation is heat radiation generally produced by anything with a
temperature above 10 degrees Kelvin (a unit of absolute temperature equal to 1/273.16 of the absolute temperature of the triple
point of water, which is equal to one Celsius degree). It has many
of the same properties as visible light, such as being reflected
or refracted. Thermal images are produced primarily by self-
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emission and by emissivity differences. Emissivity is a measure of
how much radiation is emitted from the object. Normally, object
materials and surface treatments exhibit emissivities ranging from
approximately 0.1 to 0.95.
A highly polished (mirror) surface falls below 0.1 while an
oxidized or painted surface has much higher emissivity. Oil-based
paint, regardless of color in the visible spectrum, has an emissivity
over 0.9 in the infrared. Human skin exhibits an emissivity close
to 1. Non-oxidized metals represent an extreme case of almost
perfect opacity and high specular reflectivity, which does not vary
greatly with wavelength. Reflection off of smooth surfaces such as
mirrors or a smooth surface body of water is known as specular
reflection, while reflection off of rough surfaces is known as diffuse
reflection.
Consequently, the emissivity of metals is low—only increasing with temperature. Vehicles that have a low-level emissivity,
such as automobiles, tanks, or aircraft, will normally emit thermal
radiation from their energy source while operating, making them
visible to thermal imaging devices. In other words, the hot areas
such as the engine and the exhaust system will be visible. The
same theory is true for vehicles that have recently shut down
because their engines are still warm.
Thermal Imagers
Thermal imaging is considered long range infrared and does not
require any additional lighting. Typically, the image produced is
a black-and-white image, where the hotter objects are whiter and
the cooler objects are darker. The heat sensing abilities of thermal
cameras allow them to easily identify intruders and other security
breaches at night. Thermal imaging has been proven to be a successful solution for common security needs such as:
●
●
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vision at night where lighting is undesired or unavailable
surveillance over waterways, lakes, and ports where lighting
options are impractical
surveillance in challenging weather conditions
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Thermal imaging devices extend normal vision by making thermal
heat visible. For example, burning charcoal may not give off light,
but it does emit infrared radiation, which is felt as heat. With
thermal imaging technology, the ability to see the burning coals
would be available even if the receiver (either human or mechanical) is too far away to actually feel the heat or actually see the
coals.
Image Intensifiers
There is sometimes confusion between thermal imaging technology and image intensifiers or I2 technology because the term “night
vision” is often applied to both. Night vision can be achieved by
intensifying the small amount of light present, even at night, from
the stars and the moon. A device based on this principle is called
an image intensifier (I2) or starlight scope (SLS).
Image intensifier uses have evolved from nighttime viewing
to fields including industrial product inspection and scientific
research, especially when used with CCD cameras (intensified
CCD or ICCD). I2 devices offer daylight-like conditions to the user
but do not mean the user will be able to detect objects normally
seen in daylight conditions.
An image intensifier does not work in total darkness. It does,
however, create a more realistic image than night vision because
it reveals the same type of image that the human eye sees. Not
based on temperature, I2 technology relies on amplifying available
light to detect objects and is often ineffective in extreme low-light
situations such as heavy overcast. Another disadvantage of I2 technology is blooming, which can occur if high intensity light in the
field of view saturates the sensor’s picture elements.
Digital Signal Processing/Digital
Signal Processor
The introduction of DSP in security surveillance cameras has
increased the flexibility of uses and the quality of the color image.
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DSP technology offers more consistent picture quality over a wider
range of lighting conditions. They can also provide features
such as programmable intelligent backlight compensation, Video
Motion Detection, remote set-up, and control and on-screen menus,
making them a good choice for complex surveillance conditions.
Digital video should be displayed at least at the same resolution
as the camera sending the images to avoid distortion.
DSP can either refer to digital signal processing, the term
used for processing signals digitally, or digital signal processor,
which is a type of microprocessor chip. A digital signal processor
is a programmable device and digital signal processing is exactly
what its name suggests, a method of processing signals digitally
using mathematical techniques to perform transformations or
extract information. A DSP chip is designed to carry out processing of up to tens of millions of samples per second.
Digital signal processing takes real-time, high-speed information such as radio, sound, or video signals and manipulates it
for a variety of purposes. The goal of digital signal processing is
to use the power of digital computation to manage and modify the
signal data. DSP systems translate analog signals into a digital
approximation, but DSP used in cameras do not convert digital
signals to analog signals.
LENSES
Several questions influence the choice of a lens, which determines
the area viewed by the camera and makes adjustments based on
light conditions. Will the camera be viewing a wide area fairly
close to the camera? Will images from a narrow area far away
be important? What are the lighting conditions, and will they
change?
Format is the size of the imaging area on the tube or chip and
the term that describes the size of the lens to be used for various
image requirements. The focal length of the lens along with format
determines the field of view captured. Focal length of the lens
determines the field of view. A short focal length will produce a
wide view and a long focal length, a short view. Lens speed is the
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light collection ability of the lens. The iris diameter is measured in
f-stops: f/1, f/1.4, f/2, or f/2.8. Lower numbers are faster and let
in more light, while the higher numbers reduce the light. It is
necessary to understand the expectations of the camera and its
environment before choosing a lens.
C-mount and CS-mount
There are two kinds of lenses commonly used with high-speed
video equipment, and they refer to the two standard mountings
used for connecting lenses to cameras. One is called C-mount and
the other one is called CS-mount. C-mount lenses are used for
larger image sensors. The CS-mounts are used for the more
compact image sensors.
The difference between the two standards has to do with
focusing. Every lens is designed to be a certain distance from the
imaging element, whether that imaging element is a video sensor
or film. This distance specifies the focal plane. C-mount lenses are
designed for a focal plane distance that is 5 mm greater than the
same dimension for CS-mount lenses. In other words, C-mount
lenses are designed to be 5 mm farther from the sensor than CSmount lenses.
If you have a C-mount camera, you must use C-mount lenses.
If you have a CS-mount camera, CS-mount lenses work fine with
your camera. C-mount lenses will work with your CS-mount
system, but only with an adapter. The adapter is actually a spacer
with both male and female 1–32 threads that moves a lens 5 mm
farther from the camera. A lens creates an image of a certain size
on its focal plane. That size is part of the lens specification and is
expressed in terms of the sensor diagonal dimension. It is possible
to use a lens designed for a larger sensor (to use a 1-inch lens with
a 2/3- or 1/2-inch sensor) but using a lens designed for a smaller
sensor (to use a 1/2-inch lens with a camera with a 1-inch sensor)
will bring unsatisfactory results, specifically a reduction of resolution and image size.
New lenses are available with a choice of manual DC iris and
have a variable focal length setting. There are versions with 4-pin
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and 6-pin connectors for DC-controlled iris. The advantage to
system designers or installation engineers is that they no longer
need to calculate the field of view and the required focal length in
advance. A rough estimate is sufficient. Upon installation, the
focal length of the selected lens is manually adjusted to suit the
situation, before focusing and setting the iris to meet ambient
lighting conditions.
Varifocal
Varifocal lenses are the most flexible for applications requiring a
wide range of focal lengths. Focal length adjustments are made by
turning a dial. A limited number of varifocal lenses will cover a
wide range of applications, which would have required a much
larger number of lenses with fixed focal length.
Auto-Iris Lenses are designed for outdoor use or any applications with variable lighting conditions. They are available in C or
CS Mounts from super-wide angle to telephoto (depending on the
application use), DC and Video types. The DC type is more economical and designed for the newer CCD cameras, which incorporate ALC (Automatic Level Control) circuitry of the camera.
As in every technology, many pieces determine the success
of the whole, and this is true in video technology as well. Lens
determination is an essential component of a system regardless of
its objective. It will be well worth the time involved in choosing
an appropriate lens for your application in order to achieve the
success desired.
ILLUMINATORS
When cameras are used outdoors or in low light areas such as
parking garages, there is not always enough light to provide a recognizable image. Adding lights may be an option but is not always
possible. When this is the case, other devices may be used.
Infrared illuminators transmit infrared light, which can be
used to enhance the video quality. Infrared light, while not visible
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to the human eye, is within the spectrum of useable light for
cameras. With monochrome cameras, the light emitted from an IR
illuminator provides enough light to enhance the picture quality.
Most color cameras utilize an IR filter, rendering the illuminator ineffective. If an IR filter were not used with color cameras,
the image colors could be drastically affected - particularly during
the day. For example, on a hot summer day a black car would be
much hotter than a lighter colored car. The heat given off by the
surface of the black paint causes the video image to appear as a
much lighter color.
SWITCHING EQUIPMENT
In many cases involving CCTV surveillance, a user will want to
view more than one camera at the same time. Adding a monitor
for each camera (which is what casinos used to have to do) can be
extremely expensive in and of themselves as well as in regards to
the space needed to mount them. Switchers allow a user to manipulate several camera views on one monitor. There are several
options for switching available.
Bridging Switchers
A bridging switcher can display a single camera on one monitor
and at the same time display sequencing cameras on a second
monitor, making it possible to view a continuous sequence of
cameras on one monitor and one specific camera on a second
monitor.
Multiplexers
Multiplexers have been around for quite some time and are used
to consolidate several communication channels into one channel
of data. They allow an operator to view images from up to 18
cameras on one screen. Today there are dozens of brands and
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configurations to choose from. The multiplexer allows multiple
signals to be transmitted simultaneously across a single physical
channel and process the output from multiple cameras to a monitor
or recording device, providing the ability to display the images
from multiple cameras on one monitor. Images can be reviewed
in a variety of screen formats, but all have to be played back
through the multiplexer.
Most multiplexers are either simplex or duplex. Simplex
records exactly what is seen on the monitor. A duplex records all
camera images, regardless of what is being viewed on the monitor,
and allows for review of any particular camera image by itself.
Duplex multiplexers also allow the viewer to review recorded
images without hampering the monitoring or recording of current
scenes. A duplex multiplexer is useful for applications where
monitoring is a key part of the system function and video tapes
need to be viewed regularly.
Other multiplexers offer priority recording using motion
detectors and video motion detectors. There is a distinction
between the two: motion detectors respond to any change within
its radius of detection such as temperature, pressure, or sound.
Video motion detectors respond to any change in pixels on the
screen.
Interleaving is another advanced feature that prioritizes
sequential viewing based on a high activity area or detected
motion. The priority view is seen more frequently in a sequence
of views than other camera views of lesser importance.
Matrix Switchers
A matrix is a logical network configured in a rectangular array of
intersections of input and output channels. A video matrix switcher
is a device capable of interconnecting many components in a
variety of combinations. This switcher allows any one of the inputs
to be switched to any one or all of the outputs. In other words, it
can switch more than one camera, VCR, video printer, or other
similar device, or to more than one of these devices at once.
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MONITORS—MORE THAN MEETS THE EYE
We are no longer limited to the constraints of the human eye. Now
we can literally take a live or moving scene and transport it to
another room, another state, and even another planet using the
magic of digital video. Enter the monitor.
The resolution of a monitor is indicative of how many pixels
it will display. Generally, more pixels mean better resolution. The
number of colors that can be displayed at one time is limited by
the amount of video memory installed in a system. Another classification of monitors depends upon the type of signal they accept,
i.e., analog or digital. This can be a confusing because calling a
monitor analog or digital refers to the type of color signals it uses
although it may actually have either analog or digital controls. The
size of the display area will affect the resolution in that the same
pixel resolution will look better on a smaller monitor and fuzzier
on a larger monitor because the same number of pixels is being
spread out over a larger number of inches. A good example of this
phenomenon can be seen by using a copy machine to repeatedly
enlarge a picture. Your first few enlargements will look pretty
good, but eventually the larger the picture the less definition it will
have.
The relationship of width and height of a video image is
called its aspect ratio. When an image is displayed on different
screens, the aspect ratio must be kept the same to avoid stretching
in either the vertical or horizontal direction.
CRT Monitor
Cathode-ray tube (CRT) technology has been used in most televisions and computer display screens until recent advances in flat
screen technologies have made these more easily available and
affordable. A CRT works by painting an electron beam back and
forth across the back of the screen. Each time the beam makes a
pass across the screen, it lights up phosphor dots on the inside of
the glass tube, which then illuminates the active segment of the
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Figure 10-1
CRT Monitor
screen. Phosphors are chemicals that produce light when excited
by electrons.
Monitors can actually be affected by where they are located
on the Earth, because the Northern and Southern hemispheres
have different magnetic fields. CRT monitors are manufactured
specifically for whatever hemisphere they are going to be used in.
These magnetic fields can have an effect on CRT monitors because
they work by moving electron beams back and forth behind the
screen. LCD monitors are not affected by this phenomenon. CRT
monitors cost less and produce a display capable of more colors
than LCD monitors do. See Figure 10-1.
LCD Monitor
A liquid crystal display is made up of an electrically-controlled
light-polarizing liquid trapped in cells between two transparent
polarizing sheets. The polarizing axes of the two sheets are aligned
perpendicular to each other, and each cell is supplied with electrical contacts that allow an electric field to be applied to the liquid
inside. LCDs are non-organic, non-emissive light devices—they
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Figure 10-2
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LCD Monitor and CRT Monitor Compared
do not produce any form of light but instead block light that is
reflected from an external source. Some users report lower eyestrain and fatigue due to the fact that LCD displays have no flicker.
One of the biggest advantages of LCD monitors is that they are
compact and lightweight. See Figure 10-2.
The Digital Display Working Group (DDWG) is an open
industry group lead by Intel, Compaq, Fujitsu, Hewlett Packard,
IBM, NEC, and Silicon Image. The objective of the Digital Display
Working Group is to address the industry’s requirements for a
digital connectivity specification for high-performance PCs and
digital displays.
Plasma Display Monitor
The different states of matter generally found on Earth are solid,
liquid, and gas. Sir William Crookes, an English physicist, identified the existence of a fourth state of matter in 1879, which Dr.
Irving Langmuir, an American chemist and physicist, called
plasma. Energy is needed to strip electrons from atoms to make
plasma. The energy can be of various origins such as thermal,
electrical, or light (ultraviolet light or intense visible light from
a laser).
Plasma can be accelerated and steered by electric and magnetic fields, which allows it to be controlled and applied. In a
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plasma display monitor, light is created by phosphors that are
excited by a plasma discharge between two flat panels of glass.
The use of phosphors, as in CRTs, limits their useful life to 20,000
to 30,000 hours.
LCOS Monitor
Liquid Crystal on Silicon (LCOS) is relatively new technology that
is a mixture of micro mirror and liquid crystal technologies. LCOS
devices can be smaller and are easier to manufacture than conventional LCD displays and have higher resolution.
OLED Monitor
Organic light emitting diode (OLED) technology uses substances
that emit red, green, blue, or white light. Without any other source
of illumination, OLED materials present bright, clear video and
images that are easy to see at almost any angle. When used as
pixels in flat panel displays, OLEDs offer advantages over LCDs
that need backlighting, including lower power consumption,
greater viewing angle, lighter weight, and quicker response. The
OLED screen appears unusually bright because of their uncommonly high contrast.
Touch Screen Technology
Because touch screen technology greatly simplifies the computerhuman interface, input technologies are moving from hardwarebased buttons, membranes, and keyboards to software-based
models. This software-programmable approach affords numerous
benefits for a user-friendly interaction. There are three basic types
of touch screen technologies: capacitive, resistive, and surface
wave. Each has its own strengths and weaknesses.
Capacitive touch screens use a glass overlay with a thin
metallic coating over the surface of the display screen. Touching
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the overlay surface causes a capacitive coupling with the voltage
field, drawing a minute amount of current to the point of contact.
Capacitive touch screens are typically brighter and clearer than
resistive screens, but not as bright or clear as surface acoustic
wave.
Five-wire resistive overlay technology consists of a glass
overlay with a thin metallic coating, over which a layer of polyester is placed. The polyester has a similar metallic coating on the
interior surface. Tiny spacer dots of non-coated polyester prevent
the two surfaces from contacting each other. A final hard coating
is usually applied to the external surface of the polyester to reduce
damage from sharp styli. A current is pulsed through the glass
overlay along the x-axis and then the y-axis. When a finger or
stylus presses the two layers together, the current is shunted and
the control electronics determine the coordinates of the touch location, which are then transmitted to the host computer.
Surface acoustic wave is based on transmitting acoustic
waves across the surface of a glass overlay placed over the display
surface. A transducer mounted on the edge of the glass emits the
acoustic wave, which travels on the surface of the glass overlay.
When a stylus such as a finger comes into contact with the wave,
it decreases the amplitude of the wave motion, absorbing part of
the wave. This is detected by the control electronics and determines the touch location.
As these few elements of monitor technologies point out, the
science behind video display devices can be somewhat complicated. Adequate research and investigation should be given to the
selection of these devices just as is given to other components of
the video system.
PRINTERS—WHAT YOU SEE IS WHAT YOU GET
The roles of printers in conjunction with security applications,
from printed incident reports and identification cards to the replication of video images, require reliable products that produce the
highest quality printed media. Computer printing moved through
several stages of innovation, from the first daisy-wheel and dot
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matrix (or impact printers) to common use of the non-impact
printers: ink-jet, laser, thermal-transfer. Now, the standard is
digital printers.
The printer is especially important in access control badging
applications where the exodus from conventional photographicbased ID badging toward digital imaging and printing has resulted
in a real ability to integrate ID badging with CCTV quality ID
badge. Today’s digital printers allow for the ability to integrate
information contained on the badge into the overall access control
system. Personalized card templates are sent to a desktop card
printer where personal identity information gathered during the
capture process is printed or stored on the card in a single-pass
operation. Photos, text, bar codes, and other graphics are printed
on one or both sides of a card. Biometrics, cryptographic data, and
other machine-readable information is loaded into smart cards,
encoded onto magnetic stripes or printed as bar codes. Finally, the
printer applies a polyester overlay to enhance card security and
durability.
It is obvious that many details are involved in the choice of
printer for the application. In order to make the best selection for
your job and budget you need to determine the goal of your
printer and proceed with careful research of products and
companies.
11
Integrating Digital Video
with Other Technologies
One of the most interesting aspects of the security industry is the
multifaceted utilization of its products and services. It is comparable to the communications industry in its versatility of end
users and uses. Security products and services are found in many
areas—residential, commercial, public service, transportation,
industrial, and military. Not only does the security industry supply
a limitless market, it also combines with many cross markets to
create efficiency and economy of products and services.
“Systems Integration” became a security industry buzz word
in the late 1990s and post Y2K era. Technology justified the term
by making it possible to interconnect, interface, and integrate subsystems of countless varieties, all of which resulted in a marked
increase in security systems sales. Security system dealers and
installers became more commonly known as systems integrators,
and integrated security systems simplified both maintenance and
operations, resulting in a reduced total cost of ownership.
Customers want integration for the advantages it provides,
but barriers like custom and proprietary backbones of existing
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equipment have to be considered. Historically, manufacturers
believed having a proprietary protocol protected them from competitive vendors, but today, the opposite is true. Customers are
demanding open architecture and common protocols in order to
reap the benefits of integration such as the cost savings incurred
from streamlined business processes and increased efficiency.
The Security Industry Association (SIA) has identified the
need to clarify systems integration and has created The Systems
Integration Industry Group (SIIG), a group of security professionals who are tasked with defining integration and establishing
methods and standards for the integration sector. The mission of
SIIG is to create an environment where members of the Security
Industry can gather to communicate the needs facing those who
are active in the integration sector.
INTEGRATED VERSUS INTERFACED
The term integrated is often used loosely to describe the result
when two or more systems are connected to work in conjunction
with each other. Systems are often described as integrated when
they should more accurately be described as interfaced. When a
system is interfaced with another system, an event on one system
can trigger an event on another system. For example, a door
opening on an access control system could trigger a camera to pan,
tilt, and zoom to achieve better coverage, or could change the
record rate of the images from the appropriate camera. See
Figure 11-1.
When a system is integrated, similar triggers have the same
effect, but the integrated system goes a step further. For example,
a card presented at an access control door may cause the appropriate camera to pan, tilt, and zoom for better coverage. It might then
display a live image from that camera along with the badge
holder’s picture for verification. With the interfaced system, the
video would be displayed on one monitor or workstation, while
the access control data is displayed on another. With the integrated system, an operator could potentially deny access through
the door if the person in the live image presenting the card does
Integrating Digital Video with Other Technologies
Figure 11-1
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Interfaced Systems Must Be Monitored Separately
not match the image on file as the authorized badge holder. See
Figure 11-2.
Thanks to advances in compression and telecommunications
technologies, remote video can combine several security systems
into one that is both competent and cost effective. The basic remote
system is composed of CCTV cameras installed at locations where
unauthorized intrusion, employee theft, or other criminal activities may occur. A video transmitter is integrated with the CCTV
system that connects to a receiving site. This connection may be
initiated by the sending or the receiving location, either manually
or by automatic alarm triggers. In the case of an alarm trigger,
strategically placed alarms will alert the receiver of security
breaches and begin providing live video, audio, and in some cases
specific data about the incident as it is occurring. An audio feature
can allow a receiver to announce his or her presence and inform
perpetrators that they are being observed and recorded.
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Figure 11-2 Integrated Systems Are Monitored Through a Single
User Interface
One of the greatest advantages of integrating video is alarm
verification. When an alarm is activated, the receiver can immediately view scenes of the alarm location, assess the information, and
take appropriate actions to alleviate the situation. Unnecessary
calls to law enforcement are virtually eliminated. Another distinct
advantage of remote video is that information is stored, providing
documentation of events.
BIOMETRICS
Biometrics is the science and technology of establishing the identity of an individual by measuring physiological or behavioral
features. Because it can be easily incorporated into surveillance
applications, facial recognition technology for identification and
authentication is experiencing significant growth in both the public
and private sectors.
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According to the National Defense University in Washington,
D.C., biometrics refers to the utilization of measurable physiological and/or behavioral characteristics to verify the identity of an
individual. In an authentication system, the goal is to confirm
whether the presented biometrics match the enrolled biometrics of
the same user. Biometrics falls into two categories: physiological
and behavioral. Common physiological biometrics authentication
includes such things as face, eye (retina or iris), finger (fingertip,
thumb, finger length or pattern), palm (print or topography), hand
geometry, and wrist, vein, or thermal images. Behavioral biometrics includes behaviors such as voiceprints, handwritten signatures,
and keystroke/signature dynamics.
These systems identify individuals by comparing known
images to live images from a camera. This means that the camera
system now becomes an integral part of the access control system,
with the live images helping to determine whether access is granted
or denied. By adding multiple cameras, it is then possible, in
theory, to search a building for a specific person based upon the
last known location. It is also possible to search crowds of people
for specific individuals, such as those stored in terrorist or criminal
databases.
When facial recognition is used for access control, the person
requesting access usually must initiate a comparison, such as by
presenting a card to a card reader. The facial recognition system
then only has to do a “one-to-one” comparison, comparing the live
image to the image on file for that card holder. This is also known
as a verification test. When facial recognition is used to monitor
crowds, there is no means of initiation and the system then is
performing a “one-to-many” comparison. The live image of the
person in question must be compared to the entire database of
images to determine if that person is in the database.
A form of thermal imaging called a thermogram reads the
facial heat pattern using an infrared camera. The identification
process begins by capturing the multitude of differences in each
human face. Every human thermal facial image is unique to an
individual and remains consistent from birth through old age.
Even identical twins do not share the same infrared image. The
amount of heat emitted from an individual’s face depends on nine
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factors, including the location of major blood vessels, the skeletal
system thickness, and the amount of tissue, muscle, and fat in the
area. Presently, the most accurate biometric besides thermal is an
iris or retina scanner, which is significantly more expensive than
face, finger, or palm recognition systems. It is also harder to fool.
ACCESS CONTROL
To understand the advantages of incorporating video with access
control, it is important to first understand the purpose of the access
control system. Access control is used primarily to allow or deny
access to individuals through controlled and monitored points
within a building. Typically, employees or others who are meant to
have access to certain rooms, areas, or buildings are issued cards
that must be presented at card reader locations to obtain entry.
Typically, this card is used as an identification badge; therefore it
contains employee data and often a photograph of the intended
cardholder. The card also carries information about any restrictions
that may apply, such as when and where entry is authorized.
Access control card systems range from inexpensive, stand
alone systems where the microprocessor is located in the door
without recording capabilities to more expensive systems which
link multiple doors to a central computer. When a card is inserted
into the latter type of access control unit, information from the
card is sent to the computer where validation and recording functions take place. The control of access is performed by a card
reader. Choices of card readers generally include proximity,
weigand, magnetic, or bar code.
Proximity readers, as the name implies, depend upon the
card’s proximity to the reader. The most popular of these readers
work when a card is presented within approximately five inches
from the reader. There are readers that will work from a distance
of three feet. The main advantage to using proximity is the ease
of use—the user need not stop and insert the card into the reader
but merely make sure that the card is within the prescribed ranged
of proximity. In some cases, the card itself may even remain in a
purse or wallet while activating the reader.
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Weigand card technology consists of a series of specially
treated wires, which are embedded in each card. These treated
wires possess unique magnetic properties. When the card passes
through the reader, a sensing coil picks up this unique signature
and transmits it back to the controller.
Magnetic cards are encoded with information that is read by
swiping the magnetic stripe through an appropriate card reader
that senses the code. The process used to make magnetic cards is
relatively simple, consisting of a stripe, which is a coating of iron
oxide or other substance that can be magnetized and demagnetized. Some magnetic stripes require more coercivity than others.
Coercivity is the strength of a magnetic field required to record or
change data on the magnetic strip. Everyday magnets can erase a
low-coercivity magnetic stripe; those with high coercivity are virtually non-erasable.
Bar codes are graphical representations of information
encoded within a series of bars and spaces. All bar codes have
certain bar code patterns which tell the reading device when to
start reading the bar code.
The weak link in a standard access control system is often the
lack of verification of who is presenting the card at the reader. If a
card is lost or stolen, the card reader will still function when the card
is presented until it is disabled in the database. Biometric devices
can help to eliminate the possibility of using a stolen card, but they
cannot always verify that an employee is not entering under duress.
Some devices will have the possibility of using a different body part
if under duress, such as using the right eye instead of the left on an
iris recognition reader. If the employee forgets, however, it is possible to have a false duress read or a missed duress read.
Adding video coverage at access control points can enhance
the system in several ways, depending on how the system is monitored. It is most advantageous when the access control system is
monitored in real time by an active protective force. When this is
the case, an operator can verify that the card being read is in the
possession of the rightful owner and that the cardholder is not
under duress.
With a system that is integrated in this manner, an active card
read will automatically display the proper camera on the monitor
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that shows the door that is being accessed. In addition, the badge
photo that is in the database can be displayed directly next to the
live image, allowing the operator a comparison of the person at
the door and the person authorized to use the card presented.
Video integration can also display live camera views for the
operator in other situations. An attempted entry with an invalid
card or a card that is presented outside of the authorized access
times can cause the appropriate camera to be brought up, allowing
for a live assessment. With an integrated system, it is also possible
to search for specific things, such as an individual cardholder.
For example, if an employee is suspected of taking something
such as a laptop, the investigator can search for the associated
employee to see which doors he or she accessed. The investigator
will then have a reduced amount of video to review to see if the
employee can be seen leaving with the item. If the access control
system requires personnel to use a card reader to exit (read in/
read out or anti-pass back configurations), the investigator can go
directly to video of the specific time that the employee exited.
Many central stations now have the ability to view live video
when an alarm occurs, thus allowing them to make an informed
decision prior to dispatching first responders. If the intrusion
detection system sends an alarm to the central station indicating
that a specific entrance has been breached, the operator can access
live video to visually check the situation. If all appears normal, a
review of the time immediately prior to the alarm can be done to
see what may have caused the alarm to be triggered. If the video
still shows nothing unusual, the operator may determine that a
false or nuisance alarm has occurred and choose not to dispatch
authorities. Usually, in this case, an owner or designated contact
is summoned to take appropriate actions.
PERIMETER PROTECTION
The level of protection provided for the protection of a building
or area is determined by the level of risk from intrusion and is
often comprised of several different, complimentary layers of protection. Perimeter protection can include any combination of things
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Figure 11-3 Mobile surveillance
tower from P.I.C.S (Portable Intellegence Collection System)
like bollards, security fencing, barriers, turnstiles, doors, bars,
grilles, motion detectors, PIR, open ground electronic protection,
or radio frequency intruder detection. The addition of video
surveillance cameras at the perimeter can make a significant contribution towards tightening the whole security system. See
Figure 11-3.
Video technology is commonly used to enhance perimeter
security at correctional facilities. Video technology not only
improves security but also replaces the need to man gun towers
and allows for a reduction in armed perimeter patrols. Electronics
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have, in many cases, entirely eliminated the need for towers and
the construction costs associated with them. The strategy has been
to strengthen the entire perimeter with double fences bristling
with electronics and have one or two patrol vehicles (rovers) constantly circling the facility with armed officers. As a result, staff
previously assigned to these posts could be shifted to other, more
critical areas.
External active infrared detection has been in use for perimeter protection since the late 1920s. These detectors utilize active
infrared beams to detect unauthorized entrance or movements
through an invisible barrier. An active infrared beam, also called
a photoelectric beam, is a sensor that transmits a focused infrared
beam, which is received by a photocell and responds to an interruption of the beam. Active infrared detection is susceptible to the
false alarm.
Video surveillance installed at many sites using active or
passive infrared detection can be effective in some cases, but
verification of alarms at external sites especially can be hindered
by weather and light conditions. Unless all of the cameras are
equipped with thermal imaging devices, some scenes will necessarily be missed or unidentifiable. Another difficulty is pinpointing the exact location of an alarm. With infrared beams capable of
reaching in excess of 200 meters, the result is a potential intruder
located anywhere within a 200 meter zone.
12
More Digital Video
Applications
Law enforcement facilities and correctional institutes are primary
applications for digital video surveillance systems. Video is used
for a variety of purposes in these facilities including security, evidence of brutality against prisoners, videoconferencing, and even
for the provision of medical care via telemedicine technology.
Surveillance levels depend upon the security level of a facility.
These levels are minimum, medium, maximum, and super max.
The higher the level of security, the higher the number of cameras
installed. A super max facility has virtually no area outside of
CCTV view.
Prison visitors are not exempt from the auspices of video
technology. CCTV is often used in prison visiting rooms, for
observing treatment programs, and for auditing mandatory drug
testing of prisoners. This helps to minimize the time required to
clear visitors into and out of correctional facilities as well as reduce
the number of corrections officers involved in visitor processing.
When a prison utilizes this type of system, a visitor must pass
an authentication process before being allowed to visit a resident.
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During this process, the officer may be viewing a live video display
on the PC screen from a CCTV camera. The resident’s information
is displayed, logged on a printed report, and saved in the central
database. The visitor comes to the secured door and keys in their
visitor identification number. A valid number will bring up the
visitor’s image on the correction officer’s screen. The screen also
displays a list of approved residents for this visitor. At this time,
an indication is given if visitation privileges have been revoked.
The live video can be compared to the database image displayed
on the screen where remote operation is required. The visitor
states which resident or residents they wish to visit and access is
either confirmed or denied.
An important aspect of video technology is its impartiality.
Video cannot take sides; it can only display events as they actually
occur. For this reason, video is often the advocate of the victim.
Numerous opportunities are available for using this technology in a correctional facility including employee training, business
meetings, court hearings, and parole or deportation hearings.
Videoconferencing and telemedicine technologies reduce the need
to transport dangerous prisoners. Telemedicine programs offer
significant safety, security, and cost advantages to correctional
facilities while being able to provide the services of specialists not
readily available to incarcerated individuals.
Public safety personnel around the nation are starting to use
basic technology tools such as laptops, PDAs, and Automated
External Defibrillators (AEDs). In 2004, Washington, D.C. launched
the nation’s first broadband data network for emergency crews,
an important step toward arming rescuers with the latest communication technology. High-speed wireless networks allow
emergency room doctors to see live video of a patient still in the
ambulance or police helicopters to stream live video from the air
to patrol cars on the ground. The technology enables all rescuers
to talk directly to each other.
Telemedicine
Telemedicine has been defined as the use of telecommunications
to provide medical information and services. It may be as simple
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as two health professionals discussing a case over the telephone
or as sophisticated as using satellite technology to broadcast a
consultation between providers at facilities in two countries using
videoconferencing equipment. The first is used daily by most
health professionals, while the latter is used by the military, some
large medical centers, and increasingly by correctional facilities.
The University of Texas Medical Branch at Galveston was
one of the original programs to begin providing services to inmates
and sees over 400 patients per month. The foundation of the UTMB
telemedicine network is a scalable, ISDN network operating over
leased T1 lines. Once the technology was in place and real-world
applications identified, the rollout began. One application linked
12 remote sites to UTMB to provide medical care for special-needs
children in areas where medical technology and expertise were
not readily available. The telemedicine solution included a virtual
exam room with a video interface designed to be simple enough
for medical personnel to operate, so that the bulk of their
time could be spent treating patients, not manipulating video
equipment.
Major specialties using the network are neurology, psychiatry, orthopedics, dermatology, and cardiology. The feedback from
both patients and physicians has been positive, with access to
specialty care and saved travel time cited as the most important
benefits of the encounters. Using a variety of specialized patient
cameras, comprehensive patient examinations can be performed,
including diagnostic cardiac echo cardiology and ultrasound
imaging. High-definition monitors allow the patient and the physician to interact as if they were in the same room. With the
primary care physician and the specialist both involved in a
medical consultation, pertinent history can be discussed and interventional therapies agreed upon.
For correctional facility managers, telemedicine may offer
a means of providing appropriate health care evaluation without
compromising security, reducing costs associated with transport
and protection, and gaining access to physician specialists and
resources unavailable within the prison medical system. Between
September 1996 and December 1996, a leased telemedicine network
was installed to serve four federal prisons to gather information on
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the effectiveness of this technology. One suite, located inside the
penitentiary, served inmates at both the United States Penitentiary
and the Federal Correctional Institution in Allenwood, Pennsylvania, another served inmates at the United States Penitentiary in
Lewisburg, Pennsylvania, and a third served inmates at the Federal
Medical Center (a prison health care facility) in Lexington,
Kentucky. All of these sites were networked for telemedicine with
the Department of Veterans Affairs Medical Center, also in Lexington. The VA and Federal Medical Centers in Lexington served as
the hubs in this network, providing specialist physicians and other
health care practitioners for remote (telemedical) consultations
with prisoners in the three Pennsylvania prisons.
The purpose was to test the feasibility of remote telemedical
consultations in prisons and to estimate the financial impacts of
implementing telemedicine in other prison systems. One of the
largest for-profit government and business consulting and research
firms in the country, Abt Associates Inc., was contracted to evaluate
the demonstration and estimate the costs and savings associated
with the use of telemedicine in these selected prisons. During the
demonstration, a fifth mode of care—remote encounters with specialists via telemedicine—was added to determine whether the
prisons could use telemedicine to overcome local problems in
accessing needed specialists and improve security by averting
travel outside the prison walls. The demonstration was also designed
to supply data on costs and utilization to support a decision about
whether and where to implement telemedicine in other prisons.
In a press release issued in mid-1999, results of a report from
Abt Associates (Cambridge, MA) highlighted the potential for
telemedicine to reduce health care costs in prisons, based on data
gathered in the prison telemedicine demonstration. Specifically,
use of telemedicine systems instead of traditional forms of care
(prison staff, in-person clinics, or other health care facilities) was
estimated to save approximately $102.00 per specialist encounter.
Other advantages were quicker access to care (reduced waiting
between referrals and actual consultations) and use of physicians
from outside communities who offer more competitive pricing for
their services.
A telemedicine program at Louisiana State Penitentiary (LSP)
is an outgrowth of the Louisiana State University (LSU) Medical
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Center’s telemedicine initiative that began in 1995. Before the telemedicine program, approximately 3,000 inmates from LSP were
transported to the secondary and tertiary hospitals for medicalrelated reasons during a six month period.
The goals of this project were to reduce the number of inmate
transports from LSP to the secondary and tertiary health care
service centers, reinforce the security parameters and performance
objectives of the Department of Public Safety and Corrections, and
reduce the physical presence of inmates in the general civilian
population served by hospital-based clinics.
Videoconferencing
Digital systems are used to communicate with federal courts to
conduct pre-trial, civil, and mental competency hearings when
it is not desirable to transport a particular inmate to court.
Prison staff is encouraged to use videoconferencing as a means to
reduce travel costs and reduce the risks involved in transporting
prisoners.
Arizona’s popular Sheriff Joe Arpaio made international
news by transmitting live video from the jail onto the Internet for
public viewing. The site provides real life transmissions from the
Maricopa County Sheriff’s Office Madison Street Jail. Maricopa
County is the fourth largest jail system in the world. Housing over
1500 prisoners on average, the Madison Street Jail books an average
of 300 suspects a day. The Office, headed by Sheriff Joe Arpaio, is
known throughout the world for its tough stance on how inmates
are incarcerated and overseen. Sheriff Arpaio is convinced that
using video surveillance and the World Wide Web will deter
crime. It is his hope that the only visit anyone makes to his jail is
the virtual visit provided by the jail cam site.
As with any new procedures or technologies introduced into
use at correctional facilities, video conferencing must pass certain
criteria. The American Society for Testing and Materials (ASTM)
Committee F33 on Detention and Correctional Facilities meets
four times a year in conjunction with the American Jail Association
(AJA) and American Corrections Association (ACA) Conferences
to construct guidelines. The Operational Controls Subcommittee,
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F33.06, has completed the revised “Standard Guide for the Selection of Operational Security Control Systems”, ASTM F1465-03,
and has started a new work item to develop a guide standard
for the selection of digital video recorders (DVRs). In the future,
this group plans to develop a standard for “Standard Terminology
for Security Control Systems” and a selection guide for “Video
Arraignment and Video Visitation Equipment”.
Law Enforcement and Video The Law Enforcement & Emergency Services Video Association (LEVA) is dedicated to serving
the unique needs of law enforcement and emergency services
professionals who use video. Whether it’s video for production,
training, surveillance, crime scenes or documentation, through its
members, LEVA has established itself as the premiere source for
information, quality training, and networking. Chartered in 1989,
as a volunteer, nonprofit organization, LEVA serves videographers and audio/visual specialists from local, state, and federal
law enforcement, fire, emergency medical, rescue, and other
related public safety agencies throughout the world.
Although LEVA does not endorse any particular manufacturer or company product, its members are very knowledgeable
about video equipment and are consulted by their employers and
other public safety agencies for recommendations of potential
purchases of video equipment. Areas of knowledge and expertise
include in-car video systems, surveillance video equipment, crime
scene and documentation equipment, training, and also multimedia and production equipment.
Large amounts of people, traffic, and excitement make significant public events a challenge for law enforcement. Not to be
left behind the digital movement, Louisville, Kentucky businesses
have begun converting their previously analog systems to the new
digital products. The city sets up even more cameras for the famous
Kentucky Derby festivals and events, which law enforcement use
to monitor crowds and observe traffic patterns.
Getting three-quarters of a million people in and out of the
venue is a monumental task that requires patience and extensive
planning. The Video Forensics Analysis Unit of the Louisville
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Metro Police Department was instrumental in planning and implementing the digital video surveillance aspect of security for the
past few years’ events. With digital video in place, law enforcement can view camera images via microwave, giving them the
ability to direct support to specific locations when needed.
The Civil War marked a number of important technological
advances that changed the methods used to gather and communicate intelligence. Photography was used for the first time. Aerial
photography was also carried out, using hot air balloons. Additionally, telegraphy was used for the first time though messages
were often intercepted and deciphered. By the time World War I
came along, technology had advanced to include signals intelligence that gained greater importance than in any other war. Telegraph and radio messages, in Morse code, were soon vital to the
conduct of war.
Covert Video
Covert video is accomplished fairly simply as almost any normally
occurring piece of home or office equipment can hide a video
camera, including lamps, books, smoke detectors, clocks, and even
stereo components. 2.4 GHz transmitters do better indoors because
the signal frequency is much smaller in width and can move
through walls, in between the studs, and through rebar (which is
in concrete or brick walls). The only limitation is that they cannot
penetrate solid metal walls; the signal frequency will bounce off
or reflect away. This makes it possible to place a covert camera or
radio (2.4 GHz) in a room with the receiver, antenna, monitor, and
recorder up to 500 feet away. Some types of covert equipment can
be hidden on a person, but generally speaking, microwave signal
frequencies (2.4 GHz) should not be worn on the body.
POLITICAL EVENTS
Nowhere are the efforts against crime and the use of technological
tools, including video, more prevalent than in the protection of
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our nation’s political figures. Among its uses for surveillance, live
broadcast, and documentation for the public, video is the star of
political events. During an election year, there are three major
political events where security, technology, and broadcast video
are tested to their limits:
●
●
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Political Party Conventions
President and Vice President Candidate Debates
Presidential Inauguration
While a specific discussion involving the particular elements
of security at these events cannot take place, a general examination of the significant role of video can occur. When then Texas
Governor George W. Bush received the Republican Party’s nomination for President of the United States, he was under a protective
umbrella of five high-tech command centers designed to prevent
and respond to terrorist attacks or natural disasters. The Federal
Emergency Management Agency, working with the Secret Service,
the Environmental Protection Agency, and other federal, state,
and local security agencies, established primary command centers
in the Philadelphia region during the convention. Officials estimated the total number of people in and around the First Union
Center in Philadelphia at more than 35,000. Given such a large,
compact crowd, planners placed a premium on incident reporting
and timely response coordination, according to the Federal
Response Plan.
Security officials began to set up the high-tech monitoring
effort three days before the convention. One of the primary sites
established was the Secret Service’s Multi-Agency Communication Center (MACC). The EPA and Secret Service officials staffed
the MACC around-the-clock during the convention.
13
From VTRs to VCRs,
DVRs, and NVRs
After the ability to create moving images was achieved, the next
challenge was to record the moving images. One of the first men
to attempt a type of electronic recording of information was an
American mechanical engineer named Oberlin Smith, who came
up with the idea of recording electrical signals produced by the
telephone onto a steel wire. Although Smith never actually pursued
his vision, he publicized his ideas in a journal called Electronic
World. Later, Valdemar Poulsen, a Danish telephone engineer and
inventor, patented the first apparatus for magnetic sound recording and reproduction. It recorded, on a wire, the varying magnetic
fields produced by a sound. The earliest known attempted use of
magnetic recording to store images was in the late 1920s, by Boris
Ritcheouluff of London. Ritcheouluff designed a picture recorder
based on Poulsen’s machine, developed in Denmark many years
before. Many more video recording concepts followed.
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VIDEO TAPE RECORDERS—VTRS
The first practical videotape recorder (VTR) was developed and
sold by Ampex Corporation in 1951. The Ampex VTR captured
live images from television cameras by converting the information
into electrical impulses and saving it onto magnetic tape. VTRs
were similar to reel-to-reel audio tapes, with large spools of multitrack magnetic tapes measuring 1/2″ to 2″ wide and averaging
7,000 feet in length. The company demonstrated its Ampex-Mark
IV in April of 1956 at the National Association of Radio and Television Broadcasters (NAB) convention. See Figure 13-1. Ampex sold
the first VTR for $50,000 in 1956.
The lack of interchangeability among the very early VTRs
posed a serious problem. The same head assembly used to record
a program had to be used for playback, meaning that the recording
machine head assembly had to be shipped with the tape of evidence in order to view the recorded contents. This problem still
exists in some systems today because many manufacturers use
proprietary compression codecs for their digital recorders.
Figure 13-1 Ampex-Mark IV VTR. Courtesy of Department of
Special Collections and University Archives, Stanford University
Libraries.
From VTRs to VCRs, DVRs, and NVRs
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VIDEO CASSETTE RECORDERS—VCRS
Magnetic tape recording came into play near the end of World
War II. Though the size of the tape, the speed at which the tape
passed the recording heads, and the way video is written to the
magnetic tape have changed over the years, the basic principles
have remained the same.
The first Betamax VCRs were sold by Sony in 1971. In 1976
Panasonic and JVC introduced its competitor, the Video Home
System (VHS). Originally standard VHS type video cassette recorders were used for CCTV applications. A VCR is a device that can
record images from a video camera onto magnetic tape; it can also
play pre-recorded tapes. It is helpful to understand the mechanics
of VCR recorders to also understand the shortcomings. Videotape
is a plastic ribbon impregnated with a magnetizable metal powder.
Before recording, the particles are oriented randomly. During
recording, the video heads create a magnetism that orients the
particles in certain directions converting video signals into magnetic patterns on the tape. When the tape is played back, video
heads again pass over the magnetic powder and sense the magnetic vibrations and convert these vibrations back into a video
signal.
Video signals consist of millions of electrical vibrations each
second. Each vibration represents a tiny piece of your picture.
Videotape is a ribbon of Mylar with billions of tiny magnets
glued to it with a sophisticated kind of glue called a binder. See
Figure 13-2.
The original magnet material was iron oxide, and so the side
of the tape with magnetic material on it is called the oxide side.
Notice the irregular surface of the oxide coating. When the tape is
being manufactured the mixture of magnetic material and binder
(glue), called slurry, is liquid. The slurry is spread over the Mylar
and allowed to cure or dry. When the slurry cures, some of the
magnetic material protrudes from the surface of the oxide side.
When the video is “written” to the magnetic tape, the video
heads are in intimate contact with tape. In fact, the heads actually
protrude into the surface of the tape, causing a “canoe” in the
Mylar surface. As a result of this contact, the video heads
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Figure 13-2
Construction of Video Tape
Figure 13-3
Video Head Wear
experience wear from the friction of the tape rubbing the heads.
See Figure 13-3.
In addition, there is some oxide rubbed off from the tape.
Video headwear is especially high when most of the tape is brand
new because of the irregular surface of the oxide layer. As the
heads “burnish” new tape during recording, the oxide layer surface
is more abrasive than slightly used tape. The surface irregularities
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201
are literally “sanded” off the oxide surface. As a result, the oxide
layer develops a very smooth surface. After many hours of use,
the worn out heads have to be replaced.
Debris from the oxide and head wear collects around all of
the guides. The result is that the tape transport mechanism must
be cleaned from time to time, or the oxide debris will build up and
cause the edge of the tape to be damaged. If the edge of a tape
becomes sufficiently damaged, the tape will no longer yield a good
quality of recording and playback. Debris also can clog one or
more of the video heads. This results in loss of recording and large
snowy areas in the picture on playback.
The transport mechanism is complex for a thin, half-inch
ribbon of Mylar, as Figure 13-4 illustrates. Notice that from the
supply reel to the take-up reel, the tape must go through three 180
degree turns. This complex tape path results in a fair amount of
stress on the Mylar that, in turn, results in tape edge damage and
overall quality degradation.
Industrial video recorders differ from consumer recorders in
several ways. For example, they usually operate 24 hours a day
Figure 13-4
Transport Mechanism
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and seven days a week in time lapse mode, which allows a recording of extended periods on video cassettes. High grade video
cassettes are needed to avoid damaging video recording heads.
Industrial grade tapes should be replaced after multiple uses.
DIGITAL VIDEO RECORDERS—DVRS
The biggest selling feature for digital surveillance to date has been
the switch from the video cassette recorder storage to digital
storage. The combination of affordable image compression technology and large capacity hard disks made the development of
digital video recorders feasible. Digital video storage or digital
video recorders (DVRs) are a practical replacement for analog
VCRs because of the elimination of problems such as poor image
quality from the reuse of tapes, worn out heads, scratches, and
stretching from searching back and forth for a specific scene. Wear
and tear aside, no matter how many guidelines are set up for the
management of conventional video tape, one of its biggest downfalls is the simple action of having to place a tape into the VCR.
A digital video recorder is a stand-alone unit capable of
saving images to a hard disk. DVRs look similar to a standard VCR
in some ways, but that’s where the similarity ends. Because digital
systems are not mechanical like VCRs, factors such as frame speed
and video quality are software adjustable. Unlike the VCR, a
digital video recording device provides clear, sharp images every
time it is played. There are no tapes to store and material does not
deteriorate over time. A digital system allows for auditing of activity through monitor screen menus and for images to be retrieved
as easily as opening a file, using criteria such as date, time, location, or camera number. Whatever role the DVR plays, its very
existence declares a system to be digital even though the camera,
transmission, and display technologies may be analog. Digital
video storage allows particular images to be retrieved as easily as
opening a file based on criteria such as date, time, location, camera
number, special index numbers, etc. Digital video storage
eliminates the need to store hundreds of space consuming VCR
tapes, and archived material does not deteriorate with time.
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The history of the DVR involved a wide variety of technologies and manufacturers. Costs and availability varied greatly as
well. One of the first companies to deliver a successful product
was Dedicated Micros of Manchester, England. The Dedicated
Micros DVST (Digital Video Storage and Transmission) competed
closely with a Sensormatic remote transmission product.
In the 1990s, motion detection was added to the management
software of the camera or recorder, giving us the first hint of “intelligence” in the systems. There are now literally hundreds of DVR
manufacturers with a wide variety of products and features, many
specializing in solutions by size, location, lighting conditions, or
number of cameras. DVRs are usually scalable and upgradeable
utilizing specific software. They typically have video capture circuits or cards that can process 60, 120, 240, and 480 frames per
second. These numbers represent the total number of frames per
second that can be accommodated for all of the cameras or channels per system. For example, the 120 frames per second DVR with
16 cameras has an approximate frame rate of 7.5 frames per second.
This means that each camera can be converted at 120/16 or about
7.5 frames per second.
NVR—NETWORK VIDEO RECORDING
New video storage systems work with network attached cameras.
This new technology is very flexible and provides excellent features that allow you to create a complete video surveillance system.
Network Video Recording is a digital video recording solution
that works over a TCP/IP network. IP addressable network
cameras and/or video servers transmit images over a LAN, WAN,
or across the Internet. A NVR automatically receives data from
any IP cameras on a network and store it locally or on remote
storage media. The data can be any combination of video and
audio with hundreds of streams stored on a single server.
The frequently used term client/server describes the relationship between two computer programs or, in the case of networked video, the NVR and the remote network cameras. The
client makes a service request and the server fulfills the request.
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In a network, the client/server model provides a convenient way
to interconnect programs that are distributed efficiently across
different locations. When speaking of the Internet, for example, a
web browser is the client program making requests from a web
server connected through the Internet.
Using IP surveillance, the recording function is performed by
a network video recorder—a standard PC Server loaded with
video recording software. The NVR accesses the data streams of
the remote network cameras and video servers and stores them
on hard disk. Even though this technology is backward compatible
with all legacy analog CCTV equipment, more and more network
cameras that can interface directly to IT-style Ethernet networks
are being used today.
NVR technology is cost efficient and with IT-concepts such
as Storage Area Networks (SAN) or Network Attached Storage
(NAS), capacity can reach the terabyte range.
DVS—DIGITAL VIDEO SYSTEM
Just to make life interesting, some people refer to the digital video
recording system as a DVS for Digital Video System. Just like the
DVR, the DVS is used for capturing, recording, displaying,
archiving, and retrieval of video images, usually in a PC-oriented
environment.
14
Central Station Monitoring
and Video
Retaining the services of a video central station to remotely monitor
video images has the advantage of delegating the work of product
selection, installation, maintenance, communications coordination, training, and monitoring to one agent who can be located
outside the monitored facilities. The basic remote digital video
system involves CCTV cameras installed at remote locations where
intrusion, criminal activity, or employee pilferage may occur. A
video transmitter is integrated with the CCTV system, which has
the ability to dial-up the remote video monitoring center. This
dial-up function will be activated either by the video monitoring
center or by an alarm triggered at the site.
In the case of an alarm trigger, strategically placed alarms
will alert the video monitoring center of security breaches either
by unscheduled openings, “panic buttons” activated by an
employee, or movement in sensitive locations. When an alarm is
triggered the system will automatically dial up the video monitoring center and begin providing live video of the scene.
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Alarm Verification
There are almost limitless opportunities for applying remote video
services to improve profitability and enhance business performance. Alarm verification is a key use of remote monitoring operations. Visual alarm verification goes right to the core of solving
the false alarm issues. Unnecessary calls for police service due to
false alarms have grown into an enormous problem both for law
enforcement and security providers. It has been estimated that
police are responding to somewhere between seven million to
fifteen million false alarms every year. In light of these continually
increasing numbers many police agencies have had to assess fines
to supplement rising costs, which are a direct result of the false
alarm dilemma. False alarm fines can range from $20 to $250 or
more. If false alarm fines are affecting a company’s profitability,
remote video alarm verification can help dramatically reduce these
costs.
Not only can an alarm be verified but also a detailed description of events is available for the responding security patrol or law
enforcement personnel. Facts about approximate age, demeanor,
and number of persons involved, and if they have weapons can
be made available before a response team arrives at the location
or even sent directly to response vehicles if they are equipped to
receive video images. This vital information can augment the safe
and successful resolution of many incidents.
When a video monitoring station receives an alarm, a trained
specialist can immediately view the alarm location to determine
the status of the alarm. If an alarm is determined to be false, a
remote system can automatically record information pertaining to
time, date, and location. The remote monitoring location can record
the cause of alarm for future reporting. In the case of an actual
unauthorized intrusion, the specialist can document all information and inform the appropriate authorities immediately.
REMOTE INTERACTIVE MONITORING
Remote interactive video not only provides the communication of
video to outside locations but simultaneous two-way audio as
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well. This technology allows communication between the remote
site and trained intervention specialists who can clarify, deter, or
diffuse transpiring events.
With the availability of simultaneous audio and video
transmission, the intervention specialist can influence the outcome of events either by announcing his or her presence, issuing
specific voice commands, or contacting local law enforcement
with details of the situation. A pre and post alarm feature is
usually available that insures that the stored video clearly
displays the events leading up to and immediately following an
alarm.
Remote interactive digital video solutions permit the manipulation of objects from the visual command center. Pan, tilt, and
zoom features on cameras can be controlled. Motorized gates,
electric door locks, lights, and even environmental controls can be
remotely actuated as well. On site personnel may also call up a
monitoring center to report suspicious behavior or other concerns
and ask for video monitoring and potentially intervention. Panic
buttons can also be provided which, when activated, will alert
the center of a possible incident if the client cannot overtly call
for help.
Video Guard Tours
At random intervals, a monitoring station can connect to the
remote site and conduct a visual assessment of the facility. These
tours can be announced to the facility, letting the employees know
that they are not alone and increasing their feeling of safety. The
tours also can be conducted as unannounced. This option lets
employees know the facility is being viewed but they don’t know
when or how often. This has proven over time to have a significant
impact on reducing internal shrinkage. Many users actually utilize
both types of guard tours to maximize the capability of the
technology.
Video guard tours can provide reports containing important
information about operations. The following are examples of possible items that might be reported:
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Employee rude to customer
Employees not following security procedures
Team members not wearing uniforms
Clerk working out of open cash drawer
Open safe
Unauthorized visitors or phone calls
Pilfering
Unsuitable work performance
Video guard tours increase the overall feeling of comfort and
safety for employees and customers alike because they know they
can quickly get help when they need it. They can also increase
productivity without the necessity of constant upper management
supervision.
Open/Close Escort Service
Remote monitoring services may include an escort service for
employees at the opening and closing of a store, financial institute,
or other facility. This service involves a live look-in during the
opening or closing (by an authorized employee) to ensure safety
and provide verification of events related to the procedures
involved with opening and closing. This service gives the employee
the ability to signal the monitoring station before they leave the
building to take a deposit to the bank, take the trash to the dumpster, or leave for the night. They would then follow the employee
with exterior cameras to ensure his or her safety.
Controlling Inventory Shrinkage
Each time someone takes items from a location without paying, the
bottom line suffers. It may be a no sale transaction to an acquaintance or merchandise carried out the back door. Rather than review
register tapes and inventory records, a video record of the incident
not only identifies the problem but also provides indisputable
proof of the event. The ability to monitor doors and loading docks
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and to vocally address each person in the site by their physical
description will help to make the environment less inviting to shoplifting, buddy discounts, and back door transactions.
Remote Site Management
Remote facilities such as electric sub-stations or powerhouses are
prime targets for vandals and thieves. Most of these stations are
scattered throughout a particular region, making electronic monitoring without video capability or an on-site guard a time consuming and expensive proposition. Remote digital video and audio
services can eliminate much of the travel and guard expense,
giving managers the ability to out-source many of the operations
needed to monitor their facilities.
The option of transmitting live video directly to the home or
office of management is also available. When an alarm is activated
and a premises needs inspection, a specialist can be on the scene
in seconds to see what is taking place and to record the events. A
predetermined course of action, which has been specified appropriate under those circumstances, can be initiated. It may be any
combination of direct audio intervention, calling the authorities,
or calling management.
Retail facilities benefit greatly from remote video monitoring
for many reasons. Store transactions can be observed remotely if
necessary as well as recorded and archived for future review and
dissemination. This information can be vital when following up
on situations of credit card fraud, checks of insufficient funds, or
the presentation of false identification.
Loss prevention for retail establishments has evolved through
various deterrents such as security guards, observation mirrors
(that allow staff to see throughout the store), and closed-circuit
television surveillance systems. These techniques were among the
earliest tools used to combat shoplifting. Some larger stores still
use a combination of security guards, CCTV systems, and even
mirrors, but the advent of digital video technologies has made a
great impact on how CCTV can be used to increase efficiency and
decrease manpower.
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The presence of unruly crowds, vagrants, and even graffiti
can deter customers from patronizing an establishment. Remote
interactive monitoring of facilities can alleviate these situations
while promoting the image of a safe and secure environment for
customers.
Today’s retail management has the ongoing task of improving the customer experience while at the same time keeping losses
from liability and fraud under control. Loss in the retail world is
not subjective. The small boutique and the nationwide chains are
both equally susceptible to losses from shrink, fraud, and shoplifting. With digital video in place, store transactions can be observed
remotely if necessary, as well as recorded and archived for future
review and dissemination. This information can be vital when following up on situations of credit card fraud, checks for insufficient
funds, or the presentation of false identification.
The knowledge that remote monitoring is in place can be
extremely beneficial to the peace of mind of employees, customers,
and facility managers alike. With crime rates escalating, customers
are known to patronize facilities that offer a reasonable expectation of safety. Not only is the emotional well being of staff and
clientele important, but the decrease in liability incurred by facility
owners emphasizes return on investment.
15
More Digital Video
Applications
Security products and services are found in markets including
residential, commercial, public service, transportation, industrial,
military, etc. Not only does the security industry supply a limitless
market, it also combines with many cross markets to create efficiency and economy of products and services. These are some
examples of ways in which digital video is being utilized today.
KEEPING WATCH OVER PRODUCTION
Weyerhaeuser, an international company that offers a full range
of pulp and paper products, provides an excellent example of how
the provision of safety and security services and products consistently relies upon a blending of ingenuity and teamwork. By combining CCTV technology with computer network capabilities, they
have utilized the full versatility of digital video in one of the
housing materials manufacturing facilities. During the last 30
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years, manufacturing plants have been automating their production facilities at an increasing rate, augmenting the need for monitoring systems that effectively track possible break downs and
bottlenecks along the actual production line.
Most manufacturing plants and warehouse facilities depended
on sensors and video cameras placed in many different locations
to ensure proper functionality along manufacturing lines. At
Weyerhaeuser, cameras are used by staff charged with engineering control systems in the various manufacturing facilities. The
system allows them to log onto the Internet and observe the production systems at any time, from any location.
Weyerhaeuser discovered some additional benefits to the
technology. The facility makes Oriented Strand Board (OSB),
which is a wood panel material manufactured in 12 by 24 foot
pieces weighing 500 pounds each. A jam in the OSB production
system is not only costly in production time lost but also is hard
to clean up. When installing and testing their new digital system,
a potential jam in one of the production systems was observed
over the Internet. Because of this observation, floor technicians
were immediately contacted and consequently able to prevent the
jam. According to Weyerhaeuser, a production jam that stops the
manufacturing line can cost the company several hundred dollars
a minute. Even the prevention of one jam per month can save the
company thousands of dollars per year in time that was not lost.
SECURING A WAR HERO
The Battleship Missouri, nicknamed the “Mighty Mo”, is located
on Pearl Harbor’s Battleship Row and opened as a floating museum
on January 29, 1999. The 887-foot, 45,000-ton USS Missouri served
in three wars—World War II, Korea, and Desert Storm—over a
five-decade span. It is best known for being the site of Japan’s
surrender to the Allied Forces on September 2, 1945, ending World
War II. Today, the “Mighty Mo” is berthed approximately 300
yards from the USS Arizona Memorial, and the two are memorials
symbolizing the beginning and end of America’s involvement in
the world’s deadliest war.
The USS Missouri Memorial Association is a private Hawaiibased 501(c) (3) non-profit organization designated by the U.S.
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Navy as caretaker of the Battleship Missouri Memorial. The association was instrumental in the decision and planning processes
that involved a state-of-the-art web cam system being installed on
board the Missouri. The system allows the Association to bring
the Battleship Missouri to the rest of world. Once complete, the
system will provide a comprehensive virtual experience for physically challenged visitors through a new Visitor Alternative Media
Center, allow far-away family members of U.S. serviceman to
witness their reenlistment ceremonies held on the ship, and offer
tours on the Internet for classrooms across the globe. In addition,
staff can monitor daily activities and provide direction and assistance when and where needed.
REMOTELY MONITORING NUCLEAR MATERIALS
The U.S. Department of Energy, Aquila Technologies, Los Alamos
National Laboratory, and Sandia National Laboratories launched
collaborative efforts to create a Non-Proliferation Network Systems
Integration and Test (NN-SITE) facility. Utilizing Aquila Technologies Group’s Gemini system, the facility provides unattended
(remote video) authentication, encryption, file decompression,
and decryption. The Gemini system remotely validates visual
monitoring and verifies that the video images are authentic.
The advantages of this system include reduced worker radiation exposure and reduced intrusion to facility operations. The
first remote exchange of data and images occurred between U.S.
and Russian weapons-usable nuclear material storage vaults. The
Department of Energy has also been involved in the installation
of remote monitoring systems and the initiation of field trials in
Argentina, Australia, Japan, Sweden, and the European Commission Joint Research Center in Ispra, Italy.
NTSB INVESTIGATION
At Sky Harbor Airport in Phoenix, Arizona, over 700 cameras are
connected to four rack rooms through a fiber optic backbone. Each
rack room manages the video from recording to multiplexing and
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routing the images to any of eight locations. System operators
utilize a custom graphical user interface (GUI) that displays maps
of all areas, including camera locations. Operators can view live
camera images, control pan/tilt/zoom, iris, and focus, view realtime recorded video from the previous eight hours, and view
archived video from previous months.
The project was originally designed to monitor parking areas
to help reduce car theft, assaults, and vandalism. The system was
also used to monitor baggage claim areas. Activity in both areas
was monitored and recorded in an effort to reduce the insurance
liability for the City of Phoenix, which is self-insured. Since its
installation the system has been expanded for use to view and
record airfield activity, missing person searches, and theft and has
even been instrumental in a National Transportation and Safety
Board investigation.
The system was operating at peak efficiency when, during a
routine landing, an America West A320 Airbus crashed on the
north runway. Typically, the pilot knows if there’s a problem with
the landing gear, and he issues an alert so that the airport can
prepare for the crash landing. In this situation, the pilot had no
forewarning of equipment failure. As the incident unfolded, two
of the 425 cameras installed on one of the airport parking garages
were trained on the runway and recorded the crash from two
separate angles. The video clearly shows the plane touching down,
the failure in the front landing gear, and the subsequent skid to a
stop at the edge of the runway. The NTSB is using the recorded
video to help determine the cause of the crash.
WINEMAKERS WATCH THEIR VINES
The use of technology to assist winemakers is increasing, particularly in the United States and Australia, where wine grapes are
often farmed in large, flat tracts of land where there is little change
in weather and soil conditions. California winemakers can see how
their vines are doing, day or night, with a wireless, web-based
video system. Wineries buying grapes from Scheid Vineyards in
Monterey, California can now access real-time pictures and data
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on their vines as they grow. The system allows about forty wineries across California to get a bird’s eye view of the vines from three
live, solar powered cameras located in the vineyards using a wireless network that covers 5,600 acres. The cameras can be operated
remotely over the Internet and PTZ operated for close-up viewing.
The network allows field managers to respond immediately to
changing conditions and helps keep customers in touch with the
growing process.
VIDEO MONITORING CONTRIBUTES TO
GEOLOGICAL STUDIES
The USGS (United States Geological Survey) has used remote
digital video for monitoring the variability in coastal sections.
Characterizing the changes in shoreline positions and other physical changes has traditionally been a labor and cost intensive
process, but remote video monitoring methods allow continuous
sampling and can be maintained for extended periods of time.
The USGS has joined forces with Oregon State University to
develop a program that provides inexpensive systems of data collection and analysis. Three field stations were set up to support
projects in Southwest Washington, West Central Florida, and Lake
Erie. The Florida station was designed to provide daily maps of
shoreline evolution of a recently nourished region using software
that was developed to convert video images to meaningful shoreline maps and historical descriptions.
KEEPING AN EYE ON THE COWS
A video system is being used by a large U.S. dairy farm to support
the management of its dairy operations. The facility has 10,000
cows in four parlors and is located on 17,000 acres. It produces
approximately 100,000 gallons of milk per day. Cameras view
milking operations with two PTZ cameras, and three fixed cameras
monitor the operation. A remote operator oversees whether cows
are being prepped and handled properly. The facility also plans
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to use cameras at a visitor’s center to be built in the next few years,
where video will be displayed on a large screen so that visitors
can see real time milking operations as they learn about it.
The cameras communicate video over a LAN to the main
office located four miles away, where management can view operations at any time. They can also look in on milking operations
from either home or offices at other locations. Other uses for
cameras in dairy operations include the monitoring of the maternity area, feed storage, and mixing locations.
THE BUREAU OF ENGRAVING AND PRINTING
Can you think of a bigger challenge than providing security for
the facilities that actually manufacture all of America’s money?
The Bureau of Engraving and Printing (BEP) was established in
1861 and in 1877 became the sole maker of all United States currency. Today, it is the largest producer of U.S. government security
documents and prints billions of notes (bills) for delivery to the
Federal Reserve System each year from production facilities in
Washington, D.C. and in Fort Worth, Texas.
The Bureau designs, prints, and furnishes a variety of products, including Federal Reserve notes, U.S. postage stamps, Treasury securities, identification cards, naturalization certificates, and
special security documents, and even does print runs for White
House invitations and other such announcements. All documents
with an associated dollar value are designed with advanced counterfeit deterrence features to ensure product integrity, and the
process of printing is done under the scrutiny of a state of the art
surveillance system. BEP procedures require extensive background
checks for personnel hiring and strict security practices on the job.
The digital video system has become an additional layer of confidence that procedures are followed and the facility remains highly
secure.
The BEP has a security team monitoring cameras 24 hours a
day, seven days a week, every day of the year. They also have
remote viewing capabilities for authorized users, so they have the
ability to look in any time, day or night. Security monitoring per-
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sonal are not necessarily looking for people slipping twenty dollar
bills into their pockets. In fact, there have been no successful
attempts involving staff pilfering the merchandise since 1998.
Instead, they are looking for abnormalities or inconsistencies in
everyday operations of the production facilities, as well as violations in procedures. The system also does a great service to the
employees of the BEP as errors are quickly resolved and an
employee who might otherwise look suspicious is quickly cleared
by video evidence.
For example, the job of a currency examiner is to retrieve
packets of one hundred dollar bills from a conveyer belt and check
them for printing errors. Personnel monitoring the currency examiner will make a report if a packet is missed or any other error
occurs on the production line. Another interesting and closely
monitored position is the person who checks individual currency
notes, which are returned to the Bureau as unusable. After inspection and documentation by the examiner, these bills are destroyed.
As one can imagine, destroying currency—even damaged bills—
would be a tough job. The digital system ensures that proper
procedures are followed and examiners are indeed destroying the
damaged notes.
The system has also been used to investigate and solve
Automatic Teller Machine (ATM) transaction disputes. The ATM
located within the facility for the use of employees has a camera
that records all transactions. The camera had been removed for
repair and an obvious empty spot was in its place. Thinking the
missing camera meant no video proof, a man denied having
received cash from the machine. Unfortunately (for him), other
cameras in the area recorded a perfect view of him taking his
money from the machine during the time in question.
TRAFFIC MONITORING
The monitoring and control of traffic has taken many turns and
with new technologies has become a sophisticated and progressive enterprise. In the past, electronic traffic management and
information programs relied on a system of sensors for estimating
218
Digital CCTV
traffic parameters. The more prevalent technology for this purpose
was that of magnetic loop detectors buried underneath highways
to count vehicles passing over them.
Various types of aircraft have also been used to monitor
traffic, mostly in the form of television or radio station helicopters.
These periodic flights over main arteries can communicate live
traffic conditions but are usually limited to rush hour or specific
traffic incidents and are of no real value in monitoring or controlling traffic on a 24 hour basis.
New digital video capabilities make it extremely viable for
traffic monitoring, and it provides a number of advantages over
older methods. A much larger set of traffic parameters can be
monitored such as vehicle counts, types, and speeds as well as
causes of congestion and recurrent accidents. In addition, traffic
can now be monitored continuously.
16
New Roles of
Digital Video
In 1997, the same agency responsible for the Internet, DARPA,
began a three-year program to advance Video Surveillance and
Monitoring (VSAM) technology. The purpose was to develop
automated video understanding (intelligence) technology for use
in future urban and battlefield surveillance applications. Advances
resulting from this program allow a single human operator to
monitor activities over a broad area using a distributed network
of active video sensors.
The Carnegie Mellon University Robotics Institute and the
Sarnoff Corporation teamed up to develop an end-to-end test bed
system, which demonstrated a wide range of advanced surveillance techniques such as real-time moving object detection, tracking from stationary and moving camera platforms, recognition of
object classes and specific object types among many other advanced
analysis. Twelve other contracts were awarded for research in the
areas of human activity recognition, vehicle tracking and counting, airborne surveillance, novel sensor design, and geometric
219
220
Digital CCTV
methods for graphical view transfer. Today’s digital video surveillance systems face the same difficulties that DARPA was assigned
to overcome with the VSAM project: an overload of video information transmitted for view and response. A large surveillance system
with 300 hundred cameras would need 13 operators to view every
camera one time every 60 seconds with a sequencing system
switching four monitors per operator every ten seconds. The
primary function of a video analysis feature is to relieve CCTV
operators from the stress of monitoring many screens of information that may not change for long periods. Even a moderately
sized system containing eight cameras could prove impossible for
an operator to monitor. Eight monitors could not be viewed with
any degree of concentration for more than about 20 minutes. If the
monitors were set to sequence, then activity on seven cameras is
lost for most of the time and would be totally ineffective to detect
intruders. This leaves too much time between images for adequate
surveillance, and the fatigue factor inherent with this kind of stimulation is extreme.
The solution to this problem is either more staff to monitor
the video, which could become cost prohibitive, or a system that
is intelligent enough to detect a problem and signal for a response.
Such a system would be considered to have artificial intelligence,
which is defined as intelligence exhibited by an artificial entity.
Computer vision is a subfield of artificial intelligence with
the purpose of programming a computer to understand the contents of an image. This ability is considered a class of artificial
intelligence, which is basically a machine performing activities
normally thought to require intelligence. Computer vision was
actually developed in the 1950s and has been in use for some time,
especially in the role of monitoring production lines. Now it is
being used for security applications. More methods of video intelligence currently in use or being researched follow.
IMAGE ANALYSIS
Image analysis or video analysis involves the extraction of information from digital images by a method known as digital image
New Roles of Digital Video
221
processing. Image analysis can include from simple tasks like bar
code reading to the much more complicated processes of facial
recognition. Content analysis is simply a systematic analysis of the
content rather than the structure of a communication. For example,
the algorithm used concerns itself only with the shape of moving
objects within a scene. These shapes are analyzed and classified.
Actions are put into motion based on the resulting classification.
PATTERN RECOGNITION
Pattern recognition involving images occurs when raw data is
reviewed by the computer and an action is put into motion based
on the category of the data found. Most of us use a form of pattern
recognition when we use an automatic spam filter. For example,
a predefined pattern of data such as the word “drug” is acknowledged and an action is put into motion. In most cases the action
is to block the spam. This is why so many e-mails are sent using
false references like “returning your message” or “concerning
your account.”
PEOPLE COUNTING
Automatically counting people within a defined area and providing information about the direction of movement generates accurate traffic information that can enable efficient staffing, better
queue control, and marketing data. This feature can also be set to
alert staff when a safety threshold has been reached pertaining to
occupancy limits.
INTELLIGENT VIDEO
Intelligent video refers to the analysis and extraction of video
information with specific reasoning attached for specific applications. It may be determined that specific information is not of high
enough priority, so resolution is decreased to conserve bandwidth
222
Digital CCTV
or storage space. Intelligent video can also refer to content management, such as indexing and retrieval. It could also enhance an
image by removing noise, improving resolution, or increasing the
dynamic range.
Remember that we described algorithms as a kind of recipe
or set of instructions? This explains why there are so many different capabilities offered by so many different companies. Most
manufacturers focus on one or two specialties like identification,
tracking, or determining motives for movements and incorporate
those into their systems. Then they focus on niche markets that
can best utilize those individual capabilities.
The intelligent video system can be programmed for an
endless variety of uses. For example, a particular problem often
found among train and bus stations is the gathering of loiterers.
This problem is alleviated by system alarms that are instigated by
the video itself when the presence of persons where they should
not be is indicated. Personnel who have been alerted to the scene
can view the area and determine the cause for the alarm, then
dispatch someone to disperse the loiterers if necessary.
A similar feature is used to eliminate illegally parked cars
from sensitive areas or abandoned vehicles. Automatic detection
and alert for vehicles parked in restricted areas gives security
personal immediate notice of a breach that could eliminate a
potential car bomb threat or simply result in a parking ticket.
Some behavior recognition programs utilize recursive adaptive computer algorithms. These are dynamic programs through
which normal patterns of behavior are continually learned and
updated to define acceptable behavior patterns. These types of
programs are useful because they can be programmed to alert
irregularity in behavior patterns as they occur, not just those that
have been previously identified.
FACIAL RECOGNITION
A facial recognition system is a computer driven application for
automatically identifying a person from a digital image. It does
that by comparing selected facial features in the live image and a
New Roles of Digital Video
223
facial database. A facial recognition system analyzes images of
human faces through their special characteristics, such as the distance between the eyes, the length of the nose, and the angle of
the jaw, etc. These characteristic features are called eigenfaces in
the facial recognition domain.
The software compares images producing a score that measures similarities. Because the image is analyzed by individual
characteristics the system can distinguish the same person with
different appearances; for example, with or without glasses,
shorter, longer, or even different color of hair, and seasonal skin
color changes. None of these possible alterations change the
dynamic structure of the face, meaning it remains identifiable.
Not all attempts at using facial recognition have achieved
rave reviews; for example, the 2001 Super Bowl at Tampa Bay had
very mixed reactions, but the technology continues to be refined
and false positive responses are on the decline.
THE EVIDENTIARY DEBATE
The digitization of information and the resulting growth of computing and electronic networking bring a new kind of security
threat. Not only must video information be kept from easily being
destroyed, it must also be protected from any form of manipulation. Forensic video analysis has been accepted by the courts in
reported cases since 1992. Organizations such as the International
Association for Identification (IAI) have created resolutions incorporating digital images and data into their procedures. Formed in
1915, the IAI is the oldest and largest forensic science identification
organization in the world.
A means of video authentication is necessary to use video
as evidence in a court of law. Video authentication can be
accomplished by creating a digital “fingerprint” for each digitized
video clip. Techniques for safeguarding video integrity include
technologies such as date/time stamping, watermarking, and
encryption.
Encryption is simply the conversion of data into a form that
is virtually impossible to understand by unauthorized people.
224
Digital CCTV
This provides a way to protect the privacy, security, confidentiality, integrity, and authenticity of wire and electronic communications, which can include video data. Decryption is the process of
converting encrypted data back into its original form so it can be
understood. In order to recover the contents of an encrypted signal,
a decryption key is required. The key is an algorithm that reverses
the work of the encryption algorithm. The longer the key, the
harder it is to decipher the code.
Encryption software can use keys in different ways. For
example, single-key encryption allows both the sender and receiver
to use the same key to encrypt and decrypt messages. Depending
on whether the encryption and decryption keys are the same or
not, the process is called symmetric or asymmetric. A watermark
can be embedded into an image to facilitate fingerprinting, authentication and integrity verification, content labeling, usage control,
and content protection. Watermarking can be visible with the
naked eye or may need special equipment to be seen.
Digital technology makes analysis and presentation of video
evidence for the courts a reality, especially since court authority
for electronic surveillance is not required by the Fourth Amendment for situations where there is no reasonable expectation of
privacy. For example, no warrant is required to videotape activity
in a parking lot, a bank, or other public places.
One of the more famous instances of video as evidence in the
United States involved a video camera at an apartment complex a
block from the Alfred P. Murrah Federal Building in Oklahoma
City. A camera caught the image of a Ryder truck shortly before
an explosion on April 19, 1995. It was later determined the explosion was caused by a homemade bomb hidden in the Ryder truck
whose image was captured on camera.
This, more than any other incident before 9/11, has contributed to advancements and the increase in the use of CCTV as a
surveillance and security tool in the United States.
Glossary
16 CIF: 16 × CIF (resolution 1408 × 1152).
4 CIF: 4 × CIF (resolution 704 × 576).
Analog: describes a continuous signal expressed as a continuous
waveform.
Asynchronous: signal whose data is acknowledged or acted upon
immediately, irrespective of any clock signal.
Aspect Ratio: ratio of width to height.
Bandwidth: measure of the carrying capacity of information over
a network.
Baud: speed at which data is transmitted.
Binary: base-2 numbering system.
Bit: contraction of binary digit having two possible values; one or zero.
Bitmap: defines a display space and the color for each pixel or
“bit” in the display space.
225
226
Glossary
Byte: group of eight binary digits, or bits.
Cache: portion of RAM used for temporary storage of data needing
rapid access.
CCD (Charge Coupled Device): semiconductor device (IC) that
converts images to electronic signals.
CCIR (Comite Consulatif International Des Radiocommunications): European committee responsible for professional standards
related to audio and video.
CCTV (Closed Circuit Television): television system used for
private purposes, not for public or general broadcast.
Chroma Level: relating to the amount of saturation and hue at a
particular point of an image.
Chrominance: color information contained in a video signal separate from the luminance component.
CIF (Common Intermediate Format): standard video formats
defined by their resolution.
Coaxial Cable: standard cable consisting of a central inner conductor and a cylindrical outer conductor.
Codec: software that can compress a video source as well as play
compressed video.
Color Bars: electronically generated video pattern consisting of
eight equal width colors.
Color Burst: portion of a color video signal that contains
a short sample of the color sub carrier used to add color to a
signal.
Glossary
227
Composite Video: electronic information needed to produce a
video signal.
Conductor: material that allows electrical charges to flow
through it.
Crosstalk: interference between two or more audio or video signals
caused by unwanted stray signals.
Decimal: base-10 numbering system.
Digital Signal: signal that is either zero or one volt rather than a
continuum of voltages or current.
DSP (Digital Signal Processor): primarily digital component used
to process either digital or analog signals.
Distortion: degradation of a transmitted signal.
EMI (Electromagnetic Interference): signal impairment resulting
from electromagnetic disturbances in the atmosphere.
Encryption: process applied to digital signals to ensure secure
communications.
Ethernet: type of LAN that is recognized as an industry standard.
Field: single scan of a TV or monitor screen consisting of 262.5
lines. Two fields make up a single frame.
Frame: a complete video picture.
Giga: unit qualifier (symbol = G) representing one thousand million.
Gigabit: one billion bits.
228
Glossary
Grayscale: An image type that uses black, white, and a range of
shades of gray.
Hertz (Hz): unit of frequency; one Hertz equals one cycle, or one
oscillation, per second.
HTML (Hypertext Markup Language): set of symbols or codes
used in a file intended for display on a World Wide Web
browser.
HTTP (Hypertext Transfer Protocol): set of rules for exchanging
files (text, graphic images, sound, video, and other multimedia
files) on the World Wide Web.
Internet: public network of computers and people sharing information. Anyone can access the Internet through an Internet service
provider.
Intranet: private network of computers using web-based technology not accessible by the general public.
IP (Internet Protocol): method by which data is sent from one
computer to another over the Internet.
IP Address: used to identify a particular computer on a network
to other computers.
ISDN (Integrated Services Digital Network): international telecommunications standard.
ISO (International Organization for Standardization): nongovernment organization promoting the development of standardization to facilitate the international exchange of goods and
services.
Kilo: unit qualifier (symbol = K) representing one thousand.
Kbs or Kbps: kilobits per second.
Glossary
229
LAN (Local Area Network): multiple computers connected
together to share information such as e-mail, files, and printers.
Luminance: lightness of a color measuring the intensity of light
per unit area of its source, also called Luma.
Mbs or Mbps: megabits per second.
Mega: unit qualifier (symbol = M) representing one million.
Modem (Modulator/Demodulator): sends digital signals over
analog lines.
Network: computers connected together for the purpose of sharing
information.
Noise: disturbance in a signal.
NTSC (National Television Systems Committee): American television standard.
Peta: unit qualifier (symbol = P) representing one thousand million
million.
Plasma: gaseous state in which the atoms or molecules are dissociated to form ions.
Point-to-multipoint: communications from one location to several
locations.
Point-to-point: communications between two locations.
Quantization: reduce the number of colors or shades of gray in an
image, with the goal being to reduce file size.
QCIF (Quarter CIF): resolution 176 × 144.
230
Glossary
RAM (Random Access Memory): data-storage device from which
data can be read out and new data can be written in.
ROM (Read Only Memory): “built-in” computer memory
containing data that normally can only be read, not written
on.
Router: device that connects two networks by reading the destination address of information sent over a network and forwarding
it to the next step in its route.
Saturation: strength of a color with respect to its value.
Server: computer and software that provides some service for
other computers connected to it through a network.
SQCIF (Sub Quarter CIF): resolution 128 × 96.
Tera: Unit qualifier (symbol = T) representing one million million.
TCP/IP (Transmission Control Protocol/Internet Protocol): basic
communication language of the Internet.
Twisted Pair: electrical conductor that consists of two wires
twisted around each other.
Value: brightness of a color, based on the amount of light emanating from it.
VDU (Visual Display Unit): cathode ray unit designed for display
of video pictures.
Video: signal output from a video camera.
WAN (Wide Area Network): multiple LANs connected over a
distance that share information.
Glossary
231
Wavelet: mathematical function useful in signal processing and
image compression.
Wireless: electromagnetic waves, such as radio or television, that
carry a signal from one section to another.
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Index
Access control, systems integration,
184–186
Adaptive compression, principles,
66–67
Advanced Encryption Standard (AES),
wireless security, 145
Advanced Mobile Phone Service
(AMPS), overview, 133
AES, see Advanced Encryption
Standard
Airports, security systems, 150–151
Algorithm, properties, 77–78
AM, see Amplitude modulation
American National Standards Institute
(ANSI), definition of
standard, 76
Amplitude modulation (AM),
principles, 45–46
AMPS, see Advanced Mobile Phone
Service
Analog
definition, 225
image generation, 2–5
ANSI, see American National
Standards Institute
Antenna, features, 130
Arpaio, Joe, 192
Aspect ratio, definition, 225
Asynchronous, definition, 225
Asynchronous transfer mode (ATM),
features, 124–125
ATM, see Asynchronous transfer
mode; Automatic teller
machine
Audio Video Interleaving (AVI),
features, 103
Authentication, video, 223
Automatic teller machine (ATM),
digital closed circuit
television applications, 217
AVI, see Audio Video Interleaving
Bandwidth
definition, 53–54, 225
picture quality, 53
principles, 53–55
Banks, security systems, 161
Baud, definition, 225
Bridging switcher, features, 171
BEP, see Bureau of Engraving and
Printing
BGAN, see Broadband Global Area
Network
Binary
definition, 20, 225
numbers and counting, 21–23
Biometrics, systems integration,
182–184
233
234
Index
Bit
bits per pixel, 30
definition, 20–21, 225
counting, 23
Bitmap, definition, 225
Black level, definition, 5
Broadband Global Area Network
(BGAN), features,
143
Bureau of Engraving and Printing
(BEP), digital closed circuit
television applications,
216–217
Byte, definition, 20, 226
Cache, definition, 226
Camera
optics, 6
retrace circuitry, 6–7
charge coupled device, 164–165
infrared, 165–166
thermal imaging, 166–167
image intensifiers, 167
lens
C-mount, 169–170
CS-mount, 169–170
speed, 168–169
varifocal, 170
switching equipment
bridging switcher, 171
matrix switcher, 172
multiplexer, 171, 172
Campus, security systems, 148–150
Campus area network (CAN),
definition, 96
Car lots, security systems, 158–159
Casinos, security systems, 160–161
Cathode ray tube (CRT)
monitors, 173–174
principles, 10
CCD, see Charge coupled device
CCIR
definition, 226
video standards, 25
CCTV, see Closed circuit television
CDMA, see Code Division Multiple
Access
CD-R, see Compact disc-recordable
CD-RW, see Compact disc-rewritable
Cellular transmission,
telecommunications systems,
132–135
Charge coupled device (CCD)
definition, 226
features, 164
intensified charge coupled devices,
167
Chroma level, definition, 226
Chrominance, definition, 50, 226
CIF, see Common intermediate
format
Closed circuit television (CCTV)
definition, 226
historical perspective, 39–42
overview, 1
CMG, see Computer Measurement
Group
C-mount, lens, 169–170
CMYK system, overview, 52
Coaxial cable
applications, 115
definition, 226
performance, 14
structure, 113–114
types, 114–115
Codec
definition, 60, 226
principles, 61–62
Code Division Multiple Access
(CDMA), transmission,
134
Color
additive mixing, 52–53
eye photoreceptors, 50–51
subtractive color, 51–52
transmission speed effects, 50
Color bars, definition, 226
Color burst, definition, 50, 226
Common intermediate format (CIF)
definition, 226
features, 104
Compact disc-recordable (CD-R),
storage, 107
Compact disc-rewritable (CD-RW),
storage, 107–108
Composite video
definition, 227
signal, 7–8
Index
Compression
adaptive compression, 66–67
codecs, 60–62
definition, 57
fixed length codes, 71
historical perspective, 58–60
Huffman encoding, 65–66
lossless versus lossy, 42–44
multi-resolution analysis, 91–92
predictive versus transform coding,
70–71
ratio, 72–73
relative encoding, 63–64
run-length encoding, 62–63
spatial compression, 68
standards
DivX, 102
H.261, 88
H.263, 88–89
H.263+, 89
H.264, 89
JPEG, 85–96
JPEG 2000
hierarchical mode, 87
lossless mode, 87–88
overview, 86
progressive mode, 87
sequential mode, 86–87
MJPEG, 82
MPEG, 70, 79–82
MPEG-1, 82
MPEG-2, 83
MPEG-4, 83–84
MPEG-7, 84
MPEG-21, 84–85
overview, 59–60
temporal compression, 68–70
unconditional compression, 67–68
variable length codes, 64–65
wavelets, 61–62, 89–90
Computer, historical perspective, 94
Computer Measurement Group
(CMG), function, 109
Computer vision, technology, 220
Conductor, definition, 227
Construction sites, security, 162
Convention centers, security systems,
155–156
Correctional facilities, see Prisons
235
Crosstalk, definition, 227
CRT, see Cathode ray tube
CS-mount, lens, 169–170
Cypress Cove Lodge and Marina,
security, 161–162
DAC, see Digital-to-analog converter
Dairy farm, digital closed circuit
television applications,
215–216
DARPA, see Defense Advanced
Research Projects Agency
DCT, see Discrete Cosine Transfer
Decimal, definition, 227
Defense Advanced Research Projects
Agency (DARPA)
Internet development, 99
Video Surveillance and Monitoring
technology, 219–220
Differential Pulse Code Modulation
(DPCM), compression, 59
Digital signal, definition, 227
Digital signal processor (DSP)
definition, 227
overview, 167–168
Digital subscriber line (DSL)
asymmetric, 121–122
features, 121
xDSL, 122–123
Digital-to-analog converter (DAC),
function, 34
Digital video recorder (DVR)
advantages, 202
features, 202–203
historical perspective, 203
Digital video system (DVS), overview,
204
Discrete Cosine Transfer (DCT),
compression, 59–62, 90
Distortion, definition, 227
DivX, compression, 102
Dots per inch (dpi), monitor
resolution, 30–32
DPCM, see Differential Pulse Code
Modulation
dpi, see Dots per inch
DSL, see Digital subscriber line
DSP, see Digital signal processor
DVR, see Digital video recorder
236
Index
DVS, see Digital video system
EAP-TLS, see Extensible
Authentication ProtocolTransport Layer Security
Electromagnetic interference (EMI),
definition, 227
Electromagnetic spectrum
components, 46–49
overview, 36
radiation characteristics, 129–130
EMI, see Electromagnetic interference
Encryption
definition, 227
overview, 223–224
Energy, transfer, 4
Entropy, Shannon theory, 58
Ethernet
definition, 227
features, 125–126
Extensible Authentication ProtocolTransport Layer Security
(EAP-TLS), wireless security,
145
Facial recognition, overview, 222–223
Fast Ethernet, features, 126–127
Fiber optic cable, see Optical fiber
Field
definition, 227
interlace, 9
FM, see Frequency modulation
Fractal, codec compression, 61–62
Frame
definition, 227
interlace, 9
rate, 8, 35, 42
size, 35
Frame relay, features, 126
Frequency, definition, 4
Frequency modulation (FM),
principles, 45–46
Gamma, correction, 11
Gammaray, characteristics, 49
Gigabit, definition, 23–24, 227
Global Positioning System (GPS),
features, 142–143
GPS, see Global Positioning System
Grayscale
definition, 228
gamma correction, 11
steps, 33–34
GSM-PCS, cellular system, 134
H.261, compression, 88
H.263, compression, 88–89
H.263+, compression, 89
H.264, compression, 89
HAN, see Home area network
Hertz, definition, 228
Home area network (HAN),
definition, 96
Hospitals
security systems, 154
telemedicine, 190–193
HTML, see Hypertext Markup
Language
HTTP, see Hypertext Transfer Protocol
Hub, network, 97–98
Hue, definition, 13
Huffman encoding, compression,
65–66
Hypertext Markup Language (HTML),
definition, 228
Hypertext Transfer Protocol (HTTP)
definition, 228
overview, 101
IAI, see International Association for
Identification
IEC, see International Electrochemical
Commission
IEEE, see Institute of Electrical and
Electronics Engineers
Image analysis, overview, 220–221
Information Storage Industry
Consortium (INSIC),
function, 109
Infrared
camera, 165–166
filter, 171
illuminators, 170–171
Infrared
characteristics, 48
transmission, 131–132
INSIC, see Information Storage
Industry Consortium
Index
237
Institute of Electrical and Electronics
Engineers (IEEE)
802.111 specifications, 137–140
standardization activities,
78
Integrated Services Digital Network
(ISDN)
definition, 228
features, 119–120
Intelligent video, overview, 221–222
International Association for
Identification (IAI), activities,
223
International Electrochemical
Commission (IEC), functions,
77
International Organization for
Standardization (ISO)
definition, 228
functions, 76
members, 76
International Telecommunications
Unit (ITU), video standards,
25
Internet
definition, 228
historical perspective, 99–100
streaming and downloadable video,
100–104
video distribution, 99
Internet Protocol (IP)
definition, 228
overview, 99–100
Intranet, definition, 94–95, 228
IP, see Internet Protocol
IP address, definition, 228
ISDN, see Integrated Services Digital
Network
ISO, see International Organization for
Standardization
ITU, see International
Telecommunications
Unit
LAN, see Local area network
Law Enforcement & Emergency
Services Video Association
(LEVA), functions, 194
LCD, see Liquid crystal display
LCOS, see Liquid crystal on silicon
Lens
C-mount, 169–170
CS-mount, 169–170
speed, 168–169
varifocal, 170
LEVA, see Law Enforcement &
Emergency Services Video
Association
Light wave, characteristics, 48–49
Liquid crystal display (LCD),
monitors, 174–175
Liquid crystal on silicon (LCOS),
monitors, 176
LMDS, see Local Multipoint
Distribution Service
Local area network (LAN)
definition, 96, 229
wireless, 136–137
Local Multipoint Distribution Service
(LMDS), features, 136
Luminance
black and white images, 5, 12–13
color images, 50
definition, 229
Joint Photographic Expert Group
(JPEG), compression
standard, 85–86
JPEG, see Joint Photographic Expert
Group
Macdonald, Copthorne, 40–41
MAN, see Metropolitan area network
Manufacturing, digital closed circuit
television applications,
211–212
JPEG 2000, compression
hierarchical mode, 87
lossless mode, 87–88
overview, 86
progressive mode, 87
sequential mode, 86–87
JPEG 2000 Wireless (JPWL), features,
136
JPWL, see JPEG 2000 Wireless
Kilo, definition, 23–24, 228
Kilobits per second, definition, 228
238
Index
Matrix switcher, features, 172
Mega, definition, 23–24, 229
Megabits per second, definition,
229
Metropolitan area network (MAN),
definition, 96
Microwave
characteristics, 47–48
terrestrial microwave, 143
transmission, 132
MJPEG, compression, 82
Modem, definition, 229
Monitor
cathode-ray tube, 173–174
liquid crystal display, 174–175
liquid crystal on silicon, 176
organic light emitting diode,
176
plasma display, 175–176
touch screens, 176–177
Monitoring, digital closed circuit
television systems
alarm verification, 206
inventory theft, 208–209
open/close escort service, 208
remote interactive monitoring,
206–207
remote site management, 209–210
video guard tour, 207–208
Moore’s Law, 94
Morse code, 59–60
Motion Picture Experts Group
(MPEG), compression
standards
MPEG-1, 82
MPEG-2, 83
MPEG-4, 83–84
MPEG-7, 84
MPEG-21, 84–85
overview, 70, 79–82
MPEG, see Motion Picture Experts
Group
MRA, see Multi-resolution analysis
Multi-resolution analysis (MRA),
compression, 91–92
Multiplexer, switching, 171,
172
Municipalities, security systems,
159–160
NAS, see Network attached storage
National monuments
digital closed circuit television
applications, 212–213
security systems, 151–153
National Television Systems
Committee (NTSC)
definition, 229
video standards, 2–3, 37
National Transportation Safety Board
(NTSB), digital closed circuit
television applications,
213–214
Network
definition, 95, 229
hub, 97–98
router, 98
switch, 98
topology, 96–97
types, 96
video, 98–99
Network attached storage (NAS),
principles, 109
Network video recording (NVR),
overview, 203–204
Nipkow disk, principles, 39
Noise
definition, 13, 229
sources, 13–14
NTSB, see National Transportation
Safety Board
NTSC, see National Television
Systems Committee
Nuclear material monitoring, digital
closed circuit television
applications, 213
NVR, see Network video recording
Nyquist theory, sampling rate, 24
OLED, see Organic light emitting
diode
Optical fiber
performance, 14, 116
standards
FDDI, 116
FDDI-2, 116
FTTP, 116
SONET, 116
structure, 115–116
Index
Organic light emitting diode (OLED),
monitors, 176
PAL, see Phase Alternating Line
Pattern recognition, overview, 221
PCM, see Pulse code modulation
People counting, overview, 221
Perimeter protection, systems
integration, 186–188
Peta, definition, 23–24, 229
Phase Alternating Line (PAL), video
standard, 37
Pixel
bits per pixel, 30
definition, 29
Plain old telephone service (POTS),
features, 119
Plasma, definition, 229
Plasma display, monitors, 175–176
Point-to-multipoint, definition, 229
Point-to-point, definition, 229
Political events, digital closed circuit
television applications,
195–196
POTS, see Plain old telephone service
Printer, applications and selection,
177–178
Prisons
security systems, 189–190
videoconferencing, 193–194
PSTN, see Public Switched Telephone
Network
Public Switched Telephone Network
(PSTN), features, 117, 119
Pulse code modulation (PCM),
analog-to-digital conversion,
24
Pulse modulation, principles, 45–46
Quantization
definition, 28, 229
process, 28–29
QuickTime, features, 103
Radio wave
characteristics, 46–47
frequency characteristics, 131
RAID, see Redundant array of
independent disks
239
RAM, see Random access memory
Random access memory (RAM)
definition, 230
features, 104
Read only memory (ROM)
definition, 230
features, 105
Real Time Streaming Protocol (RTSP),
overview, 101
RealVideo, features, 102
Redundant array of independent disks
(RAID), disk failure
protection, 106
Relative encoding, compression,
63–64
Retail facilities, security systems,
156–158
RLE, see Run-length encoding
ROM, see Read only memory
Router
definition, 230
network, 98
RTSP, see Real Time Streaming
Protocol
Run-length encoding (RLE),
compression, 62–63
Sampling rate, video, 24–28
Satellite, transmission, 141–143
Saturation, definition, 13,
230
School, see Campus
SECAM, see Sequential color with
memory
Security
airports, 150–151
banks, 161
campus security, 148–150
car lots, 158–159
casinos, 160–161
convention centers, 155–156
critical infrastructure protection,
148
definition, 147
hospitals, 154
municipalities, 159–160
national monuments, 151–153
retail facilities, 156–158
transportation, 153–154
240
Index
Security, wireless networks
Advanced Encryption Standard, 145
802.1x, 144
Extensible Authentication ProtocolTransport Layer Security, 145
Temporal Key Integrity Protocol,
146
Wi-Fi Protected Access 2, 145
Wi-Fi Protected Access, 144–145
Wired Equivalent Privacy, 144
Sequential color with memory
(SECAM), video standard, 37
Server, definition, 230
Shannon, Claude, 58
Spatial compression, principles, 68
SPC, see Storage performance council
Storage
capacity calculation, 35–36
hard disks, 105–106
RAM, 104
removable storage
magnetic media, 107
optical media, 107–108
solid-state storage, 108–109
ROM, 104
Storage performance council (SPC),
function, 109
SW56, see Switched 56
Switch, network, 98
Switched 56 (SW56), features, 123
Synchronization
alternating current as source, 17
importance, 15–17
vertical sync, 18
Systems integration
access control, 184–186
biometrics, 182–184
integrated versus interfaced,
180–182
overview, 179–180
perimeter protection, 186–188
standards, 180
T1, features, 123–124
T3, features, 124
TCP/IP, see Transmission Control
Protocol/Internet Protocol
TDMA, see Time Division Multiple
Access
Telemedicine, networks, 190–193
Temporal compression, principles,
68–70
Temporal Key Integrity Protocol
(TKIP), wireless security,
146
Tera, definition, 230
Terrestrial microwave (TMW),
features, 143
Thermal imaging, overview, 166–167
3G, features, 135
Time Division Multiple Access
(TDMA), transmission,
133–134
TKIP, see Temporal Key Integrity
Protocol
TMW, see Terrestrial microwave
Topology, network, 96–97
Touch screen, types, 176–177
Traffic monitoring, digital closed
circuit television applications,
217–218
Transmission Control Protocol/
Internet Protocol (TCP/IP)
definition, 230
overview, 99–100
Transmission
ATM, 124–125
connection types, 117–118
DSL, 121–123
Ethernet, 125–126
fast Ethernet, 126–127
frame relay, 126
ISDN, 119–120
media, see Coaxial cable; Optical
fiber; Twisted pair
POTS, 119
PSTN, 117, 119
selection factors, 118
SW56, 123
T1, 123–124
T3, 124
wireless
broadband, 135–141
cellular, 132–135
Global Positioning System,
142–143
infrared, 131–132
microwave, 132
Index
radio, 131
security, 143–146
terrestrial microwave, 143
Transportation, security systems,
153–154
Twisted pair
Cat 5 standard, 113
definition, 230
performance, 112
shielded versus unshielded, 112
2G, features, 135
2.5G, features, 135
Ultra-wide band (UWB), features, 138,
141
Ultraviolet, characteristics, 49
Unconditional compression,
principles, 67–68
United States Geological Survey
(USGS), digital closed circuit
television applications, 215
USGS, see United States Geological
Survey
UWB, see Ultra-wide band
Value, definition, 230
Variable length codes (VLC),
compression, 64–65
Varifocal lens, features, 170
VCR, see Video cassette recorder
Vector quantization, codec
compression, 61–62
Video, definition, 230
Video cassette recorder (VCR)
consumer versus industrial-grade
equipment, 201–202
historical perspective, 199
tape features, 199–200
transport mechanism, 201
wear, 200–201
Videoconferencing
covert video, 195
law enforcement, 194–195
prisons, 193–194
Video guard tour, overview, 207–208
Video Surveillance and Monitoring
(VSAM), technology, 219–220
Video tape recorder (VTR), historical
perspective, 197–198
241
Visual display unit, definition, 230
VLC, see Variable length codes
VSAM, see Video Surveillance and
Monitoring
VTR, see Video tape recorder
WAN, see Wide area network
Wavelength, definition, 4
Wavelet
codec compression, 61–62
compression applications, 89–90
definition, 231
WEP, see Wired Equivalent Privacy
White level, definition, 5
Wi-Fi, see Wireless fidelity
Wi-Fi Protected Access (WPA),
wireless security, 144–145
Wi-Fi Protected Access 2 (WPA2),
wireless security, 145
Wide area network (WAN)
definition, 96, 230
wireless, 141
WiMAX, see Worldwide
interoperability for
microwave access
Wineries, digital closed circuit
television applications,
214–215
Wired Equivalent Privacy (WEP),
wireless security, 144
Wireless fidelity (Wi-Fi), features,
137
Wireless local area network (WLAN),
features, 136–137
Wireless universal serial bus (WUSB),
features, 141
Wireless wide area network (WWAN),
features, 141
Wireless, definition, 231
WLAN, see Wireless local area
network
Worldwide interoperability for
microwave access (WiMAX),
features, 137–138
WORM, see Write-once-read-many
WPA, see Wi-Fi Protected Access
WPA2, see Wi-Fi Protected Access 2
Write-once-read-many (WORM),
storage, 108
242
Index
WUSB, see Wireless universal serial
bus
WWAN, see Wireless wide area
network
X-ray, characteristics, 49
YCbCr system, overview, 51
Zero crossing point, synchronization,
17
ZyGoVideo, features,
103
BONUS GLOSSARY
SURVEILLANCE TERMS
Excerpted from
Herman Kruegle, CCTV Surveillance: Analog and Digital Video
Practices and Technology, Second Edition
ISBN: 978-0-7506-7768-4
December 2006
Have you seen the new, fully updated edition of this classic Butterworth-Heinemann
Security title?
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Now that you’ve read Harwood’s Digital CCTV,
look for CCTV Surveillance, Second Edition, and take your
knowledge to the next level!
GO TO
http://books.elsevier.com/security
FOR COMPLETE INFORMATION ON
ORDERING BUTTERWORTH-HEINEMANN
SECURITY BOOKS
This page intentionally left blank
Glossary of CCTV
Surveillance Terms
Many terms and definitions used in the security industry are
unique to CCTV surveillance; others derive from the electro-optical
and information-computer industries. This comprehensive glossary will help the reader better understand the literature, interpret
manufacturers’ specifications, and write bid specifications and
requests for quotation. These terms encompass the CCTV, physical
computer and communications industries, basic physics, electricity, mechanics, and optics.
Aberration Failure of an optical lens to produce exact point-topoint correspondence between an object and its image.
ABC Automatic brightness control In display devices, the selfacting mechanism that controls brightness as a function of ambient
light.
Access point An electronic device for connecting wireless PC
cameras directly to the Internet.
Achromatic lens A lens consisting of two or more elements,
usually of crown and flint glass, that has been corrected for chromatic aberration with respect to two selected colors or light
wavelengths.
245
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BONUS MATERIAL
Active Video Lines The video lines producing the picture. All
video lines not occurring in the horizontal and vertical blanking
intervals.
ADSL Asymmetric DSL A DSL technology providing asymmetrical bandwidth over a single wire pair. The downstream
bandwidth going from the network to the subscriber is typically
greater than the upstream bandwidth going from the subscriber
to the network. See Direct Subscriber Line.
AF Auto-focus A system by which the camera lens automatically
focuses on a selected part of the video scene.
AFC Automatic frequency control A feature whereby the
frequency of an oscillator is automatically maintained within
specified limits.
AGC Automatic gain control A process by which gain is automatically adjusted as a function of input or other specified parameter to maintain the output nearly constant.
Alarming switcher
see Switcher, Alarming.
Ambient temperature The temperature of the environment. The
temperature of the surrounding medium, such as air, gas, or liquid
that comes into contact with the apparatus.
Amplifier A device whose output is essentially an enlarged
reproduction of the input and that does not draw power from the
input source.
Amplifier, distribution A device that provides several isolated
outputs from one looping or bridging input. The amplifier has
sufficiently high input impedance and input-to-output isolation to
prevent loading of the input source.
Analog Signal The representation of data by continuously variable quantities in digital format as opposed to a finite number of
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247
discrete quantities. An electrical signal that varies continuously,
not having discrete values.
Analog Television The “standard” television broadcast. Analog
signals vary continuously, representing fluctuations in color and
brightness of a visual scene.
Angle of view The maximum scene angle that can be seen
through a lens or optical-sensor assembly. Usually described in
degrees, for horizontal, vertical, or circular dimension.
Antenna An electrical signal gathering or transmitting device used
with electrical receivers and transmitters for collecting or propagating an electrical signal through the airwaves. The primary antenna
specifications are vertical and horizontal directivity and gain, input
impedance and bandwidth, and power handling capacity.
Aperture An opening that will pass light, electrons, or other
forms of radiation. In an electron gun, the aperture determines the
size of, and has an effect on, the shape of the electron beam. In
television optics, the aperture is the effective diameter of the lens
that controls the amount of light reaching the image sensor.
Aperture, clear
see Clear aperture.
Aperture, numerical
see Numerical aperture.
Aperture stop An optical opening or hole that defines or limits
the amount of light passing through a lens system. The aperture
stop takes the form of the front lens diameter in a pinhole lens, an
iris diaphragm, a neutral density or spot filter.
Arc lamp An electric-discharge lamp with an electric arc between
two electrodes to produce illumination. The illumination results
from the incandescence of the positive electrode and from the
heated, luminous, ionized gases that surround the arc.
ASIS
American Society for Industrial Security.
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Aspect ratio The ratio of width to height for the frame of the
video picture in CCTV or broadcast television. The NTSC and PAL
standard is 4 : 3. The aspect ratio for high-definition television
HDTV is 16 : 9.
Aspheric An optical element having one or more surfaces that
are not spherical. The spherical surface of the lens is slightly altered
to reduce spherical aberration, thereby improving image quality.
Astigmatism A lens aberration that causes an object point to be
imaged as a pair of short lines at right angles to each other.
ATM Asynchronous Transfer Mode The communications standard that allows multiple traffic types (voice, video, or data) to be
conveyed in fixed-length cells rather than the random length
“packets” as used in Ethernet and Fiber Distributed Data Interface
(FDDI). This enables very high speeds, making ATMs popular for
demanding network backbones. Newer ATMs also support WAN
transmissions.
ATSC Advanced Television Systems Committee An international organization with a committee responsible for digital television standards and development.
Attenuation A reduction in light or electrical signal or energy
strength. In electrical systems attenuation is often measured in
decibels or decibel per unit distance. In optical systems the units
of measure are f-number or optical density. See also Decibel.
Audio frequency Any frequency corresponding to a normally
audible sound wave—roughly from 15 to 15,000 Hz.
Auto balance A system for detecting errors in color balance in the
white and black areas of the picture and automatically adjusting the
white and black levels of both the red and blue signals as needed.
Auto light range The range of light—such as sunlight to
moonlight or starlight—over which a TV camera is capable of
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249
automatically operating at specified output and within its dynamic
range.
Automatic iris A mechanical diaphragm device in the lens that
self-adjusts optically to light level changes via the video signal
from the television camera. The iris diaphragm opens or closes the
aperture to control the light transmitted through the lens. Typical
compensation ranges are 10,000–300,000 to 1. Automatic iris lenses
are used on solid-state CCD, ICCD, and CMOS cameras and SIT,
ISIT tube cameras.
Automatic iris control An electro-optic accessory to a lens that
measures the video level of the camera and opens and closes the
iris diaphragm to compensate for light changes.
Automatic light compensation The degree to which a CCTV
camera can adapt to varying lighting conditions.
Automatic light control The process by which the illumination
incident upon the face of a pickup device is automatically adjusted
as a function of scene brightness.
Automatic sensitivity control The self-acting mechanism that
varies system sensitivity as a function of specified control parameters. This may include automatic target control, automatic light
control, etc. or any combination thereof.
Axis, optical
see Optical axis.
Backbone The part of a network that acts as the primary
network path for traffic moving between rather than within
networks.
Back focus The distance from the last glass surface of a lens to
the focused image on the sensor.
Back porch That part of a composite video signal that lies
between the trailing edge of a horizontal sync pulse and the
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trailing edge of the corresponding blanking pulse. The color burst,
if present, is not considered part of the back porch.
Band pass A specific range of frequencies that will be passed
through an optical or electronic device or system.
Bandwidth The data carrying capacity of a device or network
connection. The number of hertz (Hz, cycles per second) expressing
the difference between the lower and upper limiting frequencies of
a frequency band. Also, the width of a band of frequencies.
Bandwidth limited gain control A control that adjusts the gain
of an amplifier while varying the bandwidth. An increase in gain
reduces the bandwidth.
Barrel distortion An electronic or optical distortion in television
systems that makes the video image appear to bulge outward on
all sides like a barrel.
Beam A concentrated, unidirectional flow of electrons, photons,
or other energy: 1) A shaft or column of light; a bundle of rays
consisting of parallel, converging, or diverging rays. 2) A concentrated stream of particles that is unidirectional. 3) A unidirectional
concentrated flow of electromagnetic waves.
Beam splitter An optical device for dividing a light beam into
two or more separate beams. The splitting can be done in the
parallel (collimated) beam or in the focused image plane.
Beam width, angular beam width The angular beam width of a
conical beam of light. The vertex angle of the cone, which determines the rate at which a beam of energy diverges or converges.
Lasers produce very narrow angle or very nearly parallel beams.
Thermal light sources (filament, fluorescent, etc.) produce wideangle beams.
Beta format An original 1/2-inch Sony video cassette recorder
format not compatible with the VHS format.
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Bifocal lens A lens system having two different focal length
lenses that image two identical or different scenes onto a single
camera sensor. The two scenes appear as a split image on the
monitor.
Bit binary digit The smallest unit of computer memory. A bit is
a binary digit representing two different states (1, 0), either on or
off. A method of storing information that maps an image bit
by bit.
Bitmap A bitmap defines a display space and the color for each
pixel or “bit” in the display space. GIF and JPEG are examples of
graphic image file types that contain bitmaps.
Bit rate The bit rate is the number of bits transmitted per second
(bps).
Blackbody A thermally heated body that radiates energy at all
wavelengths according to specific physical laws.
Black clamp An electronic circuit that automatically maintains
the black video level (no light) at a constant voltage.
Black level The picture signal level corresponding to a specified
maximum limit for black peaks.
Black negative The television picture signal in which the polarity of the voltage corresponding to black is negative with respect
to that which corresponds to the white area of the picture signal.
Blanking The process whereby the beam in an image pickup or
cathode ray display tube is cut off during the retrace period so that
it won’t create any visible information on the screen.
Blanking level The level of a composite picture signal that separates the range containing picture information from the range
containing synchronizing information; also called pedestal, or
blacker-than-black.
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Blooming In a camera, the visual effects caused by over exposing a CCD or other sensor. In CRT monitors, the condition that
occurs when the phosphors on the screen are driven harder than
they should be. This causes defocusing of regions of the picture
where the brightness is at an excessive level, due to enlargement
of spot size and halation of the screen of the CRT tube.
BNC Bayonet-Neil-Concelman A connector named after its
designers and widely used in the video and RF transmission
industry for terminating and coupling coaxial cables. The BNC
connector is easy to install, reliable, and with little video signal
loss. Used with 75 ohm cable for video applications cable and
50 ohm cable for RF.
Borescope An optical device used for the internal inspection of
mechanical and other parts. The long tube contains a multiple lens
telescope system that usually has a high f-number (low amount of
light transmitted).
Boresight An optical instrument used to check alignment or
pointing direction. A small telescope mounted on a weapon or
video camera so that the optical axis of the telescope and the
mechanical axis of the device coincide. The term also applies to
the process of aligning other optical equipment.
Bounce Sudden variation in picture presentation (brightness,
size, and so on) independent of scene illumination.
Breezeway In NTSC color, that portion of the back porch between
the trailing edge of the sync pulse and the start of the color
burst.
Bridge A digital electronic device that passes data packets
between multiple network segments using the same communication protocol. If a packet is destined for use within the sender’s
own network segment, the bridge keeps the packet local. If the
packet is bound for another segment, the bridge passes the packet
onto the network backbone.
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Bridging Connecting two electrical circuits in parallel. Usually
the input impedances are large enough so as not to affect the signal
level.
Bridging amplifier An amplifier for bridging an electrical circuit
without introducing an apparent change in the performance of
that circuit.
Brightness The attribute of visual perception whereby an area
appears to emit more or less light. Luminance is the recommended
name for this photometric quantity, which has also been called
brightness.
Brightness control The manual bias control on a cathode ray
tube or other display device that determines both the average
brightness and the contrast of a picture.
Browser An application program that provides a way to look at
and interact with all the information on the World Wide Web. The
two most popular Web browsers are Netscape and Microsoft
Internet Explorer.
Buffer A temporary computer storage area usually held in RAM
and used as a temporary holding area for data.
Burn-in Also called burn. An image that persists in a fixed position in the output signal of a camera tube after the camera has been
pointed toward a different scene. An image that persists on the
face of a CRT monitor with no input video signal present.
Byte A group of 8 bits or 256 discrete items of information, such
as color, brightness, etc. The basic unit of information for the
computer.
C-mount An industry standard for lens mounting. The C-mount
has a thread with a 1-inch diameter and 32 threads per inch. The
distance from the lens mounting surface to the sensor surface is
0.69 inches (17.526 mm).
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Cable A number of electrical conductors (wires) bound in a
common sheath. These may be video, data, control, or voice cables.
They may also take the form of coaxial or fiber-optic cables.
Cable Modem A class of modem that is used for connecting to
a cable TV network, which in turn can connect directly to the
Internet. Cable based connections to the Internet are typically
much faster than dial-up modems.
Camera control unit CCU Remote module that provides control
of camera electronic circuitry such as camera shutter speed, video
amplification, and lens parameters.
Camera format Video cameras have 1/6, 1/4, 1/3, 1/2, and 2/3inch sensor image formats. The actual scanned areas used on the
sensors are 3.2 mm horizontal × 2.4 mm vertical for the 1/4-inch,
4.8 mm horizontal × 3.6 mm vertical for the 1/3-inch, 6.4 mm horizontal × 4.8 mm vertical for the 1/2-inch, and 8.8 mm horizontal ×
6.6 mm vertical for the 2/3-inch.
Camera housing An enclosure designed to protect the video
camera from tampering or theft when indoors or outdoors or from
undue environmental exposure when placed outdoors.
Camera, television An electronic device containing a solid state
sensor or an electronic image tube and processing electronics. The
image formed by a lens ahead of the sensor is clocked out for a
solid state sensor or rapidly scanned by a moving electron beam
in a tube camera. The sensor signal output varies with the local
brightness of the image on the sensor. These variations are transmitted to a CRT, LCD, or other display device, where the brightness of the scanning spot is controlled. The scanned location (pixel)
at the camera and the scanned spot at the display are accurately
synchronized.
Camera tube An electron tube that converts an optical image
into an electrical current by a scanning process. Also called a
pickup tube or television camera tube.
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Candela cd Unit of measurement of luminous intensity. The
candela is the international unit that replaces the candle.
Candle power, cp Light intensity expressed in candles. One footcandle (fc) is the amount of light emitted by a standard candle at
1-foot distance.
Catadioptric system A telephoto optical system embodying both
lenses and image-forming mirrors. Examples are the Cassegrain,
Schmidt and Maksutov telescope. Mirrors are used to reduce the
size and weight of these long focal length lenses.
CAT Cable A class of cables using unshielded twisted pairs
(UTP) for transmitting video, audio, data, and controls. The differences are based mainly on bandwidth, copper size, and electrical performance. The most common are CAT 3, 4, 5, 5e, and 6, as
defined by the EIA and TIA (Telecommunications Industry
Association).
Cathode ray tube CRT A vacuum tube in which electrons emitted
by a heated cathode are focused into a beam and directed toward
a phosphor-coated surface, which then becomes luminescent at
the point where the electron beam strikes. Prior to striking the
phosphor, the focused electron beam is deflected by electromagnets or two pairs of electrostatically charged plates located between
the electron “gun” and the screen.
CATV Cable television, Community antenna television A cable
television distribution system primarily used for consumer TV
broadcast programming to a building or small community.
CCD Charge coupled device A solid-state semiconductor
imaging device used in most current security cameras. This sensor
has hundreds of thousands of photo-sites (pixels) that convert
light energy into electronic signals and with the camera electronics
eventually into the video signal. The CCD sensor sizes is used in
security systems are: 1/6, 1/4, 1/3, and 1/2 inch (measured
diagonally).
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CCIR International Radio Consultative Committee A global
organization responsible for establishing television standards. The
CCIR format uses 625 lines per picture frame, with a 50 Hz power
line frequency.
CCTMA Closed Circuit Television Manufacturers Association
A former division of the EIA, a full-service national trade organization promoting the CCTV industry and the interests of its
members.
CCTV camera The part of a CCTV system that captures a scene
image and converts the light image into an electrical representation for transmission to a display or recording device.
CCTV Closed-circuit television A closed television system used
within a building or complex to visually monitor a location or
activity for security or industrial purposes. CCTV does not broadcast consumer TV signals but transmits in analog or digital form
over a closed circuit via an electrically conducting cable, fiberoptic cable, or wireless transmission.
CCTV monitor That part of the CCTV system which receives the
picture from the CCTV camera and displays it.
Character generator The equipment used to create titles or other
text in a video image. The device is used to generate words and
numbers in a video format.
Chroma The characteristics of color information, independent of
luminance intensity. Hue and saturation are qualities of chroma.
Black, gray, and white objects do not have chroma characteristics.
Chromatic aberration A design flaw in a lens or lens system that
causes the lens to have different focal lengths for radiation of different wavelengths. The dispersive power of a simple positive lens
focuses light from the blue end of the spectrum at a shorter distance than light from the red end. This deficiency produces an
image that is not sharp.
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Chrominance signal The portion of a video signal that carries
hue and saturation color information.
CIF Common Image Format A standard defining a digital pixel
resolution. In the HDTV format the CIF resolution is 1,920 × 1,080
pixels, not to be confused with Common Intermediate Format.
CIF Common Intermediate Format A commonly used television
standard for measuring resolution. One CIF equals 352 × 240 pixels
for NTSC and 352 × 288 for PAL. Full resolution is considered to
be 4CIF, which is 704 × 480 pixels for NTSC and 704 × 576 pixels
for PAL. Quarter resolution or 1/4CIF equals 176 × 120 for NTSC
and 176 × 144 for PAL.
Clamping The process and circuitry that establishes a fixed level
for the television picture level at the beginning of each scanning
line.
Clear aperture The physical opening in a lens or optical system
that restricts the extent of the bundle of rays incident on the given
surface. It is usually circular and specified by its diameter.
Client A networked PC or terminal that shares “services” with
other PCs. These services are stored on or administered by a
server.
Client/Server Client/Server describes the relationship between
two computer programs in which one program, the client, makes
a service request from another program, the server, which fulfills
the request. The client/server model is one of the founding concepts of network computing. Most business applications written
today use the client/server model as does the Internet’s main
program, TCP/IP.
Clipping The shearing off of the peaks of a signal. For a picture
signal, clipping may affect either the positive (white) or negative
(black) peaks. For a composite video signal, the sync signal may
be affected.
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Close-up lens A low-magnification (low power) accessory lens
that permits focusing on objects closer to the lens than it has been
designed for.
CMYK The primary colors of light are red, green, and blue. The
primary colors of pigments such as ink or paint are cyan, magenta,
and yellow. Adding all three pigments together should produce
black but often produces a poor black. Therefore black is obtained
from sources such as carbon and called the fourth “primary” in the
printing process. The letter K is used for black. The grouping of the
letters CMYK is usually associated with the color print industry.
Coaxial cable A cable capable of carrying a wide range of frequencies with low signal loss. In its simplest form it consists of a stranded
metallic shield with a single wire accurately placed along the center
of the shield and isolated from the shield by an insulator.
Codec EnCOder/DECcoder A process or device by which or in
which a signal is encoded for transmission or storage, then decoded
for play back. An algorithm that handles the compression and
decompression of video files. As a device, a box or computer card
that accomplishes the encode/decode process.
Collimated
A parallel beam of light or electrons.
Color bar test pattern A special test pattern for adjusting color
TV receivers or color encoders. The upper portion consists of vertical bars of saturated colors and white. The lower horizontal bars
have black-and-white areas and I and Q signals.
Color saturation The degree of mixture of a color and white.
When a color is mixed with little or no white, it is said to have a
high saturation. Low saturation denotes the addition of a great
amount of white, as in pastel colors.
Color temperature The term used to denote the temperature of
a blackbody light source that produces the same color as the light
under consideration. Stated in degrees Kelvin.
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Component video The uncoded output of a video camera,
recorder, etc., whereby the red, green, blue, chrominance, and
luminance signals are kept separate. Not to be confused with
composite video.
COM port A serial communication port that supports the RS-232
standard of communication.
Composite video An analog, encoded signal used in television
transmission, including the picture signal (intensity and color), a
blanking signal, and vertical and horizontal synchronizing signals.
All components of the composite video signal are transmitted
down a single cable simultaneously.
Compression, Analog The reduction in gain at one level of a
analog signal with respect to the gain at another level of the same
signal.
Compression, Digital The removal of redundant information
from a signal to decrease the digital transmission or storage
requirements. The use of mathematical algorithms to remove
redundant data (bits) at the sending end without changing its
essential content (encoding). The two generic types are lossy and
lossless. There are many compression algorithms with the most
common being MPEG, M-JPEG, H.264, and wavelet.
Concave A term describing a hollow curved surface of a lens or
mirror; curved inward.
Contrast The range of difference between light and dark values
in a picture, usually expressed as contrast ratio (the ratio between
the maximum and minimum brightness values).
Control panel A rack at the monitor location containing a number
of controls governing camera selection, pan and tilt controls, focus
and lens controls, etc.
Convergence The crossover of the three electron beams of a
three-gun tri-color picture tube. This normally occurs at the plane
of the aperture mask.
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Convex A term denoting a spherically shaped optical surface of
a lens or mirror; curved outward.
Corner reflector, corner cube prism A corner reflector having
three mutually perpendicular surfaces and a hypotenuse face.
Light entering through the hypotenuse is totally internally reflected
by each of the three surfaces in turn, and emerges through the
hypotenuse face parallel to the entering beam and returns entering
beams to the source. It may be constructed from a prism or three
mutually perpendicular front surface mirrors.
Covert surveillance In television security, the use of camouflaged (hidden) lenses and cameras for the purpose of viewing a
scene without being seen.
Cross-talk Interference between adjacent video, audio, or optical
channels.
CS-mount An industry standard for lens mounting. The CSmount has a thread with a 1-inch diameter and 32 threads per inch.
The distance from the lens mounting surface to the sensor surface
is 0.492 inches (12.497 mm).
Cutoff frequency That frequency beyond which no appreciable
energy is transmitted. It may refer to either an upper or lower limit
of a frequency band.
Dark current The charge accumulated by pixels while not
exposed to light. The current that flows in a photo-conductor
when it is placed in total darkness.
Dark current compensation A circuit that compensates for the
dark current level change with temperature.
DC restoration The re-establishment by a sampling process of
the DC and low-frequency components of a video signal that has
been suppressed by AC transmission.
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DC transmission A form of transmission in which the DC component of the video signal is transmitted.
Decibel dB A measure of the voltage or power ratio of two
signals. In system use, a measure of the voltage or power ratio of
two signals provided they are measured across the same value of
impedance. Decibel gain or loss is 20 times log base 10 of the
voltage or current ratio (Voutput/Vinput), and 10 times log base
10 of the power ratio (Poutput/Pinput).
Decoder The circuitry in a receiver that transforms the detected
signal into a form suitable to extract the original modulation or
intelligence.
De-Compression The process of taking a compressed video
signal and returning it to its original (or near original) form it had
before compression.
Definition The fidelity of a television system with respect to the
original scene.
Delay distortion Distortion resulting from the nonuniform speed of
transmission of the various frequency components of a signal, caused
when various frequency components of the signal have different times
of travel (delay) between the input and the output of a circuit.
Delay line A continuous or periodic structure designed to delay
the arrival of an electrical or acoustical signal by a predetermined
amount.
Density A measure of the light-transmitting or reflecting properties of an optical material. It is expressed by the common logarithm
of the ratio of incident to transmitted light flux. A material having
a density of 1 transmits 10% of the light, of 2 transmits 1%, of 3
transmits 0.1%, etc. See Neutral density filter.
Depth of field The area between the nearest and the farthest
objects in focus. For a lens, the area along the line of sight in which
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objects are in reasonable focus. It is the measured from the distance
behind an object to the distance in front of the object when the
viewing lens shows the object to be in focus. Depth of field increases
with smaller lens aperture (higher f-numbers), shorter focal
lengths, and greater distances from the lens.
Depth of focus The range of detector-to-lens distance for which
the image formed by the lens is clearly focused.
Detail contrast The ratio of the amplitude of video signal representing high-frequency components with the amplitude representing the reference low-frequency component, usually expressed as
a percentage at a particular line number.
Detail enhancement Also called image enhancement. A system
in which each element of a picture is analyzed in relation to
adjacent horizontal and vertical elements. When differences are
detected, a detail signal is generated and added to the luminance
signal to enhance it.
Detection, image In video, the criterion used to determine
whether an object or person is observed (detected) in the scene.
Detection requires the activation of only 1 TV line pair.
DHCP Dynamic Host Configuration Protocol A protocol that
lets network administrators automate and centrally manage the
assignment of dynamic IP addresses to devices or a network. These
are temporary addresses that are created anew for each transmission. The DHCP keeps track of both dynamic and static IP addresses,
saving the network administrator the additional task of manually
assigning them each time a new device is added to the network.
Diaphragm
see Iris diaphragm.
Differential gain The amplitude change, usually of the 3.58MHz color subcarrier, introduced by the overall video circuit,
measured in dB or percent, as the picture signal on which it rides
is varied from blanking to white level.
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Differential phase The phase change of the 3.58-MHz color sub
carrier introduced by the overall circuit, measured in degrees, as
the picture signal on which it rides is varied from blanking to
white level.
Digital 8 A Sony format that uses Hi8 or 8 mm tapes to store
digital video.
Digital signal A video signal that is comprised of bits of binary
data, otherwise known as ones and zeros (1, 0). The video signal
travels from the point of its inception to the place where it is
stored, and then on to the place where it is displayed either as an
analog or digital presentation.
Digital Zoom The process by which a camera takes a small geometrical part of the original captured frame and zooms it digitally
with interpolation. Generally causes image degradation above 2×
to 3× zoom ratios.
Diopter A term describing the optical power of long focal length
lenses. It is the reciprocal of the focal length in meters. For example,
a lens with a focal length of 25 cm (0.25 m) has a power of 4
diopters.
Dipole antenna The most common antenna used in video for
wireless transmission of the analog or digital video signal consists
of a 50 ohm coaxial with a length of exposed center conductor
equal to a quarter wavelength of the transmission frequency. See
also Yaggi antenna.
Direct-Sequence Spread Spectrum DSSS see Spread Spectrum.
Distortion, electrical An undesired change in the waveform
from that of the original signal.
Distortion, optical A general term referring to the situation in
which an image is not a true reproduction of an object. There are
many types of distortion.
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Distribution amplifier
see Amplifier, distribution.
Dot bar generator A device that generates a specified output
pattern of dots and bars. It is used to measure scan linearity and
geometric distortion in video cameras and monitors. Also used for
converging cathode ray tubes.
DRAM Dynamic random access memory A type of computer
memory that is lost when the power is turned off.
Drive pulses
Synchronizing and blanking pulses.
DSL Direct Subscriber Line A digital phone service that provides full voice, video, and digital data over existing phone systems
at higher speeds than are available in typical dial-up Internet
sessions. There are four types: ADSL, HDSL, SDSL, and VDSL. All
operate via modem pairs: one modem located at a central office
and the other at the customer site. Asymmetric DSL technology
provides asymmetrical bandwidth over a single wire pair. The
downstream bandwidth from network to the subscriber is typically greater than the upstream bandwidth from the subscriber to
the network.
DSL Modem A modem that connects a PC to a network, which
in turn connects to the Internet.
DTV Digital Television Refers to all formats of digital video,
including SDTV and HDTV.
DVD Originally called Digital video disks, now called digital
versatile disk. These high-capacity optical disks now store everything from massive computer applications to full-length movies.
Although similar in physical size and appearance to a CD or a
CD-ROM the DVD significantly improves on its predecessors’
650 MB of storage. A standard single layer single-sided DVD can
store 4.7 GB of data. The two layer, single-sided version boosts the
capacity to 8.5 GB. The double-sided version stores 17 GB but
requires a different disk drive for the PC.
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DVR Digital video recorder
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Records video pictures digitally.
Dynamic range In television, the useful camera operating light
range from highlight to shadow, in which detail can be observed
in a static scene when both highlights and shadows are present.
In electronics, the voltage or power difference between the
maximum allowable signal level and the minimum acceptable
signal level.
Echo A signal that has been reflected at one or more points
during transmission with sufficient magnitude and time difference as to be detected as a signal distinct from that of the primary
signal. Echoes can be either leading or lagging the primary signal
and appear on displays as reflections or “ghosts”.
EDTV Extended definition television A marketing term for a
standard definition television set that displays a progressive scan
(non-interlaced) picture and usually has a horizontal resolution
near the high end of SDTV (over 600 pixels).
EIA Electronics Industry Association EIA is a trade alliance for
its members engaged in or associated with the manufacture, sale
or distribution of many categories of electronic equipment.
EIA interface A standardized set of signal characteristics (time
duration, waveform, delay, voltage, current) specified by the Electronic Industries Association.
EIA sync signal The signal used for the synchronizing of scanning specified in the Electrical Industry Association standards RS170 (for monochrome), RS-170A (for color), RS-312, RS-330, RS-420,
or subsequent specifications.
Electromagnetic focusing A method of focusing a cathode ray
beam to a fine spot by application of electromagnetic fields to one
or more deflection coils of an electron lens system.
Electronic viewfinder
see Viewfinder, electronic.
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Electron beam A stream of electrons emitted from the cathode
of a cathode ray tube.
Electrostatic focusing A method of focusing a cathode ray beam
to a fine spot by application of electrostatic potentials to one or
more elements of an electron lens system.
Endoscope An optical instrument resembling a long, thin periscope used to examine the inside of objects by inserting one
end of the instrument into an opening in the object. Endoscopes
comprise a coherent fiber-optic bundle with a small objective
lens to form an image of the object onto one end of the bundle,
and a relay magnifier lens at the sensor end to focus the fiber
bundle image onto the sensor. In an illuminated version, light
from an external lamp is piped down to the object by a second set
of thicker fibers surrounding the image-forming bundle. See also
Fiberscope.
Equalizer An electronic circuit that introduces compensation for
frequency discrimination effects of elements within the television
system.
Ethernet The most widely installed local area network technology that uses collision detection to move data packets between
workstations. Originally developed by Zerox and then developed
further by Digital Equipment Corp. (DEC) and Intel. An Ethernet
local area network (LAN) typically uses coaxial or fiber optic cable,
or twisted pair wires. The most common Ethernet is called 10BASET and provides transmission speeds up to 10 Mbps. See Fast
Ethernet, Gigabit Ethernet.
Extranet A network that provides external users (suppliers,
independent sales agents, dealers) access to company documents
such as price lists, inventory reports, shipping schedules, and
more.
Fader A control and associated circuitry for affecting fade-in and
fade-out of video or audio signals.
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Fast Ethernet The 100BASE-T10 Ethernet that provides transmission speeds up to 100 Mbps, 10 times faster than 10BASE-T.
FCC Federal Communications Commission The FCC is an independent federal regulatory agency charged with establishing policies to cover interstate and international communications via
radio, television, wire, satellite, and cable.
FDDI Fiber Distributed Data Interface A LAN technology
based on a 100 Mbps token passing networking over fiber-optic
cable. FDDI is usually reserved for network backbones in larger
organizations.
Fiber-optic bundle, coherent An optical component consisting
of many thousands of hair-like fibers coherently assembled so that
an image is transferred from one end of the bundle to the other.
The length of each fiber is much greater than its diameter. The
fiber bundle transmits a picture from one end of the bundle to the
other, around curves and into otherwise inaccessible places by a
process of total internal reflection. The positions of all fibers at
both ends are located in an exact one-to-one relationship with each
other.
Fiber-optic transmission The process whereby light is transmitted through a long, transparent, flexible fiber, such as glass or
plastic, by a series of internal reflections. For video, audio, or data
transmission over long distances (thousands of feet, many miles)
the light is modulated and transmitted over a single fiber in a
protective insulating jacket. For light image transmission closely
packed bundles of fibers can transmit an entire coherent image
where each single fiber transmits but one component of the whole
image.
Fiberscope A bundle of systematically arranged fibers that transmits a monochrome or full-color image which remains undisturbed when the bundle is bent. By mounting an objective lens on
one end of the bundle and a relay or magnifying lens on the other,
the system images remote objects onto a sensor. See Endoscope.
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Field One of the two equal parts into which a television frame
is divided in an interlaced system of scanning. There are 60 fields
per second in the NTSC system and 50 in the CCIR and PAL
systems. The NTSC field contains 262 1/2 horizontal TV lines and
the CCIR, PAL 312.5 TV lines.
Field frequency The number of fields transmitted per second in
a television system. Also called field repetition rate. The U.S. standard is 60 fields per second (60-Hz power source). The European
standard is 50 fields per second (50-Hz power source).
Field lens A lens used to affect the transfer of the image formed
by an optical system to a following lens system with minimum
vignetting (loss of light).
Filter An optically transparent material characterized by selective absorption of light with respect to wavelength (color). Electrical network of components to limit the transmission of frequencies
to a special range (bandwidth).
FireWire Also known as IEEE 1394 or i.LINK, FireWire is a twoway digital connection between computers and peripherals like
digital camcorders and cameras. Most equipment uses 4-pin ports
and connectors, but some use the 6-pin version.
FFL Fixed focal length lens A lens having one or more elements
producing a singular focal length. The focal length is measured in
millimeters or inches.
FHSS Frequency Hopping Spread Spectrum
trum Modulation.
see Spread Spec-
Firewall A set of programs that protects the resources of a private
network from outside users.
Flatness of field Appearance of the image to be flat and focused.
The object is imaged as a plane.
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Fluorescent lamp A high-efficiency, low-wattage arc lamp used
in general lighting. A tube containing mercury vapor and lined
with a phosphor. When current is passed through the vapor, the
strong ultraviolet emission excites the phosphor, which emits
visible light. The ultraviolet energy cannot emerge from the lamp
as it is absorbed by the glass.
FM Frequency modulation A process of translating baseband information to a higher frequency. The process: the
two input signals that are inputs to an FM modulator are the
baseband signal (video) and the carrier frequency (a constant
amplitude and constant frequency signal). The frequency of the
carrier is modulated (i.e. changed) and increased and decreased
about its center frequency by the amplitude of the baseband
signal.
f-number The optical speed or ability of a lens to pass light.
The f-number (f/#) denotes the ratio of the equivalent focal length
(FL) of an objective lens to the diameter (D) of its entrance pupil
(f/# = FL/D). The f-number is directly proportional to the focal
length and inversely proportional to the lens diameter. A smaller
f-number indicates a faster lens.
Focal length, FL The distance from the lens center, or second
principal plane to a location (plane) in space where the image of
a distant scene or object is focused. FL is expressed in millimeters
or inches.
Focal length, back The distance from the rear vertex of the lens
to the lens focal plane.
Focal plane A plane (through the focal point) at right angles to
the principal axis of a lens or mirror. That surface on which the
best image is formed.
Focal point The point at which a lens or mirror will focus parallel
incident radiation from a distant point source of light.
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Focus (1) The focal point. (2) The adjustment of the eyepiece or
objective of a visual optical device so that the image is clearly seen
by the observer. (3) The adjustment of a camera lens, image sensor,
plate, or film holder so that the image is sharp. (4) The point at
which light rays or an electron beam form a minimum-size spot.
Also the action of bringing light or electron beams to a fine
spot.
Focus control, electronic A manual electric adjustment for bringing the electron beam of an image sensor tube or picture tube to
a minimum size spot, producing the sharpest image.
Focus control, mechanical A manual mechanical adjustment for
moving the television sensor toward or away from the focal point
of the objective lens to produce the sharpest image.
Foot-candle fc A unit of illuminance on a surface 1 square foot
in area on which there is incident light of 1 lumen. The illuminance
of a surface placed 1 foot from a light source that has a luminous
intensity of 1 candle.
Foot-lambert A measure of reflected light in a 1 ft. area. A unit
of luminance equal to 1 candela per square foot or to the uniform
luminance at a perfectly diffusing surface emitting or reflecting
light at the rate of 1 lumen per square foot.
FOV Field of view The width, height, or diameter of a scene to
be monitored, determined by the lens focal length, the sensor size,
and the lens-to-subject distance. The maximum angle of view that
can be seen through a lens or optical assembly. Usually described
in degrees, for a horizontal, vertical, or circular dimension.
Frame A frame is a complete video picture made up of two separate fields of 262.5 lines (NTSC) and 312.5 lines in (CCIR). In the
standard U.S. NTSC 525-line system, the frame time is 1/30 second.
In the European 625-line system, the frame time is 1/25 second.
In a camera with progressive scan, each frame is scanned line-byline and not interlaced.
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Frame frequency The number of times per second that the frame
is scanned. The U.S. NTSC standard is 30 times per second. The
European standard is 25 times per second.
Frequency interlace The method by which color and black-andwhite sideband signals are interwoven within the same channel
bandwidth.
Frequency response The range or band of frequencies to which
a unit of electronic equipment will offer essentially the same
characteristics.
Front (First) surface mirror An optical mirror with the reflecting
surface applied to the front surface of the glass instead of to the
back. The first surface mirror is used to avoid ghost images. In
the more common rear surface mirror the light has to first
pass through the mirror glass, strike the rear surface and then exit
back out through the front of the mirror. This causes a secondary
image or ghost image. The reflecting material on first surface
mirrors is usually aluminum with a silicon monoxide protective
overcoat.
Front porch That portion of a composite picture signal which lies
between the leading edge of the horizontal blanking pulse and the
leading edge of the corresponding sync pulse.
f-stop
see f-number.
FTP File Transfer Protocol A part of the primary Internet protocol group TCP/IP is the simplest way to transfer files between
computers from the Internet servers to the client computer. Like
HTTP which transfers displayable web pages and related files, and
which transfers e-mail, FTP is an application protocol that uses the
Internet’s TCP/IP protocols.
Gain An increase in voltage, current, power, or light usually
expressed as a positive number or in decibels.
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GaAs Gallium arsenide diode A light-emitting diode (LED)
semiconductor device that emits low-power infrared radiation.
Used in television systems for covert area illumination or with
fiber optics for signal transmission. The radiation is incoherent and
has a typical beam spread of 10 to 50 degrees and radiates at 850
or 960 nanometers in the IR spectrum.
Gallium arsenide laser A narrow-band, narrow-beam IR radiation
device. The radiation is coherent, has a very narrow beam pattern,
typically less than 1/2 to 2 degrees, and radiates in the IR spectrum.
Galvanometer A device that converts an electrical signal into
mechanical movement without the complexity of a DC motor.
Used to control the iris vanes in the camera lens.
Gamma A numerical value of the degree of contrast in a television picture that is used to approximate the curve of output magnitude versus input magnitude over the region of interest. Gamma
values range from 0.6 to 1.0.
Gamma correction To provide for a linear transfer characteristic
from input to output device by adjusting the gamma.
Genlock An electronic device used to lock the frequency of an
internal sync generator to an external source.
Geometric distortion Any aberration that causes the reproduced
picture to be geometrically dissimilar to the original scene.
Ghost A spurious image resulting from an echo (electrical) or a
second or multiple reflection (optical). A front surface mirror produces no ghost, while a rear surface mirror produces a ghost.
Airwave RF and microwave signals reaching a receiver after
reflecting from multiple paths produce ghosts.
GIF Graphics Interchange Format One of the two most common
file formats for graphic images on the World Wide Web. The other
is JPEG.
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Gigabit Ethernet The latest version of Ethernet offering
1000 Mbps or 1 gigabit per second (Gbps) bandwidth that is 100
times faster than the original Ethernet. It is compatible with existing Ethernets since it uses the same CSMA/CD and MAC
protocols.
Grayscale Variations in value from white, through shades of
gray, to black, on a television screen. The gradations approximate
the tonal values of the original image picked up by the TV camera.
Most analog video cameras produce at least 10 shades of gray.
Digital cameras typically produce 256 levels of gray.
GUI Graphic User Interface A digital user control and processing for the user of that system. The Macintosh or Microsoft
Windows operating systems are examples of GUI systems.
H.264 A powerful MPEG compression algorithm standard developed through the combined effort of the ITU and MPEG organizations providing excellent compression efficiency and motion
detection attributes. See MPEG.
Halo A glow or diffusion that surrounds a bright spot on a television picture tube screen or image intensifier tube.
Hertz (Hz) The frequency of an alternating signal formerly called
cycles per second. The U.S. in Japan power-line frequency is 60 Hz.
Most European countries use a 50 Hz power line frequency.
High-contrast image A picture in which strong contrast between
light and dark areas is visible and where intermediate values,
however, may be missing.
High Definition Television HDTV A television standard
using digital signals. HDTV signals contain over 720 TV lines
of resolution compared with 525 TV line (NTSC) and 625 TV
line (PAL) in legacy analog standards. HDTV video formats
generally use a 1080i or 720p image format and have a 16 : 9 aspect
ratio.
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High-frequency distortion Distortion effects that occur at high
frequency. In television, generally considered as any frequency
above 15.75 KHz.
Highlights The maximum brightness of the TV picture occurring in regions of highest illumination.
Horizontal blanking
of horizontal retrace.
Blanking of the picture during the period
Horizontal hum bars Relatively broad horizontal bars, alternately black and white, that extend over the entire picture. They
may be stationary or may move up or down. Sometimes referred
to as a “venetian-blind” effect. In 60-Hz systems, hum bars are
caused by approximate 60-Hz interfering frequency or one of its
harmonic frequencies (such as 120 Hz).
Horizontal retrace The return of the electron beam from the
right to the left side of the raster after scanning one horizontal
line.
Horizontal, vertical resolution
see Resolution.
HTML Hypertext Markup Language A simple document formatting language used for preparing documents to be viewed by
a tool such as a WWW browser. A set of markup symbols or codes
inserted in a file posted on the WWW browser. HTML instructs
the web browser how to display web pages and images.
HTTP Hypertext Transfer Protocol A set of rules for exchanging
files that governs transmission of formatted documents (text,
graphic images, sound, video, and other files) for viewing over the
WWW and Internet. HTTP is an application protocol relative to
the TCP/IP suite of protocols, which are the basis for information
exchange on the Internet.
Hub A networking device that enables attached devices to
receive data streams that are transmitted over a network and
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interconnects clients and servers. This device makes it possible for
devices to share the network bandwidth available on a network.
In data communications a hub is a place of convergence where
data arrives from one or more locations and is forwarded to one
or more other locations. The hub acts as a wiring concentrator in
networks based on star topologies, rather than bus topologies
in which computers are daisy-chained together. A hub usually
includes a switch, which is also sometimes considered a hub. With
respect to its switching capability, a hub can also be considered a
router.
Hue Corresponds to colors such as red, blue, and so on. Black,
gray, and white do not have hue.
Hum Electrical disturbance at the power supply frequency or
harmonics thereof.
Hum modulation Modulation of a radio frequency, video, or
detected signal, by hum.
ICCD Intensified CCD A charge coupled device sensor camera,
fiber optically coupled to an image intensifier. The intensifier is a
tube or microchannel plate.
IEC International Telecommunications Union An international
organization that sets standards for the goods and services in
electrical and electronic engineering. See ISO.
IDE Integrated Drive Electronics A hard disk drive with builtin electronics necessary for use with a computer. A popular interface to attach hard drives to PCs where the electronics of the
controller are integrated with the drive instead of on a separate
PC card.
Identification, image In television, the criterion used to determine whether an object or person can be identified in the scene. It
requires approximately 7 TV-line pairs to identify an object or
person.
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IEEE Institute of Electronic and Electrical Engineers A technical organization writing standards and publishing technical articles for the electronic and electrical industry.
Illuminance Luminous flux incident per unit area of a surface;
luminous incidence.
Illumination, direct The lighting produced by visible radiation
that travels from the light source to the object without reflection.
Illumination, indirect The light formed by visible radiation that,
in traveling from the light source to the object, undergoes one or
more reflections.
Image A reproduction of an object produced by light rays. An
image-forming optical system collects light diverging from an
object point and transforms it into a beam that converges toward
another point. Transforming all the points produces an image.
Image distance The axial distance measured from the image to
the second principal point of a lens.
Image format In television, the size of the area of the image at
the focal plane of a lens, which is scanned by the video sensor.
Image intensifier A class of electronic imaging tubes equipped
with a light-sensitive photocathode—electron emitter at one end,
and a phosphor screen at the other end for visual viewing. An
electron tube or microchannel plate (MCP) amplifying (intensifying) mechanism produces an image at its output brighter than the
input. The intensifier can be coupled by fiber optics or lenses to
a CCD or CMOS sensor. The intensifier can be single stage or
multistage, tube or MCP.
Image pickup tube An electron tube that reproduces an image
on its fluorescent screen of an irradiation pattern incident on its
input photosensitive surface.
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Image plane The plane at right angles to the optical axis at the
image point.
Impedance The input or output characteristic of an electrical
system or component. For maximum power and signal transfer,
a cable used to connect two systems or components must have
the same characteristic impedance as the system or component.
Impedance is expressed in ohms. Video distribution systems have
standardized on 75-ohm unbalanced and 124-ohm balanced
coaxial cable. UPT uses a 100 ohm impedance. RF and microwave
systems use 50-ohm impedance coax.
Incident light
The light that falls directly onto an object.
Infrared radiation The invisible portion of the electromagnetic
spectrum that lies beyond about 750 nanometers (red end of the
visible spectrum) and extends out to the microwave spectrum.
Interference Extraneous energy that interferes and degrades the
desired signal.
Interlace, 2 to 1 A scanning format used in video systems in
which the two fields comprising the frame are synchronized precisely in a 2 to 1 ratio, and where the time or phase relationship
between adjacent lines in successive fields is fixed.
Interlace, random A scanning technique used in some systems
in which the two fields making up the frame are not synchronized,
and where there is no fixed time or phase relationship between
adjacent lines in successive fields.
Interlaced scanning A scanning process used to reduce image
flicker and electrical bandwidth. The interlace is 2 : 1 in the NTSC
system.
Internet A massive global network that interconnects tens of
thousands of computers and networks worldwide and is accessi-
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ble from any computer with a modem or router connection and
the appropriate software.
Intranet A network internal to an organization that takes advantage of some of the same tools popularized on the Internet. These
include browsers for viewing material, HTML for preparing
company directories or announcements, etc.
IP Address On the Internet each computer and connected appliance (camera switcher, router, etc.) must have a unique address.
This series of numbers functions similarly to a street address,
identifying the location of both sender and recipient for information dispatched over the computer network. The IP address has
32 bits in an 8 bit quad format. The four groups in decimal format
are separated by a period (.). Two quad groups represent the
network and two the machine or host address. An example of an
IP address is 124.55.19.64. See Subnet, Subnet mask.
IP Internet Protocol The method by which data is sent from one
computer to another over the Internet. Each computer, known as
a host on the Internet has one address that uniquely identifies it
from all other computers on the Internet. A Web page or an e-mail
is sent or received by dividing it into blocks called packets. Each
packet contains both the sender’s Internet address and the receiver’s address. Each of these packets can arrive in an order different
from the order from which they were sent. The IP just delivers
them and the Transmission Control Protocol TCP puts them in the
correct order. The most widely used version of the IP is IP Version
4 (IPv4).
Iris An adjustable optical-mechanical aperture built into a camera
lens to permit control of the amount of light passing through the
lens.
Iris diaphragm A mechanical device within a lens used to control
the size of the aperture through which light passes. A device for
opening and closing the lens aperture to adjust the f-stop of a
lens.
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ISC International Security Conference A trade organization to
provide a forum for manufactures to display their products. ISC
provides accredited security seminars for attendees.
ISDN Integrated Services Digital Network A communication
protocol offered by telephone companies that permits highspeed connections between computers and networks in remote
locations.
ISIT Intensified silicon intensified target A SIT tube with an
additional intensifier, fiber-optically coupled to provide increased
sensitivity.
ISO International Organization for Standardization A worldwide federation of national standards bodies from over 130 countries to promote the worldwide standardization of goods and
services. ISO’s work results in international agreements that are
published as international standards. The scope of ISO covers all
technical fields except electrical and electronic engineering, which
is the responsibility of IEC. Among well-known ISO standards is
the ISO 9000 business standard that provides a framework for
quality management and quality assurance.
Isolation amplifier An amplifier with input and output circuitry
designed to eliminate the effects of changes made by either upon
the other.
ISP Internet Service Provider A company or organization
that provides Internet access for companies, organizations, or
individuals.
ITU International Telecommunications Union An international
organization within which governments in the private sector coordinate global telecom networks and services.
Jitter Instability of a signal in either its amplitude, phase, delay,
or pulse width due to environmental disturbances or to changes
in supply voltage, temperature, component characteristics, etc.
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JPEG Joint Photographic Experts Group A standards group
that defined a compression algorithm commonly called JPEG that
is used to compress the data in portrait or still video images. The
JPEG file format is the ISO standard 10918 that includes 29 distinct
coding processes. Not all must be used by the implementer. The
JPEG file type used with the GIF format is supported by the WWW
protocol, usually with the file suffix “jpg”.
Kell factor The ratio of the vertical resolution to the number of
scanning lines. The empirical number that reduces the vertical
resolution of television images from the actual number of lines to
0.7 of that number. For the NTSC system the maximum resolution
is reduced to approximately 350 lines.
Lag The persistence of the electrical charge image for two or
more frames after excitation is removed and found in an intensifier
tube or monitor display.
LAN Local Area Network A digital network or group of network
segments confined to one building or campus. The LAN consists
of a series of PCs that have been joined together via cabling so that
resources can be shared, including file and print services.
LASER Light Amplification by Stimulated Emission of Radiation A LASER is an optical cavity, with plane or spherical mirrors
at the ends, that is filled with a light-amplifying material, and an
electrical or optical means of stimulating (energizing) the material.
The light produced by the atoms of the material generates a
brilliant beam of light that is emitted through one of the semitransparent mirrors. The output beam is highly monochromatic
(pure color), coherent, and has a narrow beam (small fraction
of a degree).
Laser diode
see Gallium arsenide laser.
LCD Liquid Crystal Display A solid-state video display created
by sandwiching an electrically reactive substance between two
electrodes. LCDs can be darkened or lightened by applying and
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removing power. Large numbers of LCD pixels group closely
together act as pixels in a flat-panel display.
Leading edge The major portion of the rise of a pulse, waveform
taken from the 10 to 90% level of total amplitude.
Lens A transparent optical component consisting of one or more
optical glass elements with surfaces so curved (usually spherical)
that they serve to converge or diverge the transmitted rays of an
object, thus forming a real or virtual image of that object.
Lens, fresnel Figuratively a lens that is cut into narrow rings and
flattened out. In practice a thin plastic lens that has narrow concentric rings or steps, each acting to focus radiation into an image.
Lens speed Refers to the ability of a lens to transmit light. Represented as the ratio of the focal length to the diameter of the lens.
A fast lens would be rated f/1.4. A much slower lens might be
designated as f/8. The larger the f-number, the slower the lens.
See f-number.
Lens system Two or more lenses so arranged as to act in conjunction with one another.
Light Electromagnetic radiation detectable by the eye, ranging
in wavelength from about 400 nm (blue) to 750 nm (red).
Limiting resolution A measure of resolution usually expressed
in terms of the maximum number of TV lines per TV picture
height discernible on a test chart.
Line amplifier An amplifier for audio or video signals that drive
a transmission line. An amplifier, generally broadband, installed
at an intermediate location in a main cable run, to compensate for
signal loss.
Linearity The state of an output that incrementally changes
directly or proportionally as the input changes.
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Line pairs The term used in defining television resolution. One
TV line pair constitutes one black line and one white line. The 525
NTSC system has 485 line pairs displayed.
LLL Low light level Camera and video systems capable of operating below normal visual response. An intensified video camera
such as an ICCD capable of operating in extremely poorly lighted
areas.
Load That component which receives the output energy of an
electrical device.
Loss A reduction in signal level or strength, usually expressed
in dB. A power dissipation serving no useful purpose.
Lossless Compression A form of video compression that does
not degrade the quality of the image.
Lossy Compression A form of compression in which image
quality is degraded during compression.
Low-frequency distortion Distortion effects that occur at low
frequency. In video, generally considered as any frequency below
15.75 kHz.
Lumen (lm) The unit of luminous flux, equal to the flux through
a unit solid angle (steradian) from a uniform point source of 1
candela or to the flux on a unit surface of which all points are at
a unit distance from a uniform point source of 1 candela.
Luminance A parameter that represents brightness in the
video picture. Luminous intensity (photometric brightness) of
any surface in a given direction per unit of projected area of the
surface as viewed from that direction, measured in foot-lamberts.
Abbreviated as Y.
Luminance signal The part of the NTSC composite color signal
that contains the scene brightness or black and white information.
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Luminous flux
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The time rate of flow of light.
Lux International system unit of illumination in which the meter
is the unit of length. One Lux equals 1 lumen per square meter.
MAC Media Access Control Protocol The MAC is the physical
address for any device used in a network: a computer, router, IP
camera, etc. The address consists of two parts and is 6 bytes long.
The first 3 bytes identify the company and the last 3 bytes are the
device serial number.
Magnetic focusing A method of focusing an electron beam by
the action of a magnetic field.
Magnification A number expressing the change in object to
image size. Usually expressed with a 1-inch focal length lens and
a 1-inch format sensor as a reference (magnification = M = 1). A
lens with a 2-inch focal length is said to have a magnification of
M = 2.
MAN Metropolitan Area Network A large network usually
connected via fiber optics to obtain the Gbit speeds and huge
volumes of digital transmission over long distances.
Matching The obtaining of like electrical impedances to provide
a reflection-free transfer of signal.
Matrix switcher A combination or array of electromechanical or
electronic switches that route a number of signal sources to one or
more designations. In video, cameras are switched to monitors,
recorders and networks.
Maximum aperture The largest size the iris diaphragm of the
lens can be opened resulting in the lowest lens f-number.
Megabits per second Mbps Defines the speed at which data is
traveling and is measured in millions of bits per second. This is a
measure of the performance of a device.
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Mercury arc lamp An intense electric arc lamp that generates
blue-white light when electric current flows through mercury
vapor in the lamp.
Metal arc lamp An intense arc lamp that generates a white light
when an electric current flows through the multimetal vapor in
the lamp.
MHz Megahertz
Unit of frequency equal to 1 million Hz.
Microcomputer A tabletop or portable digital computer
composed of a microprocessor, active memory storage, and permanent memory storage (disk) and which computes and controls
functions via a software operating system and applications
program.
Micron
Unit of length: one millionth of a meter.
Microphonics Audio-frequency noise caused by the mechanical
vibration of elements within a system or component.
Microprocessor The brain of the microcomputer. A very large
scale integrated circuit comprising the computing engine of a
microcomputer. The electronic chip (circuit) that does all the calculations and control of data. In larger machines it is called the
central processing unit (CPU).
Microwave transmission In television, a transmission means
that converts the camera video signal to a modulated (AM or FM)
microwave signal via a transmitter, and a receiver that demodulates the received microwave signal to the baseband CCTV signal
for display on a monitor.
Mirror, first or front surface An optical component on which the
reflecting surface is applied to the front of the glass instead of the
back, the front being the first surface of incidence and reflectance.
It produces a single image with no ghost. See First Surface
Mirror.
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Mirror, rear surface The common mirror in which the reflecting
surface is applied to the rear of the glass. It produces a secondary
or ghost image.
M-JPEG A digital video compression format developed from
JPEG, a compression standard for still images. When JPEG is
extended to a sequence of pictures in the video stream it becomes
M-JPEG or motion-JPEG.
Modem Derived from its function: modulator-demodulator. A
device that enables a computer to connect to other computers and
networks using ordinary phone lines. Modems modulate the digital
signals of the computer into analog signals for transmission and
then demodulate those analog signals back into digital language
that the computer on the other end can recognize. See Codec.
Modulation The process, or results of the process, whereby some
characteristic of one signal is varied in accordance with another
signal. The modulated signal is called the carrier. The carrier may
be modulated in several fundamental ways including: by varying
the amplitude, called amplitude modulation (AM); by varying the
frequency, called frequency modulation (FM); or by varying the
phase, called phase modulation (PM).
Moire pattern The spurious pattern in the reproduced picture
resulting from interference beats between two sets of periodic
structures in the image. Usually caused by tweed or checkerboard
patterns in the scene.
Monitor A CRT based monochrome or color display for viewing
a television picture from a camera output. The monitor does not
incorporate a VHF or UHF tuner and channel selector and displays
the composite video signal directly from the camera, DVR, VCR,
or any special-effects generator. Monitors take the form of a CRT,
LCD, plasma, and other.
Monochrome signal A black and white video signal with all
shades of gray. In monochrome television, a signal for controlling
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the brightness values in the picture. In color television, that part
of the signal which has major control of the brightness values of
the picture, whether displayed in color or in monochrome. The
minimum number of shades of gray for good image rendition
is 10.
Monochrome transmission The transmission of a signal wave
that represents the brightness values in the picture, not the color
(chrominance) values.
Motion detector A device used in security systems that reacts to
any movement in a CCTV camera image by automatically setting
off an alarm and/or indicating the motion on the monitor.
Motorized lens A camera lens fitted with small electric motors
that can focus the lens, open or close the iris diaphragm, or in the
case of the zoom lens, change the focal length by remote control.
MPEG-4 A compression standard formulated by the Moving
Pictures Experts Group. The MPEG-4 standard for digital video
and audio compression is optimized for moving images in which
the compression is based on the similarity of successive pictures.
MPEG-4 files carry an .mpg suffix. See also H.264.
Multicasting Refers to the propagation from one source to a
subset of potential destinations. A technique for simultaneously
sending multiple digital video streams on a single channel.
Multiplexer High speed electronic switch that combines two or
more video signals into a single channel to provide full-screen
images up to 16 or 32 displayed simultaneously in split image
format. Multiplexers can play back everything that happened on
any one camera without interference from the other cameras on
the system.
NAB National Association of Broadcasters
Nanometer (nm)
Unit of length: one billionth of a meter.
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NA Numerical aperture The sine of the half-angle of the widest
bundle of rays capable of entering a lens, multiplied by the refractive index of the medium containing that bundle. In air, the refractive index n = 1.
ND Spot Filter A graduated filter at the center of a lens that has
minimal effect when the iris is wide open but increases its effect
as the iris closes. The filter has a varying density as a function of
the distance from the center of the lens with maximum density at
the center of the filter.
ND Neutral density filter An optical attenuating device or light
filter that reduces the intensity of light without changing the
spectral distribution of the light. Can be attached to the lens
of the camera to assist in preventing over exposure of an image.
See Density.
Negative image A picture signal having a polarity that is opposite to normal polarity and that results in a picture in which the
roles of white and black areas are reversed.
Network A collection of devices that include computers, printers, and storage devices that are connected together for the purpose
of sharing information and resources.
Newvicon A former television pickup tube with a cadmium and
zinc telluride target with sensitivity about 20 times that of a vidicon
target. It had a spectral response of 470 to 850 nm, good resolution,
and was relatively free from burn-in.
NIC Network Interface Card A device that provides for connecting a PC to a network. NIC cards are also called network adapters
and provide an essential link between a device and the network.
Noise The word noise originated in audio practice and refers to
random spurts of acoustical or electrical energy or interference. In
television, it produces a “salt-and-pepper” pattern over the televised picture. Heavy noise is sometimes referred to as “snow.”
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Non-browning A term used in connection with lens glass,
faceplate glass, fiber optics, and in radiation-tolerant television
cameras. Non-browning glass does not discolor (turn brown)
when irradiated with atomic particles and waves.
Non-composite video A video signal containing all information
except synchronization pulses.
Notch filter A special filter designed to reject a very narrow band
of electrical frequencies or optical wavelengths.
NTSC National Television Systems Committee The committee
that worked with the FCC in formulating standards for the original
monochrome and present-day U.S. color television system. NTSC
has 525 horizontal scan lines, 30 frames per second, and a bandwidth of 4.2 MHz. NTSC uses a 3.579545 MHz color sub-carrier. It
employs 525 lines per frame, 29.97 frames/sec and 59.94 fields/sec.
The NTSC standard is used in the United States and Japan.
NVR Network Video Recorder A software or computer that
records video on a hard disk. Like a DVR, it records digitally so
the user can instantly search by time, date, and camera. It collects
video from network cameras, network video servers, or a DVR
over the network.
Object distance The distance between the object and the cornea
of the eye, or the first principal point of the objective in an optical
device.
Objective lens The optical element that receives light from an
object scene and forms the first or primary image. In cameras, the
image produced by the objective is the final image. In telescopes
and microscopes, when used visually, the image formed by the
objective is magnified by an eyepiece.
Optical axis The line passing through the centers of curvatures
of the optical surfaces of a lens or the geometric center of a mirror
or window; the optical centerline.
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Optical splitter An optical lens-prism and/or mirror system that
combines two or more scenes and images them onto one video
camera. Only optical components are used to combine the scene.
Optical zoom Optical zoom is produced by the lens itself by
moving sets of lenses in the zoom lens to provide a continuous,
smooth change in focal length from wide-angle to narrow-angle
(telephoto).
Orientation, image In television, the criterion used to determine
the angular orientation of a target (object, person) in an image. At
least 2 TV-line pairs are required.
Overshoot The initial transient response to a unidirectional
change in input, which exceeds the steady-state response.
Overt surveillance In television, the use of any openly displayed
television lenses or cameras to view a scene.
Packet A block of data with a “header” attached that can indicate
what the packet contains and where it is headed. A packet is a
“data envelope” with the header acting as an address.
PAL Phase Alternating Line A European color television system
using a 625 lines per frame 25 frames/second composite analog
color video system at 5.5 MHz bandwidth. In this system the subcarrier derived from the color burst is inverted in phase from one
line to the next in order to minimize errors in hue that may occur
in color transmission. The PAL format is used in Western Europe,
Australia, parts of Africa, and the Middle East.
Pan and tilt Camera-mounting platform that allows movement
in both the azimuth (pan) and the elevation (tilt) planes.
Pan, panning Rotating or scanning a camera around a vertical
axis to view an area in a horizontal direction.
Pan/tilt/zoom Three terms associated with television cameras,
lenses, and mounting platforms to indicate the horizontal (pan),
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vertical (tilt), and magnification (zoom) they are capable of
producing.
Passive In video, cameras using ambient visible or IR, contrasted
to using an active IR illuminator. In electronics, a non-powered
device that generally presents some loss to a system and is incapable of generating power or amplification.
Peak-to-peak The amplitude (voltage) difference between the
most positive and the most negative excursions (peaks) of an electrical signal.
Pedestal level
see Blanking level.
Persistence In a cathode ray tube, the period of time a phosphor
continues to glow after excitation is removed.
Phased array antenna A transmit or receive antenna comprised
of multiple identical radiating elements in a regular arrangement
and fed or connected to obtain a prescribed radiation pattern.
Phosphor A substance capable of luminescence used in fluorescent lamps, television monitors, viewfinders, and image intensifier
screens.
Phosphor-dot faceplate A glass plate in a tri-color picture tube.
May be the front face of the tube or a separate internal plate. Its
rear surface is covered with an orderly array of tri-color lines or
phosphor dots. When excited by electron beams in proper sequence,
the phosphors glow in red, green, and blue to produce a full-color
picture.
Photocathode An electrode used for obtaining photoelectric
emission.
Photoconductivity The changes in the electrical conductivity
(reciprocal of resistance) of a material as a result of absorption of
photons (light).
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Photoconductor A material whose electrical resistance varies in
relationship with exposure to light.
Photoelectric emission The phenomenon of emission of electrons by certain materials upon exposure to radiation in and near
the visible region of the spectrum.
Photon-limited sensitivity When the quantity of available light
is the limiting factor in the sensitivity of a device.
Photopic vision Vision that occurs at moderate and high levels
of luminance and permits distinction of colors. This light-adapted
vision is attributed to the retinal cones in the eye. In contrast, twilight or scotopic vision uses primarily the rods responding to
overall light level.
Pickup tube A television camera image pickup tube. See Image
pickup tube.
Picture size The useful area of an image sensor or display. In the
standard NTSC format, the horizontal to vertical ratio is 4 : 3. The
diagonal is units. The HDTV ratio is 16 : 9.
Picture tube
see Cathode ray tube.
Pin-cushion distortion Distortion in a television picture that
makes all sides appear to bulge inward.
Pinhole lens A lens designed to have a relatively small (0.06 inch
to 0.375 inch) front lens diameter to permit its use in covert (hidden)
camera applications.
PIP Picture in a picture A video display mode which puts several
complete video images on the screen at the same time. Most
common is one small image into a large image.
Pixel Short for Picture element. Any segment of a scanning line,
the dimension of which along the line is exactly equal to the
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nominal line width. A single imaging unit that can be identified
by a computer.
Pixelization An effect seen when an image is enlarged (electronically zoomed) too much and the pixels become visible to the eye.
POTS Plain Old Telephone Service
telephone system.
The original and slowest
Preamplifier An amplifier used to increase the output of a lowlevel source so that the signal can be further processed without
additional deterioration of the signal-to-noise ratio.
Preset A term used in television pointing systems (pan/tilt/
zoom). A computer stores pre-entered azimuth, elevation, zoom
(magnification), focus, and iris combinations, which are later
accessed when commanded by an operator or automatically on
alarm.
Primary colors Three colors wherein no mixture of any two can
produce the third. In color television these are the additive primary
colors red, green, and blue (R,G,B).
Progressive or sequential scan A method of image scanning that
processes image data one line of pixels at a time. Each frame is
composed of a single field. Contrasted to interlace scanning having
two fields per frame.
PSTN Public Switched Telephone Network
wired telephone network.
The traditional,
Pulse A variation of a quantity whose value is normally constant. This variation is characterized by a rise and decay and has
finite amplitude and duration.
Pulse rise-time Time interval between upper and lower limits of
instantaneous signal amplitude; specifically, 10 and 90% of the
peak-pulse amplitude, unless otherwise stated.
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Quad An electronic device having four camera inputs that can
display the four cameras simultaneously in a quad format, singly
full screen, or full screen sequentially. Alarm input contacts are
provided so that the unit switches from a quad display to a full
screen image of the alarmed camera.
Radiation Pattern A graphical representation in either polar or
rectangular coordinates of the spatial energy distributions of an
antenna.
RAID Redundant Array of Independent Disks A system in
which a number of hard drives are connected into one large segmented mass storage device. There are RAID-0 to RAID 6 systems.
RAM Random Access Memory The location in the computer
where the operating system, application programs, and data in
current use are temporarily kept so that they can be quickly reached
by the computers processor. RAM is volatile memory, meaning
that when the computer is turned off, crashes, or loses power, the
contents of the memory are lost.
Random interlace
see Interlace, random.
Raster The blank white screen that results from the scanning
action of the electron beam in a CRT with no video picture information applied. A predetermined pattern of scanning lines that
provides substantially uniform coverage of an area. The area of a
camera or CRT tube scanned by the electron beam.
Raster burn
see Burn-in.
Recognition, image In television, the criterion used to determine
whether an object or person can be recognized in a television
scene. A minimum of 5 TV-line pairs are required to recognize a
person or object.
Reference black level The picture signal level corresponding to
a specified maximum limit for black peaks.
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Reference white level The picture signal level corresponding to
a specified maximum limit for white peaks.
Resolution A measure of how clear and sharp a video image is
displayed on a monitor. The more pixels, the higher the resolution.
It measures picture details that can be distinguished on the television screen. Vertical resolution refers to the number of horizontal
black-and-white or color lines that can be resolved in the picture
height. Horizontal resolution refers to the number of vertical blackand-white or color lines that can be resolved in a picture width
equal to the picture height.
Resolution, horizontal The amount of resolvable detail in the
horizontal direction in a picture; the maximum number of individual picture elements that can be distinguished. It is usually
expressed as a number of distinct vertical lines, alternately black
and white, that can be seen in a distance equal to picture height.
500 to 600 TV lines are typical with the standard 4.2-MHz CCTV
bandwidth. In analog video systems the horizontal resolution is
dependent on the system bandwidth.
Resolution, vertical The amount of resolvable detail in the vertical direction in a picture. It is usually expressed as the number of
distinct horizontal lines, alternately black and white, which can be
seen in a picture. 350 TV lines are typical in the 525 NTSC system.
Retained image Also called image burn. A change produced in
or on the sensor target that remains on the output device (such as
a CRT) for a large number of frames after the removal of a previously stationary light image.
RF Radio frequency A frequency at which coherent electromagnetic radiation of energy is useful for communication purposes.
The entire range of such frequencies, including the AM and FM
radio spectrum and the VHF and UHF television spectrum.
RGB Red, Green, and Blue Abbreviations for the three primary
colors captured by a CCD or CMOS imager and displayed in
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analog and digital video systems. Specifically, the CCD or CMOS
camera sensors and CRT, LCD, and plasma displays use RGB
resolution elements or pixels. The color signals are mixed electronically to create all the other colors in the spectrum.
Right-angle lens A multi-element optical component that causes
the optical axis of the incoming radiation (from a scene or image
focal plane) to be redirected by 90 degrees. It is used when a wideangle lens is necessary to view a scene at right angles to the
camera.
Ringing In electronic circuits, an oscillatory transient occurring
in the output of a system as a result of a sudden change in
input.
Ripple Amplitude variations in the output voltage of a power
supply caused by insufficient filtering.
Roll A loss of vertical synchronization that causes the displayed
video image to move (roll) up or down on a television receiver or
video monitor.
Roll off A gradual decrease or attenuation of a signal voltage as
a function of frequency.
Router A device that moves data between different network segments and can look into a packet header to determine the best path
for the packet to travel. On the Internet, a device or in some cases
software in a computer that determines the next network point to
which a data packet should be forwarded towards its final destination. The router analyzes the network status and chooses the
optimum path to send each information packet. The router can be
located at any juncture of a network or gateway including any
Internet access point. The router creates and maintains a table of
available network routes and their status. Using distance and cost
algorithms it determines the best route for any given packet.
Routers allow all users in a network to share a single connection
to the Internet or a WAN.
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RS170 The original EIA broadcast studio standard issue in
November, 1953 for the NTSC black-and-white video format. It
described a 2 : 1 interlaced, 525 line TV standard with the total
number of lines occurring in 1/30 second. The vertical frequency
was 60 hertz, signal amplitude 1.4 volts peak to peak including
sync signal, and bandwidth from 30 Hz to 4.2 MHz.
RS170A The proposed standard for the NTSC composite color
video system. Its contents were used in the television industry as
a reference, but the document was never adopted. The current
color standard is SMPTE 170-1999.
RS232, RS232C A low speed protocol established by the EIA.
The standard describes the physical interface and protocol between
computers and related devices (printers, modems, etc.). The PC
contains a universal asynchronous receiver-transmitter (UART)
chip that converts the parallel computer data into serial data for
RS232 transmission. The standard recommends a maximum
range of 50 feet (15.2 meters) and maximum baud rate of 20 Kbps.
There is a standard pinout and the connectors used are D-9 and
D-25.
RS422 A protocol established by the EIA consisting of a differential pair of conductors and specified pinout or connectors. The
differential pair is one signal transmitted across two separate wires
in opposite states: one is inverted and the other is non-inverted.
In this differential signal transmission when both lines are exposed
to external noise, both lines are affected equally and cancel out.
RS422 is usually used in full duplex, four wire mode for point-topoint communication but one transmitter can drive up to 10 receivers. Maximum recommended range and baud rate are 4000 feet
and 10Mbps, respectively.
RS485 This protocol is an upgraded version of the RS422 and can
handle up to 32 transmitters and receivers by using tri-state drivers.
Maximum recommended range and baud rate are 4000 feet and
10 Mbps, respectively.
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Saturation In color, the degree to which a color is undiluted
with white light or is pure. The vividness of a color, described by
such terms as bright, deep, pastel, pale, and so on. Saturation is
directly related to the amplitude of the television chrominance
signal.
SCADA Supervisory Control and Data Acquisition An industrial measurement and control system consisting of a central host
or master terminal unit (MTU), one or more field data gathering
and control units or remotes, and a collection of standard and/or
custom software used to monitor and control remotely located
field data elements.
Scanning Moving the electron beam of an image pickup or a
CRT picture tube horizontally across and slowly down the target
or screen area, respectively. Moving the charge packets out of a
CCD, CMOS, or IR sensor.
Scotopic vision Vision that occurs in faint light or in dark adaptation. It is attributed to the operation of the retinal rods in the eye
and contrasted with daylight or photopic vision, using primarily
the cones.
SCSI Small Computer System Interface A high speed input/
output bus that is faster than serial and parallel ports, but slower
and harder to configure than USB and FireWire ports. SCSI enables
a computer to interact with external peripheral hardware, such as
CD-ROM drives, printers, and scanners. SCSI is being supplanted
by the newer USB standard.
SDTV Standard Definition Television Used to describe our 525
line and 625 line interlaced television systems as they are used in
the context of DTV.
SECAM Séquential Couleur À Mémorie A color television
system developed in France and used in some countries that do
not use either the NTSC or PAL systems. Like PAL, SECAM has
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625 horizontal scan lines and 25 frames per second but differs
significantly in the method of producing color signals.
Sensitivity In television, a factor expressing the incident illumination upon a specified scene to produce a specified picture signal
at the video camera output.
Server A computer or software program that provides services
to other computer programs in the same computer or other computers. When a computer runs a server program, the computer is
called a server. When the server is connected to the Web the server
program serves the requested HTML pages or files to the client.
Web browsers are clients that request HTML files from Web
servers. A server provides services to clients such as: files storage
(file server), programs (application server), printer sharing
(printer’s server), fax or modem sharing.
Set Top Box A unit similar to a cable box capable of receiving
and decoding DTV broadcasts.
Sharpness Refers to the ability to see the greatest detail in video
monitor picture. Color sets marketed before the mid 1980s had
sharpness controls to optimize the fine detail in the picture. The
use of comb filters in present monitors eliminate the need for the
sharpness control. See Resolution.
Shutter In an optical system, an opaque material placed in front
of a lens, optical system, or sensor for the purpose of protecting
the sensor from bright light sources, or for timing the length of
time the light source reaches the sensor or film.
Shuttering An electronic technique used in solid-state cameras
to reduce the charge accumulation from scene illumination for the
purpose of increasing the dynamic range of the camera sensor.
Analogous to the electronic shutter in a film camera.
Signal strength The intensity of the video signal measured in
volts, millivolts, microvolts, or decibels. Using 0 dB as the standard
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reference is equal to 1000 microvolts (1 millivolt) in RF systems,
and 1 volt in video systems.
Signal-to-noise ratio S:R, S/N The ratio of the peak value of the
video signal to the value of the noise. Usually expressed in decibels. The ratio between a useful television signal and disturbing,
unwanted image noise or “snow”.
Silicon monoxide A thin-film dielectric (insulator) used as a
protective layer on aluminized mirrors. It is evaporated onto the
mirror as a thin layer, and after exposure to the air the monoxide
tends to become silicon dioxide or quartz, which is very hard and
completely transparent.
Silicon target tube The successor to the vidicon. A highsensitivity television image pickup tube of the direct-readout type
using a silicon diode target made up of a mosaic of light-sensitive
silicon material. It has a sensitivity between 10 and 100 times more
than a sulfide vidicon and has high resistance to image burn-in.
SIT Silicon intensified target A predecessor to the ICCD. An
image intensifier fiber-optically coupled to a silicon faceplate
resulting in a sensitivity 500 times that of a standard vidicon.
Slow-scan A first generation video transmission system consisting
of a transmitter and receiver to transmit single frame video images at
rates slower than the normal NTSC frame rate of 30 per second. The
CCTV frames were modulated and transmitted over the phone lines
to a distant receiver-demodulator and displayed on a CCTV monitor.
The slow-scan process periodically sends “snapshots” of the scene
with typical sending rates of 1 to 5 frames per second.
Sodium lamp A low or high-pressure discharge metal vapor arc
lamp using sodium as the luminous radiation source. The lamp
produces a yellow light and has the highest electrical-to-light
output efficiency (efficacy) of any lamp. Because of their poor color
balance neither is recommended for color CCTV systems, but can
be used for monochrome systems.
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SMPTE Society of Motion Picture and Television Engineers
A global organization based in the U.S. that sets standards for
baseband visual communications.
SMTP Simple Mail Transfer Protocol A TCP/IP that is used for
sending and receiving e-mail. To improve its usefulness it is used
with the POP3 or IMAP protocols, allowing the user to save messages in a server mailbox and download them periodically from
the server. Users use the SMTP to send messages and POP3 or
IMAP to receive messages from the local server.
Snow Heavy random noise manifest on a phosphor screen as a changing black and white or colored “peppered” random noise. See Noise.
Speckle Noise manifest in image intensifiers in the form of small,
localized bright light spots or flashes seen in the device monitor.
Spike A transient of short duration, comprising part of a pulse,
during which the amplitude considerably exceeds the average
amplitude of the pulse.
Spread Spectrum Modulation SSM A communication technique that spreads a signal bandwidth over a wide range of frequencies for transmission and then de-spreads it to the original
data bandwidth at the receiver. See Frequency Hopping.
Subnet A uniquely identifiable part of a network. The subnet
may represent a particular department at a location or a particular
geographical location of the subnet in a building on the local area
network (LAN). Dividing the network into sub-networks allows
it to be connected to the Internet with a single shared network
address. See IP address.
Subnet mask This set of numbers tells a signal router which
numbers are relevant under the IP address mask. In the binary
mask system a “1” over a number indicates that the number under
the 1 is relevant, and a “0” over a number says ignore the number
under it. Using the mask means the router does not have to look
at all 32-bits in the IP address. See IP address.
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Super VGA A video format providing high-quality analog video
by separating the video signal into three color signals, R, G, and
B, allowing for exceptionally clear and bright images.
S-VHS Super VHS A video tape format in which the chrominance and luminance signals are recorded and played back separately providing for better picture quality.
S-Video An encoded video signal that separates the luminance
(brightness) part of the signal from the chrominance (color) to
provide better picture quality.
Switch A network device that improves network performance
by segmenting the network and reducing competition for bandwidth. The switch selects a path or circuit for sending a packet of
data to its next destination. When a switch port receives data
packets, it forwards those packets only to the appropriate port for
the intended recipient. A switch can also provide the function of
routing the data packet to the next point in the network. The
switcher is faster than the router and can more effectively determine the route the data takes.
Switcher A video electronic device that connects one of many
input cameras to one or several output monitors, recorders, etc.,
by means of a panel switch or electronic input signal.
Switcher, alarming An automatic switcher that is activated by a
variety of sensing devices. Once activated, the switcher connects
the camera to the output device (monitor, recorder, etc.).
Switcher, bridging A sequential switcher with separate outputs
for two monitors, one for a programmed sequence and the second
for extended display of a single camera scene.
Switcher, homing A switcher in which: 1) the outputs of multiple cameras can be switched sequentially to a monitor, 2) one or
more cameras can be bypassed (not displayed), or 3) any one of
the cameras can be selected for continuous display on the monitor
(homing). The switcher has three front-panel controllable modes:
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1) Skip, 2) Automatic (sequential) and 3) Select (display one camera
continuously). The lengths of time each camera output is displayed are independently selectable by the operator.
Switcher, manual A switcher in which the individual cameras
are chosen by the operator manually by pushing the switch for
the camera output signal chosen to be displayed, recorded, or
printed.
Switcher, sequential A generic switcher type that allows the
video signals from multiple cameras to be displayed, recorded, or
printed one at a time in sequence.
Sync
A contraction of synchronous or synchronization.
Sync generator
A device for generating a synchronizing signal.
Synchronizing Maintaining two or more scanning processes or
signals in phase.
The level of the peaks of the synchronizing signal.
Sync level
Sync signal
scanning.
Talk-back
The signal employed for the synchronizing of
A voice inter-communicator; an intercom.
Target In solid-state sensors, a semiconductor structure using
picture elements to accumulate the picture charge, and a scanning
readout mechanism to generate the video signal. In surveillance,
an object (person, vehicle, etc.) or activity of interest present in an
image of the scene under observation. In image pickup tubes, a
structure using a storage surface that is scanned by an electron
beam to generate a signal output current corresponding to a
charge-density pattern stored on it.
TCP Transmission control protocol A protocol used along with
the IP to send data in the form of message units between comput-
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ers, over the Internet. While IP takes care of handling the actual
delivery of the data, TCP takes care of keeping track of the individual units of data (called packets) that a message is divided into,
for efficient routing over the Internet.
TCP/IP Transmission control protocol/Internet protocol The
basic communication language (or protocol) of the Internet. It is
also used as a communications protocol in private networks called
intranets, and extranets. TCP/IP communication is primarily
point-to-point in which each communication is from one point (or
host computer) to another. The TCP of TCP/IP handles the tracking of the data packets.
TDMA Time Division Multiple Access A digital multiplexing
(channel sharing) technique whereby each signal is sent at a repeating time slot in a frequency channel. Because the data from each
user always appears in the same time slot, the receiver can separate the signals.
Telephoto lens A long focal length lens, producing a narrow
field of view. Telephoto lenses are used to magnifier objects within
their field of view.
Test pattern A chart especially prepared for checking overall
performance of a television system. It contains combinations of
lines and geometric shapes of specific sizes and spacings. In use,
the camera is focused on the chart, and the pattern is viewed at
the monitor for image fidelity (resolution). The chart most commonly used is the EIA resolution chart.
TFT LCD Thin film transistor LCD A type of LCD flat-panel
display screen. The TFT technology provides the best resolution
of all the flat-panel techniques and is also the most expensive. TFT
screens are sometimes called active-matrix LCDs.
Tilt A low frequency signal distortion. A deviation from the
ideal low-frequency response. Example: Instead of a square wave
having a constant amplitude, it has a tilt.
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Time lapse
Capturing a series of images at preset intervals.
Time lapse recorder The video cassette recorder extends the
elapsed time over which it records by recording user selected
samples of the video fields or frames instead of recording in realtime. For example, recording every other field produces a 15 field/
sec recording and doubles the elapsed time recorded on the tape.
Recording every 30th field produces a 1 field/sec recording and
provides 30 times the elapsed recording time.
Token ring LAN technology in which packets are conveyed
between network end stations by a “token” moving continuously
around a closed ring between all the stations. Operates at 4 or
16 Mbps.
Transient An unwanted signal existing for a brief period of time
that is superimposed on a signal or power line voltage.
Triaxial cable A double shielded cable construction having a
conductor and two isolated braid shields both insulated from each
other. The second braid is applied over an inner jacket and an
outer jacket applied over the outer braid.
Tri-split lens A multi-element optical assembly that combines
one-third of each of three scenes and brings them to focus (adjacent to one another) at the focal plane of a video camera sensor.
Three separate objective lenses are used to focus the scenes onto
the splitter assembly.
T-stop A measurement system used primarily for rating the light
throughput of a catadioptric lens having a central obscuration. It
provides an equivalent aperture of a lens having 100% transmission efficiency. This system is based on actual light transmission
and is considered a more realistic test than the f-stop system.
Tungsten-halogen lamp An improved tungsten lamp once
called quartz-iodine having a tungsten filament and halogen gas
in a fused quartz enclosure. The iodine or bromine added to the
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fill produces a tungsten-halogen cycle that provides self-cleaning
and an extended lifetime. The higher filament temperature
produces more light and a “whiter” light (higher color
temperature).
Tungsten lamp A light source using a tungsten filament surrounded by an inert gas (nitrogen, xenon) enclosed in a glass or
quartz envelope. An AC or DC electric current passing though the
filament causes it to heat to incandescence, producing visible and
infrared radiation.
TV lines A convention used in the video industry to specify the
resolution of a video image. Horizontal resolution is measured in
TV lines across a width equal to the height of the display. Typical
horizontal resolutions in the security industry are 480 TV lines for
color and 570 TV lines for monochrome. Vertical resolution is the
number of horizontal lines multiplied by the Kell factor.
Twin-lead A transmission line having two parallel conductors
separated by insulating material. Line impedance is determined
by the diameter and spacing of the conductors and the insulating material and is usually 300 ohms for television receiving
antennas.
Twin-split lens A multi-element optical assembly that combines
one half of each of two scenes and brings them to focus (adjacent
to one another) at the focal plane of a video camera sensor. Two
separate objective lenses are used to focus the scenes onto the
splitter assembly.
UHF Ultra-high frequency In television, a term used to designate the part of the RF spectrum in which channels 14 through 83
are transmitted. The UHF signals are in the 300 to 3000 MHz
frequency range.
UL certified A certification given by Underwriters Laboratory to
certain items that are impractical to UL list and which the manufacturer can use to identify the item.
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UL listed A label that signifies that a product meets the safety
requirements as set forth by UL safety testing standards.
UL Underwriters Laboratory A testing laboratory that writes
safety standards used by manufacturers when designing products.
UL tests and approves manufactured items for certification or
listing providing they meet required safety standards.
UNIX A computer operating system like DOS or MacOS. UNIX
is designed to be used by many people at the same time and has
TCP/IP built-in. The UNIX operating system was developed by
AT& T Bell Labs and was used to develop the Internet.
URL Uniform resource locator
The address of a web site.
USB Universal serial bus A high-speed port found on most
computers that allows a much faster transfer speed than a serial
or parallel-port.
UTP Unshielded twisted pair Two insulated conductors in an
insulating jacket in which the two conductors are twisted along
the length of the cable. When provided with appropriate transmitter and receiver, UTP provides an alternative to the RG59 coaxial
cable.
UV Ultraviolet An invisible region of the optical spectrum
located immediately beyond the violet end of the visible spectrum,
and between the wavelengths of approximately 100 and 380 nanometers. Radiation just beyond the visible spectrum (at the blue end
of the visible spectrum) ordinarily filtered or blocked to prevent
eye damage.
Varifocal Lens A lens having a manually adjustable focal length
providing a range of field of view.
VCR Video cassette recorder A device that accepts signals from
a video camera and a microphone and records images and sound
on 1/2″ or 1/4″ magnetic tape in a cassette. The VCR can play back
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the recorded images and sound for viewing on a television receiver
or CCTV monitor or printing out single frames on a video
printer.
Vectorscope A special oscilloscope used for color camera and
color video system calibration. The vectorscope decodes the color
information into R-Y and B-Y signals which are used to drive the
x and y axis of the scope. The absence of color in the video signal
is displayed as a dot at the center of the display. The angledistance around the circle, and magnitude-distance away from the
sensor, indicate the phase and amplitude of the color signal. The
vectorscope graphically indicates on a CRT the absolute phase
angle between the different color signals with respect to a reference signal, and to each other. These angles represent the phase
differences between the signals.
Vertical blanking, Retrace The process of bringing the scanning electron beam in a CRT from the bottom of the picture back
to the top. Vertical retrace occurs between writing each field
of a picture. The beam is shut off and blanked during the
retrace.
Vertical resolution The number of horizontal lines that can be
seen in the reproduced image of a television pattern. The 525 TV
line NTSC system and Kell effect limits the vertical resolution to
appproximately 350 TV lines maximum.
Vertical retrace The return of the electron beam to the top of the
picture tube screen or the pickup tube target, at the completion of
the field scan. The retrace is not displayed on the monitor.
VGA A standard display format having an image resolution of
640 × 480 pixels.
VHF Very High Frequency In television, a term used to designate the part of the RF spectrum in which channels 2 through 13
are transmitted. A signal in the frequency range of from 30 to
300 MHz.
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VHS Victor home system The 1/2″ video tape cassette recording format in most widespread use.
Video A term pertaining to the bandwidth and spectrum position of the signal resulting from television scanning. In current
CCTV usage video means a bandwidth between 30 Hz and 5–6
MHz.
Video amplifier A wideband amplifier used for amplifying
video picture signals.
Video band The frequency band used to transmit a composite
video signal.
Video signal, non-composite The picture signal. A signal containing visual information without the horizontal and vertical synchronization and blanking pulses. See Composite video.
Vidicon tube An early imaging tube used to convert a visible
image into an electrical signal. The spectral response covers most
of the visible spectrum and most closely approximates the human
eye response (400–700 nm).
Viewfinder A small electronic or optical viewing device attached
to a video camera so that the operator at the camera location can
view the scene that the camera sees.
Vignetting The loss of light through a lens or optical system
at the edges of the field due to using an undersized lens or
inadequate lens design. Most well-designed lenses minimize
vignetting.
Visible spectrum That portion of the electromagnetic spectrum
to which the human eye is sensitive. The range covers from 400 to
700 nanometers.
VPN Virtual Private Network A private data network that
makes use of the public telecommunications infrastructure. The
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VPN enables IP traffic to travel securely over a public TCP/IP
network by encrypting all traffic from one network to another. The
VPN maintains privacy through the use of a “tunneling” protocol
and security procedures. It does this at a much lower cost than
privately owned or leased lines. Many companies use a VPN for
both Extranets and wide-area networks (WAN).
WAN Wide Area Network A public or private network that
provides coverage over a broad geographic area. WANs are typically used for connecting several metropolitan areas as part of a
larger network. Universities and large corporations use WANs to
connect geographically remote locations.
Waveform monitor A specialized oscilloscope with controls that
allow the display and analysis of analog and digital video waveforms. Parameters analyzed include frequency, waveform shape,
presence or absence of synchronizing pulses, etc.
Wavelength The length of an electromagnetic energy wave measured from any point on one wave to the corresponding point on
the next wave, usually measured from crest to crest. Wavelength
defines the nature of the various forms of radiant energy that
compose the electromagnetic spectrum and determines the color
of light. Common units for measurement are the nanometer
(1/10,000 micron), micron, millimicron, and the Angstrom.
Wavelet A unique mathematical function used in signal processing and video image compression. The process is similar to Fourier
analysis.
Web browser A web program that allows Web browsers to
retrieve files from computers connected to the Internet. Its main
function is to serve pages to other remote computers.
Web server A program that allows web browsers to retrieve files
from computers connected to the Internet. The web server listens
for requests from web browsers and upon receiving a request for
a file sends it back to the browser.
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White clipper A nonlinear electronic circuit providing linear
amplification up to a predetermined voltage and then unity amplification for signals above the predetermined voltage.
White compression Amplitude compression of the signals corresponding to the white regions of the picture.
White level The top end of the gray scale. The picture signal
level corresponding to a specified maximum limit for white
peaks.
White peak The maximum excursion of the picture signal in the
white direction.
White peak clipping Limiting the amplitude of the picture signal
to a pre-selected maximum white level.
Wi-Fi Wireless Fidelity The Institute of Electrical and Electronic
Engineers (IEEE) 802.11 wireless standard for transmitting video
images and other data over the airwaves between computers,
access points, routers, or other digital video devices.
WLAN Wireless Local Area Network or Wireless LAN A wireless computer-to-computer data communications network having
a nominal range of 1000 ft.
Working distance The distance between the front surface of an
objective lens and the object being viewed.
WWW World Wide Web The name of the total space for highly
graphical and multimedia applications on the Internet.
Xenon arc lamp An arc lamp containing the rare gas xenon that is
excited electrically to emit a brilliant white light. The lamps are
available in short-arc (high-pressure) and long-arc (low-pressure).
Yagi Antenna A multiple element parasitic antenna originated
by Yagi-Uda in Japan. A common means of achieving high antenna
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gain in a compact physical size in the VHF and UHF frequency
range. The Yagi antenna consists of a driven element, a reflector
element, and one or more director elements.
Y/C The term used to describe the separate luminance (Y) and
chrominance (C) signals. Separating the signals improves the final
video image.
Zoom Optical zooming using a lens to enlarge or reduce the size
of the scene image on the video sensor on a continuously variable
basis. The wide-angle setting provides low magnification. Narrowangle (telephoto) setting provides high magnification. Electronic
zooming magnifies or de-magnifies the image size of a video scene
electronically. All magnification is referenced to the human eye
with a magnification of 1.
Zoom lens A lens capable of providing variable focal lengths.
An optical lens system of continuously variable focal length with
the focal plane remaining in a fixed position at the camera sensor.
Groups of lens components are moved to change their relative
physical positions, thereby varying the focal length and angle of
view through a specified range of magnifications.
Zoom range The degree to which the focal length of a camera
lens can be adjusted from wide-angle to telephoto. Usually defined
with a numerical ratio like 10 : 1 (telephoto: wide-angle).
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