Axis Network video Specifications

Axis Network video Specifications
Technical guide to network video.
Technologies and factors to consider for the successful deployment
of IP-based security surveillance and remote monitoring applications.
Welcome to the Axis technical guide
to network video
The move to open video systems—combined with the benefits of networking, digital
imaging, and camera intelligence—constitutes a far more effective means of security
surveillance and remote monitoring than has ever been reached before. Network video
provides everything that analog video offers, plus a wide range of innovative functions
and features that are only possible with digital technology.
Before setting up your own system, you need to consider what features are required.
It is equally important to consider factors such as performance, interoperability,
scalability, flexibility and future-proof functionality. This guide will walk you through
these factors, helping you to achieve a solution that fully takes advantage of the
potential of network video technology.
The best in network video
Axis is the global market leader in network video. We were first to bring the benefits of network
video technology to professional video surveillance and remote monitoring applications, introducing the world’s first network camera in 1996. With more than two decades of experience in
networking technologies, the largest installed base of network video products, as well as strong
partnerships with leading players across all continents, Axis is the partner of choice in network
Flexible, scalable solutions
Using open technology standards that enable easy integration and scalability, Axis offers a full
range of network video solutions for surveillance and remote monitoring applications in a broad
spectrum of industry segments. Our cutting-edge portfolio comprises network cameras that
redefine the categories they represent, as well as video encoders that enable cost-effective
migration to the best in network video technology. Our offering also includes comprehensive
video management software solutions and a full range of accessories.
Table of contents
Network video: overview, benefits and applications 7
Overview of a network video system
City surveillance
Banking and finance
Network cameras 15
Camera elements
What is a network camera?
Types of network cameras
Fixed network cameras
Fixed dome network cameras
PTZ cameras and PTZ dome cameras
Day and night network cameras
Megapixel network cameras Guidelines for selecting a network camera
Light sensitivity
Lens elements
Field of view
Matching lens and sensor
Lens mount standards
F-number and exposure
Manual or automatic iris
Depth of field
Image sensors
CCD technology
CMOS technology
Megapixel sensors
Image scanning techniques
Interlaced scanning
Progressive scanning
Image processing
Backlight compensation
Exposure zones
Wide dynamic range
Installing a network camera
Camera protection and housings
Video encoders
Video compression
Camera enclosures in general
Transparent covering
Positioning a fixed camera in a housing Environmental protection
Vandal and tampering protection
Camera/housing design
Camera placement
Intelligent video
Types of mounting
Ceiling mounts
Wall mounts
Pole mounts
Parapet mounts
What is a video encoder?
Video encoder components and considerations
Event management and intelligent video
Standalone video encoders
Rack-mounted video encoders
Video encoders with PTZ cameras and PTZ domes
Deinterlacing techniques
Video decoder
NTSC and PAL resolutions
VGA resolutions
Megapixel resolutions
High-definition television (HDTV) resolutions
Compression basics
Video codec
Image compression vs. video compression
Compression formats
Motion JPEG
H.264 or MPEG-4 Part 10/AVC
Variable and constant bit rates Comparing standards
Audio applications Audio support and equipment
Audio modes
Half duplex
Full duplex
Audio detection alarm
Audio compression
Sampling frequency
Bit rate
Audio codecs
Audio and video synchronization
Network technologies
Wireless technologies
Video management systems
Local area network and Ethernet
Types of Ethernet networks
Power over Ethernet
The Internet
IP addressing
Data transport protocols for network video
Quality of Service
Network Security
Username and password authentication
IP address filtering
IEEE 802.1X
VPN (Virtual Private Network)
802.11 WLAN standards
WLAN security
WEP (Wired Equivalent Privacy)
WPA/WPA2 (WiFi Protected Access)
Wireless bridges
Hardware platforms
PC server platform
NVR platform
Software platforms
Built-in functionality
Windows client-based software
Web-based software
Scalability of video management software
Open vs. vendor-specific software
System features
Video recording
Recording and storage
Event management and intelligent video
Administration and management features
Integrated systems
Application programming interface
Point of Sale
Access control
Building management
Industrial control systems
Bandwidth and storage considerations
Tools and resources
Axis Communications’ Academy
Contact information
Bandwidth and storage calculations
Bandwidth needs
Calculating storage needs
Server-based storage
Redundant storage
System configurations
Network video: overview, benefits and applications - CHAPTER 1
Network video: overview, benefits and
Network video, like many other kinds of communications such as e-mail, web services
and computer telephony, is conducted over wired or wireless IP (Internet Protocol)
networks. Digital video and audio streams, as well as other data, are communicated
over the same network infrastructure. Network video provides users, particularly in
the security surveillance industry, with many advantages over traditional analog CCTV
(closed-circuit television) systems.
This chapter provides an overview of network video, as well as its benefits and applications in various industry segments. Comparisons with an analog video surveillance
system are often made to provide a better understanding of the scope and potential of
a digital, network video system.
Overview of a network video system
Network video, often also called IP-based video surveillance or IP-Surveillance as it is applied in
the security industry, uses a wired or wireless IP network as the backbone for transporting
digital video, audio and other data. When Power over Ethernet (PoE) technology is applied, the
network can also be used to carry power to network video products.
A network video system allows video to be monitored and recorded from anywhere on the network, whether it is, for instance, on a local area network (LAN) or a wide area network (WAN)
such as the Internet.
CHAPTER 1 - Network video: overview, benefits and applications
Axis network cameras
Axis video encoders
0 -
FNP 30
100-240 AC
50-50 Hz
4-2 A
0 -
FNP 30
AXIS Q7900 Rack
50-50 Hz
4-2 A
AXIS Q7406
Video Encoder
AXIS Q7406
Video Encoder
with web
Computer with
video management
Figure 1.1a A network video system comprises many different components, such as network cameras, video
encoders and video management software. The other components including the network, storage and servers are all
standard IT equipment.
The core components of a network video system consist of the network camera, the video
encoder (used to connect to analog cameras), the network, the server and storage, and video
management software. As the network camera and the video encoder are computer-based
equipment, they have capabilities that cannot be matched by an analog CCTV camera. The
network camera, the video encoder and the video management software are considered the
cornerstones of an IP-Surveillance solution.
The network, the server and storage components are all standard IT equipment. The ability to use
common off-the-shelf equipment is one of the main benefits of network video. Other components of a network video system include accessories, such as camera housings and PoE midspans
and active splitters. Each network video component is covered in more detail in other chapters.
The digital, network video surveillance system provides a host of benefits and advanced functionalities that cannot be provided by an analog video surveillance system. The advantages
include remote accessibility, high image quality, event management and intelligent video capabilities, easy integration possibilities and better scalability, flexibility and cost-effectiveness.
Remote accessibility: Network cameras and video encoders can be configured and accessed
remotely, enabling multiple, authorized users to view live and recorded video at any time and
from virtually any networked location in the world. This is advantageous if users would like
a third-party company, such as a security firm, to also gain access to the video. In a
traditional analog CCTV system, users would need to be at a specific, on-site monitoring
Network video: overview, benefits and applications - CHAPTER 1
location to view and manage video, and off-site video access would not be possible without
such equipment as a video encoder or a network digital video recorder (DVR). A DVR is the
digital replacement for the video cassette recorder.
High image quality: In a video surveillance application, high image quality is essential to
be able to clearly capture an incident in progress and identify persons or objects involved.
With progressive scan and megapixel technologies, a network camera can deliver better
image quality and higher resolution than an analog CCTV camera. For more on progressive
scan and megapixel, see chapters 2, 3 and 6.
Image quality can also be more easily retained in a network video system than in an analog
surveillance system. With analog systems today that use a DVR as the recording medium,
many analog-to-digital conversions take place: first, analog signals are converted in the
camera to digital and then back to analog for transportation; then the analog signals are
digitized for recording. Captured images are degraded with every conversion between analog
and digital formats and with the cabling distance. The further the analog video signals have
to travel, the weaker they become.
In a fully digital IP-Surveillance system, images from a network camera are digitized once
and they stay digital with no unnecessary conversions and no image degradation due to
distance traveled over a network. In addition, digital images can be more easily stored and
retrieved than in cases where analog video tapes are used.
Event management and intelligent video: There is often too much video recorded and lack
of time to properly analyze them. Advanced network cameras and video encoders with builtin intelligence or analytics take care of this problem by reducing the amount of uninteresting
recordings and enabling programmed responses. Such functionalities are not available in an
analog system.
Axis network cameras and video encoders have built-in features such as video motion detection, audio detection alarm, active tampering alarm, I/O (input/output) connections, and
alarm and event management functionalities. These features enable the network cameras
and video encoders to constantly analyze inputs to detect an event and to automatically
respond to an event with actions such as video recording and sending alarm notifications.
10 CHAPTER 1 - Network video: overview, benefits and applications
Figure 1.2a Setting up an event trigger using a network camera’s user interface.
Event management functionalities can be configured using the network video product’s user
interface or a video management software program. Users can define the alarms or events by
setting the type of triggers to be used and when. Responses can also be configured (e.g.,
recording to one or multiple sites, whether local and/or off-site for security purposes;
activation of external devices such as alarms, lights and doors; and sending notification
messages to users). For more on video management, see Chapter 11.
Easy, future-proof integration: Network video products based on open standards can be
easily integrated with computer and Ethernet-based information systems, audio or security
systems and other digital devices, in addition to video management and application
software. For instance, video from a network camera can be integrated into a Point of Sales
system or a building management system. For more on integrated systems, see Chapter 11.
Scalability and flexibility: A network video system can grow with a user’s needs. IP-based
systems provide a means for many network cameras and video encoders, as well as other
types of applications, to share the same wired or wireless network for communicating data;
so any number of network video products can be added to the system without significant or
costly changes to the network infrastructure. This is not the case with an analog system. In
an analog video system, a dedicated coaxial cable must run directly from each camera to a
Network video: overview, benefits and applications - CHAPTER 1 11
viewing/recording station. Separate audio cables must also be used if audio is required. Network video products can also be placed and networked from virtually any location, and the
system can be as open or as closed as desired.
Cost-effectiveness: An IP-Surveillance system typically has a lower total cost of ownership
than a traditional analog CCTV system. An IP network infrastructure is often already in
place and used for other applications within an organization, so a network video application
can piggyback off the existing infrastructure. IP-based networks and wireless options are
also much less expensive alternatives than traditional coaxial and fiber cabling for an
analog CCTV system. In addition, digital video streams can be routed around the world using
a variety of interoperable infrastructure. Management and equipment costs are also lower
since back-end applications and storage run on industry standard, open systems-based
servers, not on proprietary hardware such as a DVR in the case of an analog CCTV system.
Furthermore, Power over Ethernet technology, which cannot be applied in an analog video
system, can be used in a network video system. PoE enables networked devices to receive
power from a PoE-enabled switch or midspan through the same Ethernet cable that
transports data (video). PoE provides substantial savings in installation costs and can
increase the reliability of the system. For more on PoE, see Chapter 9.
Network camera
with built-in PoE
Network camera
without built-in
Uninterruptible Power
Supply (UPS)
PoE-enabled switch
Figure 1.2b A system that uses Power over Ethernet.
Active splitter
Power over Ethernet
12 CHAPTER 1 - Network video: overview, benefits and applications
Network video can be used in an almost unlimited number of applications; however, most of its
uses fall under security surveillance or remote monitoring of people, places, property and operations. The following are some typical application possibilities in key industry segments.
Network video systems in retail stores can significantly reduce theft,
improve staff security and optimize store management. A major benefit
of network video is that it can be integrated with a store’s EAS (electronic article surveillance) system or a POS (point of sale) system to
provide a picture and a record of shrinkage-related activities. The system can enable rapid detection of potential incidents, as well as any
false alarms. Network video offers a high level of interoperability and
gives the shortest return on investment.
Network video can also help identify the most popular areas of a store and provide a record of
consumer activity and buying behaviors that will help optimize the layout of a store or display.
It can also be used to identify when shelves need to be restocked and when more cash registers
need to be opened because of long queues.
Network video can enhance personal safety and overall security at airports, highways, train stations and other transit systems, as well as in
mobile transport such as in buses, trains and cruise ships. Network
video can also be used to monitor traffic conditions to reduce congestion and improve efficiency. Many installations in the transportation
sector require only the best systems, involving high image quality
(which can be provided by progressive scan technology in network
cameras), high frame rates and long retention times. In some demanding environments such as on buses and trains, Axis offers network cameras that can withstand
varying temperatures, humidity, dust, vibrations and vandalism.
1.3.3 Education
From daycare centers to universities, network video systems have
helped deter vandalism and increase the safety of staff and students.
In education facilities where an IT infrastructure is already in place,
network video presents a more favorable and cost-effective solution
than an analog system because new cabling is often not required. In
addition, event management features in network video can generate
alarms and give security operators accurate, real-time images on
Network video: overview, benefits and applications - CHAPTER 1 13
which to base their decisions. Network video can also be used for remote learning; for example,
for students who are unable to attend lectures in person.
Network video can be used to monitor and increase efficiencies in
manufacturing lines, processes and logistic systems, and for securing
warehouses and stock control systems. Network video can also be used
to set up virtual meetings and get technical support at a distance.
City surveillance
Network video is one of the most useful tools for fighting crime and
protecting citizens. It can be used to detect and deter. The use of
wireless networks has enabled effective city-wide deployment of
network video. The remote surveillance capabilities of network video
have enabled police to respond quickly to crimes being committed in
live view.
Network video products are used to secure all kinds of public buildings, from museums and offices to libraries and prisons. Cameras
placed at building entrances and exits can record who comes in and
out, 24 hours a day. They are used to prevent vandalism and increase
security of staff. With intelligent video applications such as people
counting, network video can provide statistical information, such as
the number of visitors to a building.
Network video enables cost-effective, high-quality patient monitoring and video surveillance solutions that increase the safety and
security of staff, patients and visitors, as well as property. Authorized
hospital staff can, for example, view live video from multiple locations, detect activity and provide remote assistance.
14 CHAPTER 1 - Network video: overview, benefits and applications
Banking and finance
Network video is used in security applications in bank branches,
headquarters and ATM (automated teller machine) locations. Banks
have been using surveillance for a long time, and while most installations are still analog, network video is starting to make inroads,
especially in banks that value high image quality and want to be able
to easily identify people in a surveillance video.
Network video is a proven technology and the shift from analog systems to IP-Surveillance is
rapidly taking place in the video surveillance industry. For case studies, visit
Network cameras
There is a wide range of network cameras to meet a variety of requirements. This
chapter describes what a network camera is and explains the different camera types.
Information is also provided about day and night, and megapixel network cameras.
A camera selection guide is included at the end of the chapter. For more on camera
elements, see Chapter 3.
What is a network camera?
A network camera, often also called an IP camera, can be described as a camera and computer
combined in one unit. The main components of a network camera include a lens, an image
sensor, one or several processors, and memory. The processors are used for image processing,
compression, video analysis and networking functionalities. The memory is used for storing the
network camera’s firmware (computer program) and for local recording of video sequences.
Like a computer, the network camera has its own IP address, is connected directly to a network
and can be placed wherever there is a network connection. This differs from a web camera,
which can only operate when it is connected to a personal computer (PC) via the USB or IEEE
1394 port, and to use it, software must be installed on the PC. A network camera provides web
server, FTP (File Transfer Protocol), and e-mail functionalities, and includes many other IP network and security protocols.
Axis network camera
PoE switch
Computer with video
management software
Figure 2.1a A network camera connects directly to the network.
16 CHAPTER 2 - Network CAMERAS
A network camera can be configured to send video over an IP network for live viewing and/or
recording either continuously, at scheduled times, on an event or on request from authorized
users. Captured images can be streamed as Motion JPEG, MPEG-4 or H.264 video using various
networking protocols, or uploaded as individual JPEG images using FTP, e-mail or HTTP (Hypertext Transfer Protocol). For more on video compression formats and networking protocols, see
chapters 7 and 9, respectively.
In addition to capturing video, Axis network cameras provide event management and intelligent
video functionalities such as video motion detection, audio detection, active tampering alarm
and auto-tracking. Most network cameras also offer input/output (I/O) ports that enable
connections to external devices such as sensors and relays. Other features may include audio
capabilities and built-in support for Power over Ethernet (PoE). Axis network cameras also
support advanced security and network management features.
Figure 2.1b Front and back of a network camera.
Types of network cameras
Network cameras can be classified in terms of whether they are designed for indoor use only or
for indoor and outdoor use. Outdoor network cameras often have an auto iris lens to regulate
the amount of light the image sensor is exposed to. An outdoor camera will also require an
external, protective housing unless the camera design already incorporates a protective enclosure. Housings are also available for indoor cameras that require protection from harsh environments such as dust and humidity, and from vandalism or tampering. In some camera designs,
vandal and tamper-proof features are already built-in and no external housing is required. For
more on camera protection and housings, see Chapter 4.
Network cameras, whether for indoor or outdoor use, can be further categorized into fixed, fixed
dome, PTZ, and PTZ dome network cameras.
Network CAMERAS - CHAPTER 2 17
Fixed network cameras
A fixed network camera, which may come with a fixed or varifocal lens, is a camera that has a
fixed field of view (normal/telephoto/wide-angle) once it is mounted. A fixed camera is the
traditional camera type where the camera and the direction in which it is pointing are clearly
visible. This type of camera represents the best choice in applications where it is advantageous
to make the camera very visible. A fixed camera usually enables its lens to be changed. Fixed
cameras can be installed in housings designed for indoor or outdoor installation.
Figure 2.2a Fixed network cameras including wireless and megapixel versions.
Fixed dome network cameras
A fixed dome network camera, also called a mini dome, essentially involves a fixed camera that
is pre-installed in a small dome housing. The camera can be directed to point in any direction.
Its main benefit lies in its discreet, non-obtrusive design, as well as in the fact that it is hard to
see in which direction the camera is pointing. The camera is also tamper resistant.
One of the limitations of a fixed dome camera is that it rarely comes with an exchangeable lens,
and even if it is exchangeable, the choice of lenses is limited by the space inside the dome
housing. To compensate for this, a varifocal lens is often provided to enable the camera’s field
of view to be adjusted.
Axis fixed dome cameras are designed with different types of enclosures such as vandal-resistant
and/or IP66-rated for outdoor installations. No external housing is required. The mounting of such
a camera is usually on a wall or ceiling.
Figure 2.2b Fixed dome network cameras. From left to right: AXIS 209FD and AXIS 216FD (also available in
ruggedized and megapixel versions), AXIS P3301 and AXIS 225FD.
18 CHAPTER 2 - Network CAMERAS
PTZ cameras and PTZ dome cameras
A PTZ camera or a PTZ dome camera can manually or automatically pan, tilt and zoom in and
out of an area or object. All PTZ commands are sent over the same network cable as for video
transmission; no RS-485 wires need to be installed as is the case with an analog PTZ camera.
Some of the features that can be incorporated in a PTZ camera or a PTZ dome camera include:
Electronic image stabilization (EIS). In outdoor installations, PTZ dome cameras with zoom
factors above 20x are sensitive to vibrations and motion caused by traffic or wind. EIS helps
reduce the affects of vibration in a video. In addition to getting more useful video, EIS will
reduce the file size of the compressed image, thereby saving valuable storage space.
Privacy masking. Privacy masking, which allows certain areas of a scene to be blocked or
masked from viewing and recording, can be made available in various network video
products. In a PTZ camera or PTZ dome camera, the functionality has the ability to maintain
the privacy masking even as the camera’s field of view changes since the masking moves
with the coordinate system.
Figure 2.2c With built-in privacy masking (gray rectangle in image), the camera can guarantee privacy for areas
that should not be covered by a surveillance application.
Network CAMERAS - CHAPTER 2 19
> Preset positions. Many PTZ cameras and PTZ dome cameras enable a number of preset
positions, normally between 20 and 100, to be programmed. Once the preset positions have
been set in the camera, it is very quick for the operator to go from one position to the next.
E-flip. When a PTZ dome camera is mounted on a ceiling and is used to follow a person in,
for example, a retail store, there will be situations when a person will pass just under the
camera. When following through on the person, images would be seen upside down without
the E-flip functionality. E-flip electronically rotates images 180 degrees in such cases. It is
performed automatically and will not be noticed by an operator.
Auto-flip. PTZ cameras, unlike PTZ dome cameras, do not normally have a full 360-degree
continuous pan due to a mechanical stop that prevents the cameras from making a
continuous circular movement. However, with the Auto-flip functionality, a PTZ network
camera can instantly flip the camera head 180 degrees and continue to pan beyond its zero
point. The camera can then continue to follow a passing person or object in any direction.
Auto-tracking. Auto-tracking is an intelligent video functionality that will automatically
detect a moving person or vehicle and follow it within the camera’s area of coverage. Autotracking is particularly beneficial in unmanned video surveillance situations where the
occasional presence of people or vehicles requires special attention. The functionality cuts
down substantially the cost of a surveillance system since fewer cameras are needed to
cover a scene. It also increases the effectiveness of the solution since it allows a PTZ camera
or PTZ dome camera to record areas of a scene with activity.
Although PTZ cameras and PTZ dome cameras may share similar functionalities, there are differences between them:
PTZ network cameras do not have a full 360-degree continuous pan due to a mechanical
stop. It means that the camera cannot follow a person walking continuously in a full circle
around the camera. Exceptions are PTZ cameras that have the Auto-flip functionality; for
example, AXIS 215 PTZ Network Camera.
> PTZ network cameras are not made for continuous automatic operation or so-called guard
tours where the camera automatically moves from one preset position to the next.
More on PTZ network cameras, which are available in mechanical or non-mechanical versions,
and PTZ dome network cameras is provided in the next sections.
20 CHAPTER 2 - Network CAMERAS
Mechanical PTZ network cameras
Mechanical PTZ cameras are mainly used indoors and in applications where an operator is
employed. The optical zoom on PTZ cameras typically ranges from 10x to 26x. A PTZ camera can
be mounted on a ceiling or wall.
Figure 2.2d PTZ network cameras. From left to right: AXIS 212 PTZ-V (non-mechanical), AXIS 213 PTZ, AXIS 214 PTZ
and AXIS 215 PTZ.
Non-mechanical PTZ network cameras
A non-mechanical PTZ network camera, such as the AXIS 212 PTZ and its vandal-resistant
version (seen above), offers instant pan, tilt, zoom capabilities with no moving parts, so there is
no wear and tear. Using a wide-angle lens, it offers a wider field of view than a mechanical PTZ
network camera.
Figure 2.2e Images from a non-mechanical PTZ network camera. At left, a 140-degree overview image in VGA resolution; at right, image when making a 3x zoom.
A non-mechanical PTZ camera uses a megapixel image sensor and allows an operator to instantly
zoom in on any part of a scene without any loss in image resolution. This is achieved by presenting
an overview image in VGA resolution (640x480 pixels) even though the camera captures a much
higher resolution image. When the camera is instructed to zoom in on any part of the overview
image, the camera uses the original megapixel resolution to provide a full 1:1 ratio in VGA resolution. The resulting close-up image offers good details with maintained sharpness. With a normal
Network CAMERAS - CHAPTER 2 21
digital zoom, the zoomed-in image often loses detail and sharpness. A non-mechanical PTZ camera
is ideal for discreet, wall-mounted installations.
PTZ dome network cameras
PTZ dome network cameras can cover a wide area by enabling greater flexibility in pan, tilt and
zoom functions. They enable a 360-degree, continuous pan, and a tilt of usually 180 degrees.
PTZ dome cameras are ideal for use in discreet installations due to their design, mounting
(particularly in drop-ceiling mounts), and difficulty in seeing the camera’s viewing angle (dome
coverings can be clear or smoked).
A PTZ dome network camera also provides mechanical robustness for continuous operation in
guard tour mode, whereby the camera automatically moves from one preset position to the next
in a pre-determined order or at random. Normally up to 20 guard tours can be set up and activated during different times of the day. In guard tour mode, one PTZ dome network camera can
cover an area where 10 fixed network cameras would be needed. The main drawback is that only
one location can be monitored at any given time, leaving the other nine positions unmonitored.
The optical zoom of a PTZ dome typically ranges between 10x and 35x. A PTZ dome is often used
in situations where an operator is employed. This type of camera is usually mounted on a ceiling
if used indoors, or on a pole or wall of a building in outdoor installations.
Figure 2.2f PTZ dome network cameras. From left to right: AXIS 231D+, AXIS 232D+, AXIS 233D.
Day and night network cameras
All types of network cameras—fixed, fixed dome, PTZ, and PTZ dome—can offer day and night
functionality. A day and night camera is designed to be used in outdoor installations or in indoor
environments with poor lighting.
A day and night, color network camera delivers color images during the day. As light diminishes
below a certain level, the camera can automatically switch to night mode to make use of nearinfrared (IR) light to deliver high-quality, black and white images.
22 CHAPTER 2 - Network CAMERAS
Near-infrared light, which spans from 700 nanometers (nm) up to about 1000 nm, is beyond
what the human eye can see, but most camera sensors can detect it and make use of it. During
the day, a day and night camera uses an IR-cut filter. IR light is filtered out so that it does not
distort the colors of images as the human eye sees them. When the camera is in night (black and
white) mode, the IR-cut filter is removed, allowing the camera’s light sensitivity to reach down
to 0.001 lux or lower.
Figure 2.3a The graph shows how an image sensor responds to visible and near-IR light. Near-IR light spans the
700 nm to 1000 nm range.
Figure 2.3b Image at left, IR-cut filter in a day/night network camera; middle, position of IR-cut filter during daytime; at right, position of IR-cut filter during nighttime.
Network CAMERAS - CHAPTER 2 23
Day and night cameras are useful in environments that restrict the use of artificial light. They
include low-light video surveillance situations, covert surveillance and discreet applications, for
example, in a traffic surveillance situation where bright lights would disturb drivers at night.
An IR illuminator that provides near-infrared light can also be used in conjunction with a day
and night camera to further enhance the camera’s ability to produce high-quality video in lowlight or nighttime conditions. For more information on IR illuminators, visit Axis’ website at
Figure 2.3c At left, image without an IR illuminator; at right, image with an IR illuminator.
Megapixel network cameras
Megapixel network cameras, available in Axis’ fixed cameras and fixed dome cameras, incorporate a megapixel image sensor to deliver images with one million or more pixels. This is at least
two times better pixel resolution than what can be provided by analog cameras.
A megapixel, fixed network camera can be used in one of two ways: it can enable viewers to see
greater details in a higher resolution image, which would be helpful in identifying people and
objects, or it can be used to cover a larger part of a scene if the image resolution is kept the
same as a non-megapixel camera.
Megapixel cameras today are normally less light sensitive than a non-megapixel network
camera. The higher-resolution video streams generated by a megapixel camera also put higher
demands on the network bandwidth and storage space for recordings, although this can be
mitigated by using the H.264 video compression standard. For more on H.264 , see Chapter 7.
24 CHAPTER 2 - Network CAMERAS
Guidelines for selecting a network camera
With the variety of network cameras available, it is useful to have some guidelines when
selecting a network camera.
Define the surveillance goal: overview or high detail. Overview images aim to view a scene
in general or view the general movements of people. High detail images are important for
identification of persons or objects (e.g., face or license plate recognition, point-of-sales
monitoring). The surveillance goal will determine the field of view, the placement of the
camera, and the type of camera/lens required. For more on lenses, see Chapter 3.
Area of coverage. For a given location, determine the number of interest areas, how much
of these areas should be covered and whether the areas are located relatively close to each
other or spread far apart. The area will determine the type of camera and number of
cameras required.
- Megapixel or non-megapixel. For instance, if there are two, relatively small areas of
interest that are close to each other, a megapixel camera with a wide-angle lens can
be used instead of two non-megapixel cameras.
Fixed or PTZ. (In the following context, fixed cameras refer also to fixed domes
and PTZ cameras refer also to PTZ domes.) An area may be covered by several fixed
cameras or a few PTZ cameras. Consider that a PTZ camera with high optical zoom
capabilities can provide high detail images and survey a large area. However, a PTZ
camera may provide a brief view of one part of its area of coverage at a time, while a
fixed camera will be able to provide full coverage of its area all the time. To make full
use of the capabilities of a PTZ camera, an operator is required or an automatic tour
needs to be set up.
> Indoor or outdoor environment.
Light sensitivity and lighting requirements. In outdoor environments, consider the use
of day and night cameras. Consider the light sensitivity of the camera required and
whether additional lighting or specialized light such as IR lamps is needed. Keep in
mind that lux measurements on network cameras are not comparable among different
network video product vendors as there is no industry standard for measuring light
- Housing. If the camera is to be placed outdoors or in environments that require protec tion from dust, humidity or vandalism, housings are required. For more on housing, see
Chapter 4.
Network CAMERAS - CHAPTER 2 25
> Overt or covert surveillance. This will help in selecting cameras, in addition to housing and
mounts, that offer a non-discreet or discreet installation.
Other important feature considerations that may be required of a camera include:
Image quality. Image quality is one of the most important aspects of any camera, but it is
difficult to quantify and measure it. The best way to determine image quality is to install
different cameras and look at the video. If capturing moving objects clearly is a priority, it is
important that the network camera uses progressive scan technology. For more on progressive scan, see Chapter 3.
> Resolution. For applications that require detailed images, megapixel cameras may be the
best option. For more on megapixel resolution, see Chapter 6.
> Compression. The three video compression standards offered in Axis network video products
are H.264, MPEG-4 and Motion JPEG. H.264 is the latest standard and offers the greatest
savings in bandwidth and storage. For more on compression, see Chapter 7.
> Audio. If audio is required, consider whether one- or two-way audio is needed. Axis network
cameras with audio support come with a built-in microphone and/or an input for an external
microphone and a speaker or a line out for external speakers. For more on audio, see Chapter 8.
Event management and intelligent video. Event management functionalities are often
configured using a video management software program and are supported by input/output
ports and intelligent video features in a network camera or video encoder. Making recordings
based on event triggers from input ports and intelligent video features in a network video
product provides savings in bandwidth and storage use, and allows operators to take care of
more cameras since not all cameras require live monitoring unless an alarm/event takes
place. For more on event management functions, see Chapter 11.
Networking functionalities. Considerations include PoE; HTTPS encryption for encrypting
video streams before they are sent over the network; IP address filtering, which gives or
denies access rights to defined IP addresses; IEEE802.1X to control access to a network; IPv6;
and wireless functionality. For more on networking and security technologies, see Chapter 9.
Open interface and application software. A network video product with an open interface
enables better integration possibilities with other systems. It is also important that the
product is supported by a good selection of application software, and management software
that enable easy installation and upgrades of network video products. Axis products are
supported by both in-house video management software and a wide variety of video
management software solutions from more than 550 of its Application Development
Partners. For more on video management systems, see Chapter 11.
26 CHAPTER 2 - Network CAMERAS
Another important consideration, outside of the network camera itself, is the selection of the
network video product vendor. Since needs grow and change, the vendor should be seen as a
partner, and a long-term one. This means that it is important to select a vendor that offers a full
product line of network video products and accessories that can meet the needs now and well
into the future. The vendor should also provide innovation, support, upgrades and product path
for the long term.
Once a decision has been made as to the required camera, it is a good idea to purchase one and
test its quality before setting out to order quantities of it.
Camera elements
There are a number of camera elements that have an impact on image quality and
field of view and are, therefore, important to understand when choosing a network
camera. The elements include the light sensitivity of a camera, the type of lens, type of
image sensor and scanning technique, as well as image processing functionalities, all
of which are discussed in this chapter. Some guidelines on installation considerations
are also provided at the end.
Light sensitivity
A network camera’s light sensitivity is often specified in terms of lux, which corresponds to a
level of illuminance in which a camera produces an acceptable image. The lower the lux specification, the better light sensitivity the camera has. Normally, at least 200 lux is needed to
illuminate an object so that a good quality image can be obtained. In general, the more light on
the subject, the better the image. With too little light, focusing will be difficult and the image
will be noisy and/or dark. To capture good quality images in low light or dark conditions, a day
and night camera that takes advantage of near-infrared light is required. For more on day and
night cameras, see Chapter 2.
Different light conditions offer different illuminance. Many natural scenes have fairly complex
illumination, with both shadows and highlights that give different lux readings in different parts
of a scene. It is important, therefore, to keep in mind that one lux reading does not indicate the
light condition for a scene as a whole.
Lighting condition
100,000 lux
Strong sunlight
10,000 lux
Full daylight
500 lux
Office light
100 lux
Poorly lit room
Table 3.1a Examples of different levels of illuminance.
Many manufacturers specify the minimum level of illumination needed for a network camera to
produce an acceptable image. While such specifications are helpful in making light sensitivity
comparisons for cameras produced by the same manufacturer, it may not be helpful to use such
numbers to compare cameras from different manufacturers. This is because different manufacturers use different methods and have different criteria for what is an acceptable image.
To properly compare the low light performance of two different cameras, the cameras should be
placed side by side and be viewing a moving object in low light.
Lens elements
A lens or lens assembly on a network camera performs several functions. They include:
> Defining the field of view; that is, defining how much of a scene and level of detail are to be
> Controlling the amount of light passing through to the image sensor so that an image is
correctly exposed.
> Focusing by adjusting either elements within the lens assembly or the distance between the
lens assembly and the image sensor.
Field of view
A consideration to take into account when selecting a camera is the field of view required; that
is, the area of coverage and the degree of detail to be viewed. The field of view is determined by
the focal length of the lens and the size of the image sensor; both are specified in a network
camera’s datasheet.
A len’s focal length is defined as the distance between the entrance lens (or a specific point in
a complicated lens assembly) and the point where all the light rays converge to a point (normally the camera’s image sensor). The longer the focal length, the narrower the field of view.
The fastest way to find out what focal length lens is required for a desired field of view is to use
a rotating lens calculator or an online lens calculator (, both of which are
available from Axis. The size of a network camera’s image sensor, typically 1/4”, 1/3”, 1/2” and
2/3”, must also be used in the calculation. (The drawback of using a lens calculator is that it does
not take into account any possible geometrical distortion of a lens.)
The field of view can be classified into three types:
> Normal view: offering the same field of view as the human eye.
Telephoto: a narrower field of view, providing, in general, finer details than a human eye can
deliver. A telephoto lens is used when the surveillance object is either small or located far
away from the camera. A telephoto lens generally has less light gathering capability than a
normal lens.
> Wide angle: a larger field of view with less detail than in normal view. A wide-angle lens
generally provides good depth of field and fair, low-light performance. Wide-angle lenses
sometimes produce geometrical distortions such as the “fish-eye” effect.
Figure 3.2a Different fields of view: wide-angle view (at left); normal view (middle); telephoto (at right).
Figure 3.2b Network camera lenses with different focal lengths: wide-angle (at left); normal (middle); telephoto (at
There are three main types of lenses:
> Fixed lens: Such a lens offers a focal length that is fixed; that is, only one field of view
(either normal, telephoto or wide angle). A common focal length of a fixed network camera
lens is 4 mm.
Varifocal lens: This type of lens offers a range of focal lengths, and hence, different fields of
view. The field of view can be manually adjusted. Whenever the field of view is changed, the
user has to manually refocus the lens. Varifocal lenses for network cameras often provide
focal lengths that range from 3 mm to 8 mm.
Zoom lens: Zoom lenses are like varifocal lenses in that they enable the user to select
different fields of view. However, with zoom lenses, there is no need to refocus the lens if the
field of view is changed. Focus can be maintained within a range of focal lengths, for
example, 6 mm to 48 mm. Lens adjustments can be either manual or motorized for remote
control. When a lens states, for example, 3x-zoom capability, it is referring to the ratio
between the lens’ longest and shortest focal length.
Matching lens and sensor
If a network camera offers an exchangeable lens, it is important to select a lens suitable for the
camera. A lens made for a 1/2-inch image sensor will work with 1/2-inch, 1/3-inch and 1/4-inch
image sensors, but not with a 2/3-inch image sensor.
If a lens is made for a smaller image sensor than the one that is actually fitted inside the camera,
the image will have black corners (see left-hand illustration in Figure 3.2c below). If a lens is
made for a larger image sensor than the one that is actually fitted inside the camera, the field
of view will be smaller than the lens’ capability since part of the information will be “lost” outside the image sensor (see right-hand illustration in Figure 3.2c). This situation creates a telephoto effect as it makes everything look zoomed in.
Figure 3.2c Examples of different lenses mounted onto a 1/3-inch image sensor.
When replacing a lens on a megapixel camera, a high quality lens is required since megapixel sensors have pixels that are much smaller than those on a VGA sensor (640x480 pixels). It is best to
match the lens resolution to the camera resolution in order to fully use the camera’s capability.
Lens mount standards
When changing a lens, it is also important to know what type of lens mount the network camera
has. There are two main standards used on network cameras: CS-mount and C-mount. They both
have a 1-inch thread and they look the same. What differs is the distance from the lenses to the
sensor when fitted on the camera:
> CS-mount. The distance between the sensor and the lens should be 12.5 mm.
> C-mount. The distance between the sensor and the lens should be 17.526 mm.
It is possible to mount a C-mount lens to a CS-mount camera body by using a 5 mm spacer (C/CS
adapter ring). If it is impossible to focus a camera, it is likely that the wrong type of lens is used.
F-number and exposure
In low-light situations, particularly in indoor environments, an important factor to look for in a
network camera is the lens’ light-gathering ability. This can be determined by the lens’ f-number, also known as f-stop. An f-number defines how much light can pass through a lens.
An f-number is the ratio of the lens’ focal length to the diameter of the aperture or iris diameter;
that is, f-number = focal length/aperture.
The smaller the f-number (either short focal length relative to the aperture, or large aperture
relative to the focal length), the better the lens’ light gathering ability; i.e. more light can pass
through the lens to the image sensor. In low-light situations, a smaller f-number generally produces a better image quality. (There may be some sensors, however, that may not be able to take
advantage of a lower f-number in low-light situations due to the way they are designed.)
A higher f-number, on the other hand, increases the depth of field, which is explained in section
3.2.6. A lens with a lower f-number is normally more expensive than a lens with a higher
F-numbers are often written as F/x. The slash indicates division. An F/4 means the iris diameter
is equal to the focal length divided by 4; so if a camera has an 8 mm lens, light must pass
through an iris opening that is 2 mm in diameter.
While lenses with automatically adjustable iris (DC-iris) have a range of f-numbers, often only
the maximum light gathering end of the range (smallest f-number) is specified.
A lens’ light-gathering ability or f-number, and the exposure time (i.e., the length of time an
image sensor is exposed to light) are the two main elements that control how much light an
image sensor receives. A third element, the gain, is an amplifier that is used to make the image
brighter. However, increasing the gain also increases the level of noise (graininess) in an image,
so adjusting the exposure time or iris opening is preferred.
Limits to the exposure time and gain can be set in some Axis cameras. The longer the exposure
time, the more light an image sensor receives. Bright environments require shorter exposure
time, while low-light conditions require longer exposure time. It is important to be aware that
increasing the exposure time also increases motion blur, while increasing the iris opening has
the downside of reducing the depth of field, which is explained in section 3.2.6 below.
When deciding upon the exposure, a shorter exposure time is recommended when rapid movement
or when a high frame rate is required. A longer exposure time will improve image quality in poor
lighting conditions, but it may increase motion blur and lower the total frame rate since a longer
time is required to expose each frame. In some network cameras, an automatic exposure setting
means the frame rate will increase or decrease with the amount of available light. It is only as the
light level decreases that artificial light or prioritized frame rate or image quality is important to
Figure 3.2d
A camera user interface with options for setting, among other things, exposure in low-light
Manual or automatic iris
In indoor environments where light levels may be constant, a manual iris lens can be used. This
type of lens either provides a ring to adjust the iris, or the iris is fixed at a certain f-number. The
latter is what Axis uses on its indoor network cameras.
A lens with automatically adjustable iris is recommended for outdoor applications and where the
scene illumination is constantly changing. The iris aperture is controlled by the camera and is used
to maintain the optimum light level to the image sensor if exposure and gain settings are not
available or used in the network camera. The iris can also be used to control the depth of field
(explained in the section below) and to obtain sharper images. Most automatic iris lenses are
controlled by the camera’s processor via a direct current (DC) and are, therefore, called “DC-iris”
lenses. All Axis outdoor cameras, whether fixed, fixed dome, PTZ or PTZ dome, use DC-iris or autoiris lenses.
Depth of field
A criterion that may be important to a video surveillance application is depth of field. Depth of
field refers to the distance in front of and beyond the point of focus where objects appear to be
sharp simultaneously. Depth of field may be important, for instance, in monitoring a parking lot,
where there may be a need to identify license plates of cars at 20, 30 and 50 meters (60, 90 and
150 feet) away.
Depth of field is affected by three factors: focal length, iris diameter and distance of the camera
to the subject. A long focal length, a large iris opening or a short distance between the camera
and the subject will limit the depth of field.
Figure 3.2e Depth of field: Imagine a line of people standing behind each other. If the focus is in the middle of the
line and it is possible to identify the faces of all in front and behind the mid-point more than 15 meters (45 feet) away,
the depth of field is good.
Figure 3.2f Iris opening and depth of field. The above illustration is an example of the depth of field for different
f-numbers with a focal distance of 2 meters (7 feet). A large f-number (smaller iris opening) enables objects to be in
focus over a longer range. (Depending on the pixel size, very small iris openings may blur an image due to diffraction.)
Image sensors
As light passes through a lens, it is focused on the camera’s image sensor. An image sensor is
made up of many photosites and each photosite corresponds to a picture element, more commonly known as “pixel”, on an image sensor. Each pixel on an image sensor registers the amount
of light it is exposed to and converts it into a corresponding number of electrons. The brighter
the light, the more electrons are generated.
When building a camera, there are two main technologies that can be used for the camera’s
image sensor:
> CCD (charge-coupled device)
> CMOS (complementary metal-oxide semiconductor)
Figure 3.3a Images sensors: CCD (at left); CMOS (at right).
While CCD and CMOS sensors are often seen as rivals, each has unique strengths and weaknesses that make it appropriate for different applications. CCD sensors are produced using a
technology that has been developed specifically for the camera industry. Early CMOS sensors
were based on standard technology already extensively used in memory chips inside PCs, for
example. Modern CMOS sensors use a more specialized technology and the quality of the sensors is rapidly increasing.
CCD technology
CCD sensors have been used in cameras for more than 30 years and present many advantageous
qualities. Generally, they still offer slightly better light sensitivity and produce somewhat less noise
than CMOS sensors. Higher light sensitivity translates into better images in low light conditions.
CCD sensors, however, are more expensive and more complex to incorporate into a camera. A CCD
can also consume as much as 100 times more power than an equivalent CMOS sensor.
CMOS technology
Recent advances in CMOS sensors bring them closer to their CCD counterparts in terms of image
quality. CMOS sensors lower the total cost for cameras since they contain all the logics needed
to build cameras around them. In comparison with CCDs, CMOS sensors enable more integration
possibilities and more functions. CMOS sensors also have a faster readout (which is advantageous when high-resolution images are required), lower power dissipation at the chip level, as
well as a smaller system size. Megapixel CMOS sensors are more widely available and are less
expensive than megapixel CCD sensors.
Megapixel sensors
For cost reasons, many megapixel sensors (i.e., sensors containing a million or more pixels) in
megapixel cameras are the same size as or only slightly larger than VGA sensors that provide a
resolution of 640x480 (307,200) pixels. This means that the size of each pixel on a megapixel
sensor is smaller than on a VGA sensor. For instance, a megapixel sensor such as a 1/3-inch,
2-megapixel sensor has pixel sizes measuring 3 µm (micrometers/microns) each. By comparison,
the pixel size of a 1/3-inch VGA sensor is 7.5 µm. So while the megapixel camera provides
higher resolution and greater detail, it is less light sensitive than its VGA counterpart since the
pixel size is smaller and light reflected from an object is spread to more pixels.
Image scanning techniques
Interlaced scanning and progressive scanning are the two techniques available today for reading
and displaying information produced by image sensors. Interlaced scanning is used mainly in
CCDs. Progressive scanning is used in either CCD or CMOS sensors. Network cameras can make
use of either scanning technique. (Analog cameras, however, can only make use of the interlaced
scanning technique for transferring images over a coaxial cable and for displaying them on
analog monitors.)
Interlaced scanning
When an interlaced image from a CCD is produced, two fields of lines are generated: a field
displaying the odd lines, and a second field displaying the even lines. However, to create the odd
field, information from both the odd and even lines on a CCD sensor is combined. The same goes
for the even field, where information from both the even and odd lines is combined to form an
image on every other line.
When transmitting an interlaced image, only half the number of lines (alternating between odd
and even lines) of an image is sent at a time, which reduces the use of bandwidth by half. The
monitor, for example, a traditional TV, must also use the interlaced technique. First the odd lines
and then the even lines of an image are displayed and then refreshed alternately at 25 (PAL) or
30 (NTSC) frames per second so that the human visual system interprets them as complete
images. All analog video formats and some modern HDTV formats are interlaced. Although the
interlacing technique creates artifacts or distortions as a result of ‘missing’ data, they are not
very noticeable on an interlaced monitor.
However, when interlaced video is shown on progressive scan monitors such as computer
monitors, which scan lines of an image consecutively, the artifacts become noticeable. The artifacts, which can be seen as “tearing”, are caused by the slight delay between odd and even line
refreshes as only half the lines keep up with a moving image while the other half waits to be
refreshed. It is especially noticeable when the video is stopped and a freeze frame of the video
is analyzed.
Progressive scanning
With a progressive scan image sensor, values are obtained for each pixel on the sensor and each
line of image data is scanned sequentially, producing a full frame image. In other words, captured
images are not split into separate fields as with interlaced scanning. With progressive scan, an
entire image frame is sent over a network and when displayed on a progressive scan computer
monitor, each line of an image is put on the screen one at a time in perfect order. Moving objects
are, therefore, better presented on computer screens using the progressive scan technique.
In a video surveillance application, it can be critical in viewing details of a moving subject (e.g.,
a person running away). Most Axis network cameras use the progressive scan technique.
1st field: Odd lines
2nd field: Even lines
Freeze frame on moving dot
[17/20 ms (NTSC/PAL) later]
using interlaced scan
Freeze frame on moving dot
using progressive scan
Figure 3.4a At left, an interlaced scan image shown on a progressive (computer) monitor. At right, a progressive
scan image on a computer monitor.
Figure 3.4b At left, a full-sized JPEG image (704x576 pixels) from an analog camera using interlaced scanning.
At right, a full-sized JPEG image (640x480 pixels) from an Axis network camera using progressive scan technology.
Both cameras used the same type of lens and the speed of the car was the same at 20 km/h (15 mph). The background
is clear in both images. However, the driver is clearly visible only in the image using progressive scan technology.
Image processing
Three features that may be supported in network cameras to improve image quality are backlight compensation, exposure zones and wide dynamic range.
Backlight compensation
While a camera’s automatic exposure tries to get the brightness of an image to appear as the
human eye would see a scene, it can be easily fooled. Strong backlight can cause objects in the
foreground to be dark. Network cameras with backlight compensation strive to ignore limited areas
of high illumination, just as if they were not present. It enables objects in the foreground to be seen,
although the bright areas will be overexposed. Such lighting situations can also be handled by
increasing the dynamic range of the camera, which is discussed in section 3.5.3 below.
Exposure zones
Besides dealing with limited areas of high illumination, a network camera’s automatic exposure
must also decide what area of an image should determine the exposure value. For instance, the
foreground (usually the bottom section of an image) may hold more important information than
the background; for example, the sky (usually the top section of an image). The less important
areas of a scene should not determine the overall exposure. In advanced Axis network cameras,
the user is able to use exposure zones to select the area of a scene—center, left, right, top or
bottom—that should be more correctly exposed.
Wide dynamic range
Some Axis network cameras offer wide dynamic range to handle a wide range of lighting conditions in a scene. In a scene with extremely bright and dark areas or in backlight situations where
a person is in front of a bright window, a typical camera will produce an image where objects in
the dark areas will hardly be visible. Wide dynamic range solves this by applying techniques,
such as using different exposures for different objects in a scene, to enable objects in both bright
and dark areas to be visible.
Figure 3.5a At left, image without wide dynamic range. At right, image with wide dynamic range applied.
Installing a network camera
Once a network camera has been purchased, the way it is installed is just as important. Below
are some recommendations on how to best achieve high-quality video surveillance based on
camera positioning and environmental considerations.
Surveillance objective. If the aim is to get an overview of an area to be able to track the
movement of people or objects, make sure a camera that is suitable for the task is placed in
a position that achieves the objective. If the intention is to be able to identify a person or
object, the camera must be positioned or focused in a way that will capture the level of
detail needed for identification purposes. Local police authorities may also be able to provide
guidelines on how best to position a camera.
> Use lots of light or add light if needed. It is normally easy and cost-effective to add strong
lamps in both indoor and outdoor situations to provide the necessary light conditions for
capturing good images.
> Avoid direct sunlight as it will “blind” the camera and can reduce the performance of the
image sensor. If possible, position the camera with the sun shining from behind the
Avoid backlight. This problem typically occurs when attempting to capture an object in
front of a window. To avoid this problem, reposition the camera or use curtains and
close blinds if possible. If it is not possible to reposition the camera, add frontal lighting.
Cameras with support for wide dynamic range are better at handling a backlight
> Reduce the dynamic range of the scene. In outdoor environments, viewing too much sky
results in too high a dynamic range. If the camera does not support wide dynamic range,
a solution is to mount the camera high above the ground, using a pole if needed.
> Adjust camera settings. It may be necessary at times to adjust settings for white balance,
brightness and sharpness to obtain an optimal image. In low light situations, users must also
prioritize either frame rate or image quality.
Legal considerations. Video surveillance can be restricted or prohibited by laws that vary
from country to country. It is advisable to check the laws in the local region before installing
a video surveillance system. It may be necessary, for instance, to register or get a license for
video surveillance, particularly in public areas. Signage may be required. Video recordings
may require time and date stamping. There may be rules regulating how long video should
be retained. Audio recordings may or may not be permitted.
CAMERA Protection and housings - CHAPTER 4 39
Camera protection and housings
Surveillance cameras are often placed in environments that are very demanding.
Cameras may require protection from rain, hot and cold environments, dust, corrosive
substances, vibrations and vandalism. Manufacturers of cameras and camera accessories employ various methods to meet such environmental challenges. Solutions include
placing cameras in separate, protective housings, designing built-in special-purpose
camera enclosures, and/or using intelligent algorithms that can detect and alert users
of a change in a camera’s operating conditions.
The sections below cover such topics as coverings, positioning of fixed cameras in
enclosures, environmental protection, vandal and tampering protection, and types of
Camera enclosures in general
When the demands of the environment are beyond a camera’s operating conditions, protective
housings are required. Camera housings come in different sizes and qualities and with different
features. Housings are made of either metal or plastic and can be generally classified into two
types: fixed camera housings and dome camera housings. When selecting an enclosure, several
things need to be considered, including:
Side or slide opening (for fixed camera housings)
Mounting brackets
Clear or smoked bubble (for dome camera housings)
Cable management
Temperature and other ratings (consider the need for heater, sunshield, fan and wipers)
Power supply (12 V, 24 V, 110 V, etc.)
Level of vandal resistance
Some housings also have peripherals such as antennas for wireless applications. An external
antenna is only required if the housing is made of metal. A wireless camera inside a plastic
housing will work without the use of an external antenna.
40 CHAPTER 4 - CAMERA protection and housings
Transparent covering
The “window” or transparent covering of an enclosure is usually made of high-quality glass or
durable, polycarbonate plastic. As windows act like optical lenses, they should be of high quality
to minimize its effect on image quality. When there are built-in imperfections in the clear
material, clarity is compromised.
Higher demands are placed on the windows of housings for PTZ cameras and PTZ dome cameras.
Not only do the windows have to be specially shaped in the form of a bubble, but they must also
have high clarity since imperfections such as dirt particles can be magnified, particularly when
cameras with high zoom factors are installed. In addition, if the thickness of the window is
uneven, a straight line may appear curved in the resulting image. A high-quality bubble should
have very little impact on image quality, irrespective of the camera’s zoom level and lens position.
The thickness of a bubble can be increased to withstand heavy blows, but the thicker a covering
is, the higher the chances of imperfections. Increased thickness may also create unwanted
reflections and refraction of light. Therefore, thicker coverings should meet higher requirements
if the effect on image quality is to be minimized.
A variety of dome coverings or bubbles are available, such as clear or smoked versions. While
smoked versions enable a more discrete installation, they also act much like sunglasses do in
reducing the amount of light available to the camera. It will, therefore, have an affect on the
camera’s light sensitivity.
Positioning a fixed camera in a housing
When installing a fixed camera in an enclosure, it is important that the lens of the camera is
positioned right up against the window to prevent any glare. Otherwise, reflections from the
camera and the background will appear in the image. To reduce reflection, special coatings can
be applied on any glass used in front of the lens.
igure 4.3a When installing a camera behind a glass, correct positioning of the camera becomes important to avoid
CAMERA Protection and housings - CHAPTER 4 41
Environmental protection
The main environmental threats to a camera—particularly one that is installed outdoors—are
cold, heat, water and dust. Housings with built-in heaters and fans (blowers) can be used in
environments with low and high temperatures. In hot environments, cameras can be placed in
enclosures that have active cooling with a separate heat exchanger.
To withstand water and dust, housings (often with an IP66 rating) are carefully sealed. In situations where cameras may be exposed to acids, such as in the food industry, housings made of
stainless steel are required. Some specialized housings can be pressurized, submersible, bulletproofed or built for installation in potentially explosive locations. Special enclosures may also be
required for aesthetic considerations.
Other environmental elements include wind and traffic. To minimize vibrations, particularly on
pole-mounted camera installations, the housing should ideally be small and securely mounted.
The terms “indoor housing” and “outdoor housing” often refer to the level of environmental
protection. An indoor housing is mostly used to prevent the entry of dust and does not include
a heater and/or fan. The terms are misleading since the location, whether indoor or outdoor,
does not always correspond to the conditions at an installation site. A camera placed in a
freezer room, for example, will need an “outdoor housing” that has a heater.
The level of protection provided by enclosures, whether built-in or separate from a camera,
is often indicated by classifications set by such standards as IP, which stands for Ingress Protection (also sometimes known as International Protection) and applicable worldwide; NEMA
(National Electrical Manufacturers Association) in the U.S.; and IK ratings for external
mechanical impacts, which apply in Europe. When a camera is to be installed in a potentially
explosive environment, other standards—such as IECEx, which is a global certification, and ATEX,
a European certification—come into play. More on IP ratings can be found here:
Vandal and tampering protection
In some surveillance applications, cameras are at risk of hostile and violent attacks. While a
camera or housing can never guarantee 100% protection from destructive behavior in every
situation, vandalism can be mitigated by considering various aspects: camera/housing design,
mounting, placement and use of intelligent video alarms.
Camera/housing design
Casings and related components that are made of metal provide better vandal protection than
ones made of plastic. The shape of the housing or camera is another factor. A housing or a traditional fixed camera that protrudes from a wall or ceiling is more vulnerable to attacks (e.g., kick-
42 CHAPTER 4 - CAMERA protection and housings
ing or hitting) than more discretely designed housings or casings for a fixed dome or PTZ dome
camera. The smooth, rounded covering of a fixed dome or PTZ dome makes it more difficult, for
example, to block the camera’s view by trying to hang a piece of clothing over the camera. The
more a housing or camera blends into an environment or is disguised as something other than a
camera—for example, an outdoor light—the better the protection against vandalism.
Figure 4.5a Examples of fixed camera housings. Only the middle and right housings are classified as vandal-resistant.
Figure 4.5b Examples of vandal-resistant housings for a small or compact fixed network camera (at left), for a fixed
dome network camera (middle) and for a PTZ camera (at right).
The way cameras and housings are mounted is also important. A traditional fixed network camera
and a PTZ dome camera that is mounted on the surface of a ceiling are more vulnerable to attacks
than a fixed dome or PTZ dome camera that is mounted flush to a ceiling or wall, where only the
transparent part of the camera or housing is visible.
Figures 4.5c Examples of flush ceiling-mounted housings for fixed network cameras.
Another important consideration is how the cabling to a camera is mounted. Maximum protection is provided when the cable is pulled directly through the wall or ceiling behind the camera.
In this way, there are no visible cables to tamper with. If this is not possible, a metal conduit
tube should be used to protect cables from attacks.
CAMERA Protection and housings - CHAPTER 4 43
Camera placement
Camera placement is also an important factor in deterring vandalism. By placing a camera out
of reach on high walls or in the ceiling, many spur-of-the-moment attacks can be prevented.
The downside may be the angle of view, which to some extent can be compensated by selecting
a different lens.
Intelligent video
Axis’ active tampering alarm feature helps protect cameras against vandalism. It can detect if a
camera has been redirected, obscured or tampered with, and can send alarms to operators. This
is especially useful in installations with hundreds of cameras in demanding environments where
keeping track of the proper functioning of all cameras is difficult. It is also useful in situations
where no live viewing takes place and operators can be notified when cameras have been tampered with.
Types of mounting
Cameras need to be placed in all kinds of locations and this requires a large number of variations
in the type of mounting.
Ceiling mounts
Ceiling mounts are mainly used in indoor installations. The enclosure itself can be:
A surface mount: mounted directly on the surface of a ceiling and, therefore, completely
A flush mount: mounted inside the ceiling with only parts of a camera and housing
(usually the bubble) visible.
A pendant mount: housing that is hung from a ceiling like a pendant.
Figure 4.6a An example of a surface mount (left), a flush mount (middle) and a pendant mount (right).
44 CHAPTER 4 - CAMERA protection and housings
Wall mounts
Wall mounts are often used to mount cameras inside or outside a building. The housing is
connected to an arm, which is mounted on a wall. Advanced mounts have an inside cable gland
to protect the cable. To install an enclosure at a corner of a building, a normal wall mount,
together with an additional corner adapter, can be used. Other special mounts include a pendant
kit mount, which allows a fixed network camera to be mounted in a style that is similar to a PTZ
dome enclosure.
Figure 4.6b An example of a wall mount with a pendent mount kit for a fixed dome camera.
Pole mounts
A pole mount is often used together with a PTZ camera in locations such as a parking lot. This
type of mount usually takes into consideration the impact of wind. The dimensions of the pole
and the mount itself should be designed to minimize vibrations. Cables are often enclosed inside
the pole and outlets must be properly sealed. More advanced PTZ dome cameras have built-in
electronic image stabilization to limit the effects of wind and vibrations.
Parapet mounts
Parapet mounts are used for roof-mounted housings or to raise the camera for a better angle of
Figure 4.6c An example of a parapet mount.
Axis provides an online tool that can help users identify the right housing and mounting accessories needed. Visit
Video encoders
Video encoders, also known as video servers, enable an existing analog CCTV video
surveillance system to be integrated with a network video system. Video encoders
play a significant role in installations where many analog cameras are to be maintained. This chapter describes what a video encoder is and its benefits, and provides
an overview of its components and the different types of video encoders available.
A brief discussion on deinterlacing techniques is also included, in addition to a section
on video decoders.
What is a video encoder?
A video encoder makes it possible for an analog CCTV system to migrate to a network video system. It enables users to gain the benefits of network video without having to discard existing
analog equipment such as analog CCTV cameras and coaxial cabling.
A video encoder connects to an analog video camera via a coaxial cable and converts analog
video signals into digital video streams that are then sent over a wired or wireless IP-based network (e.g., LAN, WLAN or Internet). To view and/or record the digital video, computer monitors
and PCs can be used instead of DVRs or VCRs and analog monitors.
Axis network cameras
Axis video encoders
0 -
FNP 30
100-240 AC
50-50 Hz
4-2 A
0 -
FNP 30
AXIS Q7900 Rack
50-50 Hz
4-2 A
AXIS Q7406
Video Encoder
AXIS Q7406
Video Encoder
AXIS 292
Network Video Decoder
Computer with
video management
with web
Axis video
Figure 5.1a An illustration of how analog video cameras and analog monitors can be integrated with a network
video system using video encoders and decoders.
By using video encoders, analog video cameras of all types, such as fixed, indoor/outdoor, dome,
pan/tilt/zoom, and specialty cameras such as highly sensitive thermal cameras and microscope
cameras can be remotely accessed and controlled over an IP network.
A video encoder also offers other benefits such as event management and intelligent video
functionalities, as well as advanced security measures. In addition, it provides scalability and
ease of integration with other security systems.
Analog input
Ethernet (PoE)
Figure 5.1b A one-channel, standalone video encoder with audio, I/O (input/output) connectors for controlling
external devices such as sensors and alarms, serial ports (RS-422/485) for controlling PTZ analog cameras and
Ethernet connection with Power over Ethernet support.
Video encoder components and considerations
Axis video encoders offer many of the same functions that are available in network cameras.
Some of the main components of a video encoder include:
> Analog video input for connecting an analog camera using a coaxial cable.
Processor for running the video encoder’s operating system, networking and security
functionalities, for encoding analog video using various compression formats and for video
analysis. The processor determines the performance of a video encoder, normally measured
in frames per second in the highest resolution. Advanced video encoders can provide full
frame rate (30 frames per second with NTSC-based analog cameras or 25 frames per second
with PAL-based analog cameras) in the highest resolution for every video channel. Axis video
encoders also have auto sensing to automatically recognize if the incoming analog video
signal is an NTSC or PAL standard. For more on NTSC and PAL resolutions, see Chapter 6.
> Memory for storing the firmware (computer program) using Flash, as well as buffering of
video sequences (using RAM).
> Ethernet/Power over Ethernet port to connect to an IP network for sending and receiving
data, and for powering the unit and the attached camera if Power over Ethernet is supported.
For more on Power over Ethernet, see Chapter 9.
> Serial port (RS-232/422/485) often used for controlling the pan/tilt/zoom functionality of an
analog PTZ camera.
> Input/output connectors for connecting external devices; for example, sensors to detect an
alarm event, and relays to activate, for instance, lights in response to an event.
> Audio in for connecting a microphone or line-in equipment and audio out for connecting to
Video encoders for professional systems should meet high demands for reliability and quality.
When selecting a video encoder, other considerations include the number of supported analog
channels, image quality, compression formats, resolution, frame rate and features such as pan/
tilt/zoom support, audio, event management, intelligent video, Power over Ethernet and security
Event management and intelligent video
One of the main benefits of Axis video encoders is the ability to provide event management and
intelligent video functionalities, capabilities that cannot be provided in an analog video system.
Built-in intelligent video features such as multi-window video motion detection, audio detection
and active tampering alarm, as well as input ports for external sensors, enable a network video
surveillance system to be constantly on guard to detect an event. Once an event is detected, the
system can automatically respond with actions that may include video recording, sending alerts
such as e-mails and SMS, activating lights, opening/closing doors and sounding alarms. For more
on event management and intelligent video, see Chapter 11.
Standalone video encoders
The most common type of video encoders is the standalone version, which offers one or multichannel (often four) connections to analog cameras. A multi-channel video encoder is ideal in
situations where there are several analog cameras located in a remote facility or a place that is
a fair distance from a central monitoring room. Through the multi-channel video encoder, video
signals from the remote cameras can then share the same network cabling, thereby reducing
cabling costs.
In situations where investments have been made in analog cameras but coaxial cables have not
yet been installed, it is best to use and position standalone video encoders close to the analog
cameras. It reduces installation costs as it eliminates the need to run new coaxial cables to a
central location since the video can be sent over an Ethernet network. It also eliminates the loss
in image quality that would occur if video were to be sent over long distances through coaxial
cables. With coaxial cables, the video quality decreases the further the signals have to travel.
A video encoder produces digital images, so there is no reduction in image quality due to the
distance traveled by a digital video stream.
Figure 5.2a An illustration of how a small, single-channel video encoder can be positioned next to an analog
camera in a camera housing.
Rack-mounted video encoders
Rack-mounted video encoders are beneficial in instances where there are many analog cameras
with coaxial cables running to a dedicated control room. They enable many analog cameras to
be connected and managed from one rack in a central location. A rack allows a number of
different video encoder blades to be mounted and thereby offers a flexible, expandable, highdensity solution. A video encoder blade may support one, four or six analog cameras. A blade can
be seen as a video encoder without a casing, although it cannot function on its own; it has to
be mounted in a rack to operate.
Figure 5.3a When the AXIS Q7900 Rack (shown here) is fully outfitted with 6-channel video encoder blades, it can
accommodate as many as 84 analog cameras.
Axis video encoder racks support features such as hot swapping of blades; that is, blades can be
removed or installed without having to power down the rack. The racks also provide serial communication and input/output connectors for each video encoder blade, in addition to a common
power supply and shared Ethernet network connection(s).
Video encoders with PTZ cameras and PTZ dome cameras
In a network video system, pan/tilt/zoom commands from a control board are carried over the
same IP network as for video transmission and are forwarded to the analog PTZ camera or PTZ
dome camera through the video encoder’s serial port (RS-232/422/485). Video encoders, therefore,
enable analog PTZ cameras to be controlled over long distances, even through the Internet. (In an
analog CCTV system, each PTZ camera would require separate and dedicated serial wiring from the
control board—with joystick and other control buttons—all the way to the camera.)
To control a specific PTZ camera, a driver must be uploaded to the video encoder. Many manufacturers of video encoders provide PTZ drivers for most analog PTZ cameras and PTZ dome cameras.
A PTZ driver can also be installed on the PC that runs the video management software program if
the video encoder’s serial port is set up as a serial server that simply passes on the commands.
twisted pair
Coax Cable
Analog dome
Video encoder
PC workstation
Figure 5.4a An analog PTZ dome camera can be controlled via the video encoder’s serial port (e.g., RS-485), making
it possible to remotely control it over an IP network.
The most commonly used serial port for controlling PTZ functions is RS-485. One of the benefits
that RS-485 allows is the possibility to control multiple PTZ cameras using twisted pair cables in a
daisy chain connection from one dome camera to the next. The maximum distance of an RS-485
cable, without using a repeater, is 1,220 meters (4,000 feet) at baud rates up to 90 kbit/s.
Deinterlacing techniques
Video from analog cameras is designed to be viewed on analog monitors such as traditional TV
sets, which use a technique called interlaced scanning. With interlaced scanning, two consecutive interlaced fields of lines are shown to form an image. When such video is shown on a
computer screen, which uses a different technique called progressive scanning, interlacing
effects (i.e., tearing or comb effect) from moving objects can be seen. In order to reduce the
unwanted interlacing effects, different deinterlacing techniques can be employed. In advanced
Axis video encoders, users can choose between two different deinterlacing techniques: adaptive
interpolation and blending.
Figure 5.5a At left, a close-up of an interlaced image shown on a computer screen; at right, the same interlaced
image with deinterlacing technique applied.
Adaptive interpolation offers the best image quality. The technique involves using only one of
the two consecutive fields and using interpolation to create the other field of lines to form a full
Blending involves merging two consecutive fields and displaying them as one image so that all
fields are present. The image is then filtered to smooth out the motion artifacts or ‘comb effect’
caused by the fact that the two fields were captured at slightly different times. The blending
technique is not as processor intensive as adaptive interpolation.
Video decoder
A video decoder decodes digital video and audio coming from a video encoder or a network
camera into analog signals, which can then be used by analog monitors, such as regular TV sets,
and video switches. A typical case could be in a retail environment where the user may want to
have traditional monitors in public spaces to demonstrate that video surveillance is used.
Another common application for video decoders is to use them in an analog-to-digital-to-analog
configuration for transporting video over long distances. The quality of digital video is not affected
by the distance traveled, which is not the case when sending analog signals over long distances.
The only downside may be some level of latency, from 100 ms to a few seconds, depending on the
distance and the quality of the network between the end points.
Analog camera
Axis video
AXIS 292
Network Video Decoder
Axis video
Analog monitor
Figure 5.6a An encoder and decoder can be used to transport video over long distances, from an analog camera to
an analog monitor.
A video decoder has the ability to decode and display video from many cameras sequentially;
that is, decoding and showing video from one camera for some seconds before changing to
another and so on.
Resolution in an analog or digital world is similar, but there are some important
differences in how it is defined. In analog video, an image consists of lines or
TV-lines since analog video technology is derived from the television industry. In a digital
system, an image is made up of square pixels.
The sections below describe the different resolutions that network video can provide.
They include NTSC, PAL, VGA, megapixel and HDTV.
NTSC and PAL resolutions
NTSC (National Television System Committee) and PAL (Phase Alternating Line) resolutions are
analog video standards. They are relevant to network video since video encoders provide such
resolutions when they digitize signals from analog cameras. Current PTZ network cameras and
PTZ dome network cameras also provide NTSC and PAL resolutions since such cameras today use
a camera block (which incorporates the camera, zoom, auto-focus and auto-iris functions) made
for analog video cameras, in conjunction with a built-in video encoder board.
In North America and Japan, the NTSC standard is the predominant analog video standard, while
in Europe and many Asian and African countries, the PAL standard is used. Both standards originate from the television industry. NTSC has a resolution of 480 lines and uses a refresh rate of 60
interlaced fields per second (or 30 full frames per second). A new naming convention, which
defines the number of lines, type of scan and refresh rate, for this standard is 480i60
(“i” stands for interlaced scanning). PAL has a resolution with 576 lines and uses a refresh rate of
50 interlaced fields per second (or 25 full frames per second). The new naming convention for this
standard is 576i50. The total amount of information per second is the same in both standards.
When analog video is digitized, the maximum amount of pixels that can be created is based on
the number of TV lines available to be digitized. The maximum size of a digitized image is typically D1 and the most commonly used resolution is 4CIF.
D1 720 x 576
D1 720 x 480
When shown on a computer screen, digitized analog video may show interlacing effects such as
tearing and shapes may be off slightly since the pixels generated may not conform to the square
pixels on the computer screen. Interlacing effects can be reduced using deinterlacing techniques
(see Chapter 5), while aspect ratio correction can be applied to video before it is displayed to
ensure, for instance, that a circle in an analog video remains a circle when shown on a computer screen.
4CIF 704 x 480
4CIF 704 x 576
2CIF 704 x 288
2CIF 704 x 240
CIF 352 x 288
CIF 352 x 240
QCIF 176 x 144
QCIF 176 x 120
Figure 6.1a At left, different NTSC image resolutions. At right, different PAL image resolutions.
VGA resolutions
With 100% digital systems based on network cameras, resolutions that are derived from the
computer industry and that are standardized worldwide can be provided, allowing for better
flexibility. The limitations of NTSC and PAL become irrelevant.
VGA (Video Graphics Array) is a graphics display system for PCs originally developed by IBM. The
resolution is defined as 640x480 pixels, which is a common format used by non-megapixel
network cameras. The VGA resolution is normally better suited for network cameras since VGAbased video produces square pixels that match with those on computer screens. Computer
monitors can handle resolutions in VGA or multiples of VGA.
Display format
4x VGA
Table 6.2 VGA resolutions.
Megapixel resolutions
A network camera that offers megapixel resolution uses a megapixel sensor to deliver an image
that contains one million or more pixels. The more pixels a sensor has, the greater the potential
it has for capturing finer details and for producing a higher quality image. Megapixel network
cameras can be used to allow users to see more details (ideal for identification of people and
objects) or to view a larger area of a scene. This benefit is an important consideration in video
surveillance applications.
Display format
No. of megapixels
1.3 megapixels
1.4 megapixels
1.9 megapixels
2.3 megapixels
3.1 megapixels
4.1 megapixels
5.2 megapixels
Table 6.3 Above are some megapixel formats.
Megapixel resolution is one area in which network cameras excel over analog cameras. The
maximum resolution a conventional analog camera can provide after the video signal has been
digitized in a digital video recorder or a video encoder is D1, which is 720x480 pixels (NTSC) or
720x576 pixels (PAL). The D1 resolution corresponds to a maximum of 414,720 pixels or 0.4
megapixel. By comparison, a common megapixel format of 1280x1024 pixels gives a 1.3-megapixel resolution. This is more than 3 times the resolution that can be provided by analog CCTV
cameras. Network cameras with 2-megapixel and 3-megapixel resolutions are also available,
and even higher resolutions are expected in the future.
Megapixel resolution also provides a greater degree of flexibility in terms of being able to provide images with different aspect ratios. (Aspect ratio is the ratio of the width of an image to its
height.) A conventional TV monitor displays an image with an aspect ratio of 4:3. Axis megapixel network cameras can offer the same ratio, in addition to others, such as 16:9. The advantage of a 16:9 aspect ratio is that unimportant details, usually located in the upper and lower
part of a conventional-sized image, are not present and therefore, bandwidth and storage
requirements can be reduced.
Figure 6.3a Illustration of 4:3 and 16:9 aspect ratios.
High-definition television (HDTV) resolutions
HDTV provides up to five times higher resolution than standard analog TV. HDTV also has better
color fidelity and a 16:9 format. Defined by SMPTE (Society of Motion Picture and Television
Engineers), the two most important HDTV standards are SMPTE 296M and SMPTE 274M.
SMPTE 296M (HDTV 720P) defines a resolution of 1280x720 pixels with high color fidelity in a
16:9 format using progressive scanning at 25/30 Hertz (Hz), which corresponds to 25 or 30
frames per second depending on the country, and at 50/60 Hz (50/60 frames per second).
SMPTE 274M (HDTV 1080) defines a resolution of 1920x1080 pixels with high color fidelity in a
16:9 format using either interlaced or progressive scanning at 25/30 Hz and 50/60Hz.
A camera that complies with the SMPTE standards indicates adherence to HDTV quality and
should provide all the benefits of HDTV in resolution, color fidelity and frame rate.
The HDTV standard is based on square pixels—similar to computer screens, so HDTV video from
network video products can be shown on either HDTV screens or standard computer monitors.
With progressive scan HDTV video, no conversion or deinterlacing technique needs to be applied
when the video is to be processed by a computer or displayed on a computer screen.
Video compression
Video compression technologies are about reducing and removing redundant video
data so that a digital video file can be effectively sent over a network and stored on
computer disks. With efficient compression techniques, a significant reduction in file
size can be achieved with little or no adverse effect on the visual quality. The video
quality, however, can be affected if the file size is further lowered by raising the compression level for a given compression technique.
Different compression technologies, both proprietary and industry standards, are
available. Most network video vendors today use standard compression techniques.
Standards are important in ensuring compatibility and interoperability. They are particularly relevant to video compression since video may be used for different purposes
and, in some video surveillance applications, needs to be viewable many years from
the recording date. By deploying standards, end users are able to pick and choose from
different vendors, rather than be tied to one supplier when designing a video surveillance system.
Axis uses three different video compression standards. They are Motion JPEG, MPEG-4
Part 2 (or simply referred to as MPEG-4) and H.264. H.264 is the latest and most efficient
video compression standard. This chapter covers the basics of compression and provides
a description of each of the three standards mentioned earlier.
Compression basics
Video codec
The process of compression involves applying an algorithm to the source video to create a
compressed file that is ready for transmission or storage. To play the compressed file, an inverse
algorithm is applied to produce a video that shows virtually the same content as the original
source video. The time it takes to compress, send, decompress and display a file is called latency.
The more advanced the compression algorithm, the higher the latency.
A pair of algorithms that works together is called a video codec (encoder/decoder). Video codecs
of different standards are normally not compatible with each other; that is, video content that
is compressed using one standard cannot be decompressed with a different standard. For
instance, an MPEG-4 decoder will not work with an H.264 encoder. This is simply because one
algorithm cannot correctly decode the output from another algorithm but it is possible to implement many different algorithms in the same software or hardware, which would then enable
multiple formats to coexist.
Image compression vs. video compression
Different compression standards utilize different methods of reducing data, and hence, results
differ in bit rate, quality and latency. Compression algorithms fall into two types: image compression and video compression.
Image compression uses intraframe coding technology. Data is reduced within an image frame
simply by removing unnecessary information that may not be noticeable to the human eye.
Motion JPEG is an example of such a compression standard. Images in a Motion JPEG sequence
is coded or compressed as individual JPEG images.
Figure 7.1a With the Motion JPEG format, the three images in the above sequence are coded and sent as separate
unique images (I-frames) with no dependencies on each other.
Video compression algorithms such as MPEG-4 and H.264 use interframe prediction to reduce
video data between a series of frames. This involves techniques such as difference coding, where
one frame is compared with a reference frame and only pixels that have changed with respect
to the reference frame are coded. In this way, the number of pixel values that is coded and sent
is reduced. When such an encoded sequence is displayed, the images appear as in the original
video sequence.
Figure 7.1b With difference coding, only the first image (I-frame) is coded in its entirety. In the two following
images (P-frames), references are made to the first picture for the static elements, i.e. the house. Only the moving
parts, i.e. the running man, are coded using motion vectors, thus reducing the amount of information that is sent and
Other techniques such as block-based motion compensation can be applied to further reduce
the data. Block-based motion compensation takes into account that much of what makes up a
new frame in a video sequence can be found in an earlier frame, but perhaps in a different location. This technique divides a frame into a series of macroblocks (blocks of pixels). Block by
block, a new frame can be composed or ‘predicted’ by looking for a matching block in a reference
frame. If a match is found, the encoder codes the position where the matching block is to be
found in the reference frame. Coding the motion vector, as it is called, takes up fewer bits than
if the actual content of a block were to be coded.
Search window
Matching block
Motion vector
Earlier reference frame
Target block
Figure 7.1c Illustration of block-based motion compensation.
With interframe prediction, each frame in a sequence of images is classified as a certain type of
frame, such as an I-frame, P-frame or B-frame.
An I-frame, or intra frame, is a self-contained frame that can be independently decoded without
any reference to other images. The first image in a video sequence is always an I-frame. I-frames
are needed as starting points for new viewers or resynchronization points if the transmitted bit
stream is damaged. I-frames can be used to implement fast-forward, rewind and other random
access functions. An encoder will automatically insert I-frames at regular intervals or on
demand if new clients are expected to join in viewing a stream. The drawback of I-frames is that
they consume much more bits, but on the other hand, they do not generate many artifacts,
which are caused by missing data.
A P-frame, which stands for predictive inter frame, makes references to parts of earlier I and/or
P frame(s) to code the frame. P-frames usually require fewer bits than I-frames, but a drawback
is that they are very sensitive to transmission errors because of the complex dependency on
earlier P and/or I frames.
A B-frame, or bi-predictive inter frame, is a frame that makes references to both an earlier reference frame and a future frame. Using B-frames increases latency.
Figure 7.1d A typical sequence with I-, B- and P-frames. A P-frame may only reference preceding I- or P-frames,
while a B-frame may reference both preceding and succeeding I- or P-frames.
When a video decoder restores a video by decoding the bit stream frame by frame, decoding
must always start with an I-frame. P-frames and B-frames, if used, must be decoded together
with the reference frame(s).
Axis network video products allow users to set the GOV (group of video) length, which determines how many P-frames should be sent before another I-frame is sent. By decreasing the
frequency of I-frames (longer GOV), the bit rate can be reduced. To reduce latency, B-frames are
not used.
Besides difference coding and motion compensation, other advanced methods can be employed
to further reduce data and improve video quality. H.264, for example, supports advanced techniques that include prediction schemes for encoding I-frames, improved motion compensation
down to sub-pixel accuracy, and an in-loop deblocking filter to smooth block edges (artifacts).
For more information on H.264 techniques, see Axis’ white paper on H.264 at
Compression formats
Motion JPEG
Motion JPEG or M-JPEG is a digital video sequence that is made up of a series of individual JPEG
images. (JPEG stands for Joint Photographic Experts Group.) When 16 image frames or more are
shown per second, the viewer perceives motion video. Full motion video is perceived at 30
(NTSC) or 25 (PAL) frames per second.
One of the advantages of Motion JPEG is that each image in a video sequence can have the same
guaranteed quality that is determined by the compression level chosen for the network camera
or video encoder. The higher the compression level, the lower the file size and image quality.
In some situations, such as in low light or when a scene becomes complex, the image file size
may become quite large and use more bandwidth and storage space. To prevent an increase in
the bandwidth and storage used, Axis network video products allow the user to set a maximum
file size for an image frame.
Since there is no dependency between the frames in Motion JPEG, a Motion JPEG video is robust,
meaning that if one frame is dropped during transmission, the rest of the video will not be
Motion JPEG is an unlicensed standard. It has broad compatibility and is popular in applications
where individual frames in a video sequence are required—for example, for analysis—and where
lower frame rates, typically 5 frames per second or lower, are used. Motion JPEG may also be
needed for applications that require integration with systems that support only Motion JPEG.
The main disadvantage of Motion JPEG is that it makes no use of any video compression techniques to reduce the data since it is a series of still, complete images. The result is that it has a
relatively high bit rate or low compression ratio for the delivered quality compared with video
compression standards such as MPEG-4 and H.264.
When MPEG-4 is mentioned in video surveillance applications, it is usually referring to MPEG-4
Part 2, also known as MPEG-4 Visual. Like all MPEG (Moving Picture Experts Group) standards,
it is a licensed standard, so users must pay a license fee per monitoring station. MPEG-4
supports low-bandwidth applications and applications that require high quality images, no
limitations in frame rate and with virtually unlimited bandwidth.
H.264 or MPEG-4 Part 10/AVC
H.264, also known as MPEG-4 Part 10/AVC for Advanced Video Coding, is the latest MPEG standard for video encoding. H.264 is expected to become the video standard of choice in the
coming years. This is because an H.264 encoder can, without compromising image quality,
reduce the size of a digital video file by more than 80% compared with the Motion JPEG format
and as much as 50% more than with the MPEG-4 standard. This means that much less network
bandwidth and storage space are required for a video file. Or seen another way, much higher
video quality can be achieved for a given bit rate.
H.264 was jointly defined by standardization organizations in the telecommunications (ITU-T’s
Video Coding Experts Group) and IT industries (ISO/IEC Moving Picture Experts Group), and is
expected to be more widely adopted than previous standards. In the video surveillance industry,
H.264 will most likely find the quickest traction in applications where there are demands for
high frame rates and high resolution, such as in the surveillance of highways, airports and
casinos, where the use of 30/25 (NTSC/PAL) frames per second is the norm. This is where the
economies of reduced bandwidth and storage needs will deliver the biggest savings.
H.264 is also expected to accelerate the adoption of megapixel cameras since the highly
efficient compression technology can reduce the large file sizes and bit rates generated without
compromising image quality. There are tradeoffs, however. While H.264 provides savings in
network bandwidth and storage costs, it will require higher performance network cameras and
monitoring stations.
Axis’ H.264 encoders use the baseline profile, which means that only I- and P-frames are used.
This profile is ideal for network cameras and video encoders since low latency is achieved
because B-frames are not used. Low latency is essential in video surveillance applications where
live monitoring takes place, especially when PTZ cameras or PTZ dome cameras are used.
Variable and constant bit rates
With MPEG-4 and H.264, users can allow an encoded video stream to have a variable or a
constant bit rate. The optimal selection depends on the application and network infrastructure.
With VBR (variable bit rate), a predefined level of image quality can be maintained regardless of
motion or the lack of it in a scene. This means that bandwidth use will increase when there is a lot
of activity in a scene and will decrease when there is no motion. This is often desirable in video
surveillance applications where there is a need for high quality, particularly if there is
motion in a scene. Since the bit rate may vary, even when an average target bit rate is defined, the
network infrastructure (available bandwidth) must be able to accommodate high throughputs.
With limited bandwidth available, the recommended mode is normally CBR (constant bit rate)
as this mode generates a constant bit rate that can be predefined by a user. The disadvantage
with CBR is that when there is, for instance, increased activity in a scene that results in a bit
rate that is higher than the target rate, the restriction to keep the bit rate constant leads to a
lower image quality and frame rate. Axis network video products allow the user to prioritize
either the image quality or the frame rate if the bit rate rises above the target bit rate.
Comparing standards
When comparing the performance of MPEG standards such as MPEG-4 and H.264, it is important to note that results may vary between encoders that use the same standard. This is because
the designer of an encoder can choose to implement different sets of tools defined by a standard. As long as the output of an encoder conforms to a standard’s format and decoder, it is
possible to make different implementations. An MPEG standard, therefore, cannot guarantee a
given bit rate or quality, and comparisons cannot be properly made without first defining how
the standards are implemented in an encoder. A decoder, unlike an encoder, must implement all
the required parts of a standard in order to decode a compliant bit stream. A standard specifies
exactly how a decompression algorithm should restore every bit of a compressed video.
The graph on the following page provides a bit rate comparison, given the same level of image
quality, among the following video standards: Motion JPEG, MPEG-4 Part 2 (no motion compensation), MPEG-4 Part 2 (with motion compensation) and H.264 (baseline profile).
Figure 7.4a Axis’ H.264 encoder generated up to 50% fewer bits per second for a sample video sequence than an
MPEG-4 encoder with motion compensation. The H.264 encoder was at least three times more efficient than an
MPEG-4 encoder with no motion compensation and at least six times more efficient than with Motion JPEG.
While the use of audio in video surveillance systems is still not widespread, having
audio can enhance a system’s ability to detect and interpret events, as well as enable
audio communication over an IP network. The use of audio, however, can be restricted
in some countries, so it is a good idea to check with local authorities.
Topics covered in this chapter include application scenarios, audio equipment, audio
modes, audio detection alarm, audio compression and audio/video synchronization.
Audio applications
Having audio as an integrated part of a video surveillance system can be an invaluable addition
to a system’s ability to detect and interpret events and emergency situations. The ability of audio
to cover a 360-degree area enables a video surveillance system to extend its coverage beyond a
camera’s field of view. It can instruct a PTZ camera or a PTZ dome camera (or alert the operator
of one) to visually verify an audio alarm.
Audio can also be used to provide users with the ability to not only listen in on an area, but also
communicate orders or requests to visitors or intruders. For instance, if a person in a camera’s
field of view demonstrates suspicious behavior, such as loitering near a bank machine, or is seen
to be entering a restricted area, a remote security guard can send a verbal warning to the
person. In a situation where a person has been injured, being able to remotely communicate
with and notify the victim that help is on the way can also be beneficial. Access control—that is,
a remote ‘doorman’ at an entrance—is another area of application. Other applications include a
remote helpdesk situation (e.g., an unmanned parking garage), and video conferencing. An
audiovisual surveillance system increases the effectiveness of a security or remote monitoring
solution by enhancing a remote user’s ability to receive and communicate information.
Audio support and equipment
Audio support can be more easily implemented in a network video system than in an analog
CCTV system. In an analog system, separate audio and video cables must be installed from endpoint to endpoint; that is, from the camera and microphone location to the viewing/recording
location. If the distance between the microphone and the station is too long, balanced audio
equipment must be used, which increases installation costs and difficulty. In a network video
system, a network camera with audio support processes the audio and sends both audio and
video over the same network cable for monitoring and/or recording. This eliminates the need for
extra cabling, and makes synchronizing the audio and video much easier.
AUDIO Stream
VIDEO Stream
Figure 8.2a A network video system with integrated audio support. Audio and video streams are sent over the same
network cable.
AUDIO Stream
Video encoder
VIDEO Stream
Figure 8.2b Some video encoders have built-in audio, making it possible to add audio even if analog cameras are
used in an installation.
A network camera or video encoder with an integrated audio functionality often provides a
built-in microphone, and/or mic-in/line-in jack. With mic-in/line-in support, users have the
option of using another type or quality of microphone than the one that is built into the camera
or video encoder. It also enables the network video product to connect to more than one microphone, and the microphone can be located some distance away from the camera. The microphone should always be placed as close as possible to the source of the sound to reduce noise.
In two-way, full-duplex mode, a microphone should face away and be placed some distance
from a speaker to reduce feedback from the speaker.
Many Axis network video products do not come with a built-in speaker. An active speaker—
a speaker with a built-in amplifier—can be connected directly to a network video product with
audio support. If a speaker has no built-in amplifier, it must first connect to an amplifier, which
is then connected to a network camera/video encoder.
To minimize disturbance and noise, always use a shielded audio cable and avoid running the cable
near power cables and cables carrying high frequency switching signals. Audio cables should also
be kept as short as possible. If a long audio cable is required, balanced audio equipment—that is,
cable, amplifier and microphone that are all balanced—should be used to reduce noise.
Audio modes
Depending on the application, there may be a need to send audio in only one direction or both
directions, which can be done either simultaneously or in one direction at a time. There are three
basic modes of audio communication: simplex, half duplex and full duplex.
Audio sent by camera
Video sent by camera
Network camera
Figure 8.3a In simplex mode, audio is sent in one direction only. In this case, audio is sent by the camera to the
operator. Applications include remote monitoring and video surveillance.
Audio sent by operator
Video sent by camera
Network camera
Figure 8.3b In this example of a simplex mode, audio is sent by the operator to the camera. It can be used, for
instance, to provide spoken instructions to a person seen on the camera or to scare a potential car thief away from a
parking lot.
Half duplex
Audio sent by operator
Audio sent by camera
Video sent by camera
Network camera
Figure 8.3c In half-duplex mode, audio is sent in both directions, but only one party at a time can send. This is
similar to a walkie-talkie.
Full duplex
Full duplex audio sent and received by operator
Video sent by camera
Network camera
Figure 8.3d In full-duplex mode, audio is sent to and from the operator simultaneously. This mode of communication is similar to a telephone conversation. Full duplex requires that the client PC has a sound card with support for
full-duplex audio.
Audio detection alarm
Audio detection alarm can be used as a complement to video motion detection since it can react
to events in areas too dark for the video motion detection functionality to work properly. It can
also be used to detect activity in areas outside of the camera’s view.
When sounds, such as the breaking of a window or voices in a room, are detected, they can trigger a network camera to send and record video and audio, send e-mail or other alerts, and activate external devices such as alarms. Similarly, alarm inputs such as motion detection and door
contacts can be used to trigger video and audio recordings. In a PTZ camera or a PTZ dome
camera, audio alarm detection can trigger the camera to automatically turn to a preset location
such as a specific window.
Audio compression
Analog audio signals must be converted into digital audio through a sampling process and then
compressed to reduce the size for efficient transmission and storage. The conversion and compression is done using an audio codec, an algorithm that codes and decodes audio data.
Sampling frequency
There are many different audio codecs supporting different sampling frequencies and levels of
compression. Sampling frequency refers to the number of times per second a sample of an
analog audio signal is taken and is defined in hertz (Hz). In general, the higher the sampling
frequency, the better the audio quality and the greater the bandwidth and storage needs.
Bit rate
The bit rate is an important setting in audio since it determines the level of compression and,
thereby, the quality of the audio. In general, the higher the compression level (the lower the bit
rate), the lower the audio quality. The differences in the audio quality of codecs may be particularly noticeable at high compression levels (low bit rates), but not at low compression levels
(high bit rates). Higher compression levels may also introduce more latency or delay, but they
enable greater savings in bandwidth and storage.
The bit rates most often selected with audio codecs are between 32 kbit/s and 64 kbit/s. Audio
bit rates, as with video bit rates, are an important consideration to take into account when
calculating total bandwidth and storage requirements.
Audio codecs
Axis network video products support three audio codecs. The first is AAC-LC (Advanced Audio
Coding - Low Complexity), also known as MPEG-4 AAC, which requires a license. AAC-LC,
particularly at a sampling rate of 16 kHz or higher and at a bit rate of 64 kbit/s, is the recommended codec to use when the best possible audio quality is required. The other two codecs are
G.711 and G.726, which are non-licensed technologies.
Audio and video synchronization
Synchronization of audio and video data is handled by a media player (a computer software
program used for playing back multimedia files) or by a multimedia framework such as Microsoft DirectX, which is a collection of application programming interfaces that handles multimedia files.
Audio and video are sent over a network as two separate packet streams. In order for the client
or player to perfectly synchronize the audio and video streams, the audio and video packets
must be time-stamped. The timestamping of video packets using Motion JPEG compression may
not always be supported in a network camera. If this is the case and if it is important to have
synchronized video and audio, the video format to choose is MPEG-4 or H.264 since such video
streams, along with the audio stream, are sent using RTP (Real-time Transport Protocol), which
timestamps the video and audio packets. There are many situations, however, where synchronized audio is less important or even undesirable; for example, if audio is to be monitored but
not recorded.
Network technologies
Different network technologies are used to support and provide the many benefits of
a network video system. This chapter begins with a discussion about the local area
network, in particular, Ethernet networks and the components that support it. The use
of Power over Ethernet is also covered.
Internet communication is then addressed with discussions on IP (Internet Protocol)
addressing—what they are and how they work, including how network video products
can be accessed over the Internet. An overview of the data transport protocols used in
network video is also provided.
Other areas covered in the chapter include virtual local area networks and Quality of
Service, and the different ways of securing communication over IP networks. For more
on wireless technologies, see Chapter 10.
Local area network and Ethernet
A local area network (LAN) is a group of computers that are connected together in a localized
area to communicate with one another and share resources such as printers. Data is sent in the
form of packets and to regulate the transmission of the packets, different technologies can be
used. The most widely used LAN technology is the Ethernet and it is specified in a standard
called IEEE 802.3. (Other types of LAN networking technologies include token ring and FDDI.)
Ethernet uses a star topology in which the individual nodes (devices) are networked with one
another via active networking equipment such as switches. The number of networked devices in
a LAN can range from two to several thousand.
The physical transmission medium for a wired LAN involves cables, mainly twisted pair or fiber
optics. A twisted pair cable consists of eight wires, forming four pairs of twisted copper wires
and is used with RJ-45 plugs and sockets. The maximum cable length of a twisted pair is 100 m
(328 ft.) while for fiber, the maximum length ranges from 10 km to 70 km, depending on the
type of fiber. Depending on the type of twisted pair or fiber optic cables used, data rates today
can range from 100 Mbit/s to 10,000 Mbit/s.
Figure 9.1a Twisted pair cabling includes four pairs of twisted wires, normally connected to a RJ-45 plug at the end.
A rule of thumb is to always build a network with greater capacity than is currently required. To
future-proof a network, it is a good idea to design a network such that only 30% of its capacity
is used. Since more and more applications are running over networks today, higher and higher
network performance is required. While network switches (discussed below) are easy to upgrade
after a few years, cabling is normally much more difficult to replace.
Types of Ethernet networks
Fast Ethernet
Fast Ethernet refers to an Ethernet network that can transfer data at a rate of 100 Mbit/s. It can
be based on a twisted pair or fiber optic cable. (The older 10 Mbit/s Ethernet is still installed and
used, but such networks do not provide the necessary bandwidth for some network video
Most devices that are connected to a network, such as a laptop or a network camera, are
equipped with a 100BASE-TX/10BASE-T Ethernet interface, most commonly called a 10/100
interface, which supports both 10 Mbit/s and Fast Ethernet. The type of twisted pair cable that
supports Fast Ethernet is called a Cat-5 cable.
Gigabit Ethernet
Gigabit Ethernet, which can also be based on a twisted pair or fiber optic cable, delivers a data
rate of 1,000 Mbit/s (1 Gbit/s) and is becoming very popular. It is expected to soon replace Fast
Ethernet as the de facto standard.
The type of twisted pair cable that supports Gigabit Ethernet is a Cat-5e cable, where all four
pairs of twisted wires in the cable are used to achieve the high data rates. Cat-5e or higher cable
categories are recommended for network video systems. Most interfaces are backwards compatible with 10 and 100 Mbit/s Ethernet and are commonly called 10/100/1000 interfaces.
For transmission over longer distances, fiber cables such as 1000BASE-SX (up to 550 m/1,639 ft.)
and 1000BASE-LX (up to 550 m with multimode optical fibers and 5,000 m with single-mode
fibers) can be used.
Figure 9.1b Longer distances can be bridged using fiber optic cables. Fiber is typically used in the backbone of a
network and not in nodes such as a network camera.
10 Gigabit Ethernet
10 Gigabit Ethernet is the latest generation and delivers a data rate of 10 Gbit/s (10,000 Mbit/s),
and a fiber optic or twisted pair cable can be used. 10GBASE-LX4, 10GBASE-ER and 10GBASE-SR
based on an optical fiber cable can be used to bridge distances of up to 10,000 m (6.2 miles). With
a twisted pair solution, a very high quality cable (Cat-6a or Cat-7) is required. 10 Gbit/s Ethernet
is mainly used for backbones in high-end applications that require high data rates.
When only two devices need to communicate directly with one another via a twisted pair cable,
a so-called crossover cable can be used. The crossover cable simply crosses the transmission pair
on one end of the cable with the receiving pair on the other end and vice versa.
To network multiple devices in a LAN, however, network equipment such as a network switch is
required. When using a network switch, a regular network cable is used instead of a crossover
The main function of a network switch is to forward data from one device to another on the
same network. It does it in an efficient manner since data can be directed from one device to
another without affecting other devices on the same network.
How it works is that a switch registers the MAC (Media Access Control) addresses of all devices
that are connected to it. (Each networking device has a unique MAC address, which is made up
of a series of numbers and letters that is set by the manufacturer and the address is often found
on the product label.) When a switch receives data, it forwards it only to the port that is connected to a device with the appropriate destination MAC address.
Switches typically indicate their performance in per port rates and in backplane or internal rates
(both in bit rates and in packets per second). The port rates indicate the maximum rates on
specific ports. This means that the speed of a switch, for example 100 Mbit/s, is often the performance of each port.
Figure 9.1c With a network switch, data transfer is managed very efficiently as data traffic can be directed from one
device to another without affecting any other ports on the switch.
A network switch normally supports different data rates simultaneously. The most common rates
used to be 10/100, supporting 10 Mbit/s as well as Fast Ethernet. However, 10/100/1000 are
quickly taking over as the standard switch, thus supporting 10 Mbit/s, Fast Ethernet and Gigabit
Ethernet simultaneously. The transfer rate and mode between a port on a switch and a connected
device are normally determined through auto-negotiation, whereby the highest common data rate
and best transfer mode are used. A switch also allows a connected device to function in full-duplex
mode, i.e. send and receive data at the same time, resulting in increased performance.
Switches may come with different features or functions. Some switches include the function of a
router (see section 9.2). A switch may also support Power over Ethernet or Quality of Service (see
section 9.4), which controls how much bandwidth is used by different applications.
Power over Ethernet
Power over Ethernet (PoE) provides the option of supplying devices connected to an Ethernet
network with power using the same cable as for data communication. Power over Ethernet is
widely used to power IP phones, wireless access points and network cameras in a LAN.
The main benefit of PoE is the inherent cost savings. Hiring a certified electrician and installing
a separate power line are not needed. This is advantageous, particularly in difficult-to-reach
areas. The fact that no power cable has to be installed can save, depending on the camera location, up to a few hundred dollars per camera. Having PoE also makes it easier to move a camera
to a new location, or add cameras to a video surveillance system.
Additionally, PoE can make a video system more secure. A video surveillance system with PoE
can be powered from the server room, which is often backed up with a UPS (Uninterruptible
Power Supply). This means that the video surveillance system can be operational even during a
power outage.
Due to the benefits of PoE, it is recommended for use with as many devices as possible. The
power available from the PoE-enabled switch or midspan should be sufficient for the connected
devices and the devices should support power classification. These are explained in more detail
in the sections below.
802.3af standard and High PoE
Most PoE devices today conform to the IEEE 802.3af standard, which was published in 2003. The
IEEE 802.3af standard uses standard Cat-5 or higher cables, and ensures that data transfer is not
affected. In the standard, the device that supplies the power is referred to as the power sourcing
equipment (PSE). This can be a PoE-enabled switch or midspan. The device that receives the
power is referred to as a powered device (PD). The functionality is normally built into a network
device like a network camera, or provided in a standalone splitter (see section below).
Backward compatibility to non PoE-compatible network devices is guaranteed. The standard
includes a method for automatically identifying if a device supports PoE, and only when that is
confirmed will power be supplied to the device. This also means that the Ethernet cable that is
connected to a PoE switch will not supply any power if it is not connected to a PoE-enabled device.
This eliminates the risk of getting an electrical shock when installing or rewiring a network.
In a twisted pair cable, there are four pairs of twisted wires. PoE can use either the two ‘spare’
wire pairs, or overlay the current on the wire pairs used for data transmission. Switches with
built-in PoE often supply electricity through the two pairs of wires used for transferring data,
while midspans normally use the two spare pairs. A PD supports both options.
According to IEEE 802.3af, a PSE provides a voltage of 48 V DC with a maximum power of
15.4 W per port. Considering that power loss takes place on a twisted pair cable, only 12.95 W
is guaranteed for a PD. The IEEE 802.3af standard specifies various performance categories for
PSE such as switches and midspans normally supply a certain amount of power, typically 300 W
to 500 W. On a 48-port switch, that would mean 6 W to 10 W per port if all ports are connected
to devices that use PoE. Unless the PDs support power classification, the full 15.4 W must be
reserved for each port that uses PoE, which means a switch with 300 W can only supply power
on 20 of the 48 ports. However, if all devices let the switch know that they are Class 1 devices,
the 300 W will be enough to supply power to all 48 ports.
Minimum power
level at PSE
Maximum power
level used by PD
15.4 W
0.44 W - 12.95 W
4.0 W
0.44 W - 3.84 W
7.0 W
3.84 W - 6.49 W
15.4 W
6.49 W - 12.95 W
treat as Class 0
reserved for future use
Table 9.1a Power classifications according to IEEE 802.3af.
Most fixed network cameras can receive power via PoE using the IEEE 802.3af standard and are
normally identified as Class 1 or 2 devices.
With IEEE 802.3at pre-standard or PoE+, the power limit will be raised to at least 30 W via two
pairs of wires from a PSE. The final specifications are still to be determined and the standard is
expected to be ratified in mid-2009.
In the meantime, IEEE 802.3at pre-standard (High PoE) midspans and splitters can be used for
devices such as PTZ cameras and PTZ dome cameras with motor control, as well as cameras with
heaters and fans, which require more power than can be delivered by the IEEE 802.3af standard.
Midspans and splitters
Midspans and splitters (also known as active splitters) are equipment that enable an existing
network to support Power over Ethernet.
Power Supply
Network camera
with built-in PoE
Network camera
without built-in
Network switch
Active splitter
Power over Ethernet
Figure 9.1d An existing system can be upgraded with PoE functionality using a midspan and splitter.
The midspan, which adds power to an Ethernet cable, is placed between the network switch and
the powered devices. To ensure that data transfer is not affected, it is important to keep in mind
that the maximum distance between the source of the data (e.g., switch) and the network video
products is not more than 100 m (328 ft.). This means that the midspan and active splitter(s)
must be placed within the distance of 100 m.
A splitter is used to split the power and data in an Ethernet cable into two separate cables,
which can then be connected to a device that has no built-in support for PoE. Since PoE or High
PoE only supplies 48 V DC, another function of the splitter is to step down the voltage to the
appropriate level for the device; for example, 12 V or 5 V.
PoE and High PoE midspans and splitters are available from Axis.
The Internet
To send data between a device on one local area network to another device on another LAN,
a standard way of communicating is required since local area networks may use different types
of technologies. This need led to the development of IP addressing and the many IP-based protocols for communicating over the Internet, which is a global system of interconnected computer networks. (LANs may also use IP addressing and IP protocols for communicating within a
local area network, although using MAC addresses is sufficient for internal communication.)
Before IP addressing is discussed, some of the basic elements of Internet communication such
as routers, firewalls and Internet service providers are covered below.
To forward data packages from one LAN to another LAN via the Internet, a networking equipment called a network router must be used. A router routes information from one network to
another based on IP addresses. It forwards only data packages that are to be sent to another
network. A router is most commonly used for connecting a local network to the Internet. Traditionally, routers were referred to as gateways.
A firewall is designed to prevent unauthorized access to or from a private network. Firewalls
can be implemented in both hardware and software, or a combination of both. Firewalls are
frequently used to prevent unauthorized Internet users from accessing private networks that are
connected to the Internet. Messages entering or leaving the Internet pass through the firewall,
which examines each message, and blocks those that do not meet the specified security criteria.
Internet connections
In order to connect a LAN to the Internet, a network connection via an Internet service provider
(ISP) must be established. When connecting to the Internet, terms such as upstream and downstream are used. Upstream describes the transfer rate with which data can be uploaded from the
device to the Internet; for instance, when video is sent from a network camera. Downstream is the
transfer speed for downloading files; for instance, when video is received by a monitoring PC.
In most scenarios—for example, a laptop that is connected to the Internet—downloading information from the Internet is the most important speed to consider. In a network video application
with a network camera at a remote site, the upstream speed is more relevant since data (video)
from the network camera will be uploaded to the Internet.
IP addressing
Any device that wants to communicate with other devices via the Internet must have a unique
and appropriate IP address. IP addresses are used to identify the sending and receiving devices.
There are currently two IP versions: IP version 4 (IPv4) and IP version 6 (IPv6). The main difference between the two is that the length of an IPv6 address is longer (128 bits compared with
32 bits for an IPv4 address). IPv4 addresses are most commonly used today. IPv4 addresses
IPv4 addresses are grouped into four blocks, and each block is separated by a dot. Each block
represents a number between 0 and 255; for example,
Certain blocks of IPv4 addresses have been reserved exclusively for private use. These private IP
addresses are to, to and to Such addresses can only be used on private networks and are not allowed to be
forwarded through a router to the Internet. All devices that want to communicate over the Internet
must have its own individual, public IP address. A public IP address is an address allocated by an
Internet service provider. An ISP can allocate either a dynamic IP address, which can change during
a session, or a static address, which normally comes with a monthly fee.
A port number defines a particular service or application so that the receiving server (e.g., network camera) will know how to process the incoming data. When a computer sends data tied to
a specific application, it usually automatically adds the port number to an IP address without
the user’s knowledge.
Port numbers can range from 0 to 65535. Certain applications use port numbers that are
pre-assigned to them by the Internet Assigned Numbers Authority (IANA). For example, a web
service via HTTP is typically mapped to port 80 on a network camera.
Setting IPv4 addresses
In order for a network camera or video encoder to work in an IP network, an IP address must be
assigned to it. Setting an IPv4 address for an Axis network video product can be done mainly in
two ways: 1) automatically using DHCP (Dynamic Host Configuration Protocol), and 2) manually by either entering into the network video product’s interface a static IP address, a subnet
mask and the IP address of the default router, or using a management software tool such as
AXIS Camera Management.
DHCP manages a pool of IP addresses, which it can assign dynamically to a network camera/
video encoder. The DHCP function is often performed by a broadband router, which in turn gets
its IP addresses from an Internet service provider. Using a dynamic IP address means that the IP
address for a network device may change from day to day. With dynamic IP addresses, it is
recommended that users register a domain name (e.g., for the network
video product at a dynamic DNS (Domain Name System) server, which can always tie the domain
name for the product to any IP address that is currently assigned to it. (A domain name can be
registered using some of the popular dynamic DNS sites such as Axis also
offers its own called AXIS Internet Dynamic DNS Service at, which is accessible from an Axis network video product’s web interface.)
Using DHCP to set an IPv4 address works as follows. When a network camera/video encoder
comes online, it sends a query requesting configuration from a DHCP server. The DHCP server
replies with an IP address and subnet mask. The network video product can then update a
dynamic DNS server with its current IP address so that users can access the product using a
domain name.
With AXIS Camera Management, the software can automatically find and set IP addresses and
show the connection status. The software can also be used to assign static, private IP addresses
for Axis network video products. This is recommended when using video management software
to access network video products. In a network video system with potentially hundreds of
cameras, a software program such as AXIS Camera Management is necessary in order to effectively manage the system. For more on video management, see Chapter 11.
NAT (Network address translation)
When a network device with a private IP address wants to send information via the Internet, it
must do so using a router that supports NAT. Using this technique, the router can translate a
private IP address into a public IP address without the sending host’s knowledge.
Port forwarding
To access cameras that are located on a private LAN via the Internet, the public IP address of the
router should be used together with the corresponding port number for the network camera/video
encoder on the private network.
Since a web service via HTTP is typically mapped to port 80, what happens then when there are
several network cameras/video encoders using port 80 for HTTP in a private network? Instead of
changing the default HTTP port number for each network video product, a router can be configured
to associate a unique HTTP port number to a particular network video product’s IP address and
default HTTP port. This is a process called port forwarding.
Port forwarding works as follows. Incoming data packets reach the router via the router’s public
(external) IP address and a specific port number. The router is configured to forward any data
coming into a predefined port number to a specific device on the private network side of the
router. The router then replaces the sender’s address with its own private (internal) IP address.
To a receiving client, it looks like the packets originated from the router. The reverse happens with
outgoing data packets. The router replaces the private IP address of the source device with the
router’s public IP address before the data is sent out over the Internet.
Port mapping in the router
External IP address
of router
External port Internal IP address
of network device
Internal port
Port 80
HTTP Request
Port 80
Port 80
Figure 9.2a Thanks to port forwarding in the router, network cameras with private IP addresses on a local network
can be accessed over the Internet. In this illustration, the router knows to forward data (request) coming into port
8032 to a network camera with a private IP address of port 80. The network camera can then begin
to send video.
Port forwarding is traditionally done by first configuring the router. Different routers have
different ways of doing port forwarding and there are web sites such as
that offer step-by-step instruction for different routers. Usually port forwarding involves bringing up the router’s interface using an Internet browser, and entering the public (external) IP
address of the router and a unique port number that is then mapped to the internal IP address
of the specific network video product and its port number for the application.
To make the task of port forwarding easier, Axis offers the NAT traversal feature in many of its
network video products. NAT traversal will automatically attempt to configure port mapping in a
NAT router on the network using UPnP™. In the network video product interface, users can manually enter the IP address of the NAT router. If a router is not manually specified, then the network
video product will automatically search for NAT routers on the network and select the default
router. In addition, the service will automatically select an HTTP port if none is manually entered.
Figure 9.2b Axis network video products enable port forwarding to be set using NAT traversal.
An IPv6 address is written in hexadecimal notation with colons subdividing the address into
eight blocks of 16 bits each; for example, 2001:0da8:65b4:05d3:1315:7c1f:0461:7847
The major advantages of IPv6, apart from the availability of a huge number of IP addresses,
include enabling a device to automatically configure its IP address using its MAC address. For
communication over the Internet, the host requests and receives from the router the necessary
prefix of the public address block and additional information. The prefix and host’s suffix is then
used, so DHCP for IP address allocation and manual setting of IP addresses are no longer
required with IPv6. Port forwarding is also no longer needed. Other benefits of IPv6 include
renumbering to simplify switching entire corporate networks between providers, faster routing,
point-to-point encryption according to IPSec, and connectivity using the same address in changing networks (Mobile IPv6).
An IPv6 address is enclosed in square brackets in a URL and a specific port can be addressed in
the following way: http://[2001:0da8:65b4:05d3:1315:7c1f:0461:7847]:8081/
Setting an IPv6 address for an Axis network video product is as simple as checking a box to
enable IPv6 in the product. The product will then receive an IPv6 address according to the
configuration in the network router.
Data transport protocols for network video
The Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) are the IP-based
protocols used for sending data. These transport protocols act as carriers for many other protocols. For example, HTTP (Hyper Text Transfer Protocol), which is used to browse web pages on
servers around the world using the Internet, is carried by TCP.
TCP provides a reliable, connection-based transmission channel. It handles the process of breaking
large chunks of data into smaller packets and ensures that data sent from one end is
received on the other. TCP’s reliability through retransmission may introduce significant delays. In
general, TCP is used when reliable communication is preferred over transport latency.
UDP is a connectionless protocol and does not guarantee the delivery of data sent, thus leaving
the whole control mechanism and error-checking to the application itself. UDP provides no
transmissions of lost data and, therefore, does not introduce further delays.
Common usage
Network video usage
(File Transfer
Transfer of files
over the Internet/
Transfer of images or video from a
network camera/video encoder to an
FTP server or to an application
(Send Mail
Protocol for
sending e-mail
A network camera/video encoder can
send images or alarm notifications
using its built-in e-mail client.
Used to browse
the web, i.e. to
retrieve web
pages from web
The most common way to transfer
video from a network camera/video
encoder where the network video
device essentially works as a web
server making the video available for
the requesting user or application
Used to access
web pages
securely using
Secure transmission of video from
network cameras/video encoders.
(Hyper Text
Protocol over
Socket Layer)
(Real Time
(Real Time
RTP standardized
packet format for
delivering audio
and video over
the Internet—
often used in
streaming media
systems or video
A common way of transmitting
H.264/MPEG-based network video,
and for synchronizing video and audio
since RTP provides sequential
numbering and timestamping of data
packets, which enable the data
packets to be reassembled in the
correct sequence. Transmission can
be either unicast or multicast.
Used to set up and control multimedia sessions over RTP
Table 9.2a Common TCP/IP protocols and ports used for network video.
When a network video system is designed, there is often a desire to keep the network separate
from other networks, both for security as well as performance reasons. At first glance, the obvious
choice would be to build a separate network. While the design would be simplified, the cost of
purchasing, installing and maintaining the network would often be higher than using a technology
called virtual local area network (VLAN).
VLAN is a technology for virtually segmenting networks, a functionality that is supported by
most network switches. It can be achieved by dividing network users into logical groups. Only
users in a specific group are capable of exchanging data or accessing certain resources on the
network. If a network video system is segmented into a VLAN, only the servers located on that
VLAN can access the network cameras. VLANs normally provide a better and more cost-efficient
solution than a separate network. The primary protocol used when configuring VLANs is IEEE
802.1Q, which tags each frame or packet with extra bytes to indicate which virtual network the
packet belongs to.
Figure 9.3a In this illustration, VLANs are set up over several switches. First, each of the two different LANs are segmented into VLAN 20 and VLAN 30. The links between the switches transport data from different VLANs. Only members
of the same VLAN are able to exchange data, either within the same network or over different networks. VLANs can be
used to separate a video network from an office network.
Quality of Service
Since different applications—for example, telephone, e-mail and surveillance video—may be
using the same IP network, there is a need to control how network resources are shared to fulfill
the requirements of each service. One solution is to let network routers and switches operate
differently on different kinds of services (voice, data, and video) as traffic passes through the
network. By using Quality of Service (QoS), different network applications can co-exist on the
same network without consuming each other’s bandwidth.
The term, Quality of Service, refers to a number of technologies such as Differentiated Service
Codepoint (DSCP), which can identify the type of data in a data packet and so divide the packets
into traffic classes that can be prioritized for forwarding. The main benefits of a QoS-aware
network include the ability to prioritize traffic to allow critical flows to be served before flows
with lesser priority, and greater reliability in a network by controlling the amount of bandwidth
an application may use and thus controlling bandwidth competition between applications. PTZ
traffic, which is often regarded as critical and requires low latency, is a typical case where QoS
can be used to guarantee fast responses to movement requests. The prerequisite for the use of
QoS within a video network is that all switches, routers and network video products must support QoS.
PC 3
PC 1
Router 1
Router 2
100 Mbit
100 Mbit
Switch 1
Camera 1
10 Mbit
Switch 2
PC 2
100 Mbit
Camera 2
Figure 9.4a Ordinary (non-QoS aware) network. In this example, PC1 is watching two video streams from cameras 1
and 2, with each camera streaming at 2.5 Mbit/s. Suddenly, PC2 starts a file transfer from PC3. In this scenario, the file
transfer will try to use the full 10 Mbit/s capacity between the routers 1 and 2, while the video streams will try to
maintain their total of 5 Mbit/s. The amount of bandwidth given to the surveillance system can no longer be guaranteed and the video frame rate will probably be reduced. At worst, the FTP traffic will consume all the available bandwidth.
PC 3
PC 1
Router 1
Router 2
100 Mbit
Switch 1
Camera 1
100 Mbit
10 Mbit
Switch 2
PC 2
100 Mbit
Camera 2
Figure 9.4b QoS aware network. Here, Router 1 has been configured to devote up to 5 Mbit/s of the available 10
Mbit/s for streaming video. FTP traffic is allowed to use 2 Mbit/s, and HTTP and all other traffic can use a maximum
of 3 Mbit/s. Using this division, video streams will always have the necessary bandwidth available. File transfers are
considered less important and get less bandwidth, but there will still be bandwidth available for web browsing and
other traffic. Note that these maximums only apply when there is congestion on the network. If there is unused
bandwidth available, this can be used by any type of traffic.
Network Security
There are different levels of security when it comes to securing information being sent over IP
networks. The first is authentication and authorization. The user or device identifies itself to the
network and the remote end by a username and password, which are then verified before the
device is allowed into the system. Added security can be achieved by encrypting the data to
prevent others from using or reading the data. Common methods are HTTPS (also known as SSL/
TLS), VPN and WEP or WPA in wireless networks. (For more on wireless security, see Chapter 10.)
The use of encryption can slow down communications, depending on the kind of implementation and encryption used.
Username and password authentication
Using a username and password authentication is the most basic method of protecting data on
an IP network and may be sufficient where high levels of security are not required, or where the
video network is segmented off from the main network and unauthorized users would not have
physical access to the video network. The passwords can be encrypted or unencrypted when they
are sent; the former provides the best security.
Axis network video products provide multi-level password protection. Three levels are available:
Administrator (full access to all functionalities), Operator (Access to all functionalities except
the configuration pages), Viewer (Access only to live video).
IP address filtering
Axis network video products provide IP address filtering, which gives or denies access rights to
defined IP addresses. A typical configuration is to configure the network cameras to allow only
the IP address of the server that is hosting the video management software to access the network video products.
IEEE 802.1X
Many Axis network video products support IEEE 802.1X, which provides authentication to
devices attached to a LAN port. IEEE 802.1X establishes a point-to-point connection or prevents
access from the LAN port if authentication fails. IEEE 802.1X prevents what is called “port
hi-jacking”; that is, when an unauthorized computer gets access to a network by getting to a
network jack inside or outside a building. IEEE 802.1X is useful in network video applications
since network cameras are often located in public spaces where an openly accessible network
jack can pose a security risk. In today’s enterprise networks, IEEE 802.1X is becoming a basic
requirement for anything that is connected to a network.
In a network video system, IEEE 802.1X can work as follows: 1) A network camera sends a request
for network access to a switch or access point; 2) the switch or access point forwards the query to
an authentication server; for instance, a RADIUS (remote authentication dial-in user service) server such as a Microsoft Internet Authentication Service server; 3) if authentication is successful, the
server instructs the switch or access point to open the port to allow data from the network camera
to pass through the switch and be sent over the network.
(Network camera)
Server (RADIUS)
or other LAN
Figure 9.5a IEEE 802.1X enables port-based security and involves a supplicant (e.g., a network camera), an authenticator (e.g., a switch) and an authentication server. Step 1: network access is requested; step 2: query forwarded to
an authentication server; step 3: authentication is successful and the switch is instructed to allow the network
camera to send data over the network.
HTTPS (Hyper Text Transfer Protocol Secure) is identical to HTTP but with one key difference: the
data transferred is encrypted using Secure Socket Layer (SSL) or Transport Layer Security (TLS).
This security method applies encryption to the data itself. Many Axis network video products
have built-in support for HTTPS, which makes it possible for video to be securely viewed using a
web browser. The use of HTTPS, however, can slow down the communication link and, therefore,
the frame rate of the video.
VPN (Virtual Private Network)
With VPN, a secure “tunnel” between two communicating devices can be created, enabling safe
and secure communication over the Internet. In such a set up, the original packet, including the
data and its header, which may contain information such as the source and destination
addresses, the type of information being sent, the packet number in the sequence of packets and
the packet length, is encrypted. The encrypted packet is then encapsulated in another packet
that shows only the IP addresses of the two communicating devices (i.e., routers). This set up
protects the traffic and its contents from unauthorized access, and only devices with the correct
“key” will be able to work within the VPN. Network devices between the client and the server
will not be able to access or view the data.
HTTPS or SSL/TLS encryption
VPN tunnel
Figure 9.5b The difference between HTTPS (SSL/TLS) and VPN is that in HTTPS only the actual data of a packet is
encrypted. With VPN, the entire packet can be encrypted and encapsulated to create a secure “tunnel”. Both technologies can be used in parallel, but it is not recommended since each technology will add overhead and decrease the
performance of the system.
Wireless technologies
For video surveillance applications, wireless technology offers a flexible, cost-efficient
and quick way to deploy cameras, particularly over a large area as in a parking lot or a
city center surveillance application. There would be no need to pull a cable through the
ground. In older, protected buildings, wireless technology may be the only alternative
if standard Ethernet cables may not be installed.
Axis offers cameras with built-in wireless support. Network cameras without built-in
wireless technology can still be integrated into a wireless network if a wireless bridge
is used.
Figure 10a An Axis wireless network camera using 802.11b/g.
Figure 10b By using a wireless bridge, any network camera can be used in a wireless network.
802.11 WLAN standards
The most common wireless standard for wireless local area networks (WLAN) is the 802.11
standard by IEEE. While there are also other standards as well as proprietary technologies, the
benefit of 802.11 wireless standards is that they all operate in a license-free spectrum, which
means there is no license fee associated with setting up and operating the network. The most
relevant extensions of the standards are 802.11b, 802.11g, 802.11a and 802.11n.
802.11b, which was approved in 1999, operates in the 2.4 GHz range and provides data rates up
to 11 Mbit/s. Until 2004, most WLAN products sold were based on 802.11b.
802.11g, which was approved in 2003, is the most common 802.11 variant on the market. It
operates in the 2.4 GHz range and provides data rates of up to 54 Mbit/s. WLAN products are
usually 802.11b/g compliant.
802.11a, which was approved in 1999, operates in the 5 GHz frequency range and provides data
rates of up to 54 Mbit/s. An issue with the 5 GHz frequency range is that it is not available for
use in parts of Europe where it is allocated for military radar systems. In such areas, 5 GHz WLAN
components should conform to 802.11a/h standard. Another disadvantage with 802.11a is that
its signal range is shorter than 802.11g’s because it operates on a higher frequency; consequently, many more access points are required for transmission in the 5 GHz range than in the
2.4 GHz range.
802.11n, which is not yet completed and ratified, is the next generation standard that will
enable data rates of up to 600 Mbit/s. Products supporting 802.11n are based on a draft of the
When setting up a wireless network, the bandwidth capacity of the access point and the bandwidth requirements of the network devices should be considered. In general, the useful data
throughput supported by a particular WLAN standard is about half the bit rate stipulated by a
standard due to signaling and protocol overhead. With network cameras that support 802.11g,
no more than four to five of such cameras should be connected to a wireless access point.
WLAN security
Due to the nature of wireless communications, anyone with a wireless device that is present
within the area covered by a wireless network can share the network and intercept data being
transferred over it unless the network is secured.
To prevent unauthorized access to the data transferred and to the network, some security technologies such as WEP and WPA/WPA2 have been developed to prevent unauthorized access and encrypt
data sent over the network.
10.2.1 WEP (Wired Equivalent Privacy)
WEP prevents people without the correct key from accessing the network. There are, however,
weaknesses in WEP. They include keys that are relatively short and other flaws that allow keys
to be reconstructed from a relatively small amount of intercepted traffic. WEP today is no longer
considered to provide adequate security as there are a variety of utilities freely available on the
web that can be used to crack what is meant to be a secret WEP key.
10.2.2 WPA/WPA2 (WiFi Protected Access)
WPA significantly increases security by taking care of the shortcomings in the WEP standard.
WPA adds a standard way for distributing encrypted keys.
10.2.3 Recommendations
Some security guidelines when using wireless cameras for surveillance:
> Enable the user/password login in the cameras.
> Enable the encryption (HTTPS) in the wireless router/cameras. This should be done before the
keys or credentials are set for the WLAN to prevent unauthorized access to the network with
stolen credentials.
> Ensure that wireless cameras support security protocols such as IEEE 802.1X and WPA/WPA2.
Wireless bridges
Some solutions may use other standards than the dominating IEEE 802.11, providing increased
performance and much longer distances in combination with very high security. Two commonly
used technologies are microwave and laser, which can be used to connect buildings or sites with
a point-to-point high-speed data link.
Video management systems
An important aspect of a video surveillance system is managing video for live viewing,
recording, playback and storage. If the system consists of only one or a few cameras,
viewing and some basic video recording can be managed via the built-in web interface
of the network cameras and video encoders. When the system consists of more than a
few cameras, using a network video management system is recommended.
Today, several hundred different video management systems are available, covering
different operating systems (Windows, UNIX, Linux and Mac OS), market segments and
languages. Considerations include choice of hardware platform (PC server-based or
one based on a network video recorder); software platform; system features, including
installation and configuration, event management, intelligent video, administration
and security; and integration possibilities with other systems such as point of sale or
building management.
Hardware platforms
There are two different types of hardware platforms for a network video management system: a
PC server platform involving one or more PCs that run a video management software program,
and one based on a network video recorder (NVR), which is a proprietary hardware with preinstalled video management software.
11.1.1 PC server platform
A video management solution based on a PC server platform involves PC servers and storage
equipment that can be selected off the shelf to obtain the maximum performance for the
specific design of the system. Such an open platform makes it easier to add functionality to the
system, such as increased or external storage, firewalls, virus protection and intelligent video
algorithms, in parallel with a video management software program.
A PC server platform is also fully scalable, enabling any number of network video products to be
added to the system as needed. The system hardware can be expanded or upgraded to meet
increased performance requirements. An open platform also enables easier integration with
other systems such as access control, building management, and industrial control. This allows
users to manage video and other building controls through a single program and user interface.
For more on servers and storage, see Chapter 12.
AXIS Camera Station
Client software
Analog cameras
Remote access via
AXIS Camera Station
Client software
Axis video encoder
Axis network cameras
AXIS Camera Station
Figure 11.1a A network video surveillance system based on a open, PC server platform with AXIS Camera Station video
management software.
11.1.2 NVR platform
A network video recorder comes as a hardware box with preinstalled video management functionalities. In this sense, an NVR is similar to a DVR. (Some DVRs, often called hybrid DVRs, also
include an NVR function; i.e., the ability to also record network-based video.)
An NVR hardware is often proprietary and specifically designed for video management. It is
dedicated to its specific tasks of recording, analyzing and playing back network video, and often
does not allow for any other applications to reside on them. The operating system can be
Windows, UNIX/Linux or proprietary.
An NVR is designed to offer optimal performance for up to a set number of cameras, and is
normally less scalable than a PC server-based system. This makes the unit suitable for smaller
systems where the number of cameras stays within the limits of an NVR’s designed capacity.
An NVR is normally easier to install than a system based on a PC server platform.
Axis network video recorder (NVR)
Viewing PC
AXIS 262 Network Video Recorder
Axis network cameras
Figure 11.1b A network video surveillance system that uses an NVR.
Software platforms
Different software platforms can be used to manage video. They include using the built-in web
interface, which exists in many network video products, or using a separate video management
software program that is either a Windows-based or a web-based interface.
11.2.1 Built-in functionality
Axis network cameras and video encoders can be accessed over a network simply by typing the
product’s IP address in the Address/Location field of a web browser on a computer. Once a
connection is made with the network video product, the product’s ‘start page’, along with links
to the product’s configuration pages, is automatically displayed in the web browser.
The built-in web interface of Axis network video products provides simple recording functions;
that is, manual recording of video streams (H.264, MPEG-4, Motion JPEG) to a server by clicking
an icon, or event-triggered recording of individual JPEG images to one or several locations.
Event-triggered recording of video streams is possible with network video products that support
local storage. In such cases, the video streams are recorded onto the products’ SD/SDHC card.
For greater recording flexibility in terms of modes (e.g., continuous or scheduled recordings) and
functionalities, a separate video management software program is required. Configuring and
managing a network video product through its built-in web interface works when only a small
number of cameras are involved in a system.
11.2.2 Windows client-based software
When it comes to separate software programs for video management, Windows client-based
programs are the most popular. Web-based software programs are also available.
With a Windows client-based program, the video management software must first be installed
on the recording server. Then a viewing client software program can be installed on the same
recording server or any other PC, whether locally on the same network where the recording
server resides, or remotely at a viewing station located on a separate network. In some cases, the
client application also enables users to switch between different servers that have the video
management software installed, thus making the management of video in a large system or at
many remote sites possible.
11.2.3 Web-based software
A web-based video management software program must be installed first on a PC server that
serves as both a web and recording server. It then allows users on any type of networked
computer anywhere in the world, to access the video management server and thereby, the network video products it manages, simply by using a web browser.
11.2.4 Scalability of video management software
The scalability of most video management software, in terms of the number of cameras and
frames per second that can be supported, is in most cases limited by the hardware capacity
rather than the software. Storing video files puts new strains on the storage hardware because
it may be required to operate on a continual basis, as opposed to only during normal business
hours. In addition, video by nature generates large amounts of data, which put high demands on
the storage solution. For more on servers and storage, see Chapter 12.
11.2.5 Open vs. vendor-specific software
Video management software programs are available from vendors of network video products.
They often support only the network video devices of the vendor. Software programs that support multiple brands of network video products also exist, often from independent companies.
A variety of software solutions are available from more than 550 Axis’ Application Development
Partners. See
System features
A video management system can support many different features. Some of the more common
ones are listed below:
Simultaneous viewing of video from multiple cameras
Recording of video and audio
Event management functions including intelligent video such as video motion detection
Camera administration and management
Search options and playback
User access control and activity (audit) logging
11.3.1 Viewing
A key function of a video management system is enabling live and recorded video to be viewed
in efficient and user-friendly ways. Most video management software applications enable
multiple users to view in different modes such as split view (to view different cameras at the
same time), full screen or camera sequence (where views from different cameras are displayed
automatically, one after the other).
Recording indicator
Links to
View groups
Audio and
PTZ controls
Alarm log
Figure 11.3a AXIS Camera Station’s live view screen.
Many video management software programs also offer a multi-camera playback feature, which
enables users to view simultaneous recordings from different cameras. This provides users with
an ability to obtain a comprehensive picture of an event, which is helpful in an investigation.
Additional features may be multi-monitor viewing and mapping, which overlays camera icons
that represent the locations of cameras on a map of a building or area.
11.3.2 Multi-streaming
Axis’ advanced network video products enable multi-streaming, where multiple video streams
from a network camera or video encoder can be individually configured with different frame
rates, compression formats and resolutions, and sent to different recipients. This capability
optimizes the use of network bandwidth.
Remote recording/
viewing at medium
frame rate and
medium resolution
Analog camera
Video encoder
Local recording/
viewing at full
frame rate and
high resolution
Viewing with a
mobile telephone
at medium frame
rate and low
Figure 11.3b Multiple, individually configurable video streams enable different frame rate video and resolution to
be sent to different recipients.
11.3.3 Video recording
With video management software such as AXIS Camera Station, video can be recorded manually, continuously and on trigger (by motion or alarm), and continuous and triggered recordings
can be scheduled to run at selected times during each day of the week.
Continuous recording normally uses more disk space than an alarm-triggered recording.
An alarm-triggered recording may be activated by, for example, video motion detection or
external inputs through a camera’s or video encoder’s input port. With scheduled recordings,
timetables for both continuous and alarm/motion-triggered recordings can be set.
Figure 11.3c Scheduled recording settings with a combination of continuous and alarm/motion-triggered recordings applied using AXIS Camera Station video management software.
Once the type of recording method is selected, the quality of the recordings can be determined
by selecting the video format (e.g., H.264, MPEG-4, Motion JPEG), resolution, compression level
and frame rate. These parameters will affect the amount of bandwidth used, as well as the size
of storage space required.
Network video products may have varying frame rate capabilities depending on the resolution.
Recording and/or viewing at full frame rate (considered as 30 frames per second in NTSC standard and 25 frames per second in PAL standard) on all cameras at all times is more than what
is required for most applications. Frame rates under normal conditions can be set lower—for
example, one to four frames per second—to dramatically decrease storage requirements. In the
event of an alarm—for instance, if video motion detection or an external sensor is triggered—
a separate stream with a higher recording frame rate can be sent.
11.3.4 Recording and storage
Most video management software use the standard Windows file system for storage, so any
system drive or network-attached drive can be used for storing video. A video management
software program may enable more than one level of storage; for instance, recordings are made
on a primary hard drive (the local hard disk) and archiving takes place on either local disks,
network-attached drive or remote hard drive. Users may be able to specify how long images
should remain on the primary hard drive before they are automatically deleted or moved to the
archive drive. Users may also be able to prevent event-triggered video from being deleted automatically by specially marking or locking them in the system.
11.3.5 Event management and intelligent video
Event management is about identifying or creating an event that is triggered by inputs,
whether from built-in features in the network video products or from other systems such as
point-of-sale terminals or intelligent video software, and configuring the network video surveillance system to automatically respond to the event by, for example, recording video, sending
alert notifications and activating different devices such as doors and lights.
Event management and intelligent video functionalities can work together to enable a video
surveillance system to more efficiently use network bandwidth and storage space. Live camera
monitoring is not required all the time since alert notifications to operators can be sent when
an event occurs. All configured responses can be activated automatically, improving response
times. Event management helps operators cover more cameras.
Both event management and intelligent video functionalities can be built-in and conducted in a
network video product or in a video management software program. It can also be handled by both
in the sense that a video management software program can take advantage of an intelligent
video functionality that is built into a network video product. In such a case, the intelligent video
functionality, such as video motion detection and camera tampering, can be performed by the
network video product and flagged to the management software program for further actions to be
taken. This process offers a number of benefits:
It enables a more efficient use of bandwidth and storage space since there is no need for a
camera to continuously send video to a video management server for analysis of any
potential events. Analysis takes place at the network video product and video streams are
sent for recording and/or viewing only when an event occurs.
> It does not require the video management server to have a fast processing capability,
thereby providing some cost-savings. Conducting intelligent video algorithms is CPU
Scalability can be achieved. If a server were to perform intelligent video algorithms, only a
few cameras can be managed at any given time. Having the intelligent functionality “at the
edge”, i.e. in the network camera or video encoder, enables a fast response time and a very
large number of cameras to be managed proactively.
Computer with video
Analog camera
Axis network
Alarm siren
Figure 11.3d Event management and intelligent video enable a surveillance system to be constantly on guard in
analyzing inputs to detect an event. Once an event is detected, the system can automatically respond with actions
such as video recording and sending alerts.
Event triggers
An event can be scheduled or triggered. Events can be triggered by, for example:
> Input port(s): The input port(s) on a network camera or video encoder can be connected to
external devices such as a motion sensor or a door switch.
> Manual trigger: An operator can make use of buttons to manually trigger an event.
> Video motion detection: When a camera detects certain movement in a camera’s motion
detection window, an event can be triggered. For more on video motion detection see page
> Camera tampering: This feature, which allows a camera to detect when it has been
intentionally covered, moved or is no longer in focus, can be used to trigger an event. For
more on active tampering alarm, see page 102.
> Audio trigger: This enables a camera with built-in audio support to trigger an event if it
detects audio below or above a certain threshold. For more on audio detection, see Chapter 8.
> Temperature: If the temperature rises or falls outside of the operating range of a camera, an
event can be triggered.
Figure 11.3e Setting event triggers using an Axis network video product web interface.
Network video products or a video management software program can be configured to respond
to events all the time or at certain set times. When an event is triggered, some of the common
responses that can be configured include the following:
Upload images or recording of video streams to specified location(s) and at a certain frame
rate. When using the event-triggered functionality in Axis network video products’ web
interface, only JPEG images can be uploaded. When using a video management software
program, a video stream with a specified compression format (H.264/MPEG-4/Motion JPEG) and
compression level can be requested from the network video product.
> Activate output port: The output port(s) on a network camera or video encoder can be
connected to external devices such as alarms. (More details are provided below on output
> Send e-mail notification: This notifies users that an event has occurred. An image can also
be attached in the e-mail.
> Send HTTP/TCP notification: This is an alert to a video management system, which can then,
for example, initiate recordings.
> Go to a PTZ preset: This feature may be available with PTZ cameras or PTZ domes. It enables
the camera to point to a specified position such as a window when an event takes place.
> Send an SMS (Short Message Service) with text information about the alarm or an MMS
(Multimedia Messaging Service) with an image showing the event.
> Activate an audio alert on the video management system.
> Enable on-screen pop-up, showing views from a camera where an event has been activated.
> Show procedures that the operator should follow.
In addition, pre-alarm and post-alarm image buffers can be set, enabling a network video product to send a set length and frame rate of video captured before and after an event is triggered.
This can be beneficial in helping to provide a more complete picture of an event.
Input/Output ports
A unique feature to network cameras and video encoders, in comparison with analog cameras,
is their integrated input and output (I/O) ports. These ports enable a network video product to
connect to external devices and enable the devices to be manageable over a network. For
instance, a network camera or video encoder that is connected to an external alarm sensor via
its input port can be instructed to only send video when the sensor triggers.
The range of devices that can be connected to a network video product’s input port is almost
infinite. The basic rule is that any device that can toggle between an open and closed circuit can
be connected to a network camera or a video encoder. The main function of a network video
product’s output port is to trigger external devices, either automatically or by remote control
from an operator or a software application.
Device type
Door contact
Simple magnetic switch that
detects the opening of doors or
When the circuit is broken (door is
opened), images/video as well as
notifications can be sent from the
Passive infrared
detector (PIR)
A sensor that detects motion
based on heat emission.
When motion is detected, the PIR
breaks the circuit and images/video
as well as notifications can be sent
from the camera.
Glass break detector
An active sensor that measures
air pressure in a room and
detects sudden pressure drops.
(The sensor can be powered by
the camera.)
When a drop in air pressure is
detected, the detector breaks the
circuit, and images/video as well as
notifications can be sent from the
Table 11.3a Example of devices that can be connected to the input port.
Device type
Door relay
A relay (solenoid) that controls
the opening and closing of door
The locking/unlocking of a door can
be controlled by a remote operator
(over a network) or be an automatic
response to an alarm event.
Alarm siren configured to sound The network video product can
when alarm is detected.
activate the siren either when motion
is detected using the built-in video
motion detection or using “information” from the digital input.
An alarm security system that
continuously monitors a
normally closed or open alarm
The network video product can act as
an integrated part of the alarm
system that serves as a sensor,
enhancing the alarm system with
event-triggered video transfers.
Table 11.3b Example of devices that can be connected to the output port.
Video motion detection
Video motion detection (VMD) is a common feature in video management systems. It is a way of
defining activity in a scene by analyzing image data and differences in a series of images. With
VMD, motion can be detected in any part of a camera’s view. Users can configure a number of
“included” windows (a specific area in a camera’s view where motion is to be detected), and
“excluded” windows (areas within an “included” window that should be ignored). Using VMD
helps to prioritize recordings, decrease the amount of recorded video and make searching for
events easier.
Figure 11.3f Setting video motion detection in AXIS Camera Station video management software.
Active tampering alarm
This intelligent video functionality, embedded in many Axis network video products, can be used
as an event trigger when a camera is manipulated in any way; for instance, through accidental
redirection, blocking, defocusing or being spray-painted, covered or damaged. Without such
detection, surveillance cameras can become of limited use.
11.3.6 Administration and management features
All video management software applications provide the ability to add and configure basic
camera settings, frame rate, resolution and compression format, but some also include more
advanced functionalities, such as camera discovery and complete device management. The
larger a video surveillance system becomes, the more important it is to be able to efficiently
manage networked devices.
Software programs that help simplify the management of network cameras and video encoders
in an installation often provide the following functionalities:
Locating and showing the connection status of video devices on the network
Setting IP addresses
Configuring single or multiple units
Managing firmware upgrades of multiple units
Managing user access rights
Providing a configuration sheet, which enables users to obtain, in one place, an overview of
all camera and recording configurations.
Figure 11.3g AXIS Camera Management software makes it easy to find, install and configure network video products.
11.3.7 Security
An important part of video management is security. A network video product or video management software should enable the following to be defined or set:
> Authorized users
> Passwords
> Different user-access levels, for example:
- Administrator: access to all functionalities (In the AXIS Camera Station software, for
instance, an administrator can select which cameras and functionalities a user may
have access to.)
- Operator: access to all functionalities except for certain configuration pages
- Viewer: access only to live video from selected cameras
Integrated systems
When video is integrated with other systems such as point-of-sale and building management,
information from other systems can be used to trigger functions such as event-based recordings
in the network video system, and vice versa. In addition, users can benefit from having a common interface for managing different systems.
11.4.1 Application programming interface
All Axis network video products have an HTTP-based application programming interface (API) or
network interface called VAPIX®, which makes it easier for developers to build applications that
support the network video products. A video management software program or building management system that uses VAPIX® will be able to request images from Axis network video
products, control network camera functions (e.g., PTZ and relays) and set or retrieve internal
parameter values. In effect, it allows a system to do everything that the network video product’s
web interface provides and more, such as capturing uncompressed images in bitmap file
A global, open industry forum called ONVIF was established in early 2008 by Axis, Bosch and
Sony to standardize the network interface of network video products. A standard network
interface would ensure greater interoperability and more flexibility for end users when building
multiple-vendor network video systems. For more information, visit
11.4.2 Point of Sale
The introduction of network video in retail environments has made the integration of video with
point-of-sale (PoS) systems easier.
The integration enables all cash register transactions to be linked to actual video of the transactions. It helps catch and prevent fraud and theft from employees and customers. PoS exceptions
such as returns, manually entered values, line corrections, transaction cancellations, co-worker
purchases, discounts, specially tagged items, exchanges and refunds can be visually verified with
the captured video. A PoS system with integrated video surveillance makes it easier to find and
verify suspicious activities.
Event-based recordings can be applied. For instance, a PoS transaction or exception, or the
opening of a cash register drawer, can be used to trigger a camera to record and tag the recording. The scene prior to and following an event can be captured using pre- and post-event
recording buffers. Event-based recordings increase the quality of the recorded material, as well
as reduce storage requirements and the amount of time needed to search for incidents.
Figure 11.4a An example of a PoS system integrated with video surveillance. This screenshot displays the receipts
together with video clips of the event. Picture courtesy of Milestone Systems.
11.4.3 Access control
Integrating a video management system with a facility’s access control system allows for facility and room access to be logged with video. For example, video can be captured at all doors
when someone enters or exits a facility. This allows for visual verification when exceptional
events occur. In addition, identification of tailgating events can also be made. Tailgating occurs
when, for instance, the person who swipes his/her access card knowingly or unknowingly
enables others to gain entry without having to swipe a card.
11.4.4 Building management
Video can be integrated into a building management system (BMS) that controls a number of
systems ranging from heating, ventilation and air conditioning (HVAC) to security, safety,
energy and fire alarm systems.
The following are some application examples:
> An equipment failure alarm can trigger a camera to show video to an operator, in addition
to activating alarms at the BMS.
> A fire alarm system can trigger a camera to monitor exit doors and begin recording for
security purposes.
> Intelligent video can be used to detect reverse flow of people into a building due to an open
or unsecured door from events such as evacuations.
> Information from the video motion detection functionality of a camera that is located in a
meeting room can be used with lighting and heating systems to turn the light and heat off
once the room is vacated, thereby saving energy.
11.4.5 Industrial control systems
Remote visual verification is often beneficial and required in complex industrial automation
systems. By having access to network video using the same interface as for monitoring a
process, an operator does not have to leave the control panel to visually check on part of a
process. In addition, when an operation malfunctions, the network camera can be triggered to
send images. In some sensitive clean-room processes, or in facilities with dangerous chemicals,
video surveillance is the only way to have visual access to a process. The same goes for electrical
grid systems with a substation in a very remote location.
11.4.6 RFID
Tracking systems that involve RFID (radio-frequency identification) or similar methods are used
in many applications to keep track of items. An example is luggage handling at airports that will
keep track of the luggage and direct it to the correct destination. If it is integrated with video
surveillance, there is visual evidence when luggage is lost or damaged, and search routines can
be optimized.
Bandwidth and storage considerations
Network bandwidth and storage requirements are important considerations when
designing a video surveillance system. The factors include the number of cameras,
the image resolution used, the compression type and ratio, frame rates and scene
complexity. This chapter provides some guidelines on designing a system, along with
information on storage solutions and various system configurations.
Bandwidth and storage calculations
Network video products utilize network bandwidth and storage space based on their configuration. As mentioned earlier, this depends on the following:
Number of cameras
Whether recording will be continuous or event-based
Number of hours per day the camera will be recording
Frames per second
Image resolution
Video compression type: Motion JPEG, MPEG-4, H.264
Scenery: Image complexity (e.g. gray wall or a forest), lighting conditions and amount of
motion (office environment or crowded train stations)
How long data must be stored
12.1.1 Bandwidth needs
In a small surveillance system involving 8 to 10 cameras, a basic 100-megabit (Mbit) network
switch can be used without having to consider bandwidth limitations. Most companies can
implement a surveillance system of this size using their existing network.
When implementing 10 or more cameras, the network load can be estimated using a few rules
of thumb:
> A camera that is configured to deliver high-quality images at high frame rates will use
approx. 2 to 3 Mbit/s of the available network bandwidth.
> With more than 12 to 15 cameras, consider using a switch with a gigabit backbone. If a
gigabit-supporting switch is used, the server that runs the video management software
should have a gigabit network adapter installed.
Technologies that enable the management of bandwidth consumption include the use of VLANs
on a switched network, Quality of Service and event-based recordings. For more on these topics,
see chapters 9 and 11.
12.1.2 Calculating storage needs
As mentioned earlier, the type of video compression used is one of the factors affecting storage
requirements. The H.264 compression format is by far the most efficient video compression
technique available today. Without compromising image quality, an H.264 encoder can reduce
the size of a digital video file by more than 80% compared with the Motion JPEG format and as
much as 50% more than with the MPEG-4 (Part 2) standard. This means much less network
bandwidth and storage space are required for an H.264 video file.
Sample storage calculations for all three compression formats are provided in the tables below.
Because of a number of variables that affect average bit rate levels, calculations are not so clearcut for H.264 and MPEG-4. With Motion JPEG, there is a clear formula because Motion JPEG
consists of one individual file for each image. Storage requirements for Motion JPEG recordings
vary depending on the frame rate, resolution and level of compression.
H.264 calculation:
Approx. bit rate / 8(bits in a byte) x 3600s = KB per hour / 1000 = MB per hour
MB per hour x hours of operation per day / 1000 = GB per day
GB per day x requested period of storage = Storage need
Approx. bit rate
Frames per
Hours of
No. 1
No. 2
No. 3
Total for the 3 cameras and 30 days of storage = 135 GB
Table 12.1a The figures above are based on lots of motion in a scene. With fewer changes in a scene, the figures can
be 20% lower. The amount of motion in a scene can have a big impact on the amount of storage required.
MPEG-4 calculation:
Approx. bit rate / 8(bits in a byte) x 3600s = KB per hour / 1000 = MB per hour
MB per hour x hours of operation per day / 1000 = GB per day
GB per day x requested period of storage = Storage need
Note: The formula does not take into account the amount of motion, which is an important
factor that can influence the size of storage required.
Approx. bit rate
Frames per
Hours of
No. 1
No. 2
No. 3
Total for the 3 cameras and 30 days of storage = 204 GB
Table 12.1b
Motion JPEG calculation:
Image size x frames per second x 3600s = Kilobyte (KB) per hour/1000 = Megabyte (MB) per hour
MB per hour x hours of operation per day / 1000 = Gigabyte (GB) per day
GB per day x requested period of storage = Storage need
Frames per
Hours of
Bit Rate (Kbit/s)
No. 1
No. 2
No. 3
Total for the 3 cameras and 30 days of storage = 1002 GB
Table 12.1c
A helpful tool in estimating requirements for bandwidth and storage is the AXIS Design Tool, which
is accessible from the following web address:
Figure 12.1a The AXIS Design Tool includes advanced project management functionality that enables bandwidth
and storage to be calculated for a large and complex system.
Server-based storage
Depending on a PC server’s central processing unit (CPU), network card and internal RAM
(Random Access Memory), a server can handle a certain number of cameras, frames per second
and size of images. Most PCs can hold between two and four hard disks, and each disk can be up
to approx. 300 gigabyte (GB). In a small to medium-sized installation, the PC that runs the video
management software is also used for video recording. This is called a direct-attached storage.
With the AXIS Camera Station video management software, for instance, one hard disk is suitable for storing recordings from six to eight cameras. With more than 12 to 15 cameras, at least
two hard disks should be used to split the load. For 50 or more cameras, the use of a second
server is recommended.
When the amount of stored data and management requirements exceed the limitations of a
direct-attached storage, a network-attached storage (NAS) or storage area network (SAN)
allows for increased storage space, flexibility and recoverability.
Axis network cameras
Network switch,
broadband router or
corporate firewall
Computer server with video
management software
Figure 12.3a Network-attached storage
NAS provides a single storage device that is directly attached to a LAN and offers shared storage
to all clients on the network. A NAS device is simple to install and easy to administer, providing a
low-cost storage solution. However, it provides limited throughput for incoming data because it
has only one network connection, which can become problematic in high-performance systems.
SANs are high-speed, special-purpose networks for storage, typically connected to one or more
servers via fiber. Users can access any of the storage devices on the SAN through the servers, and
the storage is scalable to hundreds of terabytes. Centralized storage reduces administration and
provides a high performance, flexible storage system for use in multi-server environments. Fiber
Channel technology is commonly used to provide data transfers at four gigabits per second and
to allow large amounts of data to be stored with a high level of redundancy.
Fiber channel
Fiber channel
Fiber channel switch
RAID disk
RAID disk
Figure 12.3b A SAN architecture where storage devices are tied together and the servers share the storage capacity.
Redundant storage
SAN systems build redundancy into the storage device. Redundancy in a storage system allows
video, or any other data, to be saved simultaneously in more than one location. This provides a
backup for recovering video if a portion of the storage system becomes unreadable. There are a
number of options for providing this added storage layer in an IP-Surveillance system, including
a Redundant Array of Independent Disks (RAID), data replication, server clustering and multiple
video recipients.
RAID. RAID is a method of arranging standard, off-the-shelf hard drives such that the operating
system sees them as one large hard disk. A RAID setup spans data over multiple hard disk drives
with enough redundancy so that data can be recovered if one disk fails. There are different
levels of RAID, ranging from practically no redundancy to a full-mirrored solution in which there
is no disruption and no loss of data in the event of a hard disk failure.
Figure 12.4a Data replication.
Data replication. This is a common feature in many network operating systems. File servers in a
network are configured to replicate data among each other, providing a backup if one server
Server clustering. A common server clustering method is to have two servers work with the
same storage device, such as a RAID system. When one server fails, the other identically configured server takes over. These servers can even share the same IP address, which makes the
so-called “fail-over” completely transparent for users.
Multiple video recipients. A common method to ensure disaster recovery and off-site storage in
network video is to simultaneously send the video to two different servers in separate locations.
These servers can be equipped with RAID, work in clusters, or replicate their data with servers
even further away. This is an especially useful approach when surveillance systems are in hazardous or not easily accessible areas, such as in mass-transit installations or industrial facilities.
System configurations
Small system (1 to 30 cameras)
A small system usually consists of one server running a surveillance application that records the
video to a local hard disk. The video is viewed and managed by the same server. Although most
viewing and management will be done at the server, a client (local or remote) can be connected
for the same purpose.
Application and
storage server
Workstation client
Figure 12.5a A small system.
Medium system (25 to 100 cameras)
A typical, medium-sized installation has a server with additional storage attached to it. The
storage is usually configured with RAID in order to increase performance and reliability. The
video is normally viewed and managed from a client rather than from the recording server
Application and
storage server
RAID storage
Figure 12.5b A medium system.
Large centralized system (50 to +1000 cameras)
A large-sized installation requires high performance and reliability in order to manage the large
amount of data and bandwidth. This requires multiple servers with dedicated tasks. A master
server controls the system and decides what kind of video is stored at what storage server. As
there are dedicated storage servers, it is possible to do load balancing. In such a setup, it is also
possible to scale up the system by adding more storage servers when needed and do maintenance without bringing down the entire system.
Master server 1
Master server 2
Storage server 1
Storage server 2
Figure 12.5c A large centralized system.
Large distributed system (25 to +1000 cameras)
When multiple sites require surveillance with centralized management, distributed recording
systems may be used. Each site records and stores the video from local cameras. The master
controller can view and manage recordings at each site.
Storage server RAID
Storage server RAID
Figure 12.5d A large distributed system.
Tools and resources
Axis offers a variety of tools and information resources to help design IP-Surveillance systems. Many are accessible from the Axis website:
Lens Calculators
This tool helps you calculate the focal length of the lens you will need in order to capture
a specific scene at a certain distance.
Camera Reach Tool
This tool focuses on Axis network cameras’ scene capturing and object recognition capabilities at different distances and in combination with alternate lenses. The tool also helps you
navigate through the Axis product portfolio to find the most appropriate camera for your
AXIS Design Tool
This simulation-based calculation tool, available online or on a DVD, helps determine the
bandwidth and storage needs for specific network video projects.
Axis Housing Configurator
This tool helps you find the right housings and complementary accessories such as brackets, power supplies and cables for your specific camera application.
Intelligent Network Video:
Understanding modern surveillance systems
This 390-page hardcover book is authored by Fredrik Nilsson and Axis Communications. It represents the first resource to provide detailed coverage of advanced
digital networking and intelligent video capabilities. Published in September 2008,
the book is available for purchase through Amazon, Barnes & Noble and CRC Press,
or contact your local Axis office.
Axis Communications’ Academy
Number one in network video knowledge.
Learn more about network video technologies with Axis’ training program.
Broad course offering
Hands-on training
Training from the leading experts
Gain a competitive edge
The video surveillance market is changing as older analog systems converge towards network
video technology. New technologies, applications and integration possibilities are driving the
convergence. To succeed in this increasingly competitive market, you need superior skills and
expertise on IP-based video solutions. Team up with Axis Communications’ Academy to
ensure that you are always a step ahead.
Learning the fundamentals
Network Video Fundamentals and Video Solution Fundamentals are the building blocks of
the Axis Communications’ Academy training program. The fundamentals have been developed and refined to meet the educational requirements of both traditional analog CCTV
and IT professionals. Whatever your background, you can achieve the advanced technical
proficiency you need to successfully work with and use Axis products and solutions.
For more information, visit
Contact information
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Contact information
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About Axis Communications
Axis is an IT company offering network video solutions
for professional installations. The company is the global
market leader in network video, driving the ongoing
shift from analog to digital video surveillance. Axis
products and solutions focus on security surveillance
and remote monitoring, and are based on innovative,
open technology platforms.
Axis is a Swedish-based company, operating worldwide
with offices in more than 20 countries and cooperating
with partners in more than 70 countries. Founded in
1984, Axis is listed on the NASDAQ OMX Stockholm
under the ticker AXIS. For more information about Axis,
please visit our website at
©2006-2009 Axis Communications AB. AXIS COMMUNICATIONS, AXIS, ETRAX, ARTPEC and VAPIX are registered
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trademarks or registered trademarks of their respective companies. We reserve the right to introduce modifications
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