Digital Design Guide Articles
TABLE OF CONTENTS
Digital Video for Professional A/V Systems
The Digital Connection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Digital Video Signal Formats . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Anatomy of a Digital Video Signal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Understanding EDID - Extended Display Identification Data . . . . . . . . . . . . . . . . . . . . . . . . . . 14
DRM for the A/V Professional . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Digital System Designs
HD Video Conference & Presentation Room . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Digital Upgrade to Existing Analog System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
College/University Classroom System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Network Operations Center System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Corporate Training Room System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Municipal Courtroom System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Lecture Hall System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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28
30
32
34
36
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Extenders . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Distribution Amplifiers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Switchers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Matrix Switchers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Signal Conversion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Test & Measurement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Cables & Adapters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
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49
53
58
63
64
Glossary
Digital A/V Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73
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1
The Digital Connection
The prevalence
of various digital
signal formats in
the professional A/V
industry presents
opportunities as well
as challenges for
integration.
The A/V industry is currently in the midst of
now. In the medical, visualization, and computer
a significant transition, from analog video to
graphics segments, DVI has been an established
digital video technologies and applications.
format since 1999. Continual evolution within
Every day, system designers face the challenge
the computer, broadcast, and now consumer
of integrating digital and analog video signals
electronics industries has brought digital signal
into new and previously-installed A/V systems.
connectivity to the forefront with the introduction
As digital video is associated with the cutting
of two, newer digital video standards – HDMI
edge in A/V technology, there is an increasing
for consumer products and DisplayPort for
desire by integrators and their customers to
computers and related technologies.
incorporate digital video into their systems. A
wide array of digital video ports, including DVI,
The prevalence of these various digital signal
HDMI, DisplayPort, and HD-SDI, are present in
formats presents opportunities as well as
some form on virtually every new component
challenges for integration of professional A/V
found in the market today. In addition, there is a
systems. DVI and DisplayPort are common to
very large installed base of analog hardware, as
PCs and laptops, and are standard on many
well as content, which must be kept viable even
professional displays and high-end projectors.
within new system designs. For the foreseeable
HDMI is primarily found on HDTV-capable
future, then, most presentation environments will
products such as Blu-ray Disc players, game
require mix of analog and digital video products
consoles, and satellite and cable DVRs and
and technologies.
receivers. While designed for consumer and
residential applications, some HDMI-equipped
Digital Video – It’s More Than Just HDMI
products are now being utilized in commercial
Although the digital transition is currently headline
applications as well.
news, digital video is not new to the professional
A/V industry. The broadcast, teleproduction, and
High definition digital video has also found its way
rental/staging segments adopted serial digital
into many applications beyond the broadcast
video, SDI, more than 20 years ago, and HD-
studio as a means to capture, distribute, and
SDI has been in use for more than a decade
display high definition content, extending
Figure 1-1.
Digital Transmission Can Achieve Perfect Signal Reconstruction
Digital Source Device
Internal
Digital
Functions
Serialize
Digital Display Device
Deserialize
Original
digital
video
pixels
Perfectly
reconstructed
digital video
pixels
1 0 1 0
Digital video at
serializer output
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Extron Digital Design Guide
Internal
Digital
Functions
1 0 1 0
At deserializer input,
distortions caused by
cabling, etc can readily be
corrected by practical means
into house of worship and rental and staging
Complicating the decision is the knowledge that,
environments. Just about every display available
while new A/V technologies and signal types are
today has some type of digital video capability.
continually introduced, not all of them survive
Whether it’s a desktop PC display, ceiling-
and the ones that do generally don't immediately
mounted projector, or a large flat-panel LCD on a
replace the legacy formats. For example, many
wall, chances are that a DVI, HDMI, or DisplayPort
new digital source devices incorporate an
connector is available to accept incoming signals
assortment of analog video outputs, including
from digital source devices.
composite video, S-video, and component video.
Correspondingly, most new digital displays are
Why Digital?
still equipped with analog inputs. You might ask
The implementation of digital A/V technologies
“why do manufacturers go to the extra effort,
brings the promise of several distinct advantages
and additional expense, to provide a variety
over analog technologies. First, for the
of connectors on their products?” In a word,
manufacturers of computers and displays, there is
compatibility.
the potential of removing a considerable amount
of processing circuitry from a device. Since
Most manufacturers realize that sources and
signals are already digital within the electronics
displays are rarely replaced at the same time. New
of virtually all A/V products, most if not all analog-
sources, such as Blu-ray Disc players and higher-
to-digital and/or digital-to-analog conversion can
end laptop PCs, need to maintain compatibility
be eliminated, resulting in lower manufacturing
with older displays. New, high-resolution flat panel
costs and allowing for more competitive pricing.
displays and projectors, on the other hand, need
Second, in comparison to analog-based devices
to remain compatible with older sources, such as
and systems, digital signals are by nature,
VHS recorders and DVD players that are retained
lossless, enabling the distribution of pixel-perfect
for use with legacy content.
Digital signals by
nature are lossless,
enabling distribution
of pixel-perfect and
consistent, pristine
quality images while
reducing the time
and effort required for
system and display
set-up.
and consistent, pristine quality images while
reducing the time and effort required for system
System designs for typical training and
and display set-up (see Figure 1-1). Finally, a digital
presentation facilities, therefore, very often
infrastructure can be designed to accommodate
accommodate a hybrid mix of analog and digital
the high resolutions commonly found today, such
capabilities, providing support for legacy analog
as 1920x1200 and HDTV 1080p, and provide
video formats while incorporating newer signal
support for the higher rates on the horizon.
types such as DVI, HDMI, DisplayPort and, in
some cases, HD-SDI.
Making the Choice – Analog, Digital, or
Both?
Part and parcel of any transition are uncertainty,
Extron SW4 DVI A Plus
Switcher with selectable
cable equalization
the fear of the unknown and desire to look for
expert help and assistance in making decisions.
In your role as an A/V IT manager, consultant
or A/V system integrator, your customers are
depending on you to help them make the best
choices. In the face of a wide array of products
and disparate technologies, customers want
advice during the design and implementation
phases to ensure that A/V systems meet their
requirements for functionality and performance,
stay within budget and, ideally, provide for future
growth and further changes in technology.
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3
The Digital Connection
Basic questions you
need to ask before
designing a system:
•
•
•
ill the system need
W
to accommodate both
Analog and Digital
formats?
Is this an upgrade to an
existing analog based
system?
Is the system expected
to span a technology life
of many years?
The first question to be answered, then, is the
around an all-digital switcher or matrix switcher,
most difficult, as it goes right to the core of the
with any legacy analog sources accommodated
transition. Should you:
through the use of an analog-to-digital
•Stick with a tried-and-true analog design for the
time being?
converter.
•B uild an digital / analog hybrid system that
incorporates a mix of technologies?
The bottom line is that, just as video replaced
•Or, build tomorrow’s system today with an alldigital design and some provision for legacy analog
products?
cassettes, digital technology in one or more forms
The answer, as with so many decisions and
presentation systems will move to a fully digital
choices to be made, is “It depends.”
design in the future; for the time being, however,
motion picture film and DVDs replaced VHS
will replace analog in the majority of applications
over time. Typical corporate and educational
a hybrid system design that supports both analog
Some systems are likely to remain predominantly
and digital signals takes into account a wide
analog for some time, with signal converters
range of presentation needs and technologies
added as needed to accommodate new digital
and, in the long run, is the most prudent and
displays or source devices. For example,
cost-effective approach.
technology budgets for K-12 classrooms
typically do not allow the wholesale upgrade of
Later in this Guide, you’ll find examples of real-
a media system simply to accommodate a new
world applications and the system designs used
technology. Integrating a new, HDMI-equipped
to address the particular needs of the customer
playback source, however, may require nothing
or presentation environment.
more than the appropriate digital extender and
a direct connection to the digital input on the
Matching Technology to Need
projector.
Before undertaking a system design, full
knowledge of the customer’s needs and
Others, such as in university lecture halls
expectations are necessary. Once the primary
and corporate boardrooms, are beginning to
question – analog, digital, or both? – has been
incorporate digital video technologies on a
answered, many more questions remain to be
broader, more systematic scale to accommodate
asked.
the continuously evolving needs for digital media
presentations while maintaining compatibility with
•Is there a requirement for interoperability
existing stores of analog content and playback
between digital and analog components?
equipment. Digital input capability can be added
Depending on the source content, this may not
by changing out the central switcher or scaler
be feasible due to digital rights management
to one that accepts analog and digital signals;
such as HDCP.
conversely, digital displays can be accommodated
through the use of a switcher or scaler that
outputs digital signals.
•Is this an upgrade to an existing system? If so,
is there a need to support legacy devices while
providing the flexibility to address future growth
Finally, specialized applications such as
capability? System longevity is also a key
visualization, simulation, military and medical
consideration in determining the appropriate
imaging, and command and control, are
product solutions.
adopting a fully digital approach that can deliver
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Extron Digital Design Guide
uncompromised, very high quality, very high
•Is the system expected to span a technology
resolution images – one of the major benefits of
life of many years? If so, perhaps an all-digital
digital video. These system designs are based
infrastructure should be considered to support
the continued evolution of video resolutions.
to destination. In order to compensate for this
System scope and size also determine
limitation, signal conditioning products such as
operational practicality.
equalizers can be used to recover and restore a
signal to distances up to 200 feet (60 meters).
Understanding the true operational requirements
For even longer cable runs, or to accommodate
of any system during the design phase will help
the need to run cable through conduit, digital
control potential cost overruns later. For example,
signals can be converted and distributed using
if there are HDCP requirements, does protected
standard, shielded Category cable, or with fiber
content have to be viewable on all displays within
optic technologies.
The effects of cablerelated losses for digital
signals are far more
noticeable and abrupt,
with sparkles, flashing
images, or complete
image loss all together.
the system, or only in a few, select locations?
Having an operational understanding of a system
Second, there are very specific performance
will go a long way in meeting the needs as well as
and timing parameter requirements that
the budget of the customer.
need to be maintained throughout the entire
signal path. For example, in HDMI, the RGB
Going the Distance
video lines, or channels, must be accurately
A/V professionals face three primary challenges
synchronized in order to be accurately handled
in the handling of digital signals and the
and reproduced throughout the system. Terms
management of their distribution to ensure
such as equalization, jitter, and reclocking in
robust, reliable operation. The first is to maintain
the digital world replace the familiar level and
full signal integrity from source to destination.
peaking terminology of the analog world. Signal
Digital video signals are considerably different in
conditioning requirements for digital signals are
comparison to analog. Digital video signals do
also different and must be understood accordingly
not degrade linearly as with analog video. For
before designing a system.
analog signals, the effects of cable-related losses
worsen gradually with cable length, but for digital
The third challenge in the successful integration
signals the impact is usually far more noticeable
of digital A/V systems is to be able to reliably
and abrupt, with sparkles, flashing images, or
switch, distribute, and route signals. Some digital
complete image loss altogether, as cable length
video connections, including DVI, HDMI, and
increases beyond a “digital cliff” threshold.
DisplayPort, require two-way communication
between a source and a display. If this
Technologies such as DVI, HDMI, and DisplayPort
communication is interrupted, such as following
are primarily designed for short, point-to-point
a disconnection, source switch, or signal split,
connections, for example from a computer to a
image display can be delayed, or even lost
desktop monitor, or from a Blu-ray Disc player
completely. In many cases, the content being
to a flat panel television. Distances in these
used has a direct effect on this communication
applications are relatively short and, in light of
as well. For example, some early scaling DVD
the very high data rates involved and a desire
players with HDMI output did not allow the use of
to reduce cost and power consumption, digital
a repeater, and so the signal ended at the input
source devices can rarely drive a signal more than
of the switcher and was not passed through to
a few feet. Use of high quality, high performance
the display.
cables can help to a degree and, in some cases,
can provide for reliable signal transmission up to
Later in this Guide, you’ll learn in detail about the
75 feet (25 meters) or so. While suitable for most
two primary forms of two-way communication:
consumer applications, this distance limitation
EDID - Extended Display Identification Data, where
can have a serious effect on professional A/V
applicable, DRM - Digital Rights Management.
installations where signals must be routed
Both are extremely important aspects of digital
many tens if not hundreds of feet, from source
signal formats that can significantly impact
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5
The Digital Connection
For reliable
presentation of
protected content
within a system, all
relevant signal paths
must be fully HDCP
compliant.
system reliability if not properly accommodated
player is connected directly to a flat panel display,
and implemented.
but both commercial and residential A/V systems
usually present the necessity of sending signals
In brief, EDID relates to the communication of a
from multiple sources to multiple destinations
display’s performance capabilities, such as its
(see Figure 1-2.) The primary difference, though,
native and supported resolutions, to the source
between residential and professional A/V systems,
connected to it. EDID simplifies system setup,
is the type of content that is being distributed and
in that the display “tells” the source what pixel
displayed on a regular basis.
rate and resolution it prefers, and the source then
outputs the optimum rate and resolution for the
In a home environment, virtually all content is
display, generally resulting in perfect images that
derived from commercial, copyrighted sources:
are accurate on a pixel-for-pixel basis.
movies on Blu-ray, satellite broadcast, or
streamed across the Internet; games on Blu-ray,
DRM is the protection of intellectual property, of
DVD, or solid-state memory; and sports or other
which HDCP - High-bandwidth Digital Content
live entertainment from pay-per-view satellite or
Protection is the most widely implemented.
cable TV sources. In order to protect the rights of
HDCP encryption is found on commercially-
the legitimate owners of this content, digital rights
recorded Blu-ray Discs, high-definition digital
management in general, and HDCP in particular,
satellite and cable television, downloadable
will become common.
content, and more. DRM is a primary concern
in residential applications, where content piracy
Content regularly used in professional A/V
is of great concern to copyright holders, such as
applications, on the other hand, is almost always
motion picture studios, who stand to lose millions
locally generated. This mostly includes the display
of dollars if content is made available through
of Microsoft® applications such as PowerPoint®
unauthorized replication. For reliable presentation
or Excel ®; institutionally-produced video for
of protected content within a residential
training, demonstration, or sales presentations;
entertainment system, all relevant signal paths
and custom or proprietary software applications
must be fully HDCP compliant and conforming
designed specifically for institutional operations
to specific rules. This is relatively simple in the
or command-and-control needs. Very rarely is
typical one-to-one scenario where a Blu-ray Disc
the content used in professional applications
Figure 1-2.
Professional Digital A/V System with HDCP
Blu-ray
Projector
Flat Panel
Display
DVR
Projector
Flat Panel
Display
Projector
Flat Panel
Display
1x4
DA
Flat Panel
Display
4x4
Matrix
Switcher
PC
PC
HDCP Source
HDCP Repeater
HDCP Sink
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Extron Digital Design Guide
encrypted with HDCP. Typically, rights-managed
is the goal of all system designers. The
content is limited to the occasional use of
implementation of digital signals does not change
commercially-recorded materials, for example
the fact that projectors are mounted on ceilings
when a sales manager wishes to “rally the troops”
with cables routed over long distances or run
by playing a scene from his or her favorite movie.
through conduit. Not every system involves
matrix switching capabilities, but almost every
The key is to select digital products based on
A/V system is designed to accommodate the
the day-to-day requirements of the application
need to split or switch signals, or provide the
for which the system is being designed. In all
signal conversion necessary to introduce analog
applications, proper management of EDID
signals into a digital system, or vice versa.
communications is a must. For residential
applications, compliance with a DRM scheme
Extron offers a wide variety of product solutions
such as HDCP is also mandatory for all system
that address the digital video needs of all market
components. And for commercial applications,
segments. The diversity of product lines brings
DRM must also be considered within the
flexibility and choice, giving designers the means
system design to allow the occasional use of
to address systems at all levels. Augmenting a
commercially-generated content, but may not be
legacy system with digital inputs and distribution
necessary for all system components or for every
capability can help keep upgrade costs down,
signal path within the overall system design.
while still addressing customer needs. Mixed
format systems are easily achievable and can be
Extron Digital Solutions
accommodated in small to large systems with
Professional A/V systems are highly customized,
short to extremely long distance requirements.
each one designed to meet a particular set of
An all-digital system can be designed with various
presentation requirements. Overcoming the
levels of functionality, by utilizing products with
challenges presented by various technologies,
performance features that address the exact
customer needs, or environmental parameters
needs required by the integrator. ■
Extron offers a wide
variety of product
solutions that address
the digital video needs
of all market segments.
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7
Digital Video Signal Formats
HDMI is not the only
digital video standard
found in commercial
A/V environments.
Frequently encountered
digital video formats
include:
DVI
• HDMI • DisplayPort
• SDI
• HD-SDI
• 3G-SDI
•
The video marketplace is currently dominated
Some, such as SDI, have been in use for
by high resolution plasma and LCD flat panel
many years while others, such as HDMI and
displays, and LCD and DLP projectors. These
DisplayPort, are relatively new and are being
displays are natively digital in their design,
updated continuously through the standards
construction, and operation. Similarly, the vast
revision process. At this point, it is premature
majority of sources that drive these displays,
to predict whether any one of these formats
including computers, DVD and Blu-ray Disc
will ultimately dominate professional A/V. Each
players, high definition digital video recorders or
format has its own technical advantages as well
DVRs, and A/V receivers, are inherently digital
as unique capabilities to meet specific integration
devices. These products stand in contrast
requirements within the A/V industry. Let’s take a
to the traditional, analog video sources and
look at each one in some detail.
displays such as VHS recorders and CRT-based
televisions or data monitors that utilized signal
DVI - Digital Visual Interface
interfaces such as composite video or RGBHV.
DVI and HDMI are based on a common signaling
scheme for video known as TMDS - Transition-
For a digital video source to initiate analog signal
Minimized Differential Signaling. A DVI TMDS link
transmission, its digital output signals must be
consists of three serial data channels, one for
converted to analog video, a process known
each color – red, blue, and green – plus a fourth
as digital-to-analog conversion or DAC. At the
channel carrying a pixel rate clock which provides
receiving end, a digital display must convert these
the timing reference that keeps the three color
analog signals back to digital, a process known
channels synchronized. All TMDS data and clock
as analog-to-digital conversion or ADC. Each
lines are differential, or balanced, and are carried
DAC and ADC conversion introduces errors and
on twisted pairs within DVI cable assemblies.
distortion into the video signal. By employing all-
DVI connector
digital transmission, these unnecessary errors,
To support different resolution requirements, the
as well as the extra expense of ADC and DAC
DVI specification provides for one or two video
circuitry, can be eliminated. See Figure 2-1.
links per connector, commonly known as single
link or dual link, respectively. The maximum pixel
There are several standard signal formats in use
rate for single link DVI is 165 MHz, corresponding
for digital video transmission between sources
to 4.95 Gbps, which is more than sufficient for
and displays. These include:
WUXGA 1920x1200 and HDTV 1080p/60, with a
HDMI connector
• DVI - Digital Visual Interface
• HDMI - High Definition Multimedia Interface
• DisplayPort
• SDI - Serial Digital Interface
color depth of 8 bits per color. Higher resolutions
and greater color depths can be supported by
use of dual link DVI, which handles pixel rates
up to 330 MHz and resolutions as high as
3840x2400.
Figure 2-1.
DAC/ADC Conversions Can Degrade Transmitted Signals
Digital Source Device
Internal
Digital
Functions
Digital Display Device
Unnecessary if source and destination
are both natively digital
ADC
DAC
The DVI specification also provides for two
additional lines of communication, both of
Internal
Digital
Functions
which are essential in achieving successful DVI
transmission between devices (see Table 2-1).
The DDC - Display Data Channel is a serial
connection for EDID and HDCP communication.
The HPD - Hot Plug Detect pin allows for
implementation of hot plug detection, which
Original digital
video pixels
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Extron Digital Design Guide
Transmitted analog
video with errors
due to DAC non-linearities
Reconstructed digital
video pixels with
additional distortion
caused by ADC
quantization errors
allows a computer, for example, to detect the
presence of a display without user intervention.
VGA - VESA
E-DDC host assignment
HDMI
type A
Table 2-3.
The DVI specification provides for two types of
HDMI 1.3 Basic
Performance Parameters
connectors: DVI-D, the standard connector, and
DVI-I, which can carry analog RGBHV as well as
digital signals.
DVI is a royalty-free standard originated by the
Table 2-2. HDMI pin configurations
Pin
Function
Pin
Function
✔ Performance:
- DVI compatible
- 25-340 MHz
- Upward of 10.2 Gbps data speed
- Color depth: 24-bit, plus 30, 36,
and 48-bit Deep Color
- Color space: ITU-R BT709-5,
xvYCC
1 DisplayPort
TMDS Data2+
source-side
11
TMDS Clock Shield
2
TMDS Data2 Shield
12
TMDS Clock-
1.0 of the DVI specification was released in
3
TMDS Data2-
13
CEC
April 1999, and there have been no subsequent
4
TMDS Data1+
14
N/C
revisions since then.
5
TMDS Data1 Shield
15
SCL
6
TMDS Data1-
16
SDA
✔ Integrated video, audio, and
content protection
7
TMDS Data0
17
DDC/CEC Ground
✔ High level consumer control
8
TMDS Data0 Shield
18
+5V Power
9
TMDS Data0-
19
Hot Plug Detect
10
TMDS Clock+
DDWG - Digital Display Working Group. Version
HDMI - High Definition Multimedia
Interface
The HDMI format incorporates the TMDS video
✔S
imple, plug and play
connection
✔ Only one cable required
✔ Auto lip sync
Table 2-4.
functionality of DVI and extends TMDS to
carry digital audio and control information. By
June 2002. The current version is HDMI 1.3,
consolidating high definition video, audio, and
released in August 2006. Compared to previous
control into a single, compact connector, HDMI
versions, HDMI 1.3 specifies a twofold increase
has been very successful in the consumer audio/
in the maximum TMDS single link clock rate to
video market (see Table 2-2).
340 MHz, corresponding to 10.2 Gbps (Table
2-3). The increased bandwidth of HDMI 1.3
The most common HDMI connector is the 19-pin
enables up to 16 bits per color – also known as
Type A, which contains a single TMDS link plus
Deep Color, an extended color space, the latest
DDC and HPD lines. A 5 volt power supply line
high resolution surround sound audio formats
is also provided. In addition, HDMI connectors
for Blu-ray Disc, and video resolutions up to
incorporate the CEC - Consumer Electronics
WQXGA 2560x1600. Version 1.3 also mandates
Control line, which is used for integrated control
the inclusion of High-bandwidth Digital Content
of multiple devices within an A/V system. At
Protection or HDCP, a digital rights management
this time, CEC control protocols are proprietary
scheme that prevents the copying of digital video
to each equipment manufacturer, and there is
and audio content. The next version, HDMI 1.4
no CEC compatibility between manufacturers.
(Table 2-4) was recently announced and the
However, there are implementation guidelines for
CEC and manufacturers are beginning to work
DVI-I Dual Link
analog and digital
DVI-D Dual Link
HDMI 1.4
Enhanced Functionality
✔ HDMI Ethernet Channel:
- Bi-directional data channel
supporting 100 Mbps Ethernet
connectivity
- Allows multiple devices to share
one network connection
✔A
udio Return Channel:
- Returns upstream audio from
a display's internal tuner to a
receiver
✔S
upports higher maximum
resolutions:
- 3840x2160 at 24 Hz, 25 Hz, and
30 Hz
- 4096x2160 at 24 Hz
✔ 3D Support up to 1080p
✔A
dditional color space support:
- Provides enhanced color
accuracy with digital still cameras
✔N
ew HDMI Micro Connector:
- Approximately 50% smaller than
current HDMI mini connector
DVI-I Single Link
digital only
analog and digital
DVI-D Single Link
digital only
together to develop standardized control.
Other HDMI connector variations include Type
B, a connector intended to support dual link
Table 2-1. DVI pin configurations
Pin #
Signal Name
Pin #
Signal Name
Pin #
Signal Name
HDMI applications but one that has not yet
1
TMDS Data2-
9
TMDS Data1-
17
TMDS Data0-
been implemented; and Type C, a miniaturized
2
TMDS Data2+
10
TMDS Data1+
18
TMDSData0+
connector designed for portable equipment such
as consumer camcorders.
3
TMDS Data2/4 Shield
11
TMDS Data1/3 Shield
19
TMDS Data0/5 Shield
4
TMDS Data4-
12
TMDS Data3-
20
TMDS Data5-
5
TMDS Data4+
13
TMDS Data3+
21
TMDS Data5+
6
DDC Clock [SCL]
14
+5 V Power
22
TMDS Clock Shield
The HDMI specification and licensing is
7
DDC Data [SDA]
15
Ground (for +5 V)
23
TMDS Clock +
administered by HDMI Licensing, LLC. In contrast
8
Analog vertical sync
16
Hot
Plug
Detect
VGA
- VESA
24
TMDS Clock -
to DVI, the HDMI specification has evolved
C1
Analog Red
C5
Analog GND Return:
(analog R, G, B)
C3
Analog Blue
C2
Analog Green
--
--
C4
Analog Horizontal Sync
through several standards revisions. Version
1.0 of the HDMI specification was released in
E-DDC host assignment
www.extron.com
HDMI
type A
9
HDMI
type A
Digital Video Signal Formats
DisplayPort is capable
of supporting Deep
Color, multi-channel
high resolution audio,
and video resolutions
well beyond WUXGA
1920x1200 and
HDTV 1080p/60.
specification is expected to be published by
DisplayPort
source-side
June 30, 2009.
DisplayPort
Table 2-5. DisplayPort pin configuration (Source-side)
DisplayPort is a royalty-free digital interface
Pin
between sources and displays that is being
1
ML_Lane 0 (p)
11
GND
positioned as a low-cost alternative to HDMI for
2
GND
12
ML_Lane 3 (n)
PC equipment manufacturers. DisplayPort uses a
3
ML_Lane 0 (n)
13
GND
digital video transmission scheme that differs from
4
ML_Lane 1 (p)
14
GND
5
GND
15
AUX CH (p)
6
ML_Lane 1 (n)
16
GND
7
ML_Lane 2 (p)
17
AUX CH (n)
8
GND
18
Hot Plug Detect
Type A and Type C connectors, can be used to
9
ML_Lane (n)
19
Return
pass HDMI signals, provided that the device
10
ML_Lane 3 (p)
20
DP_Power
TMDS and is therefore not directly compatible with
HDMI and DVI. However, the 20-pin DisplayPort
connector, with characteristics similar to the HDMI
Function
Pin
Function
supports HDMI (see Table 2-5). For example, if
a video source only has a DisplayPort connector,
In addition to zero licensing fees, DisplayPort
but also has HDMI signaling capability, then it is
is intended to provide further cost savings by
possible to use a DisplayPort-to-HDMI adapter
unifying the interface signals for both internal and
to connect the source to an HDMI-equipped
external connections within a device, such as the
display. Such DisplayPort connections, referred to
connection between the motherboard and display
as “dual-mode” or “multi-mode,”
on a laptop PC. The VESA - Video Electronics
are symbolized by a special logo
Standards Association released the initial version of
to indicate this capability:
the DisplayPort standard in 2006. The most recent
revision, 1.1a, was released in January 2008.
DisplayPort video and audio signals are carried
DisplayPort connector
on four lanes of differential wires, with each
SDI - Serial Digital Interface
lane running at either 1.62 Gbps or 2.7 Gbps
SDI is a set of video standards, defined by the
for a maximum data rate of 10.8 Gbps. As with
Society of Motion Picture and Television Engineers
HDMI 1.3, DisplayPort is capable of supporting
or SMPTE, for serial transmission of video and
Deep Color, multi-channel high resolution audio,
audio over standard RG59 or RG6 coaxial cable
and video resolutions well beyond WUXGA
(see Table 2-6). SDI standards encompass a
1920x1200 and HDTV 1080p/60. Analogous
variety of data rates from 270 Mbps to 2.97 Gbps
to the DDC channel for HDMI, DisplayPort
per link and are primarily utilized on professional
connectors provide for a differential AUX channel
broadcast and video production equipment,
for EDID communication. In addition, DisplayPort
with secondary use in live events, rental and
incorporates digital rights management similar
staging, medical imaging, digital cinema, and
to HDCP - DisplayPort Content Protection
telepresence cameras and recording devices.
or DPCP.
An SDI-based video infrastructure is becoming
increasingly popular for A/V signal distribution,
Table 2-6. SMPTE - Society of Motion Picture and Television Engineers SDI Standards
due to the benefits of inexpensive or existing
cabling, ease of termination, and transmission
Standard
Name
Data
Rate
Video
Format
Color
Encoding
Coax
Distances
SMPTE 259M-C
SDI
270 Mb/s
480i, 576i
4:2:2 YCbCr
300 meters
for HD-SDI and 3G-SDI signals. SDI is strictly a
1.485 Gb/s 720p, 1080i, 1080p/30 4:2:2 YCbCr
100 meters
serial, one-way protocol for video, audio, and
distance capabilities up to 330 feet (100 meters)
SMPTE 292M
HD-SDI
SMPTE 372M
Dual Link HD-SDI
2.97 Gb/s
1080p/60, 2K
various
100 meters
metadata such as time and date stamps or GPS
SMPTE 424M
3G-SDI
2.97 Gb/s
1080p/60, 2K
various
100 meters
coordinates, with no provisions for other auxiliary
communications. ■
­10 Extron Digital Design Guide
Anatomy of a Digital Video Signal
Digital video signals are considerably different
in comparison to traditional analog video
signals, with specific performance and timing
Clock Period
requirements that must be maintained throughout
Signal
Swing
the entire signal path. Terms such as equalization,
jitter, and reclocking in the digital domain replace
the familiar level and peaking terminology for
Low
Level
analog signals. Signal conditioning requirements
for digital signals are also different, and must
Clock Period
High
Level
Fall
Time
Rise
Time
Figure 3-1. Digital Data Parameters
be understood accordingly before designing a
digital-based A/V system.
All standard digital video signal formats, including
disappears, otherwise known as cliff effect. This
SDI, DVI, HDMI, and DisplayPort are synchronous,
is in contrast to analog transmission, whereby the
that is, the value of a synchronous digital signal
receiver’s output gradually degrades as the signal
may change only at specific intervals determined
worsens, but still remains viewable long into its
by a reference signal known as the clock. Digital
degraded state.
video signals are binary in nature - the signal can
be either a high or a low level, with rapid transitions
One of the key contributors to timing errors is
in between (see Figure 3-1). The amount of time
jitter. Jitter is defined as the variation of the clock
it takes for a digital signal to transition from low
period in relation to the reference clock signal.
to high is known as the rise time, and the time it
Jitter can occur over long lengths of low quality
takes for the signal to transition from high to low
cable, or through the cumulative effect caused
is known as the fall time. The difference between
Period
by cascading several
digital devices Clock
between
the
High
the high and the low values of the signal level is
source and the destination.
Level
called the signal swing. The minimum allowable
Jitter can occur over
long lengths of low
quality cable, or
through the cumulative
effect caused by
cascading several
digital devices or
cables between
the source and the
Clock Period
destination.
Signal
time interval between transitions is known as the
Swingin quantifying digital
Eye diagrams are useful
clock period.
signal integrity. They can be produced on an
Low
oscilloscope by sampling
a series of digital pulses
Level
Because it is binary, a digital signal is fundamentally
robust, since a receiver only needs to distinguish
Clock Period
in
succession,
and overlaying theRise
samples on the
Fall
Signal
Level
Time
Uncertainty
oscilloscope display (see Figure 3-2).
Time
between “high” and “low” levels for each clock
period in order to completely reconstruct the
original transmission. However, this becomes
increasingly difficult as the signal swing is
decreased and as timing becomes less accurate.
Rise and fall times, signal swing, and timing
accuracy are all subject to degradation in digital
Usable
Signal
Swing
Minimum
Eye Opening
Mask
Figure 3-2. An eye diagram is
formed by repeated sampling
of a digital signal.
Signal Level
Uncertainty
Timing Jitter/Uncertainty
Timing Jitter/Uncertainty
signal transmission caused by cable attenuation,
cable capacitance, impedance mismatch, noise
coupling, crosstalk, and so forth. It is important
to quantify the amount of signal degradation
so that standards for signal integrity can be
defined. If the signal is degraded beyond the
receiver’s ability to distinguish high and low signal
values with correct timing, the receiver’s output
abruptly becomes meaningless, and the signal
www.extron.com
11
Anatomy of a Digital Video Signal
cable capacitance and attenuation will degrade
Clock Period
Signal Level
Uncertainty
signal rise time and amplitude as cable length
increases. Since DVI, HDMI, and DisplayPort
signals are transmitted over twisted pair-type
Minimum
Eye Opening
Mask
Usable
Signal
Swing
cables, skew is introduced at long cable lengths
due to the variations in twist rates of individual
wire pairs in the cabling, which in turn impacts the
Signal Level
Uncertainty
relative timing between the video data lines. The
Timing Jitter/Uncertainty
Timing Jitter/Uncertainty
Figure 3-3. Eye Diagram Parameters
compromised “eye” pattern in Figure 3-4 shows
the resulting distortion caused by attenuation
losses and skew-related timing errors from long
The resulting diagram displays the aggregated
cable lengths. The resulting waveform encroaches
levels and timing characteristics of the signal
on the limit mask, which potentially leads to erratic
being transmitted (see Figure 3-3). The open, eye-
images, or no image displayed at all.
shaped regions between the waveforms give the
The direct signal
output for the source
device is often
assumed to be good,
but just one adapter
or low quality cable
may degrade the
signal to the extent
that no image is
displayed.
“eye” diagram its name. To determine whether
Signal conditioning can be applied within digital
the value of the signal is “high” or “low,” the signal
video equipment via features such as input signal
should be captured at intervals corresponding
equalization and output signal reclocking.
to the midpoints within these regions. These
These advanced features provide compensation
intervals are also the midpoints in time between
for losses experienced throughout the signal
signal transitions. The smaller the opening of the
chain. It is important to note that such losses
eye, the more difficult it is to accurately determine
are not limited to the signal path, but may also
the signal value. Digital video format specifications
be related to the source device itself. The direct
include required values for eye openings as
signal output from the source device is often
minimum standards for signal integrity. These
assumed to be good, but this is not always the
values can be overlaid onto eye diagrams as a
case. Awareness of this is key to managing the
reference or limit “mask” when making signal
integrity of the overall system. In situations where
quality measurements.
long cable lengths are unavoidable, active cable
equalizers can be deployed to restore signal
Maintaining Digital Signal Integrity
integrity and extend drive distances. Active
A clean digital signal path is crucial for signal
equalizers are designed to compensate for the
integrity. Cable lengths should not exceed the
effects of long cable runs. Special amplifiers and
driving capability of digital signal sources, as
filters matched to cable losses restore signal
swing as well as rise and fall times. Clock and data
recovery circuitry can remove jitter and restore
clock timing, resulting in a measurable opening
Assessing signal integrity using a standardized minimum eye opening mask
of the signal eye pattern. Figure 3-5 shows the
result of signal conditioning applied by the Extron
DVI 201xi Twisted Pair Extender to the distorted
“eye” pattern in Figure 3-4. Signal conditioning
features including input equalization and output
reclocking are common to many Extron digital
product solutions.
As video resolutions and associated signal
Figure 3-4. Fail
Figure 3-5. Pass
frequencies increase, the signal becomes more
and more susceptible to discontinuities along
­12 Extron Digital Design Guide
the cable. Such discontinuities cause reflections
which will degrade the signal. Therefore, the
Substantial signal degradation caused by simply inserting a DVI gender changer
bend radii of cables should be kept as large as
DVI
Female to Female
Adapter
possible, and cable splices, joiners, or gender
6 ft. (1.8 m) DVI Cable
changers should be avoided. Figure 3-6 depicts
the substantial degradation that can be caused by
simply inserting a gender changer between two
6 ft. (1.8 m)
DVI Cable
6 ft. (1.8 m)
DVI Cable
cables. In this example, the eye diagram shows
the result of a 1920x1200 source signal passing
through a 6 foot (1.8 m) DVI cable, then through
a DVI female-to-female coupler, and finally an
Figure 3-6.
additional 6 foot DVI cable. This emphasizes
the importance of proper design considerations
or fiber optic cable. This approach provides a
for management of all high resolution digital
means to conveniently route cabling through
signals. System interconnects should be kept
walls and within furniture, the convenience of field
to a minimum, and signal distribution equipment
terminating connectors, and the ability to send
should always feature signal conditioning
signals extended distances.
capabilities to best accommodate specific design
challenges that may compromise digital video
Category 5-type twisted pair cable offers a cost-
signal integrity.
effective, easily installed and terminated option
for digital signal transmission distances up to 200
Solutions for Extending Digital
Video Signals
feet (60 meters). For longer distance transmission
The customized nature of professional A/V
applications where security or outside electrical
systems usually presents many digital video
interference are of concern, fiber optic products
distribution challenges to the integrator, including
may be selected for a variety of reasons:
the need to send signals over significant
•High image quality – Pixel-for-pixel performance up
to 1920x1200 resolution
distances. Extron offers a variety of products
for specific digital video formats to help meet
infrastructure-related requirements. For example,
most installations call for cable runs of 35 feet
(11 m) or beyond, and also require that cables be
managed within walls and up into ceiling spaces.
This can be a problem with standard digital cable
assemblies, since the connectors are often too
large to conveniently run through conduits and
requirements, up to several miles, and for
System interconnects
should be kept to a
minimum, and signal
distribution equipment
should always feature
signal conditioning
capabilities.
•Long distance transmission – Image quality can be
maintained at distances up to 30 km
•Immunity to outside interference – Can be utilized
in environments that can’t be served by copperbased cabling. such as elevator shafts or near
HVAC and other electric machinery
•Ideal for secure environments – Well-suited for
government, military, and judicial environments ■
raceways, and terminating HDMI and DVI cables
1" Conduit
OD = 1.16" (29.5 mm)
ID = 1.05" (26.6 mm)
in the field is difficult with very few tools available
(see Figure 3-7). Even when this is possible,
most standard cable assemblies offer insufficient
Type A (Female) HDMI
Width = .547" (13.9 mm)
Height = .175" (4.45 mm)
performance to send signals over significant
distances. Fortunately, products and solutions
are available that offer the flexibility to address
0.53"
(13.46 mm)
specific system needs. A popular alternative to
standard cable assemblies is to use an active
transmitter and receiver pair to send digital
signals over standard, shielded Category 5-type
0.80"
(20.32 mm)
Figure 3-7. Running a preterminated HDMI cable
through conduit can be inconvenient
For more information, see Extron’s white
paper at www.extron.com/digitalvideopaper
www.extron.com
13
Understanding EDID - Extended Display Identification Data
EDID is used
by a display to
communicate
information to a
source device about
the range of signals
it can support as
well as additional
information such as
native resolution and
preferred timing.
What is EDID?
with data formatting defined by the EDID
EDID data exchange is a standardized means for a
specification.
display to communicate its capabilities to a source
device. The premise of this communications is for
As display types and capabilities increased, 128
the display to relay its operational characteristics,
bytes became insufficient, and both EDID and
such as its native resolution, to the attached
DDC were extended so that multiple 128-byte
source, and then allow the source to generate
data blocks could be exchanged. This is known
the necessary video characteristics to match
as E-EDID and has been implemented in many
the needs of the display. This maximizes the
consumer devices. In fact, the CEA - Consumer
functional compatibility between devices without
Electronics Association has defined its own EDID
requiring a user to configure them manually, thus
extensions to cover additional video formats
reducing the potential for incorrect settings and
and to support advanced multi-channel audio
adjustments that could compromise the quality
capabilities.
of the displayed images and overall reliability of
the system.
What EDID information is exchanged
between display and source?
Where is EDID utilized?
The base EDID information of a display is
Generally, the source device will be a computer
conveyed within a 128-byte data structure (see
graphics card on a desktop or laptop PC, but
Table 4-2) that contains pertinent manufacturer
provisions are in place for many other devices,
and operation-related data. The current EDID
including HDTV receivers and DVRs, DVD and
version defines the structure as follows:
Blu-ray Disc players, and even gaming consoles,
Table 4-1.
EDID Development History
EDID
Defines the data
structures sent from a
video display to a source
over E-DDC lines to
describe its capabilities
to read EDID and output video accordingly.
Vendor/Product Identification Block – The first
Originally developed for use between analog
18 bytes identify the display manufacturer and
computer-video devices with VGA ports, EDID is
product, including serial number and date of
now implemented for DVI, HDMI, and DisplayPort.
manufacture.
History
EDID Structure Version & Revision – The next
EDID was developed by VESA - the Video
two bytes identify the version and revision of the
EDID 1.0
Defined original
128-byte data structure
(Deprecated)
Electronics Standards Association, with version
EDID data within the structure.
EDID 1.1
Defined some
alternative uses for
space in data structure
(Deprecated)
DDC standard. See Table 4-1.
1.0 introduced in 1994 within version 1.0 of the
five bytes define characteristics such as whether
Prior to the development of EDID, pins 4, 11, 12,
the display accepts analog or digital inputs, sync
and 15 on the VGA connector were sometimes
types, maximum horizontal and vertical size of the
used to define monitor capabilities. These ID bit
display, gamma transfer characteristics, power
pins carried either high or low values to define
management capabilities, color space, and
different screen resolutions. VESA extended
default video timing.
EDID 1.2
Defined some
alternative uses for
space in data structure
(Deprecated)
EDID 1.3
Current definitions for
128-byte EDID data
fields
EDID 2.0
Introduced new
256-byte data structure
this scheme by redefining VGA connector pins
E-EDID
Defined optional
additional 128-byte
extension blocks for
EDID 1.3, incorporated
EDID 2.0 as optional
extensions
DisplayID
Introduced variable
length data structure
­14 Extron Digital Design Guide
Basic Display Parameters/Features – The next
9, 12, and 15 as a serial bus in the form of the
Color Characteristics – The next 10 bytes define
DDC - Display Data Channel. This allowed for
the RGB color space conversion technique to be
much more information to be exchanged, so that
used by the display.
EDID and other forms of communication were
possible between the source and the display.
Established Timings – The next three bytes
define the VESA-established video resolutions/
The original DDC protocol defined 128 bytes
timings that are supported by the display. Each
to be sent from the display to the video source,
bit represents an established timing such as
640x480/60. The last of the three bytes defines
EDID information is typically exchanged when the
the manufacturer’s reserved timing, if any.
video source starts up. The DDC specifications
define a +5V supply connection for the source to
Standard Timing Identification – The next 16
provide power to a display’s EDID circuitry so that
bytes define eight additional video resolutions
communication can be enabled, even if the display
supported by the display. These resolutions must
is powered off. At startup, the video source will
adhere to standard VESA defined timings.
send a request for EDID over the DDC. The EDID/
DDC specifications support hot plug detection,
Detailed Timing Descriptions – The next 72
so that EDID information can also be exchanged
bytes are organized into four 18-byte blocks that
whenever a display is re-connected to a video
describe additional video resolutions in detail,
source. Hot plug detection is not supported
so that custom video timings/resolutions can be
for VGA, but is supported in digital interfaces
supported. The first of the four blocks is intended
including DVI, HDMI, and DisplayPort. For these
to describe the display’s preferred video timing.
interfaces, the display device will supply a voltage
The timing data can be structured according to
on an HPD - Hot Plug Detect pin, to signal to
the VESA GTF - Generalized Timing Formula or
the video source device that it is connected. The
CVT - Coordinated Video Timings standards.
absence of a voltage on the HPD pin indicates
Consumer displays
are prevalent
in commercial
environments. Before
EDID 1.3, EDID data
was not properly
communicated
between the consumer
displays and PC’s.
disconnection. The video source device monitors
Extension Flag – EDID versions 1.3 and higher
the voltage on the HPD pin and initiates EDID
allow for additional 128-byte blocks of data
requests as it senses incoming voltage.
to describe increased capabilities. This byte
indicates the number of additional extension
blocks available. Various structures for these
extension blocks have been defined, including
DI-EXT - Display Information Extension,
VTB-EXT - Video Timing Block Extension, and
LS-EXT - Localized String Extension. But the
Table 4-2. EDID File Structure
Address
(Decimal)
Data
0-7
Header
most prevalent extension is CEA-861, which
8-9
Manufacturer ID
was defined to support advanced capabilities
10-11
Product ID Code
of consumer devices incorporating HDMI. The
12-15
Serial Number
significance of the CEA-861 extension is that it
16-17
Manufacture Date
aims to address previous operational disparities
18
EDID Version #
19
EDID Revision #
20
Video Input Type
21
Horizontal Size (cm)
22
Vertical Size (cm)
23
Display Gamma
experienced with integrating consumer-based
display devices into computer-based commercial
A/V systems, allowing for proper conveyance of
EDID information between devices.
24
Supported Features
EDID/DDC Protocols
25-34
Color Characteristics
The DDC uses a standard serial signaling scheme
35-36
Established Timings Supported
known as the I2C bus. I2C is used extensively
37
Manufacturer's Reserved Timing
where electronic devices and components need
38-53
EDID Standard Timings Supported
54-71
Detailed Timing Descriptor Block 1
to exchange information, due to its simplicity,
72-89
Detailed Timing Descriptor Block 2
I2C bus consists of three wires: SDA (data), SCL
90-107
Detailed Timing Descriptor Block 3
108-125
Detailed Timing Descriptor Block 4
(clock), and a logic “high” DC pull-up voltage.
126
Extension Flag
127
Checksum
low pin count, and bi-directional capability. An
For the DDC, the logic “high” voltage is specified
to be +5V.
General Description
Constant Fixed Pattern
Display Product Identification
EDID Version Information
Basic Display Parameters: Video input
type (analog or digital), display size, power
management, sync, color space, and
timing capabilities and preferences are
reported here.
Color Space Definition
Timing information for all resolutions
supported by the display are reported here
Number of (Optional) 128-byte Extension
Blocks to Follow
www.extron.com
15
Understanding EDID - Extended Display Identification Data
EDID management
is most important
when multiple
displays with varying
native resolutions
are integrated into
multi-source A/V
environments.
Inconsistent video
output can be avoided
by utilizing products
that properly manage
EDID.
EDID Issues
Display devices can have various levels of
EDID implementation and, in some cases, they
may lack EDID information altogether. Such
inconsistencies can cause operational issues
ranging from overscan and resolution problems,
to the display device not displaying the source
content at all.
The following are examples of some potential
issues with EDID communications, along with the
reducing the likelihood of no image being displayed. If
this does not match the native resolution the display,
fonts will likely appear to be abnormally large, small,
or fuzzy.
•The PC is connected to multiple displays with
different native resolutions. Since it can only read
EDID from one display, the output will be mismatched
in resolution with all other displays, resulting in less
than optimal image quality, or no image displayed at
all. This issue is a common occurrence in professional
systems when digital video signals need to be
distributed or routed to multiple displays.
possible causes:
Problem
No image is shown on the display.
Possible Cause
•The source device, such as a PC graphics card, or
laptop, cannot read the EDID information from the
display. As a result, in some cases the PC will not
output any video signal.
EDID Tools
Third-party software can be used to help
troubleshoot possible compatibility issues
between the display device and the source. A
Google search using “EDID viewer” will result
in many usable tools, such as those offered by
ViewSonic including EDID Editor or EnTech Monitor Asset Manager. These tools allow you to
Problem
read the display’s EDID and determine whether
The display loses the image when a new
source has been selected.
a graphic card and the display device may be
experiencing EDID handshake problems.
Possible Cause
•This is a common occurrence with VGA sources, due
to the lack of hot plug detection.
•While hot plug detection is supported for DVI, HDMI,
and DisplayPort, EDID communication problems
can arise from inconsistencies in the implementation
of HPD signaling between devices from different
manufacturers. This frequently becomes an issue
for professional integration, since the ability to switch
digital video signals is a necessity.
A/V systems typically comprise several remotely
located displays and often include multiple
source devices. It is important to realize this can
potentially contribute to EDID-related issues. The
necessity to switch, distribute, and route signals
from sources to displays presents a considerable
challenge in terms of ensuring proper EDID
communications and therefore reliable system
Problem
operation.
n image is shown, but the source resolution
A
does not match that of the display.
While there is not always a solution to every
Possible Cause
EDID-related problem, Extron products include
•A PC cannot read the EDID information, so it defaults
to a standard resolution, such as 640x480. If the user
subsequently attempts to manually set the resolution
to match the display, some graphics card drivers
may enforce the lower default resolution and create a
scrolling/panning desktop without actually changing
the video resolution.
•The PC is able to read the EDID information, but
the graphics card limits the output resolution to
XGA 1024x768, a resolution most displays can
accommodate, ensuring a usable image and
­16 Extron Digital Design Guide
EDID Solutions
features to help prevent or solve many of them
by properly managing EDID communications
between sources and displays in A/V systems.
These features provide automatic and continuous
EDID management with attached source devices,
ensuring proper power-up and reliable output of
content.
EDID Emulation is a feature of many Extron
DVI and HDMI products, including switchers,
distribution amplifiers, and matrix switchers. It
algorithm to determine a common resolution,
maintains constant EDID communication with
refresh rate and color space, and then uses
source devices by providing pre-stored EDID
the EDID protocol to set up the input sources.
information for various signal resolutions. A user
This powerful convenience feature simplifies
can select the desired signal resolution, and then
system setup for the integrator, helps ensure
the corresponding EDID block is conveyed to all
consistent and reliable image display, and makes
attached source devices. This EDID information
system operation virtually transparent to the
is constantly available to the sources, even in a
end user. ■
switching application where inputs are regularly
selected and de-selected. The output of the
sources should match the native resolution of the
intended display device.
EDID Minder ™ is an advanced, Extronexclusive technology for EDID management.
It encompasses EDID Emulation, but also
incorporates an additional level of “intelligence.”
Extron products with EDID Minder can
Extron EDID Minder
captures, stores,
and conveys EDID to
connected sources to
ensure proper, optimal
video format output.
communicate with the display device, and
automatically capture and store EDID information
from the display (see Figure 5-1). This captured
information can then be used as the reference
EDID for the sources. EDID Minder is a standard
feature in most Extron DVI and HDMI extenders,
switchers, distribution amplifiers, and matrix
switchers, as well as products that incorporate
DVI or HDMI switching.
Extron EDID 101 D Emulator for DVI
with EDID Minder
For more information, see Extron’s white
paper at www.extron.com/edidpaper
The functional role of a given product as a
distribution amplifier, switcher, or matrix switcher
determines the complexity of EDID Minder
implementation. Matrix switching environments
represent the most difficult EDID management
Figure 5-1. EDID Minder Communications
situation, with simultaneous EDID communications
required for multiple inputs and outputs. The
displays connected to the outputs are very likely
EDID
OK, sending
video to fit
your format.
Output
Video
to be of different models and native resolutions.
The EDID information between them is different
and needs to be conveyed to the source devices.
Proper EDID management within the system is
crucial to consistent and reliable operation.
Extron HDMI and DVI matrix switchers with
EDID Minder achieve this by managing EDID
communications for each input/output tie. EDID
Minder first analyzes the EDID for all displays
Video
EDID Minder
Input
Video
EDID Minder
OK, here is my
native resolution
and vertical
refresh rate.
Input
Video
EDID Minder
Input
connected to the system, applies a complex
www.extron.com
17
DRM for the A / V Professional
What is DRM?
familiar adage of “Just because one can, doesn’t
DRM - Digital Rights Management is used by
mean one should” is fully appropriate in this case.
owners and holders of IP - Intellectual Property to
HDCP-compliant systems are increasingly being
enforce restrictions on the use of their copyrighted
requested by customers and integrators alike. This
content.
type of system could be used to show protected
content in public spaces. Therefore, users should
In the A/V industry, DRM is used to secure digital
be made aware of the potential issues that may
music and video content to prevent unauthorized
arise from inadvertent public display of private-
playback or copying. For digital video content
use, content-protected materials. During system
protection, the most prevalent DRM systems
commissioning and training, the integrator should
are HDCP - High-bandwidth Digital Content
consider educating system operators, and even
Protection and AACS - Advanced Access Content
include discussion of DRM and content protection
System. HDCP is an encryption protocol applied
within system documentation. Of course, this is
to digital interfaces including HDMI, DVI, and
not as much of an issue for residential installations,
DisplayPort. AACS is a standard for encrypting
where the entire system is generally intended for
high definition optical discs that also works in
personal use.
conjunction with HDCP.
Users should be made
aware of the potential
issues that may arise
from inadvertent
public display of
private-use, contentprotected materials.
Multiple display system in a public space
environment.
DRM exists to protect the rights of content
DRM for Video - Separate Protocols
That Work Together
creators and owners to receive compensation
HDCP is designed to prevent unauthorized
for their initial ideas and subsequently bringing
access of protected video content and to enforce
them to market. Movies and music are the
restrictions on authorized playback. HDCP-
most recognized source content within the A/V
enabled video sources, such as Blu-ray Disc
industry that is impacted by DRM enforcement.
players, PCs, and other digital media devices
An individual who purchased a copy-protected
always undergo through a three-step process to
Blu-ray Disc, for example, is entitled to utilize
protect the video from unauthorized access:
that disc only within a personal-use environment,
which extends to the home or other private
1. Authentication: The video source determines
viewing locale. For that movie to be played in a
that all devices connected to its outputs are
public space, additional licensing requirements
authorized and able to receive encrypted video. This
must first be met. If that licensing has not been
is accomplished by means of an initial authorization
obtained, significant fines can be levied against
handshake protocol, where cryptographic public
the offender. These fines may very well extend to
keys, KSV - Key Selection Vector, and encrypted
the owner of the installed system.
messages are exchanged between the source and
the downstream devices connected to its outputs.
­18 Extron Digital Design Guide
A/V systems in public spaces are the center of our
The HDCP 1.3 specification calls for a maximum of
industry, with installations taking place on a daily
127 simultaneous devices connected downstream
basis. It is for this reason that DRM considerations
from the source, and up to seven allowable levels
must be made and addressed at the earliest point
of repeater devices between the source and the
of system design. The time when needs are being
display - also known as the sink. The source uses
assessed for an A/V integration project is also the
the initial handshake protocol to determine that
time to determine the functional requirements of
these system size restrictions are not violated.
a given system. This is when the sales engineer
HDCP version 1.3 is the currently implemented
should ask the right questions and inform the
specification. As will soon be discussed, the latest
prospective customer on the legalities involved
version, HDCP 2.0, further restricts the allowable
with personal-use devices and/or material being
maximum number of simultaneous devices and
used in public and commercial spaces. The old,
repeater levels.
2. Content Encryption: After the source
With the release of version 2.0 in October 2008,
authenticates that all downstream devices are
HDCP became interface-independent, and can
HDCP compliant and in good standing, and
be applied to any two-way digital transmission
that no system size restrictions are violated, the
between sources and displays, wired or wireless,
source sends encrypted video downstream. The
compressed or uncompressed. See Table 5-1.
source periodically revises the encryption key for
the video as an additional security measure.
HDCP 2.0 calls for many other important changes.
For wireless connections, HDCP 2.0 adds a
3. Renewability: Since HDCP relies on digital
locality check to the authentication protocol, to
encryption using secret keys, the system can
ensure that only devices nearby will be able to
be circumvented if the secret keys residing in
receive protected content. Furthermore, HDCP
HDCP-licensed products fall into the wrong
2.0 replaces the specialized 56-bit HDCP 1.x
hands. Therefore, a means has to be established
encryption scheme with two standard algorithms
to revoke any compromised keys. The HDCP
from the data security industry: for authentication,
administration authority, Digital Content
an RSA system with 1024 and 3072-bit keys; and
Protection, LLP can add a list of public keys of
for content encryption, a 128-bit AES - Advanced
compromised products to video content such as
Encryption System. In addition, the maximum
Blu-ray Disc. Video sources will read this data,
number of connected devices is reduced to 32,
store it in non-volatile memory, and compare the
and the maximum level of repeaters is reduced to
public keys of any downstream devices against
four. As of result of all these changes, HDCP 2.0
this revocation list. If any key matches, no video
is not directly backward compatible with HDCP
will be transmitted.
1.x. The new specification provides for converters
When switching
between sources, HDCP
authentication needs
to be re-established
between the new source
and display. Depending
on the number of
devices within the
system, this can cause
the displayed image to
be delayed.
between HDCP 1.x and HDCP 2.0 devices to
Figures 5-1 and 5-2 on the next page provide a
support mixed A/V systems with devices that
step-by-step illustration of the communications
comply with both versions. These converters are
that occur between source and sink devices
important, because the HDCP license agreement
within an HDCP-based system.
requires that licensees support any new
specification within eighteen months of release.
The multi-step process of HDCP authentication
can take several seconds to complete. This is a
primary reason for the perceived sluggishness
of some digital video systems, especially during
startup and when video signals are switched
HDCP 1.x
or re-routed, requiring HDCP re-authentication.
The best switching performance can be realized
in HDCP-compatible video equipment built
Encryption Method
Applicable Interfaces
DVI, HDMI, DisplayPort
Any two-way digital interface
Maximum Downstream
Receivers for Each Transmitter
< 128
< 32
Maximum Repeater Levels for
Each Transmitter
<7
<4
Backward Compatibility
Yes, no electronic
components required
Yes, using specialized electronic
HDCP-1.x-to-2.0 and HDCP-2.0-to-1.x
converters
Wireless Support
Not specified
Explicitly specified with new locality
check requirement
internal design and proper deployment of HDCP
Until the introduction of HDCP 2.0, the basic
protocol of HDCP had not changed substantially.
The only major differences between HDCP
versions 1.0 through 1.3 is in the types of physical
A/V connections. HDCP version 1.0 applied to the
DVI interface. Version 1.1 incorporated HDMI, and
support for DisplayPort was added for version 1.3.
Authentication:
Data security industry standard RSA
1024 and 3072-bit asymmetric system
Specialized 56-bit
symmetric system used
for both authentication
and video encryption
to minimize re-authentication through careful
processing components.
HDCP 2.0
Video encryption:
Data security industry standard
AES 128-bit symmetric system
Table 5-1. Major changes in HDCP 2.0
www.extron.com
19
DRM for the A / V Professional
HDCP specifications
define total
supported device
counts, maximum
repeater levels, and
timing expectations
for system-wide
communications
exchange
Communication process that occurs between source and sink devices within an HDCP-based system.
Phase 1
Figure 5-1. Phase 1
Initial Key Exchange
Phas
Initial Key Exchange
You have 100ms
to get thru this
Here’s my public key
Aksv: 101101...
Remember this number
An: 010011...
Here’s my public
key Bksv:
001100...
I’m NOT a repeater
REPEATER!?
You have 5 seconds
to tell me who’s
downstream
Here’s my p
key Aksv:
101101...
Data
Transmitting
Calculate Shared Secret Keys
Your public key
checks out. Now I can
compute the secret
key Km from our
public keys*:
1110100...
Repeater Performs Initial Aut
- Downstream Device Keys a
Phase 1
Authentication
Procedure
(Described
Before)
Now I can
compute the secret
key Km’ from our
public keys*:
1110100...
* Km and Km’ are computed using each device’s private key along with the public keys of both
devices. This is a special calculation that results in matching Km=Km’ IF all the keys are valid.
Encrypt a Message Using Secret Key
Now I can use MY
secret key Km to
encrypt An to form a
message RO:
0000110...
Repeater Reports Key List an
Now I can use My
secret key Km’ to
encrypt An to form a
message RO’:
0000110...
Data
Transmitting
Receiver Demonstrates Secret Key Knowledge
Here is an encrypted
message RO’:
0000110...
Transmitter Validates Connec
√ You we
downs
than 5
Data
Transmitting
√ The do
keys ha
Initial Authentication
√ There a
total do
Your encrypted
message matches
mine, and you gave it
to me in less than
100ms
√ There a
of repe
downs
Repeater Authentication Com
OK, here is your
encrypted video:
1111111100
0011001101
1011100010
1000000001...
Transmit Video
HDCP
Rx
OK, here is your encrypted video:
1111111100 0011001101
1011100010 100000001
0001111000 000100000
1111000100 0011000100
0111110110 1011000010...
H
Data
Transmitting
Data
Transmitting
­20 Extron Digital Design Guide
H
e’s my public
Bksv:
100...
NOT a repeater
Phase 2
Figure 5-2. Phase 2
Initial Key Exchange
REPEATER!?
You have 5 seconds
to tell me who’s
downstream
HDCP
Tx
Here’s my public
key Bksv:
001100...
I’m a REPEATER
Here’s my public
key Aksv:
101101...
HDCP
Rx
Data
Transmitting
ing
•
•
•
•
•
HDCP
Tx
Repeater Performs Initial Authentication with Connected Devices
- Downstream Device Keys are Collected
HDCP
Tx
Phase 1
Authentication
Procedure
(Described
Before)
can
te the secret
m’ from our
keys*:
0...
•
•
•
•
•
HDCP
Rx
ey along with the public keys of both
hing Km=Km’ IF all the keys are valid.
Phase 1
Authentication
Procedure
(Described
Before)
HDCP
Tx
•
•
•
•
An A/V device with
digital video inputs
must support HDCP,
if a user expects to
connect a PC to it
and play commercial
Blu-ray Discs.
Repeater Reports Key List and Topology
can use My
t key Km’ to
pt An to form a
age RO’:
10...
Data
Transmitting
owledge
Here are the keys of
downstream devices:
0010011...
.
.
.
0001100...
Here is how they are
connected:
HDCP
Tx
HDCP
Rx
Sink
Repeater
ncrypted
O’:
Sink
Sink
•
•
•
•
•
HDCP
Tx
Sink
Transmitter Validates Connections
HDCP
Tx
√ You were ready to give me
downstream info in less
than 5 seconds.
ing
√ The downstream device
keys haven’t been revoked.
√ There are less than 128
total downstream devices.
HDCP
Rx
√ There are less than 7 levels
of repeaters connected
downstream.
•
•
•
•
•
HDCP
Tx
Repeater Authentication Complete
OK, here is your
encrypted video:
1111111100
0011001101
1011100010
1000000001...
HDCP
Tx
HDCP
Rx
pted video:
1
1
0
00
0...
Data
Transmitting
•
•
•
•
•
HDCP
Tx
OK, here is your
encrypted video:
0110001100
0011011110
1110000010
0001101110...
Separately Encrypted
Data Transmitting
OK, here is your
encrypted video:
1111111100
1011100010
0001111000
1111000100...
•
•
•
•
ing
www.extron.com
21
DRM for the A / V Professional
The HDCP licensing
agreement does not
allow for analog video
outputs on repeater or
display devices.
Therefore, this implies that HDCP 2.0-compliant
The final AACS specification will include a
devices will soon emerge on the market. An
provision for making authorized copies of Blu-ray
existing A/V system incorporating HDCP 1.3 will
Discs, whereby a recording device can connect to
require converters if newly acquired HDCP 2.0
Internet servers at the AACS LA - AACS Licensing
devices are to be incorporated into the system.
Administrator to obtain electronic permission to
make a legitimate copy of protected content.
AACS is the DRM standard adopted for Blu-ray
Disc. AACS is designed to protect Blu-ray Disc
Analog Outputs
content similar to the way that the CSS - Content
The HDCP licensing agreement does not allow
Scramble System protects commercial DVDs,
for analog video outputs on repeater or display
but with additional features. Both AACS and
devices, but does not restrict analog outputs for
CSS encrypt the video data on-disc, so that only
sources. Nonetheless, this does not preclude
authorized players can read the content (see Table
separate agreements that would prevent analog
5-2). Both AACS and CSS prevent unauthorized
outputs on source devices. Such agreements
copying of commercial Blu-ray Disc and DVD,
could be negotiated on an ad hoc basis between
and both systems have mechanisms for revoking
content providers and hardware makers.
compromised players. AACS offers greater
However, the AACS licensing agreement is very
protection than CSS in the following areas:
specific about analog outputs and provides
for several measures to control them. Blu-ray
•AACS employs AES 128-bit encryption, while CSS
implements 40-bit encryption
Disc titles that support AACS have usage rules
•AACS allows for the revocation of individual Blu-ray
Disc players, whereas CSS can only revoke entire
models of DVD players
producer to limit the analog output resolution by
•AACS encrypts the digital outputs of Blu-ray Disc
players with HDCP
•AACS provides for the eventual elimination of
analog video outputs on Blu-ray Disc players
data embedded in them that allow the content
invoking the ICT - Image Constraint Token, or
even to disable the analog outputs entirely by
invoking the DOT - Digital Only Token. As of the
first quarter of 2009, no Blu-ray Disc titles have
included these restriction tokens, but this may
change with future releases. The AACS license
agreement also provides for an “analog sunset”
for newly manufactured Blu-ray Disc players,
such that models manufactured after 2010 can
DVDs (CSS)
Blu-ray Discs (AACS)
only include standard definition analog outputs,
and after 2013, no Blu-ray Disc players may be
Encryption Method
Specialized 40-bit stream
cipher
Data security industry standard AES
128-bit symmetric system
manufactured with any analog outputs.
Player Revocation
All players in a model
range are revoked
Individual players can be revoked
Computers
Disc Copy Prevention
Hidden disc lead-in area
prevents bit-for-bit disc
copy
Encrypted volume ID prevents bit-for-bit
disc copy
Output Signal Scrambling
Macrovision applied at
analog outputs
Managed Disc Copying
Analog Sunset
No provisions
No provisions
computers. The computer industry is a major
HDCP applied at digital outputs
source of innovation for content creation as
Macrovision applied at analog outputs
well as for unauthorized reproduction of that
Authorized copies are possible by
connecting to AACSLA server and
obtaining permission (details to be
finalized)
content. Computer DRM methods have been
Players manufactured after 2010 may not
have high definition analog outputs
Players manufactured after 2013 may not
have any analog outputs
Table 5-2. Differences between CSS and AACS encryption
­22 Extron Digital Design Guide
There are numerous DRM schemes for
devised to protect software, digital music, digital
video, digital books, games, etc. The present
discussion will be limited to video content
played on a computer and the associated DRM
schemes therein. These DRM schemes are
mainly for preventing unauthorized access to
protected commercial video such as Blu-ray Disc
Conclusion
or downloaded content including movies or TV
Any A/V system that is intended to support
shows. But non-commercial video files can also
playback of protected video content, such as
be protected with DRM, if the content creator has
Blu-ray Disc and consumer-purchased HD
access to DRM technology. The DVI, HDMI, and
video downloads, must be compliant with the
DisplayPort outputs of computers should have no
associated DRM. Since DRM implementations
DRM restrictions when the content being played
such as HDCP and AACS are meant to restrict
is not protected.
what the end user can do with protected content,
it makes sense for the A/V professional to inform
As of the first quarter of 2009, for Blu-ray
the end user of these restrictions at the outset.
Disc playback, only PCs running Windows
®
Such restrictions include limiting the number of
operating systems have software authorized to
simultaneous displays for content-protected video
play Blu-ray Discs. The same AACS and HDCP
playback, disallowing recording or copying, and
restrictions apply for PC Blu-ray Disc playback
disabling analog outputs. For example, an A/V
as for standalone players. Thus, a PC must be
system may have the capability to distribute HDMI
equipped with a video card that is capable of
video to 16 displays and provide analog video
HDCP encryption. An A/V device with digital video
recording. These functions will always be available
inputs must support HDCP, if a user expects to
when a PC with HDMI output is connected
connect such a PC to it and play commercial
for PowerPoint presentations and other non-
Blu-ray Discs.
protected material. But once a protected Blu-ray
Disc is inserted into the PC for playback, HDCP
The market for authorized downloads of
and AACS restrictions may disable output to
commercial video content is crowded with
several displays and to the recorder.
companies and products, with frequent
turnover of market entries and exits. Current
Since many large-scale A/V systems can display
market players include Amazon, Apple iTunes,
unencrypted video on a large number of displays,
Blockbuster, Netflix, and Vudu, to name just a
freely distribute analog signals, and provide
few. These companies offer a plethora of options
video recording capabilities, end users of such
for the end user. Movies or TV shows can be
systems must be made aware that some system
rented or purchased, some in high definition, but
functions may not be available when playing
most in standard definition. The video may be
DRM-protected content. ■
Since DRM
implementations such
as HDCP and AACS
are meant to restrict
what the end user
can do with protected
content, it makes
sense for the A/V
professional to inform
the end user of these
restrictions at the
outset.
either streamed or stored locally to a computer, a
networked set-top receiver, Blu-ray Disc player, a
video game console equipped with a hard drive, or
even a display with Internet access capability. The
one constant among all these different options
is the existence of DRM for protected content,
which is used to restrict the allowable viewing
duration of “rented” video content and the ability
to transfer the video to different computers. In the
case of protected HD video downloads, HDCP
support is required on any device that is playing
the video. Therefore, a display with digital video
inputs must support HDCP, if a user expects to
connect a computer to it and play downloaded
commercial HD content.
For more information on HDCP,
see Extron’s white paper at
www.extron.com/hdcppaper
www.extron.com
23
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