Specifications

Video Formats and Interfaces
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27
images and greater colour depth.
M
eanwhile, VESA (Video
Electronics Standards Association)
standards have brought structure
a
nd interoperability to a market
that was becoming a mixture of
competing and often incompatible SVGA graphics cards.
H
ere‘s a comparison of maximum resolutions with the various VGA
formats:
Format Max. Resolution
VGA (Video Graphics Array) 640 x 480
SVGA (Super Video Graphics Array) 800 x 600
X
GA (Extended Graphics Array) 1024 x 768
W
-XGA (Wide Extended Graphics Array) 1366 x 768
SXGA (Super Extended Graphics Array) 1280 x 1024
UXGA (Ultra Extended Graphics Array) 1600 x 1200
W-UXGA, WUXGA
1920 x 1200
(
Wide Ultra Extended Graphics Array)
VESA also developed the DDC (Data Display Channel) standard,
which has made VGA plug-and-play by defining a physical
communication channel between the graphics card and monitor. This
allows the graphics card to automatically select appropriate display
settings using information from the display device.
Graphics cards supporting the SVGA standard and higher are usually
capable of supporting a range of resolutions, allowing backwards
compatibility with lower-resolution display technologies.
Connectors for Sun
®
systems
New Sun computers often have VGA graphics adaptors for
interoperability with PC hardware, but older Sun machines have 13W3
video connectors that carry analogue red, green and blue signals with
composite sync (unlike VGA which
uses separate sync signals). Multi-
ple resolutions are supported and
the resolution used is determined
by ID bits that signal the monitor’s
capabilities to the interface.
Several other computer types
also use 13W3 video connectors including IBM Power PCs and Silicon
Graphics
®
computers, but the pinning of these connectors and the way
the sync signals are transmitted differs between manufacturers.
DVI
DVI was created by the DDWG (Digital Display Working Group), with
DVI 1.0 being realised in April 1999. DVI was created to accommodate
both analogue and digital interfaces with a single connector. A single
DVI link operates at up to 165 MHz, so the image can be displayed at
1920 x 1080 at 60 Hz on a digital flat-panel display. And with a dual-link
channel, resolutions of 2560 x 1600 can be achieved.
There are three DVI standards, and it’s important to understand each
when selecting DVI equipment and cables:
DVI-D—This digital-only interface provides a high-quality image
and fast transfer rates. All signals from PCs are digital, so a purely digital
video channel means no signal degradation is introduced though
digital-to-analogue/analogue-to-digital conversions. This connector type
is still relatively unusual because of the lack of backwards compatibility
with analogue displays.
DVI-A—This high-resolution, analogue-only standard provides
improvements over standard VGA formats, but because of the digital-to-
analogue conversion process, does not deliver the picture quality of
Digital DVI. This connector type is very rarely found on equipment.
DVI-I—DVI-I supports either an analogue-to-analogue connection
or a digital-to-digital connection
and is the most common DVI
connector currently in use. It can
be used with adaptors to enable
analogue connectivity to a VGA or
DVI-I display or digital connectivity
to a DVI-D display. You can achieve
the best picture quality by using a digital DVI display with a Digital DVI
video source.
HDMI—High-Definition Multimedia Interface (HDMI) is the first
digital interface to combine uncompressed high-definition video,
multichannel audio, and intelligent format and command data in a
single cable.
The HDMI standard was introduced in December 2002, and HDMI
1.2 was released in August 2005. HDMI is supported by many leading
consumer electronics manufacturers, motion picture studios, cable
p
roviders and satellite services.
The HDMI connector is compact and is somewhat similar to a USB
connector.
U
se this serial interface to connect audio/video equipment, such as
DVD players, a set-top box and A/V receivers with an audio and/or
video monitor, such as digital TV over a single cable. HDMI works with
standard, enhanced, and high-definition video. It has a bandwidth of
up to 5 Gigabytes per second so it supports all HDTV standards and has
bandwidth to spare for future applications.
What's more, HDMI is backward compatible with DVI equipment,
such as PC's, TV's and other electronic devices using the DVI standard.
The DVI device simply ignores the extra data.
HDMI offers significant benefits over older analogue AV
connections. It provides superior video and audio clarity because there's
no signal loss from digital-to-analogue conversions. It supports
resolutions of 1920 x 1080 and multiple audio formats from standard
stereo to multichannel surround sound. Plus, it provides two-way
communication between the video source and the digital TV, enabling
simple, remote, point-and-click configurations.
HDMI is emerging as the connection standard for HDTV and the
consumer electronics market. Because HDMI transmits all signals over
one cable, it's quite desirable for home cinema electronics and systems.
It greatly simplifies the installation of home entertainment systems by
eliminating the tangle of cables running behind the system. It's also very
cost effective because only one cable is needed.
D
VI-D male
DVI-D female
V
GA female
13W3 female 13W3 male
HDMI connector
See pages 22 & 23 for a selection of
HDMI products including switches,
splitters, converters and extenders.