Life in An HD World
High-definition video. Those words represent a dream come true for everyone from video engineers and camera manufacturers to retailers and consumers. The idea of higher-resolution video images has been discussed, researched, debated, and tested since the 1930s, and finally came to fruition as part of a process that started 40 years ago in Japan.
Interfacing and Switching
Now comes the fun part–getting those HD images up on the screen. You'll need some sort of media player or converter box to take apart your transport stream and separate it into video, audio, and control packets. Once you get past the modulation system (VSB, OFDM, QPSK, QAM) or transport protocol (TCP/IP or whatever proprietary system is in use), it all comes out the same way.
Crestron Digitalmedia Switcher
There are a few reasons for this change. One is the addition of copy protection layers to digital interfaces used on consumer HDTVs, specifically through High Definition Multimedia Interface (HDMI) connectors. HDMI, which evolved from the older Digital Video Interface (DVI) standard, can carry video and audio, as well as control data, as fast as 10.7 Gbps (DVI is limited to display data only).
One thing that digital video interfaces bring to the mix is the ability to communicate with the video signal source and automatically setup the optimum display resolution and image timing parameters. This is done with Electronic Display Interface Data, a "handshake" between display and media player or computer. (In the language of HDMI, those are known as the sink and source, respectively.)
While HDMI wasn't really intended for the professional marketplace, it is now appearing on numerous LCD and plasma monitors and projectors. That can cause big problems for switching and distributing the signals, as the EDID connection typically works only with a direct connection from source to sink.
As a result, a new crop of EDID-friendly switchers and distribution amplifiers are now coming to market–and you'd better figure on using them to avoid problems with image dropout and lost connections. These interfaces can store EDID info from many displays and reflect it back to a source (or sources) to prevent them from shutting down or, in the case of computers, going into sleep mode.
EDID-friendly interfaces can also poll multiple displays that are being fed and determine the highest common display resolution that all can use, even as one or more display are powered down or "hot switched" out of the loop. Note that this "smart" EDID emulation and configuration ability applies to both HDMI and DVI signal connections.
How you choose to make your DVI and HDMI connections is up to you; conventional cables, ultra-long cables with repeaters, conversions to optical fiber, and even conversions to Cat-5 cables are all being used successfully. Just remember that digital data is agnostic about how it moves around–it only cares that it has enough bandwidth to get there.