HDTV development may include compatibility with other displays

Last month, some Federal Communications Commission administrators went to the Massachusetts Institute of Technology to check how MIT’s digital video efforts were coming along.

As a conversational aside, the FCC folks commented that each of the contenders for the high-definition television (HDTV) standard was saying it was “the most compliant” with the specifications of the Committee on High Resolution Systems (COHRS); that is, it seemed, everyone’s proposals were interoperable, extensible and scalable.

The FCC folks also wondered aloud if the most general of HDTV standards, that for a universal header/descriptor, could be ready by the end of the year so it could be incorporated into the FCC’s consideration.

The universal header. What is the header/descriptor and why is it so important? Here’s an example from the communications world: When you make an ISDN phone call, complex descriptors called “compatibility information” identify the call as either telephony, fax group 2/3 or 4, videotex, telex, X.400 (electronic mail), Open System Interconnect (OSI) applications or, perhaps soon, video.

The computer world calls such descriptors “emulations,” as in “terminal” or “look-and-feel” emulations. But all such descriptors require additional processing power. In the world of high-resolution systems, such complex descriptors or emulations for each connected device greatly increase processing requirements.

Headers would identify the variable channel rates and compression ratios being used for digital video, as well as what version of PAL, SECAM or NTSC is being transmitted, and the different transfer functions — such as contrast and color lookup curves –that each HDTV format uses.

Fast results. If this had been a normal standards effort, with reams of material and interminable international meetings stretching over years with little real effect, the FCC’s request for such a specification by year’s end would have been laughable.

But the header/descriptor group, which began in early 1991 as the idea of Dave Staelin of MIT, Gary Demos of DemoGraFx and Branko Gerovac of Digital Equipment, comes out of the experience of COHRS Systems). COHRS members gather regularly at major trade shows — as much to meet each other and pass information as to do standards work — and almost all its work is done via electronic mail over the global Internet and a monthly conference call. As a result, members were able to deliver some general agreements in little more than a year.

Vast potential. Although what’s called the “FCC HDTV tests” are a driving force for the header/descriptor task force, other fields also must be included, such as computer graphics, scientific visualization, medical imagery, computer-aided design and military displays.

The results of this work will be flexible and abstract. All concerned hope that the open nature of the standards-development process will give the header/descriptor specification a good chance to be universally applied to these fields as well as to HDTV. If it is, the potential of interoperable, modifiable digital material will be much closer to reality.

Perhaps even more important, if this open process — using Internet and audio conferences as the main means of transferring information, articulating concerns and generating dialogue — is adapted to other projects, the entire process by which standards are developed could change.

- Tom Hargadon