ATV alliance bends on display scan rift

Electronic News, July 5, 1993 by Jack Robertson

WASHINGTON--The Advanced Television (ATV) Grand Alliance has acceded to TV set maker demands and backed off from its original plan to require all 34-inch and above sets to use only computer-like progressive scan displays, the consortium revealed last week. The FCC Advisory Committee Technical Subgroup was told the Grand Alliance now believes barring current TV interlace scan displays from the larger size sets "may not be appropriate."

Further Grand Alliance differences on scanning formats came to light when the FCC Advisory group was told one of the consortium's five partners--the Massachusetts Institute of Technology's Advanced Television Labs--continues to register "a minority position" opposing any use of interlace scanning at all in the new ATV (formerly HDTV) standard being developed.

The scanning format has erupted as one of the most controversial areas of the new combined ATV system being put together by the Grand Alliance of the original contenders: an AT&T/Zenith Electronics team, a General Instruments/MIT team, and a group consisting of the David Sarnoff Research Center, Thomson Consumer Electronics and North American Philips (EN, May 31).

MIT and a bevy of U.S. computer firms want progressive scan mandated for ATV sets to handle interactive and multimedia displays that suffer in interlaced displays. By contrast, TV set makers want to prolong the use of interlaced displays they now use.

As a compromise, the Grand Alliance originally proposed making both interlaced and progressive scanned displays an option in TV sets under 34-inch size, but mandating only progressive scan in the larger size sets.

Japanese TV set makers especially questioned the exclusion of interlace scanning from large size HDTV receivers. Japan has been concentrating HDTV efforts on large size sets--almost totally with interlaced scanning. Laurence Thorpe, Sony America vice-president of production technology, wrote the FCC advisory panel that the Grand Alliance proposal "would appear to fly in the face of historical precedent, which generally leaves receiver performance and features to the dynamics of a competitive marketplace."

The foreign opposition to progressive scanning is in contrast to U.S. computer industry arguments that this scan mode would give American companies a competitive edge in the new ATV market. Rep. Edward Markey (D., Mass.), chairman of the House Commerce telecommunications subcommittee, suggested in hearings last month that foreign rivals entrenched in the older interlaced scan technology could be surpassed by U.S. firms which already have a major lead in progressive scanned displays.

The Grand Alliance last week tried to assure industry and government interests that their final ATV design "hasn't been set in concrete." Robert Rast, GI vice president of HDTV business development, told the FCC panel, "We're still in the development phase. The cake hasn't been baked yet." He said the group welcomed outside comments, as it tried to put together its final system design.

Scanning format isn't the only unresolved issue within the Grand Alliance, the FCC advisory group heard last week. Questions still remain on the video compression standard, which proposes a variant of the upcoming MPEG-2 standard. The Alliance has its own customized algorithm it hopes can be accepted as an extension of MPEG-2, and the group also does not use the "B frame" portion of MPEG because of the cost and complexity this could add to ATV receivers.

Other open issues are said to include how to migrate to higher line scans from the present 720 and 960-line format, using 59.95Hz or 60Hz frame rates, and total pixel counts of the lines.

The timetable calls for the Grand Alliance to have its final plan completed by September 30. That will be submitted to the FCC body to get a green-light to build the prototype that will go into testing next year. The Grand Alliance is now the only ATV concept being considered, since the FCC Advisory panel last week officially dropped the four original ATV proposals from consideration.

The Grand Alliance is now discussing what portions of the prototype each partner will make--in transport, transmission, video encoder, and video decoder. It is still undecided where these subsystems will be integrated into a total product to be tested. The group must also select from three contenders--Dolby, MIT or Musicam--to build the audio portion for the prototype.

Mr. Rast said the alliance expects to build and integrate its ATV prototype in nine months, which would be ready for testing by May 1, 1994. If the laboratory checkout is successful, the system would then go into field tests in Charlotte, N.C.