DTV Format Issues: ATSC Chairman Robert Graves Defends 1080i Standard Against Computer Industry Claims

by Robert Graves, Chairman, Advanced Television Systems Committee
Sunday, March 29, 1998

A report in the February 23 issue of Communications Daily regarding Chairman Tauzin's recent West Coast trip raises several issues regarding the formats included in the ATSC Digital Television Standard.

Computer Interoperability

The report implies that Microsoft Chairman Bill Gates told Chairman Tauzin "that the 1080-line interlaced screen standard won't work with computer equipment "

Perhaps this report inaccurately quotes Mr. Gates, because this statement is absolutely false, unless a computer manufacturer purposely makes products that do not work with the 1,080-1 format. The ATSC DTV transmission standard supports several different video formats in order to give great flexibility to broadcasters, and it contemplates the use of TV receivers and computers that receive all of the formats that a broadcaster might choose. A receiver or computer is expected to render a viewable picture for any of the HDTV or SDTV formats that a broadcaster might send, even though it might actually display the picture in a different format that could show lower resolution.

The fundamental breakthrough that made the Digital HDTV Grand Alliance possible and permitted an industry consensus to gel around the ATSC DTV Standard was that multiple formats—both progressive and interlaced--would both be supported with effective performance at negligible added cost. Cost-effective means of providing this all-format decoding capability have been demonstrated.

Working with the Consumer Electronics Manufacturers Association, the ATSC has developed a certification program, whereby computers and receivers that render viewable pictures for all of the ATSC formats will be permitted to display a logo that gives consumers assurances that the product they purchase will never go black because a broadcaster sent a format that the device couldn't handle.

About one year ago, Microsoft, Compaq and Intel advanced a different proposal, urging broadcasters to limit themselves initially to a subset of the ATSC picture formats. They argued that broadcasters should only provide SDTV, and leave HDTV to be implemented years later, when it could be provided by transmitting a second layer of supplemental information to augment the SDTV data. (Their proposal did include one of the six HDTV formats contained in the ATSC Standard, but this format only supports 720-line film-based material, not 720-line video or any 1080-line formats. Moreover, their unproven layered coding approach had already been tried by the world's leading video compression experts and abandoned due to inefficiencies.) As far as I know, no broadcaster has ever endorsed this approach, because in my opinion broadcasters need a proven, tested system and fall HDTV capability in a DTV standard from day one in order to make a successful transition to digital TV.

Last December, Intel changed course, deciding to join with the great majority of manufacturers in supporting all of the ATSC formats, with Intel spokespeople saying its April 1997 proposal was "a smashing failure," and that broadcasters "had it right, while we had a naive notion" of the television business. (reference San Jose Mercury News article.)

(It's important to note that Microsoft and Intel are valued members of ATSC. Intel, in particular, is leading an intensive ATSC program to develop data broadcasting extensions to the ATSC DTV Standard.)

The issue of computer interoperability of the DTV Standard was hotly and repeatedly debated in the FCC's Advisory Committee and in the FCC rule making proceeding over a five-year period. The ATSC and the Grand Alliance filed extensive comments in the FCC proceedings, demonstrating conclusively that the ATSC DTV Standard fully meets the needs of broadcasters while providing tremendous interoperability with computers, better than any other digital television standard in the world.

The FCC finally resolved this issue in December, 1996 by accepting a compromise agreed to by those members of the computer industry who had been opposing adoption of the standard. Under this compromise, originally proposed by these computer companies, the Commission did not mandate any specific video formats in its standard, but left this issue to the marketplace. Now that the marketplace has spoken, and the industry is implementing DTV based on the complete, voluntary ATSC Standard adopted in 1995, the Congress must not allow itself to be used to overturn this industry consensus based on false claims and groundless concerns. (See the attached November 1996 letter to FCC commissioner Susan Ness in which these computer companies agreed not to oppose or delay adoption of this compromise by legislative or any other means.)

Demonstrations and DTV Formats

The report mentions side-by-side demonstrations of various DTV formats, and demonstrations being planned by the Subcommittee this month.

A few words of caution are in order about DTV demonstrations, especially those that attempt to compare different formats side-by-side. Such demonstrations are difficult to do correctly, because they are inevitably subject to a number of subtle factors that are unrelated to the formats but can nevertheless influence the perceived comparison. One of these factors is the quality of the displays being used. Some displays today are incapable of showing the full resolution available from the HDTV formats supported by the Standard. Until recently, there has not been a great motivation for innovation in television displays, because the analog NTSC standard did not provide any better resolution to display. With the HDTV formats in the ATSC Standard, all that has changed. There is now a powerful incentive for receiver manufacturers to differentiate their products by incorporating better displays that take full advantage of HDTV resolution. Both the 720 and the 1080-fine HDTV formats already provide significantly better resolution of any of the SDTV formats, even viewed on today's displays, but the perceived difference is also likely to increase dramatically over the next five years as display technology improves. It would be like driving by looking through the rear-view mirror to base format decisions entirely on today's display technology.

Ultimately, the spatial resolution of pictures is largely determined by the number of picture elements (pixels) in the displayed image. (The effective number of pixels seen at the display is less than the total number of pixels in the original image by a "Kell factor," which is .9 for progressively scanned images and. 7 for interlaced images.) The 1080-line progressive (1080-P) HDTV formats in the ATSC Standard (which can be used for material originally produced in film-like movies and about 80% of today's prime time TV programming) can display about 1.87 million pixels. The 1080-I HDTV format can support a display of about 1.5 million pixels, while the 720-P HDTV formats can support displays of about 0.83 million pixels. The 480-P SDTV formats can support displays of about 0.30 million pixels, while the 480-1 SDTV formats can support displays of about 0.24 million pixels. By comparison today's analog TV broadcasts can support displays of only about 0. 1 5 million pixels. Delivered picture quality is far more complicated than simple pixel counts available at the display, and current picture quality is often limited by the quality of consumer displays. However, these pixel counts make clear that HDTV formats offer potentially far better resolution than any of the SDTV formats. Side-by-side comparisons that show little difference between HDTV and SDTV formats wan-ant inquiry into what other factors unrelated to the formats might be operating to mask the differences.

This discussion merits a word about the definitions of HDTV and SDTV. Throughout the Advisory Committee process, the FCC rule making process, and the development and documentation of the ATSC DTV Stan@ the 720-line and 1080-line DTV formats were defined as HDTV, while the 480-line formats were collectively referred to as SDTV, even though some SDTV formats offer better resolution from others. Recently, some cable providers have violated this terminology by referring to "480-P HDTV." 480-P certainly offers better resolution than 480-1, and reasonable people can differ over the benefits of 480-P versus the HDTV formats, but it is an oxymoron under the definitions and terminology consistently used in the development of the Standard to refer to "480-P HDTV." (See the attached press release in which the ATSC recently reiterated these definitions.)

The genius of the ATSC Standard is that it supports multiple formats to give broadcasters a wide variety of options. ATSC supports all of the formats in the Standard, and does not favor one format over another. In the competitive marketplace, broadcasters will succeed or fail based on the quality of service they provide, and this will be affected by the formats and applications they choose to provide.

My personal opinion, however, is that within a few short years, consumers will demand full HDTV quality for sports and other popular programming and a broadcaster who does not offer full HDTV quality for these programs will be unable to compete against other broadcasters or other service providers who do. When viewers see the Super Bowl in HDTV, they will never want to watch it with today's resolution again. If free over-the-air television is to survive in the years and decades to come, I believe that broadcasters must rapidly upgrade their top programming to full HDTV quality. This has been the goal of Congress and the FCC over the past decade, and I urge the Subcommittee not to do anything that would jeopardize the rapid adoption of HDTV.