It's a High-Definition World
by Bernard J. Lechner
This issue of Information Display magazine is dedicated to High-Definition Television (HDTV). The transition from analog 525-line NTSC television to HDTV is now in full swing. Today, most prime-time programs and almost all major sports programs are being broadcast in HDTV, and analog terrestrial broadcast of NTSC television is scheduled to be shut down on February 17, 2009. According to the Consumer Electronics Association (CEA), as of July 2007, 32% of American households had one or more HDTV receivers and that penetration will rise to 36% by the end of 2007.
The current version of HDTV is the result of a process that started in Japan during the 1970s. I say "current version" because the 441-line black-and-white television system introduced at the New York World's Fair in 1939 was referred to as "high definition" and indeed it was compared to the 120- and 240-line experimental systems of the earlier 1930s. There will certainly be a future version of HDTV; in fact, Nihon Hoso Kyokai (NHK), the Japan Broadcasting Corporation, demonstrated a 4320-line Super-Hi-Vision system during the National Association of Broadcasters (NAB) convention in Las Vegas in 2006 and again in 2007.
I first saw the predecessor to the current HDTV system when I visited the NHK Laboratories in Tokyo in 1979, where Dr. Takashi Fujio demonstrated the 1125-line analog HDTV system for me. The camera occupied an entire room. It was built on a large optical bench and could not pan or tilt. A CRT-based projection display was in the next room. NHK had just received the first 5:3-aspect-ratio direct-view CRT made for them by Matsushita. My recollection is that the diagonal was about 20 in. I was quite nervous about the tube since it did not have an implosion band and was out in the open, unprotected, on a lab bench. The following year, NHK demonstrated the 1125-line system in the U.S.
The ball really got rolling in the U.S. in 1987, when the Federal Communications Commission (FCC), responding to a petition from the broadcasters, issued a Notice of Inquiry (NOI) concerning the adoption of new standards for terrestrial broadcast that would permit an Advanced Television Service (ATS) to be established. Later that year, the FCC created an Advisory Committee on Advanced Television Services (ACATS) to gather information on possible systems and to recommend a standard to the FCC. The process took 8 years. ACATS voted on November 28, 1995 to recommend that the FCC adopt the Advanced Television Systems Committee (ATSC) standard.
Quite a bit happened along the way. What started out to be an analog HDTV-only system became an all-digital system that accommodated standard-definition video and multicasting as well as HDTV. The 15 organizations that originally proposed 21 analog systems were whittled down to the seven members of the so-called "Grand Alliance" that was responsible for the final digital system specification. After the ACATS recommendation, it took more than a year before the FCC adopted rules on December 24, 1996 that included all but Table 3 of the ATSC standard. By omitting Table 3, the rules – which are the law of the land today – do not establish requirements on the video-compression format, i.e., frame rate, line count, pixel count, aspect ratio, and whether the scanning is interlaced or progressive. Each broadcaster is free to choose these parameters as he sees fit provided that he broadcasts one program that is "at least comparable in resolution" to that of NTSC. Fortunately, the broadcasters and the receiver manufacturers agreed to voluntarily adhere to the ATSC Table 3 formats, and the broadcast community has settled on a limited number of its 18 formats. Some broadcasters use 720 lines progressively scanned (720p) and others use 1080 lines interlaced (1080i) for transmission of HDTV.
In the 10 years since the FCC adopted rules for digital broadcasting, there has been a major sea change in the television industry. Direct Broadcast Satellite delivery has become a major factor. Cable TV systems have been transformed from all-coaxial cable to hybrid fiber-coaxial cable with increased bandwidth and carriage of many programs, including HDTV, in digital form. The venerable CRT has virtually disappeared from the market, its place taken by large LCDs, plasma displays, and microdisplay-based rear projectors. Moore's Law has increased the capabilities of integrated circuits to the point where very sophisticated digital-signal and image-processing capability is routinely built into consumer television receivers. For this special issue, we have assembled four articles written by experts who are highly qualified to address some of these important aspects of the current transition to HDTV.
In our lead article, Walter Ciciora, a well-known consultant with a long and distinguished career in television, observes that the transition to HDTV has been accompanied by many other changes in the way television programming is delivered and watched. The convergence of communications and computing has enveloped television, increasing the number of ways in which television is transmitted and the number of devices to which it is interfaced. Not only are there myriad new hardware interfaces, but, as Ciciora points out, the human interface between viewer and screen has changed too, creating new business competition between program deliverers and receiver manufacturers for control of the gateway to the consumer.
Flat-panel displays have taken over the HDTV receiver display market at screen sizes up to about 42 in. on the diagonal, with LCDs and plasma displays battling fiercely for market share. HDTV pictures, however, are best appreciated on a larger screen. At a typical home-viewing distance of 9 ft., HDTV resolution matches the human visual system at a screen diagonal of 60 in. or so. At screen sizes of 50 in. and above, microdisplay-based rear-projection television (MD-RPTV) receivers currently have a significant cost advantage over LCD and plasma TV, but are they thin enough to compete with the flat panels? In our second article, Arthur Berman and Matthew Brennesholtz of Insight Media review both the technological and business issues of thin MD-RPTV receivers.
Every HDTV receiver sold contains a format converter. The ATSC standard allows 18 (actually 36 if the 0.1% NTSC offset is included) different video formats to be transmitted. The 18 combinations include three frame rates (24, 30, and 60), four raster formats (480 x 640, 480 x 704, 720 x 1280, and 1080 x 1920), and a 16:9 or 4:3 aspect ratio. Both interlaced and progressive scan are included. Whatever format the broadcaster chooses to transmit must be converted to the native format of the display in the receiver. Until recently, the most common HDTV receiver display format was 720 lines progressively scanned (720p) at 60 frames per second (fps), but this is rapidly changing to 1080p at 60 fps, which, interestingly, is not one of the 18 ATSC transmission formats. Our third article by Larry Pearlstein and his colleagues at Advanced Micro Devices (AMD) presents the current state of the art in three important areas of the format-conversion process: de-interlacing, frame-rate conversion, and super-resolution.
Since 1993, the development and maintenance of digital television broadcasting standards, including HDTV, in Europe has been carried out as part of the Digital Video Broadcasting (DVB) Project. The DVB Project is an industry consortium with over 260 members and is governed by a Steering Board and a General Assembly. The final article in this special issue, written by Dietrich Westerkamp of Thomson, who is a member of the DVB Steering Board, begins with a concise history of the HDTV developments in Europe prior to the creation of the DVB Project. The article continues with a description of the development of the DVB standards and the introduction of HDTV broadcasting by satellite, and the article concludes with a summary of the current rollout of terrestrial HDTV broadcasting in Europe.
I hope that you find this special issue on HDTV both enjoyable and informative. Please join me, as your Guest Editor, in thanking our authors for their efforts in preparing the articles published in this issue. •