Television, Digital and High-Definition Systems

The term ‘‘high definition’’ was first applied to television in the 1930s to compare all-electronic analog television (TV) systems with the older and partially mechanical systems then still used experimentally. Regular television service as inaugurated by the British Broadcasting Corporation (BBC) in 1936 (using 405 scanning lines) and in the U.S. in 1941 (525 lines) was often termed ‘‘high definition,’’ as was a Dumont experimental system of 1939-1940 that briefly achieved 800 lines. Decades later, however, the term came to mean something quite different.

Originally restricted to analog technology, highdefinition (usually defined as greater than 1,000 scanning lines, roughly equivalent to 35-millimeter film quality) television development focused on digital methods after 1990. By the early twenty-first century, however, a multiplicity of digital television technical standards appeared more likely than world agreement on any single approach.

Digital television was thus following in the footsteps of analog, where in the 1960s three different color TV systems developed more for economic and political than technical reasons: NTSC, National Television System Committee, from the U.S.; PAL, phase alternative (or alternating) line, from Germany; and SECAM, sequential colour avec memoire, from France.

HDTV Origins. Modern era high-definition television research began in Japan in the late 1960s as Nippon Hoso Kyokai (Japan Broadcasting Corp.) engineers sought to improve on the NTSC 525-line standard. This effort expanded into full-time research into both video and audio aspects of an improved system about 1970.

The resulting 1125 scanningline analog ‘‘Hi-Vision’’ system was first demonstrated to American policymakers in early 1981, four years after American engineers had also begun to investigate HDTV’s potential. Interlaced scanning and field or frame standards matched existing NTSC practice, but the picture’s aspect ratio was widened to 16:9 rather than NTSC’s 4:3 (to better approximate telecasting of widescreen motion pictures), and multiple sound channels were digital.

Because the highly complex HDTV signal would require the equivalent of six (later four) NTSC 6-megahertz channels to transmit, however, Hi- Vision was designated for production and not transmission.

Concern over the likely high cost of any highdefinition system led to development of several analog alternatives—dubbed ‘‘advanced’’ or ‘‘enhanced’’—which, providing far fewer than 1,000 scanning lines, would require less spectrum space while still offering improved picture quality.

Major U.S. manufacturers and trade associations established an Advanced Television Systems Committee (ATSC) in 1983 to coordinate American research efforts and conduct comparative tests. Some proponents argued for a gradual transition to HDTV through these intermediate systems. Research continued into developing HDTV systems that could be ‘‘downward compatible’’ (receivable in lower-quality analog form) on existing NTSC sets to ease the introduction of HDTV.

Several European countries had by the mid- 1980s begun cooperative development of analog HDTV technology based on their 50 hertz electrical standard, seeking to avoid acceptance of a Japanese system, imports of which might wipe out their domestic consumer electronics industry as had happened earlier in the U.S.

Europe soon focused on perfecting the MAC (multiplexed analog components) family of transmission standards. The Japanese concentrated increasingly on their MUSE (multiple sub-Nyquist sampling encoding) transmission standard which applied signal compression to force HDTV into only 8.1 (later 6) megahertz of bandwidth, thus making a broadcast service more likely. Both European and Japanese efforts focused on satellite-delivered HDTV, bypassing bandwidth-limited broadcast stations.

Faced with substantial industry pressure not to pursue a satellite option, however, the U.S. focused more on a terrestrial broadcast service when the U.S. Federal Communications Commission issued its first inquiry concerning advanced modes of television in mid-1987. The FCC also soon made clear its preference for a true HDTV system, bypassing intermediate ‘‘advanced’’ or ‘‘enhanced’’ stages. What then appeared imminent, however, took more than a decade to even begin to achieve.

Digital Breakthrough. In mid-1990, General Instrument transformed the HDTV picture by announcing computer models of a proposed fully digital system (‘‘DigiCipher’’) of high-definition television. Practical models were soon being tested in laboratories. Under industry and FCC pressure, several competing digital HDTV proponents merged the best parts of their systems into a so-called ‘‘Grand Alliance’’ in 1993 as laboratory and field testing continued.

The FCC allotted an additional channel to each on-air station to encourage development of HDTV parallel to continuing analog transmissions. In late 1996 the commission adopted the Grand Alliance system as a formal set of standards. No less than 13 different video scanning modes were included, ranging from 480 to 1080 lines, and allowing either interlaced or progressive scanning. Agreement was reached on use of the MPEG-2 (Motion Picture Experts Group-2) set of compression tools to condense the HDTV signal by a ratio of 55 to 1, allowing it to fit into the 6-megahertz (8- megahertz in Europe) channels presently used for analog service.

In Europe, cooperation on what had become known as the D2-MAC standard collapsed early in 1992 for lack of sufficient demand and the expense of introducing the system. Growing European satellite television success was based on existing analog formats, further undermining the attempt at a continent-wide digital standard. Faced with the digital transition elsewhere, Japan reduced its backing of analog MUSE, despite the fact the system was in regular NHK operation (though to few receivers given their very high cost) and commenced active work on a digital system.

Japan’s introduction in 1991 of regular analog HDTV service (transmitted eight hours daily from a domestic satellite) was the world’s first. Scheduled HDTV first aired in the U.S. when WRAL-TV (Raleigh, NC), began a limited but regular digital HDTV service five years later. Other stations slowly followed, most of them transmitting only a few hours a week. Costs of converting a station’s facilities to full digital HDTV operation ranged up to $10 million or more. Stations in the ten largest markets began offering a few HDTV hours weekly in November 1988 and the system’s use slowly expanded to smaller markets. By FCC rules, all stations were to be providing at least some HDTV service by May 2002.

Complicating the digital TV picture, American broadcasters by the turn of the century had become increasingly interested in an application of digital television that promised more immediate rev- enue—the ability to transmit four or more ‘‘standard’’ (or slightly degraded) NTSC channels rather than a single high-definition signal.

They argued that this would avoid the huge expense of HDTV conversion (which showed little promise of creating additional industry revenue) while allowing broadcasters to better compete in a multichannel environment. In Europe and Japan, ‘‘enhanced’’ definition TV services were available by the late 1990s. Still, by 2002 it was increasingly clear that widespread use of HDTV would take far longer than proponents had earlier projected—easily another decade or more would pass before existing analog systems could be turned off.

Part of the delay and confusion is because, contrary to widespread opinion even within the industry, there is no single digital television standard for either production (there are actually thirteen) or transmission (where there are five, two of them for high-definition service). Another problem is confusion over nomenclature—when does high definition really mean high definition.

Different players are pursuing different HDTV strategies using different standards, helping to confuse the marketplace. Finally, the cost of receivers (in the aggregate, far more costly than the industry’s conversion costs) are off-putting to many would-be set buyers. Prices still averaged $3000 early in 2002 (though down from ten times that level a few years earlier). This last point means that ‘‘downconversion,’’ or the ability of existing analog receivers to receive (with a conversion box) at least a semblance of ‘‘lower’’ definition television, is a hugely important aspect of what is now clearly going to be a slow transition.

Still, the promise of digital high definition remains strong. While the analog systems of today provide a video image made up of about 210,000 pixels (individual picture elements), digital HDTV images provide ten times that number. That image can be formatted in either a standard (three units high by four units wide) or wide-screen (nine high by sixteen wide) frame.

The latter is closer to theatrical film’s format, and thus avoids having to use either letterbox (leaving gray bars above and below the film) or pan-and-screen (editing the picture to better ‘‘fit’’ the television screen) techniques when showing films on television. A major controversy in developing digital standards has been whether to continue the use of interlaced picture scanning (standard in analog systems), or adopt the progressive scanning used on computer screens.

The latter is better in many ways (smoother transitions and generally more capable), but requires more bandwidth. U.S. policymakers have allowed the use of either mode, leaving the eventual decision to individual broadcasters. This may force the manufacture of television receivers able to do both, at greater expense than a clear FCC standards decision one way or the other.

Finally, the approved audio standard for digital television— the five-channel Dolby Digital (AC-3) surround sound system—compresses 5.1 channels of audio to a 640 kilobytes per second stream. While sophisticated, most current television production and transmission equipment cannot adequately handle it and some time will pass before consumers can receive the full advantage of this system.