A few definitions of digital television

The term ‘digital' simply means that information is broken down into a series of 1s and 0s and put into a form that can be easily manipulated by the ever-speedier microchips that lie at the heart of every digital device. This distinguishes computers and their many subsequent offspring from older analogue media like film, radio, television and audio/video recordings as we knew them prior to 2000. Analogue media rely on a physical replica (or analogue) of a physical phenomenon, like sound or pictures, that can be transmitted or preserved through some kind of physical medium; whether it is magnetic signals on a tape, electronic waves transmitted through the spectrum, or chemical changes on a strip of celluloid. Digitization - in production, distribution and reception - transformed traditional media, starting in the mid-1990s: in satellite communications, in recording technology, in a new generation of television sets, in cable television, in radio and television broadcasting, and many more. Industrial convergence soon followed.

From compact discs (CDs) to digital audiotape (DAT) to digital video discs (DVDs) and smart VCRs (DVR and TiVo), from high-definition television (HDTV) to multiplexed digital television (DTV) to direct broadcast satellite (DBS) to YouTube, from video cell phones to iPods to satellite radio (XM, Sirius) - all these draw on various forms of industry convergence as well as digital technology. They threaten to break down the borders of older media, and challenge old structures of ownership, control, content and audience uses as well. They make some things easier - like sharing various forms of media across national and intellectual property barriers, and some things harder - like protecting privacy and figuring out who will pay.

The story of digital television begins in the 1980s with the development of what looked like the next big thing in television technology: high-definition television, or HDTV. This was a technology developed in Japan that promised to greatly improve the quality of the television image by increasing the definition, or number of scanning lines, of the picture, using analogue methods. It also rearranged the aspect ratio of the screen, from the boxy 4 to 3 ratio of traditional television to a more cinemascope-like 16 to 9, allowing movies to be shown on home television sets in their usual proportions, without cropping the picture or having to letterbox it. Japan became the first country to initiate regular HDTV broadcasts in 1992. The prospect of HDTV made a particular impact in the USA, which has always had a poorer quality television standard (NTSC) than most of the rest of the world, having settled for a 525-line picture - each television image is electronically scanned, back and forth, 525 times top to bottom - instead of the higher quality 625-line PAL standard prevalent elsewhere. But transmitting the Japanese MUSE standard highdefinition picture (up to 1,080 lines) required far more bandwidth than its NTSC equivalent - six times more than the standard US broadcasting frequency.

This meant that HDTV could not be broadcast over the television channels now assigned to US broadcasters; they would need a new, bigger frequency in order to successfully broadcast HDTV to the public. The public, meanwhile, would have to invest in new HDTV sets in order to receive such an image. By some reports, the interest of US broadcasters in HDTV technology was spurred by the prospect of the Federal Communication Commission's plan in 1986 to auction off a large chunk of the valuable UHF spectrum (never fully utilized by broadcasters) to mobile telephone companies. The National Association of Broadcasters, the leading industry trade group, appealed to the Federal Communications Commission (FCC) to hold off on letting the spectrum space go, since it would be needed if HDTV were to have a chance in this country. The US government, worried about Japanese domination of the electronics manufacturing industry, wanted to encourage the development of homegrown US high-definition technology, rather than becoming dependent on Japan. It agreed to reserve the UHF frequencies for television, if US broadcasters and manufacturers could come up with a workable competitive technology. But as US companies struggled to design their own HDTV device, the digital revolution overtook them. With new digital technology - homegrown in Silicon Valley - a much higher definition television picture could be produced, as good or better than the Japanese MUSE technology that had started the whole thing off. By 1993, US manufacturers had come up with the strategic Grand Alliance standard, representing a technical compromise between the competing needs of different industry segments that could handle a variety of digital high-definition formats with varying degrees of resolution, pixel density, frame rates and scanning methods. However, a funny thing happened on the way to the Grand Alliance: it dawned on everyone that, with digital technology, you can do many more things with that spectrum space than simply provide beautifully clear pictures.

One advantage of digital is that its signals can be compressed, so that it is possible to transmit up to six standard definition television signals (SDTV) in an existing broadcast frequency, all of them with as good or better clarity than existing television images (a single cable channel could carry 12 or more!). This was called multiplexing. Only if broadcasters wanted to opt for the highest density, richest definition picture possible did they need the spectrum capacity that the old HDTV systems had required; otherwise, the owner of a license to broadcast now in effect controlled six channels rather than one, an enormously profitable prospect. The US Telecommunications Act of 1996 laid out a plan to introduce HDTV (or multiplexed DTV) across the country over the next decade. Each holder of an existing television license was given, free of charge, a new channel assignment on the UHF spectrum large enough to be used for fully fledged HDTV. They would also be allowed to keep their old channels in the VHF band and continue broadcasting in analogue, since the transition to digital television would take a while; for many years, some consumers would only be able to receive old-fashioned, standard broadcast signals on their old sets. In return, broadcasters agreed to begin terrestrial digital broadcasting in 1998. By 2006 - by which time, it was assumed, HDTV sets would have reached 85 per cent penetration of US homes (an overly optimistic projection, it turned out) - broadcasters would have to return their old frequencies in the VHF or UHF spectrum to the federal government (to be auctioned off to fill treasury coffers).

This was called ‘digital switchover'. Many predicted that 2006 was far too early a deadline for television to convert entirely to digital, especially since consumer prices for HDTV sets in 2000 remained in the $4,000 range. But the big US networks, and several cable channels, began limited high-definition digital broadcasting as scheduled in 1998, and by the end of 1999 those in the top 30 markets had gone partially digital, even though few consumers had the ability to receive the signals. Cable television seized its broadband advantage and introduced digital cable in 1998, though mostly in multiplexed form - high-definition television would take longer. Satellite television (DBS) had begun transmitting digitally in 1994 and initiated high definition in 1998. The date for digital switchover in the USA was set for midnight on 17 February, 2009 (FCC). Digital television launched across western Europe in 1998 as well, both by satellite and by terrestrial (land-based antenna) distribution. Rupert Murdoch's Sky Digital satellite channels began transmitting that year, on top of its analogue DBS in existence since 1989. By 2001 it discontinued analogue and signed up its five millionth subscriber.

Terrestrial digital television rolled out in the UK in 1998, with six multiplexed services allocated by the Independent Television Commission to six different companies, including the BBC's Freeview service. Currently, over 50 channels serve the British public, most of them at no extra cost and many of them with interactive capacities. In the next few years most European countries would introduce the new technology and formats, spreading eventually around the world. Luxembourg became the first country to complete digital switchover, in 2006, with many others planned for 2007 and 2008. Digital switchover in the UK is planned for 2012.

A few definitions of digital television

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