Science: The day of digital TV is dawning: Steve Homer charts the progress of technology that is going to give us clearer television pictures

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British viewers should be able to watch digital television next year. SES, the owner of the satellites used by BSkyB, and the European satellite operator Eutelsat are expected to start digital services then. Terrestrial services are likely to be some years away, however.

Digital seems to be the technology of the future. The CD, which contains music encoded digitally, has replaced the vinyl disc; the Digital Compact Cassette and Mini Disc are trying to replace the ordinary audio cassette (albeit with mixed success); and all the new mobile phone systems are digital. Most of the 'ordinary' phone system is now digital, and computers have never been anything else. There is even a digital video-recorder being developed that has the backing of Philips, Panasonic, Sony and Thomson.

Digital TV should be clearer and sets more economical. It will allow more signals to be fitted into a limited amount of frequency, and could offer the ability to send pictures in wide-screen format and different picture qualities, ranging from that of a VHS cassette to the very best high-definition image. With a digital system, broadcasters will have the flexibility to choose between more channels or better picture quality for the same amount of frequency band width. They will even be able to vary that during an evening.

But moving to the next generation of television has been a political nightmare. Until recently, the politicians

focused exclusively on high-definition television (HDTV), which did not necessarily need digital technology. Amid a great deal of hype, it was widely proclaimed that the public wanted television pictures of startling clarity. Commentators agreed that HDTV images would be wonderful but the early sets were bound to cost a lot - at least pounds 3,000. Private broadcasters, on the other hand, could see only a tiny market for HDTV and were not too keen on producing special programmes and setting up new transmission systems to service only a few customers. Last year the European Commission admitted defeat and the ill-fated European drive

towards an analogue system, called HD-MAC, was scrapped.

But perhaps organisations can learn from their mistakes. The whole of the European television establishment - private and public broadcasters, manufacturers, satellite operators, transmission organisations, cable TV companies, telephone companies, chip makers and others - sat down together and without political interference started speedily to define new services.

The Digital Video Broadcasting Group (DVB) started off as a closed group of about 10 companies formed by the German Ministry of Posts and Telecommunications.

'We started very clearly seeing that the future is digital and feeling that something needed to be done,' says Peter Kahl, chairman of the DVB's steering committee. 'We decided at an early stage that we had to keep it away from any regulatory influence,' says Mr Kahl, who is also director general of technical regulation at the Ministry of Posts and Telecommunications.

The European Commission had observer status from an early date. Sceptical at first, it watched as the organisation grew. Today, with more than 120 members from across Europe, the DVB is seen by the commission as the way forward. Members include broadcasters such as BSkyB, the BBC and Canal Plus, and manufacturers such as Thomson, Philips and Sony as well as regulators and programme distributors.

The DVB has already decided on standards for satellite and cable transmission, which are being considered by ETSI, the main European telecommunications standards organisation. The standard for terrestrial transmission is trickier and may not be ready to send to ETSI until the end of the year.

But digital television is not just a European phenomenon. In the United States, which started off the digital TV revolution, introduction is moving on apace. The mainly unregulated satellite and cable markets are furthest ahead. This month a 150-channel digital satellite service should be launched. The

cable industry is gearing up to launch digital services over the next few years. But the US has invested most effort in trying to get the best from its digital terrestrial service. The Federal Communications Commission (FCC), which regulates terrestrial broadcasting, is finalising the introduction plans and digital terrestrial broadcasting could start as early as next year. The only major market where the imminent arrival of digital television is more in doubt is in Japan. It was the Japanese who started the HDTV ball rolling. And it is only there that you can watch HDTV pictures on television every day. However, even before recession bit, the Japanese found it difficult selling their expensive HDTV sets. Earlier this year a senior official from the Japanese Ministry of Posts and Telecommunications hinted that Japan might abandon its analogue Muse HDTV strategy and pursue a digital approach. While the storm of protest drew a partial retraction, Muse's days are numbered.

As all pictures are made up of only 0s and 1s on digitial systems, a world standard for television transmission coold be possible. However, despite being widely trumpeted, this will not happen for many years.

'We can never have total uniformity between the 60Hz (as used in the US and Japan) and 50Hz (as used in Europe) television systems,' says Richard E Wiley, chairman of the FCC's Advisory Committee on Advanced Television Services and a former chairman of the FCC. 'But systems can be harmonised to minimise the differences.' Mr Wiley, who has long believed that analogue would be overtaken and has been trying to persuade Europe to abandon its analogue HDTV efforts, confirms that discussions have been going on between the FCC, the DVB and the Japanese to find what common ground is possible. His insistence on harmonisation has slowed up the introduction of the American digital system as he wanted to wait for a compression technology called MPEG 2 which will also be at the heart of the European system. Commonality, he says, will help programme exchange and should reduce the cost of components of digital televisions.

Even if the world divides into three camps for transmission standards, this need not be bad news for consumers or manufacturers. 'In terms of economies of scale, if you can't break even in Japan, the US or Europe on their own then you shouldn't be making TV sets, you should rather be making Swiss chocolate,' says Jean-Luc Renaud, president of the international communications consultancy Globalcom Ltd. He warns, however, of a big battle looming in the market for scrambled programmes. 'While the DVB wants a single-access system, the large companies like BSkyB, Canal Plus and others are backing their own standards and trying to persuade the DVB to carve up the market on language terms.' This, he says, could seriously hamper development of the market.