Digital Video Discs are the Next Big Thing. But don't expect to find one under the tree this Christmas. Steve Homer reports
By this time next year you could well be thinking of side-lining your VCR and buying a shiny new DVD player. This moment of buying frenzy was supposed to have hit the shops this year. Industry squabbles have held back the launch of DVD, but nothing seems likely to stop this technology revolution for long.

The Digital Video Disc looks so much like the next "Big Thing" that just about every major hardware and software company in the world wants to jump on the bandwagon. DVD will not just revolutionise the sitting-room. The implications for the computer market, both domestic and business, are huge.

DVD uses CD-sized discs to store more than two hours of studio-quality video and sound. The discs can have two sides and, more cleverly, each side can have two layers, with the laser reader focusing through the first layer. That means over eight hours of superb-quality video on one tiny, easy-to-store disc.

Each disc can have up to eight soundtracks and 32 subtitle tracks. But DVD's cleverness does not stop there. There is a system for storing multi- camera-angle filming. So a concert could be filmed with one camera on the whole orchestra, another on the conductor, a third on the soloist and a fourth on the audience. When you played back this title, you would be able simply to jump between cameras instantly. In sports, this has obvious rather amusing applications as well. More seriously, there are many educational and training applications for this clever technology.

DVD has other tricks up its sleeves. While normally companies will go for the highest possible image quality, the technology will allow longer programmes of lower picture quality. Typically, DVD programmes will be recorded at around 4Mb per second, allowing over an hour of video to be stored on each layer. Lower bit rates down to 1.5Mb per second, as used in current video CDs, will allow some eight hours to be stored on each layer.

More far-reaching is the ability to store computer material, such as a Web browser or Web browser plug-in, on film or other video disc. As well as DVD players for the sitting-room, the computer industry is panting to launch a CD-Rom variant of DVD called DVD-Rom. DVD-Rom discs will store 4.7 gigabytes on a single layer with 8.5 gigabytes on a dual layer - that's some 13 times as much as a standard CD-Rom today.

By mixing a little DVD-Rom information on to a Digital Video Disc, the studios realise they will be able to include merchandising information to encourage you to see more of their products and to buy related material. All for next to no cost.

So if DVD is so wonderful, what is holding it up? Until the spring of this year, everything was going fine for the planned launch in mid-1996 in Japan and the US, with Europe due to follow this Christmas. But then the Hollywood studios decided they wanted not only copyright protection to help control bootlegging of their discs, but they also wanted regional coding. Regional coding means that discs intended for one region will not play on DVD players in another region. Well, that's the theory.

The consumer electronics companies, and especially the CD-Rom manufacturers, hate regional coding. It means they have to know exactly where their products are going at the time of manufacture. Fine in theory, but products intended for one market are often diverted to satisfy demand in another. Initially, the studios had asked for dozens of different regions, but the manufacturers and studios have now agreed on just six regions. This should make life a lot easier.

But for the CD-Rom manufacturers this is still a nightmare. Typically, they have manufactured 10,000 CD-Rom drives in Japan, shipped them to the UK, sent some of them off to Germany, some to Poland and some to Argentina. Regional coding makes such distribution unworkable. Hence the grumbles in the DVD world are from the CD-Rom manufacturers and not the Hollywood studios, which seem to have pretty much got what they wanted - for the moment, at least.

"I really don't think regional coding will last more than a year or two," said a senior executive from a major European manufacturer at a recent DVD forum in Brussels. "I think there will be too many problems, and even the studios will start to find it troublesome."

Despite a lot of flak, however, the studios are hanging on to regional coding like grim death. "It allows us to protect a release schedule," says John Powers, director of marketing for DVD at Warner Home Video. "We are still going to want to have theatrical windows and so on. And we will not own rights for properties in certain territories."

If the last few arguments can be sorted out, DVD could still launch in a limited fashion in Japan by Christmas. It may launch in the US as well, but it looks almost certain that the real push for DVD will not come until next year.

However, the DVD that launches will not be the final form that will eventually sweep the market. The early version will be a read-only model costing around pounds 500 to pounds 800. This machine will be ideal for people who use their VCR mainly to watch rented videos. But DVD will really take off when a recordable version is launched, which may not be until 1998 or, judging from past form, 1999.

This will be a convenient digital replacement for the VCR. DVD will revolutionise home entertainment. With 13 times the capacity of a CD-Rom, DVD-Rom will similarly revolutionise the PC. It is exactly what multimedia has been waiting for.

Steve Homer is the BT Newspaper Technology Journalist of the Year.