Sound and vision

With the Internet gaining new users at the rate of thousands per day, there is an increasing hunger for information about it.

Many people newly hooked up to the Internet use it for entertainment rather than business. But business and academic users are becoming more sophisticated in their needs. This has resulted in a move towards more variety in the material which can be delivered via the Internet, including sophisticated graphics, speech, music and video.

A commercial music distribution system via the Internet is being set up by Cerberus in the UK, which will allow users (who have first registered and been given special 'player' software) to download encrypted sound recordings and play them on their PCs.

This may suggest that there will be a rapid increase in music and video on the Net. However, there are still technical problems to overcome before it is possible to download full-motion video via PCs.

The main barrier to video on the Internet is the amount of space the material takes up when in digital form. Even today, a standard PC is only likely to have a hard disk which can carry about 500Mb of data. A standard music CD carries the equivalent of 650Mb of data. Video takes up much more space. A single minute of full-motion video takes up about 50Mb of space so a two-hour feature film requires 6,000Mb, or 6Gb.

However, storage is not the main problem. Communication via the Internet depends on standard telecomms systems. The telephone lines which form the 'pipes' to carry the traffic on the Internet are very small relative to the amount of data to be transferred. A standard Internet connection can only carry 64Kb at any one time. Trying to push standard full motion video in digital format down this is rather like trying to empty an Olympic-sized swimming pool through a hole made with a pin. A feature film would take about 2 months to download.

However, if everyone is trying to download huge quantities of data via the Internet, the network would quickly clog up with all the traffic.

Before transfer of sound and video via the Internet becomes commonplace, a faster method of data transfer will have to be found.

This is on its way. Increasing sophistication in telecomms networks will provide more bandwidth across which video can be transmitted. A fibre optic ISDN line can carry a vast amount of data which a normal copper-cored cable cannot.

Software engineering is also coming up with increasingly sophisticated algorithms to compress data into smaller packages, so it can be transmitted in compressed form and decompressed for use at the other end.

This has already allowed the transmission of limited motion video in real time via the Internet, even if it does appear a bit jerky, because there are considerably less frames per second than normal video.

Compression techniques are starting to reach the stage where it is possible to transmit full-motion video in real time across normal cable, although as this means a two-hour film will still take two hours to download, the technology still needs to advance before downloading significant quantities of sound and video over the Internet is a realistic commercial possibility.

It will not be long before it is commonplace to download records and films on to computer, rather than buy them from shops.