Special Report on Multimedia: Discs at the heart of a revolution: Patrick Gibbins examines the developments that are changing personal computing

COMPACT disc technology has succeeded in transforming the way we enjoy recorded music. The same basic technology also lies at the heart of a revolution in the world of personal computing. Because CD technology is digital it can be used to distribute different types of information including text, photos, motion video, software and, of course, digital sound.

The low cost storage capacity of compact disc combined with the power of modern personal computers has created a new medium for communication. Compact Disc Read Only Memory (CD-ROM) can be used to distribute large volumes of data in a form which can be instantly accessed by personal computer users.

A single disc can store over 550 million bytes (megabytes) of data. This is equivalent to 300,000 pages of printed text. It costs between pounds 1 and pounds 3 to replicate a CD-ROM disc, making it cheaper to distribute large quantities of data on disc than on any other media. The format of CD-ROM discs is standardised, which means that any player connected to a standard PC can read any disc.

The fact that CD-ROM technology is based on CD audio technology ensures the economies of scale in manufacturing which are necessary to keep down the cost of manufacturing drives and discs. But because CD audio technology was not engineered for fast access, early CD-ROM drives suffered from performance limitations. In the last few months several manufacturers have announced a new generation of 'double speed' drives which are capable of delivering the performance necessary for rapid transfer of data intensive information from the disc to the memory of the PC.

Improvements in drive performance, combined with dramatic progress in compression technology, mean that it is now possible to play quite acceptable digital motion video directly from a CD-ROM, without the addition of expensive hardware on the PC. Two further innovations have served to extend the capabilities of CD-ROM technology. CD-ROM Extended Architecture (CD ROM-XA) allows different types of data to be 'interleaved' on the disc. Interleaving is necessary to achieve synchronisation between pictures and audio played off the disc.

The second key technical innovation is Kodak's Photo CD, which is designed to record and store digital images at full photographic quality. It provides computer users with an easy and affordable way of transferring photographic images off film and on to the PC where they can be cropped, edited and combined with standard computer applications.

(Photographs omitted)