HOW is it that we are able to become emotionally involved in a film on TV, yet find video conferencing and CD-Rom images alien? Children complain of "blocky" CD images, and we might detect that jerky motion as the football streaks across the screen. Where has the reality gone?

We start with 100 per cent reality, and then we make it digital. But this is not the problem per se, for the digital form ensures longevity and almost perfect reproduction, independent of transmission distance and storage time. The reality disappears in a quest to squeeze more and more information into fixed pipes and storage volumes. When bandwidth and storage are expensive, it is sensible to compress the signal. However, when optical fibre and CDs are plentiful, then so is bandwidth, and we can afford to transmit and store signals at much greater bit rates and in more detail.

Reality degradation is perhaps most evident in today's video-conferencing terminals. These are remarkable pieces of electronic engineering that present reasonable images transmitted over ISDN circuits at 128k bps or higher. They allow telemeetings across the planet that are effective for many business, medical and educational applications, but you would not try to court a lover on this medium. He or she would appear inhuman, devoid of appeal, a mere facsimile presented on the wrong scale, in a blocky, distorted manner, and off-colour.

So far, a solution for lifelike display has eluded us and we need something revolutionary beyond the paradigm of television

It is extremely difficult to sell someone a car or propose marriage when your eyes are perceived to be looking over the top of his or her head. Eye contact, gaze awareness and body language are all important for effective human communication. Real-time movement - co-ordinated hands, eyes and voice - is also vital for realism. Interestingly, high-quality sound creates the illusion of enhancing the visual image in the human mind, a fact that has been neglected in telecommunications

but not by Hollywood.

Digital compression to save bandwidth brings with it a processing delay that is increasing rapidly. A single photon can now traverse the planet on an optical fibre in a shorter time than it takes a GSM phone to convert a speaker's voice into a digital signal. Perversely, switching and routing systems now add to this problem, with uncontrolled delays necessary to efficiently pack all time slots and save bandwidth. When your image and your voice arrive late, become detached, have an unreal jerky, blocky quality, and you sound as if you are talking down a cardboard tube, communication suffers.

Until we create wall-size screens with daylight brightness and high contrast, we will continue to put up with the slog of travelling to meetings in person. To really make a dent in the number of people travelling, and slow the damage to our environment, we need to overcome the limitations of coding, bandwidth and display technology.

Optical fibre and storage systems can provide sufficient bandwidth for the accurate reproduction of sound and visual images. But so far, a solution for lifelike display has eluded us and we need something revolutionary beyond the paradigm of television. Perhaps we have to wait for the holographic projector to realise that true sense of being there.

Until then, we will either have to travel or try to become emotionally involved with blocky, nasal and artificially distant beings.

Peter Cochrane holds the Collier Chair for the Public Understanding of Science & Technology at the University of Bristol. His home page is:
http://cochrane.org.uk