Now, however, technology that can turn computer monitors into television receivers is making immediate access to live television an attractive and affordable option for many screen-based workers, from journalists and researchers to business executives.
Video cards - printed circuit boards that can be plugged into spare slots in the back of a personal computer - are available now for less than pounds 500, a price that puts them within reach of the mass personal computer market. The cards allow integration of live television, pre- recorded material or home video with computer processing power.
IBM, the market leader, is a good touchstone. Until less than two years ago, incorporating video into its personal computer required seven expensive cards, which kept this facility largely in the laboratory. In 1990, IBM, in conjunction with Intel, the chip manufacturer, reduced the number of boards needed to incorporate video to just two, bringing the cost of its digital video interactive (DVI) down to about pounds 3,500.
Less than a year later this had been further refined to one card, costing just over pounds 1,500, which allowed replays of digital video. A clip-on addition that converted the analogue signals used by ordinary television or video recorders into the digital form used by the computer cost just over pounds 600.
The most significant development was the arrival last year of digital video cards on the vast PC-clone market for pounds 1,000 or less. Earlier this year, Digihurst, the Hertfordshire-based multimedia company, launched its Micro Eye 2C card at pounds 495, a price now matched by Rombo, which spearheaded low-cost cards to capture still frames from a video source.
These cards still need a tuner to run live television, but a video recorder provides a ready source. A stand-alone tuner card was launched by Digihurst at Cebit, the computing and telecommunications exhibition in Hanover, in March, also at pounds 495. But such is the pace of development that Vision Dynamics of Watford promises one soon at about pounds 175, to work with its ELViS (Entry Level Video System) card, which it sells in two versions, at pounds 750 and just under pounds 500. SAI Technologies of Greenford, London, offers a replay card and tuner for pounds 895, with the tuner selling for pounds 150 by itself.
Computer databases of digitised moving pictures are still limited because the amount of storage needed is colossal. Further advances will be needed in the data compression of digitised images to be able to store moving picture sequences on a hard disk and accessible immediately in the same way as text or still graphics.
Even a high-capacity laser disk can store only about 36 minutes of moving images, compared with 54,000 still photographic images. Manufacturers are waiting for completion of a standard for high data compression rates being worked on by the computer industry's Motion Picture Experts' Group. But some have gone ahead with an interim standard based on the Joint Photographic Experts Group standard for still images, which gives 30:1 compression rates.
VideoLogic of Kings Langley, Hertfordshire, in May launched its Mediaspace system, which will allow the capture and storage of moving images on to a fast hard disk. But sequence lengths will still be limited.
An interim step towards a creating databases of moving pictures is offered by Digihurst, which has just started shipping a television card at pounds 495 that decodes teletext and controls a video recorder via an infrared signal. Using the subtitles sent out on teletext with most programmes, the PC can be programmed to pick up key words from the running text and switch on the VCR by emitting an infrared signal to start recording.
It is another small step towards the 'intelligent' television, making it possible to scan news programmes to record items of interest, or to create an educational database.
But the biggest area of expansion for digital video could be the delivery of live television to the PC as a service in itself. The pictures can be displayed on the PC screen in a window, which can be scaled to any size or moved to any position, so it can be run in a corner while another application is running.
At least one City broking firm has already dispensed with the cost of hiring televisions for Budget and financial statements by using full-motion video cards to deliver live television to its dealers' screens. In a world where fractions of a second can make or lose money, the ability to keep an eye on breaking news in a screen window and pick up news of disasters or political changes first is an advantage.
Most financial institutions now have some sort of dealing operations. Mike Waite of Desisco, Digital's subsidiary and one of the main dealing room systems suppliers, says that although the recession has slowed down investment in new equipment, he believes most dealers 'watching for coups and Bundesbank statements' will be plugged in over the next two years.
Cable and Wireless, the telecommunications company, is evaluating cards from Magnifeye, the UK subsidiary of the German multimedia specialist, to set up a similar system for its senior managers.
Magnifeye's Screen Machine cards are still priced at more than pounds 1,000, with a tuner/teletext card costing a further pounds 350. But it seems to have advanced furthest in this area. Several national newspapers use its cards for 'screen- grabbing' stills from television, and it has made a breakthrough by being sold through some branches of Dixons, the electronics retailer. Louise Cole, Magnifeye's technical director, is hopeful of a growing market in 'executive information systems' similar to the one under consideration at Cable and Wireless.
Security is another 'live television' application, this time linking the PC to closed-circuit camera. This would allow a secretary, receptionist or other staff member to monitor entry doors while working on screen. The window can be enlarged when someone is at the door and a still of the person stored. But David Furby, of Vision Dynamics, says: 'Applications are limited only by the imagination to think of them'.
That imagination is bound to be spurred as prices continue to tumble. Steve Gooderham of MV Multimedia, the subsidiary of Microvitek, the Bradford monitor manufacturer, whose card is familiarly called David - digital and audio interactive video device - reckons that in two to three years video cards will be standard on motherboards, the main computer processing unit, at an extra cost of probably no more than about pounds 75.
In the longer term it heralds a convergence between the television and computer industries, with the lines between the two increasingly blurred and display technologies merging.
Philips has already offered a television tuner for its top-selling medium resolution CM8833 monitor. But Peter Wyatt, Philips marketing manager, says that at pounds 80, it was too expensive in comparison with portable televisions - although Dixons has done well selling the monitor and tuner as a package at about pounds 270, pounds 50 above the normal price of the monitor.
The exercise will not end here. As television moves to higher definition and all-digital systems, television receivers will have to become computers to decode and unravel the highly compressed signals transmitted.
However, there may well be immediate advantages to watching television through a video card on your PC rather than a standard receiver. What could be more satisfying than cutting your least favourite politicians down to size by letting them drone on in a postage stamp- sized window while you get on with something more useful?
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