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Working with Video


This month we look at videodiscs, what they do, what they don't do, how they do it if they do it and how they will affect you.

It is easy to draw parallels between video discs and video tapes on the one hand and audio discs and tapes on the other. Some of these comparisons are valid, others are misleading. Audio discs are simpler to manufacture than tapes because the process is a relatively straight-forward moulding/stamping operation as opposed to the long-winded business of recording a piece of tape, cutting it to length and assembling it inside a complex housing. The action of making a video disc is a far more expensive and precise activity than making an audio disc but it is still more straightforward than making a tape. It is also a faster process than making a tape: tapes are still made in 'real time'. In other words, if you are producing a two hour film it will take you two hours to copy the film from the master recording and additional time to finish the assembly. This time factor alone restricts the number of video cassettes that can be produced. Video discs can be produced as fast as the machine can turn them out and this should therefore make them a cheaper item to make, all other factors being equal.

Continuing our comparison, audio discs are replay-only devices, whereas with cassettes you can make your own recordings. Exactly the same applies in video - but video discs have not yet appeared in this country - we only have tapes. Whereas records outsell music cassettes this is not yet the case in video and it may never turn out that way. However, given the choice of video tape or disc, which would you choose?

The first point to appreciate is that the quality of reproduction offered by video discs and tape is not the same. Many people find the quality of reproduction of a home video recorder perfectly adequate but most would admit that broadcast TV is better. Video discs on the other hand promise pictures and sound every bit as good as broadcast TV, with the promise of full hi-fi sound (even stereo in some cases) or a selectable foreign language soundtrack. The price of video discs and their players should be less than that of tapes and video recorders, say a third or a half, cheaper. All sorts of 'trick' features will be standard such as slow motion, perfect freeze frame, reverse, fast scan and random access. The contents of the disc can even be still pictures, up to 54,000 on one side! You could put an encyclopedia on a disc and access any individual page at random in less than 15 seconds.

With all these marvellous features there must be a couple of snags. Experience in the USA has shown picture quality to be variable due to poor disc pressings, though this can obviously be cured by better quality control. One side of a disc cannot contain a complete film, so you will have to interrupt your viewing to turn over, but this is not really a problem. No, the only real drawback with these devices is that they cannot record!! This is a serious disadvantage for the majority of video enthusiasts who use their video machines to 'timeshift', that is to record a favourite programme while they are away from home or even while watching another programme. Hopefully, some of the people who read this column are interested in things more creative such as shooting their own material, but once again this is something you cannot do with videodiscs. Even if films on video disc turn out to be as cheap as, say, £10, the cost of the special player (say £250 to £400) is likely-to outweigh the attractions of the pre-recorded programmes. Some people will of course be able to afford both tape and disc machines, and market research indicates that people who are already into video (i.e. existing VCR owners) have a greater interest in owning both systems than people who don't have a VCR. On the other hand, three out of five VCR owners expressed no interest in video discs.

Later this year video disc equipment will come on to the UK market and it will be interesting to see if these predictions are fulfilled. In any case, the increased competition and awareness in video will benefit all video enthusiasts. It is extremely likely that the arrival of video discs will force down the cost of video tapes, both blank and pre-recorded, and machines may well become cheaper. The VCR manufacturers may even retaliate with a low-cost replay-only machine!

Finally, we ought to take a quick look at how video discs work. There is (predictably) more than one format and the three formats are (also predictably) totally incompatible. So discs made for one system will not be playable on machines of other types and considering the deals which manufacturers will make to sign up exclusive material for their own system this will probably reduce your choice of programmes, more so than with tape.

The three systems are known as VHD, Laservision and Selectavision. VHD is promoted by JVC and in this country by Thorn-EMI, so it seems set to enjoy the same success as their VHS system. The records are grooveless and the actual information is recorded by laser in minute pits. These are played back by a capacitance sensing stylus which glides over the recorded surface. The stylus is guided not by grooves but by rows of even smaller pits on either side of the programme track. The disc itself is 10.2 inches in diameter and made of high-quality, conventional PVC, like an audio disc. To prevent contamination, the record must be handled in a protective sleeve.

System two was invented by Philips and is known as the Philips/MCA/Pioneer Laservision system. In this system the recorded information exists in the form of microscopic pits on the surface of a silvered disc, twelve inches in diameter. The silvered layer has its own built-in protective plastic surface - this avoids contamination from dust and all but the deepest of scratches. The pits are scanned optically, using a miniature laser. Again, there are no grooves.

The third system, Selectavision, is the property of the American RCA organisation and unlike the other two systems will not be available in Europe for some time. It lacks several of the impressive features offered by the other two systems because it has opted for a simpler but more restrictive method of operation. Like VHD it also senses capacitance variations as an electrode passes over microscopic pits in the disc surface. But, unlike VHD, the pickup travels in a physical groove which simplifies player technology but prevents freeze framing. The disc is also 12 inches in diameter and must be protected in a special sleeve.

Over the next few months you will hear a lot of claims and counter claims about discs and their merits - use this guide to form your own opinions.


The Philips LaserVision (formerly VLP) video disc system, which will be launched in the UK in mid-1981. Designed for the modern home, LaserVision produces high-quality pictures and sound on any domestic colour television set. The player can simultaneously be connected to a hi-fi system for full stereo sound.

LaserVision (formerly VLP) is capable of a multitude of functions, all at the touch of a button and with no wear to the disc. These include freeze frame, varying slow motion speeds in both forward and reverse and rapid forward and reverse search, enabling any section of the disc to be found in seconds.

An exciting range of disc albums will be available when LaserVision is launched, including top feature films such as Alien, Star Trek — The Motion Picture and Saturday Night Fever.



Previous Article in this issue

Sound on Stage

Next article in this issue

Wersi Pianostar


Electronics & Music Maker - Copyright: Music Maker Publications (UK), Future Publishing.

 

Electronics & Music Maker - Jul 1981

Feature by Andy Emmerson

Previous article in this issue:

> Sound on Stage

Next article in this issue:

> Wersi Pianostar


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