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Macrovision Copy Protection
How does Macrovision copy protection work?
In the case of, say, a television broadcast, the author of the broadcast includes a code (called "setting bits") which the receiving equipment detects. The receiving equipment (e.g. a Sky Digibox) contains a special I.C. which turns the Macrovision system on when the code is detected. One form of protection is simply to insert a large pulse into every picture "frame". This has the effect of confusing a modern video recorder so that it thinks the contrast level is too high, and turns it down. The effect is to make the recorded picture alternate between light and dark, often with loss of synchronisation, causing the picture to "roll".
Of course the pulses have no effect on most TV sets (but see below).*
Can it be defeated?
Yes. Obviously the simplest way is to use an old fashioned video recorder that does not react to the pulses so the recording is unaffected. I haven't tried it myself so I can't tell you what makes or models might work. However, you'll probably have trouble in finding such an old video recorder, even if you knew what you were looking for.
The other method is to use a circuit which detects and removes the copy protection pulses. The use of such circuits is illegal in most countries and there is pressure on manufacturers and sellers to stop supplying them. Nevertheless, these "macrovision busters" can still be found if you know where to look!
*Some TV sets ARE affected by the inserted pulses so it's a good idea to ensure that any TV that you buy is compatible with your receiver (e.g. Sky Digibox) before you spend your hard earned cash on it. If the worst comes to the worst, you'll have to buy a "Video Cleaner" (they go under various names but you know now what they do!) in order to view copy protected programmes on your poorly designed TV set.