there was a time when they played with the video levels so that when copying the video level would drop below the threshold that the copyiny device could handle. This gimmick was quite easy to see when the signal was run through a time base corrector with a video meter attachment. When we used to do corparate event & project them on a 20' screen for a meeting, it would drive the projectors crazy. It became standard practice to include a time base corrector with the rental of all non live video feeds at a cost $225 plus the cost of the projector rental $1200 per day. (As background, i worked in philadelphia in the 80's & 90's doing large indoor & outdoor events/concerts for crowds up to 70,000 people at a time) This gimmick was not used on all prerecorded video & seemed to have predated the more formal version that became macrovision. My current vcr proscan 84 has this circuitry included & allows me to copy from all video sources including the matrix DVD.