Quote:
Macrovision probably isn't perfected enough to work on every deck since the 70s

In fact, it relies on some technology that was introduced after the 70s. Most, if not all, ancient VCRs won't be affected by Macrovision at all. The way it works is that it fakes out the automatic video gain control on the VCR into thinking that the picture is oscillating between being really light and dark by injecting lots of noise into parts of the signal that you don't actually watch. The AGC circuitry is really stupid and just tests the whole signal instead of just the video frame. Old VCRs didn't even have that rudimentary gain control circuitry, so they're unaffected, but they do pass the Macrovision signal on; they don't strip it. Of course, now we can't progress with better gain controls because the VCR industry doesn't want to piss off Macrovision, and, by extension, the movie industry.
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Bitt Faulk