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July 1996, Week 4


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Film and TV Studies Discussion List <[log in to unmask]>
Michael Sime <[log in to unmask]>
Wed, 24 Jul 1996 15:42:24 -0400
Film and TV Studies Discussion List <[log in to unmask]>
text/plain (58 lines)
>> Can anyone shed light on this?  This has really aroused my curiosity as to
>> nature of the relationship between copyguard companies and tape
>> distributors.  It would seem that the former would have a strong incentive
>> to insure that a tape has *actually been encoded with a particular
>> protection mechanism* if it wears such a label, wouldn't it?  Or, is it
>> likely that the video store itself is attaching the labels for some
>> Is this common?
>> More generally, does anyone know technical details about how these things
>> actually work (beyond the obvious, I mean)?
Macrovision uses a process that causes the video signal to fluctuate
wildly between the acceptable levels for use on a television. The reason
it's supposed to prevent copying is that most consumer VCR's will not
accept that level of shift in the video levels it's trying to record. The
TV's on the other hand, will correct for it and show a stable picture
(kinda like with broadcast signals).
the way around this usually is to use a Time Base Corrector (TBC) which
corrects for timing errors in the differnt signals that make up the
entire video signal (chrominance, luminance, timing, synch, etc.) and in
essence, evens out the signal fluctuations that Macrovision induces.
Now a less-than-exact-in-its-tolerances VCR might do the same thing. A
really 'tight' deck may spite you if you tell it to record MV signals,
but one that is a little 'loose' may just take it and record an
acceptable signal.
To answer the second part of your question, was the Macrovision 'label' a
 sticker on the cassette? or was it actually PRINTED on the spine of the
tape? Was there a splash screen on the tape somewhere near the FBI
warning? That's a sure sign that it was protected. If it was just a
sticker, then maybe the place that rented you the tape just slapped it on.
Hope this helps...aren't you glad you asked?
Mike the Techie
Michael Sime        <[log in to unmask]>
Video Schmideo!      <[log in to unmask]>
It's not the time it takes to take the takes,
it's the time it takes BETWEEN the takes,
that takes the time to take the takes.
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