🚀 go-pugleaf

In article <2859@perl-sun.dwrsun4.UUCP> perl@dwrsun4.UUCP (Robert Perlberg) writes:
>In article <1992Sep2.133450.18671@panix.com>, schuster@panix.com (Michael Schuster) writes:
>> Macrovision inserts very bright pulses in the vertical blank interval.
>> Most VCR's use this when setting AGC video level, and get fooled into
>> thinking the video levle is much brighter than the picture area really
>> is. Most TV's don't. Dunno why.
>
>Some years ago a VCR maker (forgot which one) came out with a machine
>which used a different kind of AGC circuit which was not affected by
>Macrovision.  It was not their intention to defeat Macrovision, it just
>worked out that way because Macrovision takes advantage of an
>unintended behavioral characteristic of the extant AGC circuit.  The
>Macrovision people complained and the VCR maker modified the new
>circuit so that it would reject a Macrovision signal.


I've posted about this before but perhaps this would be a good time to
bring it up again. The pros on CompuServe's CE Forum said during a
discussion of Macrovision that with the schematic you can modify any
VCR to ignore Macrovision. You do this by clipping the capacitor which
forms the time constant for the AGC circuit, effectively disabling the
AGC. Yes, you won't get automatic level control, but the video signals
fed to most comsumer VCR's are so compressed anyway that there wouldn't
be much danger.



-- 
_______________________________Mike Schuster________________________________
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