🚀 go-pugleaf

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.

Robert Perlberg
Dean Witter Reynolds Inc., New York
{murphy | philabs}!dwrsun4!perl
	-- "I am not a language ... I am a free man!"