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From: berggren@eecs.cs.pdx.edu (Eric Berggren)
Newsgroups: sci.electronics
Subject: Re: VCR copy protection
Message-ID: <784@pdxgate.UUCP>
Date: 28 Nov 90 07:22:41 GMT
References: <1923@mts.ucs.UAlberta.CA> <746@pdxgate.UUCP> <1990Nov27.210457.26202@sunee.waterloo.edu>
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dcschuur@sunee.waterloo.edu (DC Schuurman) writes:
>>  There are several companies using a "copy protection" scheme called...

>MACROVISION ENCODING !

>BUT a VCR will adjust it's Automatic Gain Control (AGC) to these large   
>incoming spikes and because of the finite time constant involved with the
>AGC response the following picture field will appear dark and murky
>if copied from another MacroVision protected tape.  These large spikes
>are visible (as the genetleman above mentioned) as flashing squares
>in the black line on your TV which appears during vertical retrace.

>The scheme is effective yet simple - however there have been some problems
>with very expensive multi-synch TV's which interpret these high frequency
>noise bursts as a higher horizontal synch frequency and vainly try to 
>adjust to these noise pulses mistaking them as a change in H synch.
>The cheapest TV's seem to be least susceptible to MacroVision 
>interference while viewing Macrovision encoded tapes - strange but true.

  Makes sense why R-E called it a "Macroscrubber"...
  I heard that this protection system wreaks havok with the HDTV in
the labs. I doubt "they" are going to make changes just to deal with VHS
copy protection schemes. I'm sure the industry will eventually develop 
ssomething else, probably just to elude all of the "macroscrubbers" and
make our lives, and pictures, more enjoyable.
Might as well let the Japanese buy Paramount too; I doubt they care
about the whole issue of protection...

==============================================================================

     "Round and round the while() loop goes;
           Whether it stops," Turing says, "nobody knows."
==============================================================================

     "Round and round the while() loop goes;
           Whether it stops," Turing says, "nobody knows."