Path: utzoo!censor!geac!torsqnt!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!cs.utexas.edu!sdd.hp.com!hplabs!hpfcso!hpfcbig!bame
From: bame@hpfcbig.SDE.HP.COM (Paul Bame)
Newsgroups: sci.electronics
Subject: Re: How does MacroVision CopyGuard work?
Message-ID: <6560005@hpfcbig.SDE.HP.COM>
Date: 8 Jan 91 22:43:17 GMT
References: <35277@netnews.upenn.edu>
Organization: HP SESD, Fort Collins, CO
Lines: 12

> I'm curious....does anyone know how MacroVision copy protection works?
> Can someone please email me recent sci.e articles on it?

Go check the periodical guide for the last couple of years looking for
the Macrovision "Scrubber" plans described in Radio Electronics.  They
do a fair description of the technique.  My fading memory believes
they insert some pulses into the vertical retrace interval which makes
it difficult for your VCR to lock onto the vertical sync and nearly
impossible for the next VCR in the copy chain to do so.

			-Paul "Spice is the Variety of Life"
			bame@hpfcbig.sde.hp.com	N0KCL