Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!uakari.primate.wisc.edu!aplcen!haven!udel!rochester!rit!cci632!ccicpg!paulm
From: paulm@ccicpg.UUCP (tmp Paul Moreau usenet acct)
Newsgroups: sci.electronics
Subject: Re: Cable TV descramblers / Rental movie stabilizers
Summary: Rental Movie Stabilizer
Message-ID: <54357@ccicpg.UUCP>
Date: 16 Jan 90 16:46:14 GMT
References: <235@mojo.UUCP>
Organization: ICL North America (Business Systems), Irvine, CA.
Lines: 53

> For the past year or so, I've been subscribing to Video Review Magazine,
> and in every issue there are lots of advertisements for so-called "Cable
> TV Descramblers" and "Rental Movie Stabilizers" by Oak, Hamlin, Jerrold,
> and more. Does anyone have any experience with these things, or know if
> they work or not? I am most of all wondering what the "Descramblers" are 
> capable of descrambling. HBO, Cinemax etc. (i.e. "pay channels"), or just 
> ESPN, FOX, etc. ("basic service channels")? 
> Why does one need a rental movie stabilizer? Does it really help? I assume
> that the device is mostly used for copying rental movies, something the
> advertisers ofcourse state in their ads is highly illegal. 
> I have been contemplating buying my own cable box, since the one from the
> cable company is at least 10 years old, and distorts the picture substan-
> cially. I need a box, even though my TV is cable ready. I get about 12 of
> 36 channels w/o the box. Before I go shopping, I would like to know a little
> more about these descramblers, and other TV/Cable gadgets not mentioned here.
> 

    I'm not sure of the make but I have a rental movie stabilizer.
    Some rental movies, not all, use a system called MacroVision to copy
    protect thier movies.   On most TVs this is no problem as long as
    the original tape is used.   I believe the method involved is in
    modulating the amplitude of the horizontal sync pulses.   The output
    of VCRs are not run through an AGC (Automatic Gain Control) circuit
    so the fluctuations have no efect.  But the input of VCRs do go
    through an AGC.  The AGC is sensitive to the change in Sync pulse
    amplitude and tries to keep a constant voltage level on the incomming
    signal.  Varying the sync amplitude causes the AGC to clamp down
    on the signal causing the Video section 'which is not modulated' to
    be also cut down.  This causes very noticable Contrast and briteness
    changes to occur on the copy.   The stablizer, I believe, strip and
    condition the sync and then re-mix them with the video.  Now this
    covers the 'copied tape' problem.   The other problem as I said earlier
    is that the Macrovision doesn't bother 'Most' TVs with the original
    tape.   However, the RCA XL-100 series of TVs are not included.
    Most decent TVs condition the Video sync pulses but it seems the
    RCA took a short cut and didn't condition them.  This causes screen
    'Jitter' and 'tearing' (SP) to happen.  I know, my dad 'HAD' an RCA
    that he could no play any 'protected' tapes on.
    As far as the box being worth it, YOU BET!

    Well I hope this helped a little.
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