Article View: sci.electronics
Article #4170Re: Cable TV descramblers / Rental movie stabilizers
From: tmp Paul Moreau usenet acct
Date: Tue, 16 Jan 1990 16:46
Date: Tue, 16 Jan 1990 16:46
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> 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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Path: arc1-ca.pugleaf.net!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