From: glen@gagme.chi.il.us (Glen R)
Newsgroups: rec.video.cable.tv,sci.electronics,rec.video.sattelite
Subject: Info wanted on strange new 'copyguard' on cable tv system.
Date: 31 Aug 92 03:35:34 GMT
Organization: Gagme Public Access UNIX, Chicago, Illinois.
Originator: glen@gagme

I am in need of some technical assistance regarding a seemingly new
form of copy protection which I have encountered recently on our cable
television system.  I will describe.

Within the past month, I have begun experiencing, on most scrambled
channels from 37 to about 48, a bizzare situation.  If I run the
decoder (Jerrold 450-drzin) direct into the tv, I get a variety of
results from near normal picture (sometimes with a hint of buzzing) to
a tearing, and unstable picure (depending on WHICH channel i tune to).

Once I switch the VCR in-line, the picture 'jitters' randomly up and
down within the frame.  On dark scenes I notice (with or without the
VCR) a rapid 'flicker' of light at the bottom of the screen which
looks kind of like someone is shining a pen-light flashlight under the
picture tube upwards, and turnuing it on and off alost like a strobe.
This flicker seems random and flashes rapidly in time with the picture jitter.

A look at the vertical blanking interval bar reveals a thin white line
along the very top of the interval bar which is doing the flickering.
This little thin horizontal line of white light is near  the center of
the black blanking bar and along the VERY top of it.  It is only
present on those channels I am having trouble with.  

This is NOT macrovision, or at least not the macrovision which is used
on rental tapes.  That system has 5 or 6 little 'squares' of light in
the vertical blanking interval which pulse slowly causing the VCR's
AGC to breathe and the picture to go bright and dim.  This system (or
whatever it is) is not like that.  The only visible symptom seems to
be this vertical instability, or 'jitter' which is markedly worse when
the VCR is in line.  Tapes made from those channels, obviously,
contain the same jitter and are unwatchable.  

Now here is the clincher.  The only two premium channels in this range
of channels are The Movie Channel (46) and Disney (48) (also American Movie
Classics (41), but that is a basic channel).  HBO, Showtime, Cinemax and
the two pay-per-veiw channels are below the affected range and therefore
are clean.  Our system is one that scrambles many 'basic' channels.
Even TNT (37) and VHI (40) are scrambled and suffer from this 'jitter'.

HOWEVER, I just got word that the cable folks are moving  HBO
(three channels) and Showtime (two channels) right into these affected
slots.   I have also heard rumors of industry plans to 'copy protect'
the premium channels at some future time (a move that IMHO will remove ANY
possible reason that anyone would want to pay for these repetitive
movie mills).  Could this be the beginning of that?

So, has anyone heard of, or experienced this 'jitter' scheme?  What is
it called, can it be eliminated?  Unlike Macrovision, which has
minimal effect, if any, on regular playback, this system has a great
impact on the channels EVEN when the VCR is not in line.  Disney is
unwatchable, even w/o the VCR.  At this time Pay-Per-Veiw's (28, 29,
52, and 53) are unaffected.  After the channel switch (Sept.1) the
only premium NOT in the affected range of channels will be Cinemax (ch
24). Of course, I am sure there is nothing to stop them from applying it to
ANY channel.

Please reply if you have ANY info about this situation.  E-mail or
followup article will be great (e-mail prefered, since I only have
limited time to read news).

Thanks.