From: net@gagme.chi.il.us (Whoami Anyway)
Subject: Seeking info on unusual cable scramble
Originator: net@gagme
Organization: Gagme Public Access UNIX, Chicago, Illinois.
Distribution: na
Date: Fri, 20 Nov 1992 04:39:19 GMT

Here in Chicago we have a cable company that has recently started
doing something strange to their premium (and some basic) channels.
The standard scramble is the tri/bi inband gated sync system.  For the
most part, though, the system stays on the 6db (low) side of the
tri/bi, only to go to the high side (10 db) for ultra premium PPV
events and the porn channels.

In the past, the system used Jerrold 450's exclusively.  In the past
few years, these have been replaced by Pioneer 6000's that use the
same basic system and are cross-compatible with the Jerrolds.  I
believe that all Jerrolds are now out of circulation, or at least most
of them.

As of (I believe) September first, the cableco has been doing
something totally different with all premium channels (except PPV's)
and some (encoded) basic channels.  The scramble is the same, IE the
Jerrold that I have still decodes everything fine, except that on
these channels there is an added effect that is described below.

The vertical blanking interval has a pulsating white line on its top
edge, near the middle of the vbi.  This white line pulses rapidly and
has very little effect on the received picture (except for an annoying
flicker near the bottom of the screen), but if a VCR is switched in
line, the picture jittrers rapidly up and down.  Not too much, maybe
an inch or so.  If a tape is made on these channels, all horizontal
stability is lost and the picture floats left and right in addition to
the jittering up and down.  Also, if the recording is made on a slower
speed (other than SP) the speed is sloppy too.

Here is the rub.

On Cableco supplied converters, this little pulse on the vbi is masked
with a line of black positioned 'over' the pulse to hide it.  You can
see the edges of the pulse flickering slightly, but the bulk of the
pulse is covered over, rendering it invisible and tapes made on those
decoders are clean.  Scrambled channels that DO NOT contain this pulse
ecord fine on either decoder.  

What I want to know is;

1) what is this pulse and what is it used for?  
2) Is it an anti piracy move to make decoders other than cableco's
   ineffective  for taping?  
3) Is this a copyguard system that the Pioneer boxes can either mask,
   or not mask, alowing the cableco to (perhaps) charge a subscriber
   extra for the privledge of taping movies in the future?
4) Is this just a bi-product of the Pioneer scrambling system (perhaps
   a timing pulse)that the older Jerrold system did not use, and now
   that the cableco boxes are all Pioneer, this is surfacing?
5) Would aftermarket Pioneer units automatically mask this pulse?
6) Why would cableco ONLY use this on premium channels AND such basic
   stuff as ESPN, AMC, and CNBC.. but NOT on the PPV channels?  Other
   scrambled basic channels DO NOT have it. Is it just a matter of
   time till ALL scrambled channels have this? 

Please only reply if you have actual knowledge of this as I have
described it.  No guesswork, please.  I know that this is NOT
macrovision and no one I have spoken to has any knowledge.  Obviously
cableco is of no use either.  Post or send e-mail, I would appreciate
any info.

Thanks