[net.video] Copyguard

smith@umn-cs.UUCP (03/13/85)

  I've been collecting graphics examples from TV with my VCR and I'm
wondering about what's in store if I try to collect examples from cassette
movies as well.  In particular I'm wondering about 'copyguarding'.
I've heard that it essentially weakens a synch signal so that the image
can usually be displayed but can't be accurately recorded.  A side-effect
seems to be that some TVs can't reliably display copyguarded tapes.

Questions:

1. Do all manufacturers routinely copyguard tapes?  Is there a degradation
   in the image of copyguarded tapes even on 'modern' TVs?

2. Is there some way of controlling the effects without buying one of those
   copyguard defeaters?  For example, I have both RF and audio/video output
   from my deck.  Is one or the other less succeptible?  Would my tracking
   control do me any good?

brown@nic_vax.UUCP (03/16/85)

> Questions:
> 
> 1. Do all manufacturers routinely copyguard tapes?  Is there a degradation
>    in the image of copyguarded tapes even on 'modern' TVs?
In the case of VHS commercial tapes, no, manufacturers do NOT use copyguard
anymore.  It turned out not to do any good for two reasons.  One, because of
the third party boxes that replaced the butchered vertical synce with good
vertical sync and two, almost all of the table model, three speed, VHS machines
will lock onto any signal that is even remotely close to vertical sync.  I have
been thru three VHS table top units and they don't even blink at the copyguard.
I run a lot of commercial tapes thru my VHS machines and I haven't found a one
that uses copyguard anymore.

Now, if you have a Beta machine, that is another story.  Sony likes to build
sync separator circuits that like only good sync.  Some of their machines will
not record unless the sync is perfect.  Copyguard works very good on those
units.  A anti-copyguard box is needed.  But, since I do not have a beta unit,
I can only go by what I find out from users of Beta machines.  Another good
point for VHS.

As for the image, it is not touched.  All copyguard does is change the
characteristics of the vertical sync.

> 2. Is there some way of controlling the effects without buying one of those
>    copyguard defeaters?  For example, I have both RF and audio/video output
>    from my deck.  Is one or the other less succeptible?  Would my tracking
>    control do me any good?

Like I said above, if you have a fairly recent (a couple of years old),
tabletop VHS unit, you shouldn't have to worry about making copies.
If you have Beta, you may need one of the copyguard boxes.

Whenever you make copies, the direct video connections should always be used.
Going via the RF always adds more noise to the signal and degrades the
bandwidth a little bit.  The RF modulators in video decks are cheap compared
to the rest of the unit.

I hope this helps you a little bit.  If you have anymore questions, just
send me some mail via uucp.

Mr. Video

smith@umn-cs.UUCP (03/20/85)

  I got two or three useful mail replies to my query.  The concensus seems
to be that hardly anyone uses copyguard, probably because the newer equipment
isn't adversely affected by the weakened synch signal that copyguard is
based on.
  One fellow reported that his copyguard defeater actually caused more trouble
than it eliminated, since it provided one more electronic stage to muddy the
signals.
  It is also likely that copying excerpts from videotapes is at least as
illegal as xeroxing excerpts from copyrighted computer manuals.  In both
cases the providers don't consider extraction of excerpts to be 'fair use'.

  "But Inspector Erskine, I didn't mean any harm...."