[sci.electronics] TV distortion from copy protected video tapes?

ajb@mhuxo.UUCP (Andrew Becker) (02/18/89)

     I have noticed that some commercially produced video tapes produce
a distorted picture and sound track when played on my moderately old
television set; I have no such problem with videos I have taped myself.
     The distortion consists of several rows of white line segements
in the top portion of the screen, slightly left of center, which fade in
and out about once a minute, on average.  The sound track also exhibits
static which fluctuates in and out with the picture as well.
     I have been told that some commercially made videos are incompatible
with older TV sets and produce a bending of the picture in the top section
of the screen.  While this is not the symptom I experience, could there be
some other incompatibility which could create this problem, perhaps from
the copy protection scheme used in commercial videos?
    If this is the likely problem, is there a filter or conditioning device
which can be constructed to fix it?  Thanks for the help.       

                                               ajb!mhuxo
                                               AT&T Bell Labs
                                               Murray Hill, NJ

u546025938ea@vega.ucdavis.edu (0040;0000003281;0;340;141;) (02/18/89)

In article <1502@mhuxo.UUCP> ajb@mhuxo.UUCP (Andrew Becker) writes:
>
>     I have noticed that some commercially produced video tapes produce
>a distorted picture and sound track when played on my moderately old
>television set; I have no such problem with videos I have taped myself.
This might not be an explanation of your problem, but I'll give it a shot:

Many new videocassettes on the rental market are employing a form of
copy protection.  One of the popular methods involves playing with the
level of the video signal.  The protection scheme makes the output level
seem to be higher than it actually is, causing the video load (i.e. your
television, second VCR, etc.) to reduce the video gain via the automatic
gain control.  This results in a low-level picture.  A cassette with this
protection is supposed to play properly when the VCR is connected directly
to the television, but it is recommended that there be no other devices
between the VCR and TV.

What might be happening is that the gain control on your (older) television is
getting confused, and setting an improper level.

I'm not very familiar with methods of copy-protection, but this is my
$0.02     :-)

Hope this helped........

Steve Meyer

Instructional Television              and     Student
Univerisity of California, Davis              UC Davis

ries@arcturus (Marc Ries) (02/20/89)

>     I have noticed that some commercially produced video tapes produce
>a distorted picture and sound track when played on my moderately old
>television set; I have no such problem with videos I have taped myself.
[...]
>    If this is the likely problem, is there a filter or conditioning device
>which can be constructed to fix it?  Thanks for the help.       

  Sounds like the copy-guard by-products of Macrovision(TM).

  Yes, it can wreck havoc on older TVs (as well as some new ones).
  Yes, there are some filters for it.  Check the back-section ads
  in the likes of Video and Video Review magazines.

  PS: This sounds likes a "rec.video" question. 

Marc Ries
TRW Defense Systems Group/HMI
UUCP: ...!spp2!ries@trwspp.UUCP