[net.video] Picture distortion on playback

mom@sftri.UUCP (Mark Modig) (07/14/85)

I am having a problem with playing back pre-recorded tapes of movies
from one particular company.  I have bought blank video tapes and
recorded them; they play back fine, along with all of the other prerecorded
tapes I have gotten, except for most, but not all, of the movies I have
gotten from this one particular company.  When one of the troublesome
tapes is played, a small strip across the top of the screen is distorted--
the picture bends sharply to the left:

------------------
|\\\\\\\\\\\\\\\\| <-- bent sharply to the left
||||||||||||||||||
|||||||||||||||||| <-- normal
||||||||||||||||||
------------------

The effect sometimes is only barely noticeable at the very top; other
times it creeps down from the top until about 1/4 of the screen is
affected.

I have tried adjusting everything I could think of on the VCR,
including the tracking and picture controls-- there is even a
vertical lock adjustment on the underside of the VCR that you need a
special "key" to adjust, but there is no change.
Since all the other tapes work, I don't really think
there is anything wrong with my VCR, but I'm wondering if the signal
is too weak for the TV (my TV is rather old) or if the tape might be
copyguarded and so the signal is not as good.  Any ideas on what
else it might be, and how it could be fixed?

Thanks

Mark Modig
ihnp4!sftri!mom

P.S.  I have a Panasonic PV-1630 VHS VCR

davew@shark.UUCP (Dave Williams) (07/15/85)

In article <468@sftri.UUCP> mom@sftri.UUCP (Mark Modig) writes:
>I am having a problem with playing back pre-recorded tapes of movies
>from one particular company............
>
>------------------
>|\\\\\\\\\\\\\\\\| <-- bent sharply to the left
>||||||||||||||||||
>|||||||||||||||||| <-- normal
>||||||||||||||||||
>------------------
>

The condition you describe is called "flagging". It is generally caused
by improper tape wrap during recording or playback. The tape is pulled 
away from the hub before the recording head has had a chance to 
fully pass by. Tape stretch may also
produce this problem, but usually in localized areas of the tape. It
appears the one company you mentioned has a problem with a duplicator.
This usually points to poorly maintained or worn equipment. Pirated
tapes suffer from this problem more than those produced by legitimate
duplicators.
-- 


                                    Dave Williams
                                    Tektronix, Inc.
                                    Graphic Workstations Division

    "The 6000 Family"
"The workstations that made
    Wilsonville famous."

lauren@vortex.UUCP (Lauren Weinstein) (07/17/85)

It might be added that some "flagging" can be helped through proper
use of the VTR "skew" control.  Unfortunately, few consumer VTR
units bother to include this (mechanical) adjustment as an external
control, though it does exist externally on U-MATICs and above...

--Lauren--

albert@ucbvax.ARPA (Anthony Albert) (07/17/85)

In article <1462@shark.UUCP> davew@shark.UUCP (Dave Williams) writes:
>In article <468@sftri.UUCP> mom@sftri.UUCP (Mark Modig) writes:
>>I am having a problem with playing back pre-recorded tapes of movies
>>from one particular company............
>>
>>------------------
>>|\\\\\\\\\\\\\\\\| <-- bent sharply to the left
>>||||||||||||||||||
>>|||||||||||||||||| <-- normal
>>||||||||||||||||||
>>------------------
>>
>
>The condition you describe is called "flagging". It is generally caused
>by improper tape wrap during recording or playback. The tape is pulled 
>away from the hub before the recording head has had a chance to 
>fully pass by. 

I would say that a more likely reason is the older model television.
I recently had a 1972 RCA TV which bent on some tapes but not on all;
after replacing it with a new monitor, NO tapes show picture bending.
This question is raised often in Video magazines, and this is the reason
usually given for the phenomenon.

-- 
				Anthony Albert
				..!ucbvax!albert
				albert@ucbvax.ARPA

nessus@nsc.UUCP (Kchula-Rrit) (07/17/85)

> I am having a problem with playing back pre-recorded tapes of movies
> from one particular company.  I have bought blank video tapes and
> recorded them; they play back fine, along with all of the other prerecorded
> tapes I have gotten, except for most, but not all, of the movies I have
> gotten from this one particular company.  When one of the troublesome
> tapes is played, a small strip across the top of the screen is distorted--
> the picture bends sharply to the left:
> 
> ------------------
> |\\\\\\\\\\\\\\\\| <-- bent sharply to the left
> ||||||||||||||||||
> |||||||||||||||||| <-- normal
> ||||||||||||||||||
> ------------------
> 
> The effect sometimes is only barely noticeable at the very top; other
> times it creeps down from the top until about 1/4 of the screen is
> affected.
> 
> ...
> 
> Mark Modig
> ihnp4!sftri!mom
> 
> P.S.  I have a Panasonic PV-1630 VHS VCR

*** REPLACE THIS LINE WITH YOUR MESSAGE ***

     A few months ago, I rented a tape that did this on my G.E. VCR.  I
     "re-wound" the tape then "fast-forwarded" it and let it auto-rewind.  This
     cured the problem.

					From the alter ego of--

					Kchula-Rrit