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November 1999, Week 3

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From:
LLTI-Editor <[log in to unmask]>
Reply To:
Language Learning and Technology International Information Forum <[log in to unmask]>
Date:
Thu, 18 Nov 1999 16:57:09 EST
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--- Forwarded Message from Derek Roff <[log in to unmask]> ---

>Date: Wed, 17 Nov 1999 15:38:15 -0700
>From: Derek Roff <[log in to unmask]>
>To: LLTI-Editor <[log in to unmask]>
>Subject: PAL conversion and copy protection
>Originator-Info: login-id=derek; server=mail.unm.edu

Our university's legal staff has instructed us that we may, for research
purposes, make NTSC conversions of sections of PAL videos from a purchased
and retained original.  Leaving aside for the moment the quality of this
instruction and the important copyright issues, we have been unable to
comply with the requests of some professors, using our Panasonic AGW1 VCR.
Many originals produce copies which have good sound, but the picture blinks
on and off every second or two.  The picture is off more than on, and the
result is unwatchable.  The original can be viewed via the AGW1, but making
a conversion copy for the professor to take to their office is
unsuccessful.

I have been told that this visual dropout is caused a copy protection
technique placed on the tape by the publisher.  Up until last week, I had
not found any way around this problem.  Then serendipity struck.  We have
five VCR's chained together, allowing us to make five simultaneous copies
of a single original (assuming copyright permits this).  On a recent
occasion, I used this setup to copy/convert from a PAL tape some clips
requested by the professor, and the NTSC copy worked fine.   A short time
later, I was asked for another clip from the same tape.  I could not get a
decent copy, due to the video dropout described above.  But the first clips
from this tape had been good.  How is this possible?

After much head scratching, I discovered/remembered what was different in
the two incidents.  For reasons now forgotten, when I copied the first
clips, I put the original PAL tape in the AGW1 and the blank tape in the
last VCR in the chain.  The copy was fine.  On the later try, I put the
blank tape in the VCR directly connected to the AGW1.  I got dropout.
Weird, but useful.  I have found that I can make good copies, if I use the
second through fifth VCR's in the copy chain, but not if I use the first.
I don't know why this happens.  It appears that the distorting copy
protection signal is absorbed, filtered or attenuated by the first VCR.

Of course, I do not advocate breaking copyright.  I offer this information
as an aid to legitimate research.  In the VCR duplicating chain, we have
two inexpensive types of JVC S-VHS VCR's, but the recordings in question
were standard VHS, not S-VHS.  I don't know if the type of VCR is a factor
or not.

Derek Roff
Language Learning Center, Ortega Hall Rm 129, University of New Mexico
Albuquerque, NM 87131  505/277-4804 fax 505/277-3885
Internet: [log in to unmask]

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