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February 1998, Week 4

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Subject:
From:
Leo Enticknap <[log in to unmask]>
Reply To:
Film and TV Studies Discussion List <[log in to unmask]>
Date:
Fri, 27 Feb 1998 09:30:48 GMT
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On Thu, 26 Feb 1998 13:12:44 -0500 Scott Hutchins wrote:
 
> Wouldn't preservation through copying videotapes cause severe
> deterioration in image and sound quality.  Collectors who pass on bootlegs
> at cost always make a big deal about the number of generations down a copy
> is, and in my experience I have noted it can be even worse than the
> difference between SP and EP.
 
If the video signal is digital, then it is theoretically possible to make an
 identical copy.  All home
VHS formats are analogue; that is to say the picture and sound is recorded as a
 series of
waveforms on a magnetic oxide.  As you say, when you copy, some of the
 definition in those
waveforms is lost, resulting in replicative fading.  With a digital signal, the
 waveform is
represented as numbers and all you have to do is to copy the numbers (exactly
 like copying a file
on a computer disc).  However, some professional video formats use a technique
 called
compression: basically, the numbers are crunched to reduce the amount of storage
 space
needed on the tape.  Some would argue that the compression and decompression
 process can
have a visible effect on the screen, hence the question mark over format
 migration and
authenticity.
 
As you point out, pirated domestic videos look awful due to this replicative
 fading.  No doubt this
is part of the reason why domestic digital videotape has not materialised, as it
 might result in
people being able to make perfect pirate copies.
 
Leo.
 
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