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Posted by mmaker@my-deja.com on 10/05/54 11:52
PTravel wrote:
> Bits don't get corrupted during a firewire transfer,
Yes they do.
> and drop-out, i.e.
> uncorrectable data loss, is incredibly rare for digital video media.
No they're not.
> In the
> 200-300 hours of digital video that I've shot, I've never had a single
> instance of drop-out -- not one.
Really? Your deck actually tells you when it gets an uncorrectable
error?
Or are you just guessing you've never had a dropout because you've
never noticed it?
> There is no generation loss when copying digital video.
Here's an idea: take a DV file, record it from tape to tape a hundred
times, capture it back into your computer, then do a bit-by-bit compare
of the original file and the hundredth-generation copy. I think you'll
be surprised by the result.
> Both hard drives and digital tape employ error correction,
But one can do something _before_ dropouts become a problem, for
example by moving the data from that block to a different block... and
the other can't.
>which is one of
> the reasons why drop-out is so rare for digital video tape.
Except it's not. When DV error correction can't fix a block read from
tape it simply replaces it with the same block if it's video, or
silence if it's audio. If the camera is stationary and there's no
movement in that block of pixels you probably won't notice, but you
still got a drop-out and you still lost the bits.
Mark
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