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Posted by Richard Crowley on 12/12/05 04:07
"P.C. Ford" <wrote ...
> I know the accepted generationalization is that there is no
> generational loss in DV. "It's all 1s and 0s."
It is significantly more than an "accepted generalization".
Bit-perfect digital storage and transmission has been around
for many decades (longer than most people on this newsgroup. )
DV is just one form of digital storage and transmission.
Granted, some forms of digital storage/transmission use less
robust error detection/correction than others, but that is a
conscious tradeoff between how much extrapolation you can
get away with for certain kinds of data (like red-book audio
CDs, for example) vs. storage efficiency.
> Is that true going from DV to AVI for editing then back to DV?
Assuming that by "DV" you mean the DV stream coming from
playing back a tape on a camcorder or VCR. Yes, it is true that
you will get "generational loss" (or more correctly "soft error
rate") so vanishingly low (and so well recovered) that it is
indistinguishable from zero.
> There is recompression going on here.
You will have to explain what you mean by that.
Otherwise, as a standalone statement it is false.
There is no "recompression" when capturing a DV
bitstream into an AVI file and conversely from AVI
back to a DV stream. This is generally true for the
DV-AVI codecs most of us use. It is possible to write
a DV-AVI codec with compression, but I'm not aware
that any of the popular ones are anything but straight
one-for-one (and zero-for-zero) transfers.
Unless you are talking about video which has been
modified in post-production (editing, etc.) such as
title overlays, transitions, color/exposure correction,
etc.
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