>John Campbell wrote:
> > Walter Knapp wrote:
> >
> >
> >>oryoki2000 wrote:
> >>[edit]
> >>
> >>>This is because ATRAC will always be
> >>>criticized for creating, by design,
> >>>an approximation of the original source.
> >>>Saying the result is "indistinguishable
> >>>from the original" doesn't change the
> >>>fact that 80% of the original digital
> >>>material is discarded, and other data
> >>>added, when creating the ATRAC version.
> >>
> >>As I've noted it's a error to think ATRAC even keeps 20% of the origina=
l
> >>data. The more I dug into it, the more it became clear that it should
> >>rather be thought of as synthesizing a whole new set of data, and
> >>storing instruction on how to do this. Yes, a approximation, but so is
> >>anything that comes out of a A/D - D/A cycle.
> >
> >
> >
> > Maybe the reason you have to keep preaching this gospel is due to
> > your wilful mis-reading of other's comments. The original statement,
> > and those preceding it, are figurative - you are being literal (or
> > trying to be, at least). You seem determined to hide from the fact
> > that ATRAC and other audio data reduction systems are not called
> > lossy compression for nothing.
>
>Or maybe I understand how others will read it. Posts into the internet
>are near immortal. I look at these statements and ask how all possible
>readers will interpret what's said. What was said contained a error that
>leads to false conclusions.
A couple of people used imprecise terminology, but to say there was
"a [sic] error" is somewhat mis-stating the case. Data reduction via
perceptual encoding is achieved through requantisation of the
original data. That means reduction of the number of bits, or what
some might think of as a process where "material is discarded" or
"only 20% of the original information" is saved. Those statements
are vague, from a scientific perspective, but so too is your
"synthesizing a whole new set of data". Not exactly a textbook
explanation, is it?
>
>DAT is lossy compression, hard disk digital is lossy compression, every
>single digital sampling method for sound is lossy. The question is not
>is it lossy, they all are. The question is what does that mean. Saying
>it's lossy is just the beginning, not the end of the discussion.
DAT and HD are not "lossy compression" at all. Having captured bits
via analogue to digital conversion, they do not then purposefully
reduce the bit-rate through requantisation - and that is, I repeat,
what lossy compression means. So the issue IS that ATRAC is lossy.
I recommend chapter 3 of Francis Rumsey's "The Audio Workstation
Handbook" (Focal Press) to anyone seeking clarification on audio data
reduction.
John
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