* Sean Buckingham <[EMAIL PROTECTED]> on Mon, 05 Jun 2000
| Whilst I would have little technical comprehension of how discs could be
| coded differently yet still read on the same machines, surely this is what
| is happening?
Not even close.
What is different is the psychoaccoustic model used for the encoding
process. The way ATRAC functions is that it takes an input stream and
breaks it up into a number of bands, each of which has a fixed data width.
The first thing that happens is that the psychoaccoustic model is used to
determine how many bands or channels are allocated to different frequency
ranges. That is, if a chunk of music has a lot of high frequency sounds
but few low frequency sounds, more bands will be allocated to the high
frequency ranges and fewer to the low frequency ranges. More bands means
greater resolution and fidelity. Once bands have been allocated, each band
is processed with the psychoaccoustic model to remove sounds that cannot be
heard.
Improvements to ATRAC are really improvements to the psychoaccoustic models
used for encoding. The "format" of data on a disc is identical; the
difference is in which bits are recorded and which are not. And as the
psychoaccoustic model has absolutely nothing to do with playback, there is
100% forward and backward compatability.
--
Rat <[EMAIL PROTECTED]> \ Warning: pregnant women, the elderly, and
Minion of Nathan - Nathan says Hi! \ children under 10 should avoid prolonged
PGP Key: at a key server near you! \ exposure to Happy Fun Ball.
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