[vorbis] Lossless/lossy hybrid?

[Chun-Yu]

On May 31, 2001, Wilson wrote:

>SACD:  Freaky "DSD" (Direct Stream Digital) format, rather than PCM.
>I'll quote a Phillips page, since I don't really understand the details
>of this new format: "DSD is a revolutionary process based on 1-bit
>sigma-delta modulation, and operates with a sampling frequency of
2.8224 MHz."
>I gather that this makes it capable of an arbitrary number of channels,
>and roughly 100KHz of sampling rate.

Nope.  The sampling rate is really 2.8224 MHz.  SACD will record up to
over
100,000 Hz.Each "sample" is just 1 bit.
If you think about it, this is better than PCM because PCM requires good
DACs to convert from digital to analog.  The way DSD works, it is much
simpler
to perform the digital->analog conversion.  A PCM file of all -32768s
(in 16-bit
audio) would be all 0s in DSD.  A PCM file of all 32767s would be all 1s
in DSD.
A PCM file of all 0s would be half 0s and half 1s in DSD.  If the
digital signal
is converted to analog and passed through an analog lowpass filter, it
will
sound like whatever it's supposed to be.  It's that simple to do the
digital->analog
conversion with DSD.  I read all this at http://www.superaudio-cd.com/ a
while ago.
For a ton info about SACD, check it out.

Chun-Yu

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