>From: "Alex LeVine" <[EMAIL PROTECTED]>
> In closing: what is the maximum decompressed PCM output wordlength according
> to the MD spec? And what is the maximum PCM wordlength that can be fed into
> the MD compression DSP stage?
Well, after searching around, minidisc.org came through as usual, and I
think that I might have answered my own question (doh!). Here's the link to
a great interview from 1995 with Sony engineers:
http://www.minidisc.org/mj_ja3es.html It explains MD Theory better than
anything I've read yet, as long as you are sort of familiar with the basics
of lossy digital audio compression.
The pertinent quote:
"Fujiyama: Right. The scale factor is held in 6 bits of the data, this
allows from -120dB to +6dB of dynamic range to be expressed. And in so
doing, if you only look at this, MiniDisc has in principal 126dB dynamic
range. However, to realize this you'd have to use a DSP with an awful lot
of processing power. Since the current products are not able to do that, it
is of course less than that [126dB]."
So it would seem that if you can feed your MD 20 (120dB) or even 21 (126dB)
clean bits, the DSP can use all the data, and you could get a dynamic range
that blows away CDs and DATs! Of course, you would need a 24 bit converter,
and that explains Sony's new machines. Note that the interview is 4 years
old; I assume that by now the DSPs actually have the power that he speaks of
in the above quote. Now the real question: when do we get the ATRAC Type
R/24 bit ADC in portable Sonys? I'll sell my Sharp in a second for that
sound ;-)
Of course, the analog preamp before the ADC is gonna hafta be incredibly
quiet...
-Alex in NYC
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