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From: EHARNDEN@AUVM.BITNET (Eric Harnden)
Newsgroups: bit.listserv.emusic-l
Subject: pcm data
Message-ID: <EMUSIC-L%90021023100697@AUVM.BITNET>
Date: 11 Feb 90 03:52:12 GMT
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ok, i think i'm a little confused here...
a lot of synths these days take 'pcm' data in one form or another.
recently i did a dump from my waveframe, and looked at the data. the tech in
boulder had said something about it being 'pcm' (in one conversation),
and '16 bit linear' (in another). it looked like 2's complement to me.
now, isn't linear normally what you call it when the zero is just offset,
so the most negative value is near numeric zero, the most positive is up
at the top, and the relative zero is in the middle of the numeric range?
was i just having a fuzzy conversation, or is linear becoming confused
with 2's complement these days? and what's 'pcm' anyway? the data is clearly
just simple sample points in the old style... each word represents an
amplitude level. if this is pulse code modulation, then what is the pulse that
is being modulated? i see the code changing form word to word, but that
doesn't sufficiently describe the term. also, 'pcm' didn't come to my
attention as a term until it was used to describe the technique for encoding
digital sound on linear tape. now i know that what's going on that tape is
some kind of modulated carrier, and i presumed some time ago that the
'pulse code' in pcm was sort of like that in SMPTE sync tone... a data
word that controlled the modulation of the carrier. but i never really bothered
to find out. still, i get the distinct impression that the term has fed
back into the technology under a different meaning, since i now hear of
run-of-the-mill parallel-bit sample data referred to as pcm.
so what gives?
any enlightenment out there in emusicland?

Eric Harnden (Ronin)                         Mailing From:
<EHARNDEN@AUVM>                              Physics Dept./Audio Tech.
Transmedia Music                             The American University
(202) 347-8050                               Wash., D.C