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From: brad@kontron.UUCP (Brad Yearwood)
Newsgroups: net.audio,net.analog,net.graphics
Subject: Digital audio - sample rate conversion
Message-ID: <531@kontron.UUCP>
Date: Sun, 23-Feb-86 22:40:50 EST
Article-I.D.: kontron.531
Posted: Sun Feb 23 22:40:50 1986
Date-Received: Wed, 26-Feb-86 06:02:57 EST
Distribution: net
Organization: Kontron Electronics, Irvine, CA
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Xref: linus net.audio:7146 net.analog:692 net.graphics:1441

There has been some discussion recently about digital audio tape formats,
and about how sampling rates are being made purposely incompatible with
the Compact Disc standard, presumably to prevent verbatim high-quality
copying.  This raises a question - what techniques could one use to
implement a clean conversion from one sample rate to another - either
upward or downward, without converting back to analog and then re-digitizing
at the other rate?

Intuitively, I can more-or-less grasp the use of an FIR digital filter to
interpolate in the Philips 4x "oversampling" CD playback filter system.  What
happens if you are not resampling to a convenient integer multiple of the
original rate?  Would a similar technique be applicable for increasing
or decreasing the sampling by non-integer factors?  Resampling to a decreased
rate is particularly baffling.

I suspect that the problem is similar (and a dimension simpler)
to conversion of television signals from one standard to another or
image magnification/shrinking.  If anyone is familiar with literature
relevant to any of these areas, I would appreciate some pointers.


Brad Yearwood
Kontron Electronics  {voder, pyramid, loral}!kontron!brad
Mountain View, CA