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From: ben@catnip.UUCP (Bennett Broder)
Newsgroups: net.audio,net.analog,net.graphics
Subject: Re: Digital audio - sample rate conversion
Message-ID: <241@catnip.UUCP>
Date: Tue, 25-Feb-86 20:28:52 EST
Article-I.D.: catnip.241
Posted: Tue Feb 25 20:28:52 1986
Date-Received: Fri, 28-Feb-86 05:20:10 EST
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In article <531@kontron.UUCP>, brad@kontron.UUCP (Brad Yearwood) writes:
> 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?
>                                 If anyone is familiar with literature
> relevant to any of these areas, I would appreciate some pointers.

This is a very real concern faced by record companies today.  Many of
the best digital tape recorders available operate at a higher sampling
rate than used on CDs (e.g., the Soundstream at ~50k samples/sec).  Last
I heard, the only digital recorder to operate at 44.1 is the Sony PCM 1610,
which has a reputation for mediocre analog electronics.

What I am leading up to is, this problem has been solved using a commercial
device called (of all things), a sampling rate converter.  According to
Telarc (who uses this device on almost all their CDs), this transformation
occurs *completely* in the digital domain.  The device Telarc uses is made
by Studer/Revox (1425 Elm Hill Pike, Nashville, Tenn 37210).  I don't know
how helpful the folks at Studer would be, but if they were willing to sell
you a service manual, send you literature, or just chat on the phone, you
could probably get a handle on how the thing works.

-- 

Ben Broder
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