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Date:      Sat, 27 Dec 97 9:48:08 CST
From:      "Daniel M. Eischen" <deischen@iworks.InterWorks.org>
To:        jmz@cabri.obs-besancon.fr
Cc:        freebsd-hackers@FreeBSD.ORG, tlambert@primenet.com, jkh@time.cdrom.com, mike@smith.net.au, grog@lemis.com, mheller@student.uni-kl.de
Subject:   Summary: Converting DAT audio tapes to CD
Message-ID:  <199712271548.JAA03419@iworks.InterWorks.org>
In-Reply-To: <9712270434.AA11388@cabri.obs-besancon.fr>; from "Jean-Marc Zucconi" at Dec 27, 97 5:34 am

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[ Re: audio DAT to CD conversion ]

I'd thought I'd summarize to make a future archive search easier.

Greg Lehey
> There's a lot more involved than just copying.  IIRC, CDs record at
> 41.4 ksamples/second, and DATs record at 44 or 48 ksamples/second, so
> you'd effectively have to remaster.  I suppose straight interpolation
> would work, but it's still a lot of processing.

Jordan Hubbard
> The Zefiro Acoustics ZA2 (http://www.zefiro.com/za2/).  The software
> for it runs under Win95 (ack) though the folks at http://www.opensound.com/
> also claim it among their supported sound cards for FreeBSD, though lord
> only knows in what capacity.  It might be worth at least asking them.

Martin Heller
> Getting Audio data from a DAT is not trivial.
> To do this you need a special ROM on your
> DAT drive, SGI DATs are the only ones to have such a beast AFAIK.
> There is no known way around this problem - ever put a audio DAT
> tape into a DAT streamer ? my DAT doesnt like them and throws them
> out.

Terry Lambert
> DAT frequencies are such that when combined with CD frequencies,
> a harmonic "beat frequency" is created.  This makes CD's digitally
> transscribed to DAT -- suck.

Jean-Marc Zucconi
> No. DAT sampling rates are 32KHz, 48KHz and 44.1KHz (and some can do
> 96KHz too). If you record at 44.1KHz there is no problem to transfer
> digital data.

Mike Smith
> Linear interpolation is trivial, and would probably yield an acceptable 
> result.  A polynomial interpolation would yield a rather more faithful 
> conversion, with a speed tradeoff of course.

The general consensus seems to be that it can be done (in software),
with a couple of problems:

  1) Reading the audio data from the DAT tape.  Martin Heller
     has said that not many DAT drives will do this, perhaps
     only SGIs.  We have some SGIs here, so I may be able to
     try this if they're standard DAT drives have this ability.

  2) Converting audio data format to DAT audio format.  It seems
     we need to first detect at what rate the DAT tape was recorded,
     and then perhaps perform some interpolation to get it into
     CD format.

Thanks,

Dan Eischen
deischen@iworks.InterWorks.org




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