Try FLAC lossless encoding at
http://flac.sourceforge.com/ It's open source
and available for Window$ and *nix style OSes.
On a straight tone it does about 2:1 compression. Not great, but better than
nothing, and yields an EXACT (to the bit) replica when expanded. Cutting out
noise should yield better compression ratios, use a good quality tape deck
and audio digitizer. An external USB/IEEE1394 digitizer would be ideal,
cutting out internal computer EMI/RFI noise. Also, to save space, figure out
what frequency the tones are encoded at and adjust the sampling rate
accordingly (If it uses 2KHz tones, you only need a 4KHz sampling rate, and
can get away with an 8KHz sampling rate for recording) You can pass it
through a brickwall filter to clean out all the junk/noise above your
frequency if you have a nice enough audio processor. Sox might do it.
----- Original Message -----
From: "John Foust" <jfoust_at_threedee.com>
To: <cctalk_at_classiccmp.org>
Sent: Wednesday, August 21, 2002 7:41 PM
Subject: Re: Digitizing ancient cassette data (was Re: COSMAC VIP
documentation)
> At 12:08 AM 8/22/2002 +0100, Tony Duell wrote:
> >I'd do both. For some reason I feel that good old analogue tape is going
> >to be a lot easier to understand in he future than some of these modern
> >compressed digital formats....
>
> I wouldn't use anything but a straight digitization of the
> audio, either, if it was a purely audio recorder. Turning
> it to MP3 could yield mush in a spot and you'd never know it.
> Many tape readers for PC-level machines were just doing zero-crossing
> counting and other simple tricks. MP3 and other codecs are
> aimed at making sound that pleases the ear, not other machines.
>
> - John
>
Received on Thu Aug 22 2002 - 10:08:01 BST