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------------------- Message requiring your approval ------------------From:
"Gillespie, Douglas" <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Subject: Summary of lossless compression
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Thanks to all of you who replied to my query regarding lossless
compression. Before continuing I must confess that I have not had a chance
to try any of them yet but I did download the C source code for FLAC and
it's pretty readable - if anyone is interested in how I get on, ask me at
the end of the summer field season.
Generally, respondents agreed that you don't get much better than 50%
compression with lossless algorithms (lossy MP3 by comparison gives about
90% compression, but possibly throws out that odd little bit of the sound
that only you really care about).
The most open sourced, legally free, code I could find was FLAC available
at <a href="http://flac.sourceforge.net/";
rel="nofollow">http://flac.sourceforge.net/</a>. Source code is all there for
the taking.
There is also shorten (FLAC claims to have based a lot of it's ideas on
shorten). It's not totally open source, but you get the impression from the
web site that it's well worth asking:
<a href="http://mi.eng.cam.ac.uk/comp.speech/Section3/Software/shorten.html";
rel="nofollow">http://mi.eng.cam.ac.uk/comp.speech/Section3/Software/shorten.html</a>
(I couldn't get the downloads on that page to work.) There is more
information at <a href="http://research.umbc.edu/~hamilton/shnfaq.html";
rel="nofollow">http://research.umbc.edu/~hamilton/shnfaq.html</a>. I couldn't
find any source code.
For wavelet fans, there is information on lossless compression using this
technique at <a
href="http://www.bearcave.com/misl/misl_tech/wavelets/compression/";
rel="nofollow">http://www.bearcave.com/misl/misl_tech/wavelets/compression/</a>
There is C code available too.
There is also a lossless compression format bundled up with the new ipod
software (iTunes). I've not yet had the opportunity to check this out, but
I assume that the source code is not available.
There are apparently lossy formats which work out better than MP3 in terms
of reproduction quality and size - <a href="http://www.xiph.org/ogg/vorbis/";
rel="nofollow">http://www.xiph.org/ogg/vorbis/</a> comes
recommended.
One respondent suggested it will be less trouble to buy bigger hard drives,
which now work out at around 1 US$ per gigabyte - probably true, but I have
a crowded office and even halving the pile of hard drives on my desk would
make me happy.
Thanks again to Julian Rohrhuber, Jim Partan, Daniel Margoliash, Eric
Delroy, Patrick Clemins, John Burt and Claude Nozeres for your help.
Douglas.
=====================================
Douglas Gillespie
Song of the Whale research team
International Fund for Animal Welfare
<a href=":[EMAIL" rel="nofollow">:[EMAIL</a> PROTECTED]
web <a href="http://www.ifaw.org"; rel="nofollow">http://www.ifaw.org</a>
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