Subject: [linux-audio-dev] Reverse-engineering files
From: Paul Winkler (slinkp23_AT_yahoo.com)
Date: Wed Nov 29 2000 - 21:12:02 EET
Hi folks,
<exposition style="rant">
I recently bought a Yamaha SU700 phrase sampler.
While it has some really cool features that sold me on it, and fills a
gaping void in my live rig, and it was by far the most flexible and
useable device of its kind that I could find short of spending twice
as much on an Akai MPC ... it has so many really stupid limitations
that I'm determined that this will be the last piece of dedicated
digital hardware or closed-source software I will buy.
One of the big dumb issues is that its support for working with a PC
is unbelievably limited. No MIDI sample dump, no SCSI sample dump even
with the SCSI expansion card.
All you can do is import and export AIFFs on a floppy disk, one at a
time - you can't even do it with a SCSI device if you hook one up; you
can only ever import and export AIFFs on floppy. And guess what -
about half the AIFFs I try to load don't work.
Stupid.
</exposition>
So I'm sneaking in the back door. I've got about 90% of the sample
file format figured out and I can now read and mostly write its
proprietary file format with a module I wrote today for SoX. Once this
is working more reliably I will release it to the general public - if
Chris Bagwell & co. approve, it will become part of SoX.
Now my question:
I don't suppose anyone else on this list has one of these samplers?
And I don't suppose anyone has the time or inclination to help me
figure out the last bits of the file format? I could really use
another set of eyeballs in there, I'm losing steam.
There's about 10 bytes of the header that I have no idea what they do,
except that if you get them wrong your sample either doesn't load in
the SU or it loads and eats up all available memory. The format is
mostly right out of the AIFF standard except the mystery data in the
APPL chunk (which is where they put the sound data too, just to be
perverse).
It took me a while to figure out as much as I did, so as is my habit,
I took way too many notes. Anyone interested in helping out can read
them at:
http://www.slinkp.com/pw_linux/su700notes.txt
This is my first attempt at reverse-engineering a sound format, so
it's slow going, even with the AIFF spec at hand, and Chris' excellent
audio file format FAQ.
Thanks,
PW
................. paul winkler ..................
slinkP arts: music, sound, illustration, design, etc.
web page: http://www.slinkp.com
A member of ARMS: http://www.reacharms.com
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