I read a post on FriendFeed about listening to MP3 backwards, it uses Audacity to do the trick.
I came out with this command:
ffmpeg -i src.mp3 /tmp/src.wav && python -c "import wave ; s = wave.open('/tmp/src.wav', 'rb') ; r= wave.open('/tmp/rev.wav', 'wb') ; r.setparams(s.getparams()) ; count = s.getnframes()
while count > 0:
count -= 1
s.setpos(count)
r.writeframes(s.readframes(1))" && ffmpeg -i /tmp/rev.wav rev.mp3
It uses ffmpeg to convert mp3 to wave, then convert reversed wave back to mp3. The reversing process uses Python's wave module. Here is a better formatting of code:
import wave
s = wave.open('/tmp/src.wav', 'rb')
r= wave.open('/tmp/rev.wav', 'wb')
r.setparams(s.getparams())
count = s.getnframes()
while count > 0:
count -= 1
s.setpos(count)
r.writeframes(s.readframes(1))
If readframes() returned a list of frames, line count would be reduced by four, and it could run much faster. It runs pretty slow, because it reverses frame by frame, I think Audacity could do this in a blink of second. But my point is to make the code one-liner (it actually is five lines).
"Boom De YaDa" is the audio file I used to test, the result is pretty interesting (or creepy?). You can listen it here (Hope Discovery wouldn't mind).
Updated
Now this is a true one-liner:
ffmpeg -i src.mp3 /tmp/src.wav && python -c "import wave ; s = wave.open('/tmp/src.wav', 'rb') ; r= wave.open('/tmp/rev.wav', 'wb') ; r.setparams(s.getparams()) ; d = [s.readframes(1) for i in range(s.getnframes())] ; d.reverse() ; r.writeframes(''.join(d))" && ffmpeg -i /tmp/rev.wav rev.mp3
Python part:
import wave
s = wave.open('/tmp/src.wav', 'rb')
r= wave.open('/tmp/rev.wav', 'wb')
r.setparams(s.getparams())
d = [s.readframes(1) for i in range(s.getnframes())]
d.reverse()
r.writeframes(''.join(d))
And it runs much faster!
