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Recovering a corrupted .wav file with Python

Recovering a corrupted .wav file with Python

Last night, I lost the recording of the Procrastination Cure workshop I was giving, due to a crash of PowerGramo, the recording software I use with Skype.  Luckily, a participant had a pair of recordings they made with Gizmo, which was what he was using to call in to the teleconference.

Unfortunately, the reason he had two recordings was because his machine had crashed, about two and a half hours into the workshop, so the first recording was corrupted and couldn’t be played back in Media Player, and I tried using several audio editors to recover it, but it was a no-go.  The only thing I found on the net about recovering corrupted .wav files was this Gizmo FAQ answer, so it’s apparently a common problem.  I tried the audio editor they recommended there, but it didn’t work either.

So it was time to pull out the big guns.  I found this handy .wav format guide via Wikipedia, and then whipped out my Python interpreter.  After a little bit of playing around, I figured out that the problem was the program writing the file simply hadn’t filled in the length fields in the header structure, and so I manually recovered the file, using steps roughly equivalent to this:

from struct import pack, unpack

wav_header = "4si4s4sihhiihh4si"

f = file(filename, 'rb+')
data = list(unpack(wav_header,f.read(44)))
assert data[0]=='RIFF'
assert data[2]=='WAVE'
assert data[3]=='fmt '
assert data[4]==16
assert data[-2]=='data'
assert data[1]==data[-1]+36

filesize = f.tell()
datasize = filesize - 44

data[-1] = datasize
data[1]  = datasize+36

f.write(pack(wav_header, *data))

And now the file plays. Yay! Unfortunately, the recordings aren’t of very good quality, but there’s nothing that Python can do about that, as far as I know. 😉

Join the discussion
  • this script saved me!! thank you so much! I recorded myself djing a party the other night and an hour and 30 minutes into it, someone unplugged my power strip… being that I was on laptop power I didn’t realize until later on that the wave file recording was corrupt… after trying to so many different audio apps and trying to rescue the “raw data” from the file, I stumbled upon this script… ran it, boom! fixed! Thanks again!!

  • The script didn't quite work for me on my ~2 hr recording–the latter three assert commands failed, and the final write command reports an integer out of range. The latter I may be able to fix by setting a lower "datasize," but I am not familiar with assertions. Do you know what may be the problem?

  • I think you probably have a file with a different format than the one I fiddled with; you should read the .wav format guide I linked in order to find out what the values in your file mean.



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