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I have an algorithm for decompressing IMA ADPCM from http://wiki.multimedia.cx/index.php?title=IMA_ADPCM, but no way to re-compress it back to IMA ADPCM. Is there a simple pseudo code description, or do I have to reverse engineer it from the decompression algorithm?

I'm doing this because I'm writing a server that needs to receive audio, merge the audio tracks together, then send it back out.

Thanks for any help.

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  • I'm even more confused now because I found this: http://yxit.co.uk/source/. There's an implementation of IMA ADPCM in there (gotta scroll a little), and it seems almost completely different and doesn't work – skagzilla Feb 07 '11 at 05:23

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Oops...

I did look around a bit and even found my way to this question: What is the algorithm of converting pcm to adpcm?. And to the site that held the answer for both questions: http://www.cs.columbia.edu/~hgs/audio/dvi/.

But I was too frustrated with looking through so many pages and documents that I gave up looking when I couldn't find the page.

But I found it. Pages 31-35 give the algorithm and a examples of running through it.

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