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IMA ADPCM encoding
post Oct 21 2005, 04:52
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From: Buenos Aires
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Hi, I recently acquired a cheap chinese MP3 Player with voice recording/encoding capability.

The max voice quality you can get from this is "IMA ADPCM 16bit 32kbps mono".

I downloaded some voice encodings from the player and opened them with Adobe Audition, edited useless parts and saved as the same format.

There is supposedly a re-encoding process going on, but I canīt notice any quality degradation. I really donīt want to save to plain PCM because, correct me if Iīm wrong, the files would be 4 times bigger (I already tried with approximately 4x size increase).

What would you do to preserve as much quality as possible without increasing the size (I mean keeping it around the same bitrate)?


Edit: it was actually 32kbps

This post has been edited by Megaman: Oct 23 2005, 01:40
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post Jun 19 2009, 01:37
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Most algorithms referred to as ADPCM work on a sample by sample basis. So you can splice without much surprise in any "leaky adaptation", "leaky predictor" kind of ADPCM, i.e. any kind of Goodman-Gersho or later, as opposed to the original Jayant, et al. quantizer.

J. D. (jj) Johnston
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