Efika 5200B Project Reggae on Efika in category Multimedia proposed by Grzegorz Kraszewski on 21st February 2006 (accepted on 20th March 2006) [View Full Project]

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	Did I write something about ADPCM? posted by Grzegorz Kraszewski on 24th January 2007 Well, 3-bit decoder is done. Documentation was wrong, so I had to find some details by experimenting. What is interesting 3-bit IMA ADPCM is rarely supported, for example WinAMP complains about missing codec (it plays 4-bit files however). Libsndfile has no 3-bit decoder as well. The only application I've found, able to generate 3-bit files is CoolEdit 2.0 (it has buggy encoder BTW, as it happily writes truncated block at the end). Anyway Reggae decodes now both 3- and 4-bit IMA ADPCM, for any number of channels up to 256. I've tried to optimize a bit, discarding index update table and replacing it with a few conditionals. It seems to be slower however. The last thing I want to try is replacing main step table (89 entries of 16-bit words) by polynomial approximation (3-rd order). It may be faster, but I'm not sure. After checking this I will consider ima-adpcm.decoder as finished and release it.