assuming that the file is aac encoded: libfaaad (http://www.audiocoding.com/) provides aac decoding on linux: "FAAD2 is the fastest ISO AAC audio decoder available. FAAD2 correctly decodes all MPEG-4 and MPEG-2 MAIN, LC (Low Complexity), HE (High Efficiency), LTP (Long Term Prediction), LD (Low Delay) and ER (Error Resiliency) object type AAC files." mplayer includes it internally, so (having paid the requisite fee to the MPEG Licensing Authority) you *should* be able to decode to wav like this: mplayer -ao pcm -aofile <o/p audiofile> x.m4a; if you wanted to get advanced you could pipe directly into flac or vorbis encoders. mplayer rocks!:-) cheers -- Tim Orford