You are correct; mp4 and m4a are the same with the exception of its extension. ACC, isn't that where they have all the surround sound component (guessing)? Maybe you need the codec for the wma.
what is the difference between mp4, m4a and aac files?
I tried creating one track at the same quality using all 3 formats, mp4 and m4a file sizes were the same, aac was slightly smaller
which format delivers better quality at the same bitrate? they sound pretty much the same!
also which format is the most compatible one? (like aac doesnt seem to work on winmedia player 10)

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