... in GStreamer never worked, uh? :). This bug contained a non-functional patch for a while (memory issues, pretty bad, even valgrind didn't find anything useful), until I decided to pick it up again and found the issue! MPEG-2/4 AAC audio, AC-3 and DTS multichannel audio now works, lots of other stuff is still TODO (some demuxers (matroska, maybe mpeg, avi, quicktime), some decoders (vorbis/mp3) and encoders (ffenc_ac3/faac), maybe muxers). Vorbis and MP3 apparently can contain 5.1 audio too, but the channel-mapping (so which channel index number represents which position in a room?) is unknown to me. OggDS seems to indicate it's similar to that of AC-3, so maybe I'll add that to at some point. Info is appreciated.
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Ah what the hell, I fixed vorbis too. :-).