The FFmpeg API needs to be fixed before this can be done sanely.
ffdca wants the desired output channel count to be set in
avctx->channels. Unfortunately it also completely fails if the requested
number of channels is not available rather than returning a different
amount (if 6 channels are requested we'd probably rather use stereo than
fail completely).
ffvorbis ignores caller-set values in avctx->channels. It writes the
channel count there once during init. This means the caller can only
set the count before init because later there would be no indication
whether the channel count in avctx reflects real output.
ffwma requires the caller to supply the encoded channel count
in avctx->channels during init or it fails. So it is not possible to
set a different number of desired output channels there before init
either.
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@23998 b3059339-0415-0410-9bf9-f77b7e298cf2
