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Hi
I would like to transcode AAC from stereo to mono
is the same with AAC stereo to AMR mono


LOG:
[00000293] stream_out_duplicate private debug: duplicated a new stream codec=mp4a (es=1 group=0)
[00000295] stream_out_transcode private debug: creating audio transcoding from fcc=`mp4a' to fcc=`mp4a'
[00000330] main decoder debug: looking for decoder module: 23 candidates
[00000330] main decoder debug: using decoder module "faad"
[00000331] main encoder debug: looking for encoder module: 6 candidates
[00000331] ffmpeg encoder debug: libavcodec initialized (interface 3348736 )
[00000331] ffmpeg encoder debug: found encoder MPEG AAC Audio
[00000331] main encoder debug: using encoder module "ffmpeg"
[00000346] main private debug: looking for audio filter2 module: 4 candidates
[00000346] linear_resampler private debug: fl32/44100KHz/2->fl32/8000KHz/1
[00000346] main private debug: using audio filter2 module "linear_resampler"
[00000353] main private debug: looking for audio filter2 module: 4 candidates
[00000353] audio_format private debug: fl32->s16l, bits per sample: 32
[00000353] main private debug: using audio filter2 module "audio_format"
[00000355] main private debug: looking for audio filter2 module: 4 candidates
[00000295] stream_out_transcode private error: no audio filter found for mixing from 2 to 1 channels
[00000330] main decoder debug: removing module "faad"
[00000331] main encoder debug: removing module "ffmpeg"
[00000346] main private debug: removing module "linear_resampler"
[00000353] main private debug: removing module "audio_format"
[00000295] stream_out_transcode private error: cannot create audio chain
[00000293] stream_out_duplicate private debug: - failed for output 0
[00000326] main packetizer error: cannot create packetizer output (mp4a)

AAC stereo -> mpeg audio mono

[00000295] stream_out_transcode private debug: creating audio transcoding from fcc=`mp4a' to fcc=`mpga'
[00000330] main decoder debug: looking for decoder module: 23 candidates
[00000330] main decoder debug: using decoder module "faad"
[00000331] main encoder debug: looking for encoder module: 6 candidates
[00000331] ffmpeg encoder debug: libavcodec initialized (interface 3348736 )
[00000331] ffmpeg encoder debug: found encoder MPEG Audio layer 1/2
[00000331] main encoder debug: using encoder module "ffmpeg"
[00000346] main private debug: looking for audio filter2 module: 4 candidates
[00000346] linear_resampler private debug: fl32/44100KHz/2->fl32/48000KHz/1
[00000346] main private debug: using audio filter2 module "linear_resampler"
[00000353] main private debug: looking for audio filter2 module: 4 candidates
[00000353] audio_format private debug: fl32->s16l, bits per sample: 32
[00000353] main private debug: using audio filter2 module "audio_format"
[00000355] main private debug: looking for audio filter2 module: 4 candidates
[00000295] stream_out_transcode private error: no audio filter found for mixing from 2 to 1 channels
[00000330] main decoder debug: removing module "faad"
[00000331] main encoder debug: removing module "ffmpeg"
[00000346] main private debug: removing module "linear_resampler"
[00000353] main private debug: removing module "audio_format"
[00000295] stream_out_transcode private error: cannot create audio chain
[00000293] stream_out_duplicate private debug: - failed for output 0

it's same with leatest build of VLC