[FFmpeg-trac] #1474(undetermined:open): Some audio encoders stopped encoding strange channel layouts

FFmpeg trac at avcodec.org
Wed Jul 4 20:22:06 CEST 2012

#1474: Some audio encoders stopped encoding strange channel layouts
             Reporter:  dcoffey3296  |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  important    |                Component:
              Version:  git-master   |  undetermined
             Keywords:  regression   |               Resolution:
             Blocking:               |               Blocked By:
Analyzed by developer:  0            |  Reproduced by developer:  1

Comment (by Cigaes):

 I would say that the current behaviour is correct: you are trying to
 encode an audio stream that has only a single left channel, and libfaac
 does not support that: it supports stereo, mono (which is a single
 ''center'' channel) and various surround layouts.

 There is no obvious way of converting a left channel into a center one: if
 it will be mixed with a right channel, then it needs to be divided by 2.

 We could add an exception to libswr to accept any single channel → single
 channel conversion, but I am not sure it would be a good idea: if not for
 that error, you may never have noticed that the file had a strange channel

 The correct course of action, IMHO, when dealing with such a file, is to
 tell ffmpeg exactly what you want to do: treat the left channel as center?
 mix it with the right? anything else?

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1474#comment:16>
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