[FFmpeg-trac] #5718(avcodec:open): ffmpeg not remapping channels for libopus automatically

FFmpeg trac at avcodec.org
Sun Jul 17 23:28:12 EEST 2016

#5718: ffmpeg not remapping channels for libopus automatically
             Reporter:  agressiv     |                    Owner:
                 Type:  defect       |                   Status:  open
             Priority:  important    |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  libopus      |               Blocked By:
  regression                         |  Reproduced by developer:  1
             Blocking:               |
Analyzed by developer:  0            |

Comment (by mgraczyk):


 libopusenc can accept many channel layouts that are not possible to
 express using the channel_layouts bitfield system. There are channel
 layouts which are supported by libopus which are not expressible by the
 channel_layouts member.  I removed channel_layouts from the codec
 definition to prevent ffmpeg.c from halting with an error when one of
 these unexpressible layouts was passed in.

 Is there a way to specify at the command line "no channel layout", or
 "unknown layout"? With such a flag, I could add channel_layouts back to
 libopusenc and also add code to handle the "no layout" case. I believe
 last time I asked about this, it was problematic because the channel count
 is represented by the popcount of the layout bitfield, and the "no channel
 layout" layout could have any channel count.

Ticket URL: <https://trac.ffmpeg.org/ticket/5718#comment:9>
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