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

[FFmpeg]

#5718: ffmpeg not remapping channels for libopus automatically
-------------------------------------+-------------------------------------
             Reporter:  agressiv     |                    Owner:  (none)
                 Type:  defect       |                   Status:  open
             Priority:  important    |                Component:  avcodec
              Version:  git-master   |               Resolution:
             Keywords:  libopus      |               Blocked By:
  regression                         |
             Blocking:               |  Reproduced by developer:  1
Analyzed by developer:  0            |
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Comment (by everlanes):

 I also ran into this problem and the suggested workaround is not working
 for me.

 I want to convert MKV files with multiple audio channels to opus audio
 keeping the layout of every single channel. When using the `-af
 channelmap=channel_layout="5.1"` option I get an error message for all
 stereo channels:
 {{{
 [Parsed_channelmap_0 @ 0x55a7dde59300] input channel #2 not available from
 input layout 'stereo'
 [Parsed_channelmap_0 @ 0x55a7dde59300] input channel #3 not available from
 input layout 'stereo'
 [Parsed_channelmap_0 @ 0x55a7dde59300] input channel #4 not available from
 input layout 'stereo'
 [Parsed_channelmap_0 @ 0x55a7dde59300] input channel #5 not available from
 input layout 'stereo'
 [Parsed_channelmap_0 @ 0x55a7dde59300] Failed to configure input pad on
 Parsed_channelmap_0
 Error reinitializing filters!
 Failed to inject frame into filter network: Invalid argument
 Error while processing the decoded data for stream #0:5
 }}}

 Furthermore I expect all 7.1 channels to be downmixed to 5.1 as well with
 these settings. I don't want that either.

 When removing the filter I get the original error:
 {{{
 [libopus @ 0x563a3830d9c0] Invalid channel layout 5.1(side) for specified
 mapping family -1.
 Error initializing output stream 0:2 -- Error while opening encoder for
 output stream #0:2 - maybe incorrect parameters such as bit_rate, rate,
 width or height
 }}}

 This seems to be a trivial problem as all it takes would be changing
 metadata `5.1(side)` to `(5.1)`. No downmixing, no recompressing of data,
 nothing. But yet, this bug is unresolved since five years now!

 Is there a solution (or another workaround ...) for this situation?
 Maybe a 3rd party tool or separate ffmpeg run just to change metadata of
 all 5.1(side) channels to 5.1?
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/5718#comment:20>
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