[FFmpeg-trac] #4884(swresample:open): Segfault processing audio when using -f lavfi

FFmpeg trac at avcodec.org
Wed Sep 30 16:43:37 CEST 2015

#4884: Segfault processing audio when using -f lavfi
             Reporter:               |                    Owner:
  bobziuchkovski                     |                   Status:  open
                 Type:  defect       |                Component:
             Priority:  important    |  swresample
              Version:  git-master   |               Resolution:
             Keywords:  crash        |               Blocked By:
  SIGSEGV                            |  Reproduced by developer:  1
             Blocking:               |
Analyzed by developer:  0            |

Comment (by Cigaes):

 The second audio frame is quad while the others are 5.1; lavfi does not
 support formats changes yet, but the movie source does not check for it,
 hence the failure.

 (As a side note, before trying a debugger backtrace, try to rebuild with
 {{{--assert-level=2}}}, the error message would have been much clearer.)

 I am not sure how to fix this. Implementing format reconfiguration is a
 lot of work. Detecting it would not solve the problem, only make the
 failure cleaner; and some filters actually work with format
 reconfiguration, that would break things for them.

 In the meantime, you can get things working by separating audio and video

 ffmpeg -f lavfi -i 'movie=file.mpg:s=v[out0+subcc]' \
   -i file.mpg \
   -map 0:v -map 1:a -map 0:s output

Ticket URL: <https://trac.ffmpeg.org/ticket/4884#comment:2>
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