[FFmpeg-trac] #2342(avfilter:open): ebur128 filter output seems to break format auto negotiation

[FFmpeg]

#2342: ebur128 filter output seems to break format auto negotiation
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             Reporter:  cus         |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  avfilter
              Version:  git-master  |               Resolution:
             Keywords:  ebur128     |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  0           |
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Changes (by Cigaes):

 * status:  new => open
 * reproduced:  0 => 1


Comment:

 The problem is that {{{ebur128}}}'s {{{query_formats()}}} function sets
 the supported channel layouts (and formats) separately on its input and
 its audio output. That means lavfi is allowed to select them
 independently, and that {{{ebur128}}} is expected to convert somehow. That
 is not what happens: {{{ebur128}}} assumes that its input and audio output
 have the same format and channel layout; for that, it is supposed to set
 the supported formats and layouts together.

 That is exactly what the fallback {{{query_formats()}}} code does,
 therefore just removing the code fixes the bug.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2342#comment:1>
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