[FFmpeg-trac] #3079(FFmpeg:open): libavfilter caches and drops frames with multiple desynched input streams

[FFmpeg]

#3079: libavfilter caches and drops frames with multiple desynched input streams
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             Reporter:  richardpl   |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  FFmpeg
              Version:  git-master  |               Resolution:
             Keywords:  bounty      |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  1           |
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Changes (by Cigaes):

 * analyzed:  0 => 1
 * component:  avfilter => FFmpeg


Comment:

 The problem has actually nothing to do with lavfi: lavfi request frames on
 the correct input. Unfortunately, ffmpeg decides to provide frames on the
 other one.

 The reason is the multithreaded handling of inputs in ffmpeg: geq is
 slower than the rest of the processing, therefore frequently ffmpeg tries
 to read a frame from it when it is not ready, and reverts to reading from
 the file. This behaviour may be useful when reading from network streams,
 but it is harmful in other cases.

 Fixing it withoug losing the benefits of multithreaded inputs will be
 tricky.

 Your bug reports suck.

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/3079#comment:15>
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