[FFmpeg-trac] #6285(avfilter:open): ffmpeg hangs when using framerate filter since filtering rework

[FFmpeg]

#6285: ffmpeg hangs when using framerate filter since filtering rework
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             Reporter:  cus         |                    Owner:
                 Type:  defect      |                   Status:  open
             Priority:  important   |                Component:  avfilter
              Version:  git-master  |               Resolution:
             Keywords:  regression  |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  0           |
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Comment (by Cigaes):

 The {{{request_frame()}}} method of framerate returns 0 without sending a
 frame to its output. This is a bug in framerate. The new scheduling of
 filters is more strict, but it was already a break of internal API before.

 The code path goes through the final line of {{{request_frame()}}}:
 {{{
 return process_work_frame(ctx, 0);
 }}}
 and the block in {{{process_work_frame()}}} that starts with:
 {{{
 // should filter be skipping input frame (output frame rate is lower than
 input frame rate)
 }}}

 I do not know how framerate works, so I can not investigate further.

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Ticket URL: <https://trac.ffmpeg.org/ticket/6285#comment:2>
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