[FFmpeg-trac] #5856(undetermined:closed): filter_complex significantly slower than -vf for the same task.

[FFmpeg]

#5856: filter_complex significantly slower than -vf for the same task.
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             Reporter:  Zibri        |                    Owner:
                 Type:  defect       |                   Status:  closed
             Priority:  normal       |                Component:
              Version:  git-master   |  undetermined
             Keywords:               |               Resolution:
             Blocking:               |  needs_more_info
Analyzed by developer:  0            |               Blocked By:
                                     |  Reproduced by developer:  0
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Comment (by Misaki):

 The command that uses the slow preset has the highest fps during
 recording. The fast preset command is slow.

 Some complications: a live source, the minor changes made to change from
 complex filtergraph to a 'simple' one. What happens if you use a video
 file as the input and change the '-vf' in the second command back to
 '-lavfi' or '-filter_complex'?

 In my experience, filter_complex uses bilinear filter for scaling by
 default instead of bicubic, and sometimes has varied output between runs
 instead of always the same for vf, but haven't noticed it to be slower.

 I did once find that having an extra filter (showinfo) seemed to result in
 better performance, but I think this might actually have been due to
 keeping CPU or GPU at a high frequency.

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Ticket URL: <https://trac.ffmpeg.org/ticket/5856#comment:6>
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