[FFmpeg-trac] #1339(avfilter:new): Auto insert fps filter as adapter for overlay filter inputs with different framerates

[FFmpeg]

#1339: Auto insert fps filter as adapter for overlay filter inputs with different
framerates
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             Reporter:  annorax      |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avfilter
              Version:  git-master   |               Resolution:
             Keywords:  fps overlay  |               Blocked By:
  filter                             |  Reproduced by developer:  0
             Blocking:               |
Analyzed by developer:  0            |
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Comment (by rogerdpack):

 A few notes here:

 1) the "main" video fps always wins for the output.
 2) according to what I can see in
 https://github.com/FFmpeg/FFmpeg/blob/master/libavfilter/vf_overlay.c what
 it does is, for each "main" frame coming in, it looks for the overlay
 frame that "overlaps" that one in PTS (or matches it).  So it basically
 outputs the original video, with a synchronized overlay on it. So order
 really matters here. Maybe the documentation could be updated a bit to
 make this more clear?  It seems like reasonable functionally...unless you
 have 2 inputs with variable frame rates, so couldn't decide which one is
 the "main" one but I'd imagine that's pretty rare...

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Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/1339#comment:7>
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