[FFmpeg-trac] #10795(ffmpeg:open): scale2ref filter crash

[FFmpeg]

#10795: scale2ref filter crash
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             Reporter:  Axel Terizaki  |                    Owner:  (none)
                 Type:  defect         |                   Status:  open
             Priority:  important      |                Component:  ffmpeg
              Version:  git-master     |               Resolution:
             Keywords:  bounty         |               Blocked By:
             Blocking:  7.0            |  Reproduced by developer:  0
Analyzed by developer:  0              |
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Comment (by Niklas Haas):

 Looking at it more, I think scale2ref is fundamentally broken - there is
 no synchronization whatsoever between the two inputs, so the ref
 parameters may change at any time.

 I think the proper fix here would be to switch scale2ref to use
 FFFramesync, to synchronize the frames to be scaled with the correct ref
 frames. This will fix such issues and conveniently also avoids this bug,
 which happens only because of using the default .activate on a filter with
 multiple inputs and multiple outputs.

 The downside is that passing through the ref stream as well as the scaled
 stream becomes nontrivial. I'm wondering whether it's okay to just drop it
 - there is no reason for this filter to pass through the ref frames as
 well when it's already trivial to just re-use the input pin in a different
 filter with the existing filter graph infrastructure.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/10795#comment:10>
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