[FFmpeg-trac] #8987(documentation:new): zmq doesn't work in this filter chain

[FFmpeg]

#8987: zmq doesn't work in this filter chain
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             Reporter:  mkoch        |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  normal       |                Component:
                                     |  documentation
              Version:  git-master   |               Resolution:
             Keywords:  zmq          |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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Comment (by mkoch):

 After I've worked with zmq for about a week, I suggest to add the
 following revised note to the documentation of the zmq filter:

 It's possible to send zmq messages to all those filters and options that
 support commands. Don't send messages to other options, as this may lead
 to malfunction.
 However, not everything that's possible is also useful. For example, a
 message can be sent to the "width" option of the "scale" filter for
 changing the size of a video stream. But changing the size mid-stream
 isn't supported by many other filters (for example "eq", "colorkey" and
 "despill"). In some cases it works (for example the output of "scale" can
 be used as the second input of "overlay"), but in most other cases it
 fails.

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Ticket URL: <https://trac.ffmpeg.org/ticket/8987#comment:8>
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