[FFmpeg-devel] [PATCH] Allow 'concat' filter to support inputs with different frame rates

Nicolas George george at nsup.org
Wed Mar 8 20:27:56 EET 2017


L'octidi 18 ventôse, an CCXXV, Calvin Walton a écrit :
> Right now, the concat filter does not set the frame_rate value on any of
> the out links. As a result, the default ffmpeg behaviour kicks in - to
> copy the framerate from the first input to the outputs.
> 
> If a later input is higher framerate, this results in dropped frames; if
> a later input is lower framerate it might cause judder.
> 
> The simplest fix is to just set the out links to have '1/0' as the frame
> rate, the value meaning "unknown/vfr". Note that this changes the filter
> chain to use AV_TB on the output rather than converting the timebase to
> match the listed framerate.
> 
> A test is added to verify the VFR behaviour. The change of output timebase
> means the existing concat test needs to be updated with new pts values.

I do not think that setting it to 1/0 is the correct fix for this issue.
Unless I am mistaken, the frame rate is available on all inputs when the
corresponding code is called: I think the correct fix would be to check
if all inputs have the same.

Regards,

-- 
  Nicolas George
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