[FFmpeg-devel] [PATCH 3/4] ffmpeg: with filter_complex, avoid random in<->out mapping.

Nicolas George nicolas.george at normalesup.org
Thu May 24 12:28:03 CEST 2012

Le sextidi 6 prairial, an CCXX, Michael Niedermayer a écrit :
> maybe, until a more powerfull system exists we could simply select
> the input with matching type with the finest timebase ?

I think it would be a bad idea: imagine something like that:

	[24fps] [25fps] overlay [out]

The overlay filter is driven by its main input, so it will output 24 fps,
and the overlay will skip a frame and stutter once per second, which may be
acceptable. With your suggestion, the output will be selected at 25 fps, and
thus get another round and stutter with frame duplication.

> (one could also pick the largest timebase that allows all timestamps
>  of all inputs with same type to be exactly represented, but iam not
>  sure this is better with actual real world data)

With an input at 24 and an input at 25, it requires time base = 1/600 and
that is already too much for a container that only supports constant frame

I believe using the link time base, and letting the user set the frame rate
if necessary is the best option for now.


  Nicolas George
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