[FFmpeg-user] Explanation of how -r affects frame rate of filtergraph

Nicolas George george at nsup.org
Thu Feb 27 09:32:23 EET 2020

Peter (12020-02-27):
> This also results in a 30fps output with all frames present but seems
> counter intuitive to put the frame rate on an image input.

FFmpeg works with videos. You are feeding it an image, it's considered
as a video, it needs a frame rate. If you don't specify it, you get a
default value. Relying on default value is rarely a good idea.

>				       Is someone able to explain how this is
> working internally?

All frames have a timestamp. If there is a regular frame rate, it is
only the inverse of the constant time difference between frames.

>			And whether or not this "fix" is actually reliable or
> just a lucky coincidence?

Yes, except the option is really named framerate.


  Nicolas George

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