[FFmpeg-user] Extract image every x frames?

Nicolas George nicolas.george at normalesup.org
Tue Aug 7 14:22:26 CEST 2012

Le primidi 21 thermidor, an CCXX, Peter B. a écrit :
> However, it's incredibly slow!
> When I extract the keyframes using the looping method, it's done in a
> second, whereas using the "-vf select" filter it takes almost 15
> minutes (!) to process a 30 minute ffv1 PAL/SD file.
> The image file for the first frame (frame #0) is written after a few
> seconds, whereas I'd assume that it should be instant, no?
> Am I doing something wrong?

You are doing nothing wrong: filters work with decoded frames, so even if
you want to extract only one frame out of 1500, all must be decoded, even
those that do not change the output at all. Doing things more efficiently is
possible, but would be more complex, and nothing is implemented in ready to
use solutions.


  Nicolas George
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