[FFmpeg-user] Use cropdetect only every xth frame

[Gerion Entrup]

Am Mittwoch, 9. Oktober 2013, 07:32:45 schrieb Carl Eugen Hoyos:
> Gerion Entrup <gerion.entrup <at> t-online.de> writes:
> > > The select filter should allow you to do this.
> > 
> > I think, this is not in the way I want it, because
> > ffmpeg decodes every frame and then drop it (or is
> > this wrong?).
> 
> You can use -skip_frame (see the documentation).
Does not change that much:

$ time ffmpeg -skip_frame nokey -i test.mp4 -filter:v 
select='not(mod(n\,10))',cropdetect -filter:a volumedetect -map 0 -f null 
/dev/null 2>/dev/null

real    0m21.118s
user    0m58.030s
sys     0m1.508s
$ time ffmpeg -skip_frame nokey -i test.mp4 -filter:v cropdetect -filter:a 
volumedetect -map 0 -f null /dev/null 2>/dev/null

real    0m19.979s
user    0m59.553s
sys     0m1.434s

Many thanks for your help, by the way.

Gerion