[FFmpeg-user] Extract image every x frames?

[Peter B.]

Quoting Nicolas George <nicolas.george at normalesup.org>:

> Le primidi 21 thermidor, an CCXX, Peter B. a écrit :
>> I've tried with:
>> //---------------------
>> $ ffmpeg -i video.avi -vf select='not(mod(n\,1500))' -f image2 -sameq
>> -vsync 0 delme_images/%03d.jpg
>> //---------------------
>>
>> Same result: Gets stuck at frame #1500 and exports 100 images.
>
> This command works for me. I can not help you more without the full console
> output.

Hm. Puzzling.
I've now tried it on another computer (at work) and here it works now.
I'll check my installation at home to see what went wrong there. Thanks.

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?

Thanks,
Pb