[FFmpeg-user] extract 1 image every 0.04s (25fps) whatever fps

[Sebastien WILLEMIJNS]

Hello,

I'd like to extract one image every 0.04s (25 fps) whatever the fps... 
some images can be the same also if i extract a file with less than 25
fps.

ffmpeg -i inpu.avi -t 0.04 -s 4cif d:\image%%06d.bmp
ffmpeg -i inpu.avi -t 0.08 -s 4cif d:\image%%06d.bmp
ffmpeg -i inpu.avi -t 0.12 -s 4cif d:\image%%06d.bmp
ffmpeg -i inpu.avi -t 0.16 -s 4cif d:\image%%06d.bmp
[...]

works well but ffmpeg read the whole file at every loading...
7 minutes to extract image from time 2.96, 3 and 3.04 second but 7 hours
to extract image from time 
3999.96 4000 4000.04 ;-(

a 1h40 movie make 1 or 2 weeks to be extracted...