ffmpeg -r / fps over time?

Question

ok - going round in circles here so any help welcome...

using ffmpeg to generate frames from a movie. But i want to limit the total frames to 10 per movie.

So im trying to figure out the -r (fps) to use in the code.

So if the video is 10secs long i want 10 files which is -r 1 fps.

but if the video is 100 secs long and i want 10 files th -r should be 0.1 fps.

i just can't seem to figure out the formula?!

please help!

Answer 1

ok its r = frameswanted / totalseconds