When using ffmpeg to output a series of frames as images, the only format I can find documentation for is frame_%d.jpg. The %d identif
ffmpeg
frame_%d.jpg
%d
I hacked up a bash script that creates file names based on time into the film. It uses a format: "hh_mm_ss" in the file name. You can see it at:
https://github.com/pozar/makemoviethumbs