The command
ffmpeg -ss 00:00:25 -t 00:00:00.04 -i YOURMOVIE.MP4 -r 25.0 YOURIMAGE%4d.jpg
will extract frames
- beginning at second 25 [-ss 00:00:25]
- stopping after 0.04 second [-t 00:00:00.04]
- reading from input file YOURMOVIE.MP4
- using only 25.0 frames per second, i. e. one frame every 1/25 seconds [-r 25.0]
- as JPEG images with the names YOURIMAGE%04d.jpg, where %4d is a 4-digit autoincrement number with leading zeros
Check you movie for the framerate before applying option [-r], same applicable for [-t], unless you want to extract the frames with the custom rate.
Never tried this with the cropped (corrupted?) input file though.
Worth to try.