Quick commands for pulling screenshots from a video at fixed intervals. One per minute, one per second, or whatever. Add -qscale if you care about quality. If you want full contact sheets, use mtn instead.

One screenshot every 60 seconds:

ffmpeg -i VIDEO.mp4 -vf fps=1/60 folder/%03d.jpg

One screenshot every second:

ffmpeg -i VIDEO.mp4 -vf fps=1/1 folder/%03d.jpg

With Quality Settings:

ffmpeg -i VIDEO.mp4 -vf fps=1/1 -qscale 2 folder/%03d.jpg