Capture frames from video before archiving

With the video portion of meetings disappearing after some time, it would be nice if we had a way to "capture" important moments in the recording to keep as archived images with the audio recording.
It would be spectacular if it was automatic (e.g. ffmpeg can detect more than X% of the image changed between frames). It would still be useful if we were able to manually open the recording and "mark" a place in the video to keep that frame indefinitely.