How to determine key frames in a video for video classification?
Most video formats should already mark such frames marked as "Key Frames" (Frames 1 in this example).



It is possible to get identifiers of such frames (or split video around such frame). For example, mkvmerge tool.

https://mkvtoolnix.download/doc/mkvmerge.html

http://nickyguides.digital-digest.com/keyframes.htm