Are there any guides for recoding video game FMV cutscenes?

I apologize if this is in the wrong category, but I'm running out of hard drive space, and it's gotten to the point where no matter what I delete or uninstall, I have major difficulty getting my free space out of the "red zone." But since there are some games I would like to keep on my machine, I was thinking that, if possible, maybe recoding some of my game's prerendered cutscenes (assuming using h.264 compression will still leave them compatible/playable) would at least shave a couple GB off. So my question is, does anyone know how to do this exactly? From what I've seen, not many games actually have their cutscenes stored in a video format like .avi, .mp4, .mkv, etc. But if anyone knows if, and how this can be done, could someone please explain to me the proper process? Thank you for your time.