Thanks for all the replies. It sounds like the things people record and the ways that they record are too diverse for a catch-all solution. I was hoping that crypto might be able to make it really hard (cryptographically hard) to make fakes, while still being easy for people to record their regular speedruns (that's why I thought a simple plugin might be okay). Well, if anyone comes up with a good idea for how to do this, I would be interested to hear it

And yes, you could just upload a video, but if the community moved towards more secure ways of recording gameplay, then a video without any way of verifying it would be suspicious

the plugin would sign each frame with the current time, so if they tried to edit the video, it would either look messed up during playback or it would be obvious from the timestamps on each frame that parts were skipped. It would essentially just ensure that the video you took was continuous. I'm sure you could still find ways to break it, but it's a step in the right direction I think.

re: Xsplit, yes this would just be a proof-of-concept at first, I guess. I'm aware there are other streaming / recording software, but OBS is open-source so I figured I could start with that if there was any interest

what do you mean by "download a clip and manually check"? I'm pretty sure a motivated splicer could make it pretty hard to find the splices using some simple video-editing tricks

Would any mods be interested in a tool that could help verify that a speedrun is real and not faked? I was thinking it might be possible to make a plugin for OBS that uses cryptography to ensure that the run wasn't spliced or something. So the runner would just need to have this plugin running, and then maybe a feature on the speedrun.com website could be to show what the timestamps were for each of the frames, and if they're not in sequence you'll know that the video was tampered with. What do you think? Also open to other ways of accomplishing it, this was just what I thought of