Uh... then why is there a frame rate counter in the bottom right of the screen giving variable numbers between 40-70? :) Because that's the rate of the frames

Uh... then why is there a frame rate counter in the bottom right of the screen giving variable numbers between 40-70? :) Because that's the rate of the frames being displayed during capture. Again, the in-game time between two frames is the same, so if it captures at 50fps, that just means the game runs at 50/60=5/6 times normal speed. It's similar to how you can capture a 1000fps recording in Counterstrike: the game doesn't actually have to run at 1000fps, it just slows down the game accordingly. I agree that the smaller file looks jumpier. But it's still reporting the same frame rates as the bigger file, which leads me to believe the jumps are an artifact of translation somewhere. Certainly nothing seems to be "locked". It sounds like your media player is broken, because ffmpeg gives 60fps for the higher framerate file and 30fps for the lower one.