It's not like I hadn't tried to find out before, it's just that nothing ever worked. It's just been so much googling, finding things that are supposed to work, not getting them to work, and repeat.
But thanks to nightbulbs I tried again and this time it worked! And I've finally made that gif I've wanted to make since forever:



I used this tutorial. It's a bit annoying that the caps turned out squished, but in Photoshop I could distort them to correct the aspect ratio and the quality didn't seem to have suffered. Huh, I can actually make caps with my 2.1.2 VLC Player, but I need to have the 1.1.11 version there, because it has an important menu that the new version doesn't. Somehow the 2 versions seem to share settings.