How to improve performance of mplayer with libcaca?

I'm using mplayer and libcaca on Gentoo. My framebuffer (uvesafb) is running at 1920x1200 (I don't know how many characters that is) and mplayer has problems filling up the screen, so video and audio lose synchronization.

I'm looking for ways to improve performance. The most obvious solution would be to decrease resolution of mplayer, so I'm looking for ways to do that. Any other performance tips would be appriciated.