If you already tried changing the “do not use texture RAM for bg images” setting in the OpenGL page of prefs, then I have no more suggestions.
You can tell if the slowdown is happening because of drawing or because of file loading by zooming the stage out quite small (25% or less) with bg images/video loaded. If playback is much faster, then it’s a drawing issue — maybe you need updated drivers, or maybe your graphics hardware is not fast enough.
If zooming out makes no difference, then it’s the loading and decoding of the file that is taking the most time, and there’s not much you can do about that without changing hardware.
If you’re using AVIs, maybe the codec used is the issue. Some older codecs are really slow. If you’re using uncompressed AVIs, that could be the problem too.
Alan.
http://www.wondertouch.com