artifacts while decoding: need help

[mod]

Hi all, I've big problems decoding videos and I have no idea what's happened, so any help is appreciated.

http://img120.imageshack.us/img120/7002/immagine2th9.th.png (http://img120.imageshack.us/my.php?image=immagine2th9.png)

The problem is that on my Notebook with Ubuntu64 I get this king of artefacts, no matter what player I use (VLC, Mplayer, Totem). The same movies play perfectly on another machine with Ubuntu32.

Note: this happens with DVDs, Xvid AVIs and other video formats. I checked decoders but it seems all ok (same libraries of the other machine, but 64 bit).

This causes videos to look terrible @ fullscreen, because the artifacts get interpolated with fantastic results (blocks, loss of contrast etc..).

I already tried reinstalling video drivers (not the Ati ones, and I'm not going to install them) but it didn't work.
If anyone has any idea..

Thanks

HW: Asus a6je008h - Core2Duo / ATI Radeon X1450
SW: Mplayer / VLC / Totem
LB: gstreamer, wincodecs (via Automatix)

[nm]

That could be a problem with the XVideo overlay in the video driver. Try mplayer -vo x11 videofile.avi. You can also try OpenGL output (-vo gl), which could be almost as fast as Xv if your drivers have 3d acceleration support (and if you optimize the parameters; read the mplayer manual page). See mplayer -vo help for a list of possible outputs.