If you see error that read as follows while playing video files:
It seems there is no Xvideo support for your video card available.
Try mplayer command as follows:
$ mplayer -vo xv file.avi
Under XFree86 4.0.2 or newer, you can use your card's hardware YUV routines using the XVideo extension. This is what the option -vo xv uses. Also, this driver supports adjusting brightness/contrast/hue/etc. Type following for other (non-xv) video out drivers list:
$ mplayer -vo help