Mplayer and Gnome's screensaver.

#!/bin/sh
#DTPD
gnome-screensaver-command --inhibit &
INHIBIT_PID=$!
mplayer -dvd-device /dev/scd0 -ontop \
	-fs dvdnav:// -nocache 2> /dev/null
kill $INHIBIT_PID

This is how to use gnome-screensaver's inhibit command with a video player such as mplayer.