mplayer -loop 0 -rootwin -ao null -noconsolecontrols -fs VIDEOPATH

#!/bin/sh

while true; do
  ## launch mplayer in the background
  mplayer -loop 0 -rootwin -ao null -noconsolecontrols -fs VIDEOPATH &
  ## wait for 15 seconds
  sleep 15
  ## kill the 1st backgrounded job of this subshell
  kill %1
done