Ubuntu running on "server", ie computer with screen and access to files. Ssh installed.
User on machine across the room, with some sort of ssh ability (either *nix or putty)
ssh into server :
>vlc /location/of/file --intf rc
gives the options available to adjust the playing file. play, volume 500 (min 0, max 1000), seek (+seconds), f (fullscreen)
if the screensaver is on,
d deactivate, a activate.