I'm not sure where a slider control can come in helpful, because for me, time is still linear. I'd be very interested if you could show me how to control/adjust the flow of time through a slider, especially if it works in both directions :).

But if you want to farm out start/stop/rewind of a movie to another control (which is sensible), my approach of reading single frames won't work out unless the control has a way for you to feed it single frames. Maybe you can hand the control a filehandle instead of an URL or a filename, but (pipe) filehandles have the disadvantage of not being seekable...