Drawing lines over video display

I'm trying to create an application that will allow me to draw lines and other simple graphics on top of a video display (MPG, AVI, etc) and have the lines remain visible during playback of the video. I guess it's kinda like the "telestrator" they use on TV broadcasts of sporting events.

I've got my video working fine and I'm drawing lines like hotcakes until I open the video. At that point, the lines disappear, not to be seen again until the video file is closed.

Any suggestions?

Thanks in advance for any help...