Well, I've left the line slurper for now. In the meanwhile, I've added code for playing Theora video in the movie state, and although there are some problems, it seems to play back video and audio quite nicely.

Now, for the problems. First, Plugin_TheoraVideoManager will not even bother determining the length (in time) of a video unless you turn on seeking. Which leads to problem #2, seeking causes a plane shift in the video (colours are shifted wierdly) for some reason, although it fixes itself after about 5 seconds. Last of all, when playback ends, the object that plays the video (which is a registered FrameListener, by the way) gets deleted by another frame event handler, leaving me with a crash when the program tries to call a virtual function of an object that doesn't exist.