A video player that works well on machines that aren't fast enough to decode the video in real time by "scaling" the audio to match. Obviously you'd need some sort of buffer for decoded frames.
The easy approach would simply be to smoothly slow down audio playback when the video can't be decoded fast enough, so the pitch would change; a neater approach would be to do that, but also pitch-shift the audio back to where it should be, so the audio sounds correct (well, distorted, but not too bad), just slowed-down.