Automatically capturing stills from video presentation
You can do this with Processing.  You would have to write a processing sketch to step through the movie frame-by-frame, and calculate how different each was from the previous frame.  When the difference is above a certain threshold, save the whole frame as an image file.  Here is a forum post about something very similar.  

Other than processing, you may also be able to use Max/MSP's Jitter, Quartz Composer, or a bonafide programming language such as Python.