Just a note of marginal importance: I'm pretty sure that speeding up movie 1.5 times would bring its runtime from 2hrs to 1hr:20mins (not 1.5hrs as mentioned). With 24 frames per second 2hr movie has 172800 frames. Speedup brings framerate to 36 fps, and dividing we get 4800 seconds, or 80 minutes.

Edit: Thank your for pointing that out leberwurstsaft!