I’ve been messing around with iMovie on my iPhone 4 and I’m realizing that the songs that come with the iMovie themes vary in length upon being exported. For instance, the song by Phoenix that comes with one of the themes, I have it playing until the very end of the movie (when I preview it), but upon exporting the movie, I have about 10 seconds of silence at the end. What is the reason for this? Does the audio/video playback speed slow down or speed up on export?