Sample project demonstrating misaligned sound timing.

Compile & run the project, then hit the play button. Notice that the first two sounds don't play exactly at the same time when they should.

If you hit the play button again (or listen to the synchronized sounds slightly later in the track) they match up fine. Reload the app again to hear the offset.

Posted on stackoverflow: http://stackoverflow.com/questions/14114542/misaligned-sound-playback-using-avplayer-and-avmutablecomposition