A/V sync method [Audio Clock, Video Clock(resample audio) or Video Clock(Drop/Dupe Audio)]
Audio has to stay in sync, this can either be done by resampling, skipping/duplicating packets, or adjusting the clock if it gets out of sync too far. Resampling has the advantage that the speed of the video can be changed considerably, so 24 fps can be sped up to 25 fps to play at PAL speed. The disadvantage of resampling is that it doesn't work with passthrough, and there is a slight loss of audio quality. Skipping/duplicating audiopackets has no loss of audio quality, but the speed of the video can only be changed a little to avoid doing a skip/duplication too often, most of the time it's inaudible, but it can produce a very audible click. Adjusting the clock has the best audio quality, but some extra video jitter can occur, also the speed of the video can't change much, as the audio will sync the clock more often the more the speed of the video is changed.