The audio/internal synch is a possibility... I switch that depending on which device I use as a clock. My machine has plenty of horse power even with tons of effects and tracks running in real time. The sample rate may be an issue - I'll have to look at that but it would seem to me that that is the frequency for recording the digital image and not effect play back lengths. Like I said the audio remains the same length in time but the video seems that its longer than the first export.