Correct me if I'm wrong: it appears that I have to wait for a complete rendering before making sure separate video and audio tracks are in sync. I need perfect sync because I am creating 3-minute songs but it seems to take an hour for rendering process to conclude. In the meantime everything in the monitoring screen is so choppy there is no way to do anything but wait. Is there a way to 1) speed up the rendering process, and 2) test video / audio sync without having to wait for rendering to be completed? Thanks!
It depends on your source video and how fast your processor is.
For standard definition video, rendering usually only take a few seconds -- less than the running time of what you're rendering.
But, for AVCHD, particularly on less than a state-of-the-art quad-core system, it can take several very long minutes to render.
This is aimed at Premiere Pro, but may help
A link with many ideas about computer setup http://forums.adobe.com/thread/436215?tstart=0
Work through all of the steps (ideas) listed at http://ppro.wikia.com/wiki/Troubleshooting
If your problem isn't fixed after you follow all of the steps, report back with the DETAILS asked for in the FINALLY section, the questions at the end of the troubleshooting link... most especially the codec used... see Question 1