So you snag a flash video file (.flv), convert it to your preferred video format, and the audio/video sync is off. Then you google the issue and spend hours reading and trying out various solutions.
Demux. Framerate. Audio VBR. Re-mux. Audio is longer than video. Video is longer than audio. Adjust framerate. Adjust audio length.
Nothing works, but you now have a vague clue as to what the problem is: the audio and video streams in the FLV have different lengths (or framerates or...), and when being converted one is being stretched to fit the other. Or something.
Well, finally I figured out a solution. It's a longer process than I would like, but it works.
First, I followed the basic instructions found here. (It's an offsite link but the best guide I've seen. If there's an equally as good guide here on the wonderful Afterdawn site let me know.)
If we just followed that guide, you may still have A/V sync issues. I did. But there's an option in VirtualDubMod that fixed my sync issue!
After you have the video and audio loaded, and Video set to Direct Stream Copy, select Video > Framerate and set to Change so video and audio durations match.
That's it! My audio and video are now synced perfectly, and my long nightmare is over.
