You are talking about directly embedding the video into the main timeline, correct?
For the most part, believe what Adobe says about not embedding video in the timeline or you may have audio sync problems..... which are actually video syncing problems. The auto will play exactly as it's supposed to, it's the video that gets out of sync.... NOT the audio.
The problem usually come up because you are attempting to match the audio up with the video... which is really the wrong way to go about it. Video can to speed up a little or slowwed down a little without really affecting the end result that much.
Not so with audio! Any speeding up or slowing down in an attempt to "match up" with the video, changes the frequence of the audio, distorting the sound. That only makes sense, right?
So if you have one minute of audio, you can't change that to 1:05 by slowing it down slightly, and you can't speed it up to play in :55 unless you want a little "chipmunk" effect. Either method changes the frequency and pitch of the sound.
Understanding that is key to using this particular embed method.
So if for some reason I just have to embed a video, here's a method that works pretty well for me. Set the Flash doc frame rate to exactly match the frame rate of the original video.
That means, for example, if the video was captured at 29.97 frames per sec., set the Flash doc to exactly match that....29.97fps. This will tend to keep the video and audio pretty well synced.
Here is a quick sample of an embedded video. The video bitrate is 400kbps.
You can test and judge for yourself how well this method works.
Now there are some potential problems. If the video bitrate is too high, the video may not download fast enough... just like any other high bitrate video. Second, there are Flash timeline limits, so you can't really embed a 20 min. video into the timeline and expect it to work.... but then you shouldn't really be using the "embed in timeline" method anyway.
But it is possible to get pretty good results with short videos (with audio) embedded directly into the main timeline provided you set the Flash doc framerate to exactly match the original video and you use a reasonable video bitrate.