I thought of this while answering a post in the CS3 forum, but I wanted to post it here under its own topic heading where the software developers might have a better chance of seeing it. Maybe this will give them some idea of what might be causing the problem with sound sync that so many people seem to be having lately. I'm not sure though.
Years ago I used to see a lot of guys new to digital audio who were getting their feet wet with Cakewalk. These guys didn't have a high quality soundcard yet, and were just using a SoundBlaster. I used to read post after post at the Cakewalk email list from these guys where almost everyone with an SB Live card was having trouble keeping multitrack waves in sync with each other. Generally after a couple of minutes into the song the tracks would begin to fall out of sync noticably. I still had an SB Live I was using for playing back video files and whatnot, so I tried recording with it in various combinations of bitrates/resolutions and eventually found that everything I recorded at 16/48 stayed in sync just fine every time. After scouring through Craetive's website for about an hour I finally found where it says that those cards back then had a default recording bitrate/resolution of 16/48.
What was happening was this; if you tried to record at 16/44.1 or anything else other than 16/48 the soundcard and the recording software both acted like it was no problem. Behind the scenes, however, the soundcard was still recording at 16/48 and then converting the new tracks to 16/44.1 (or whatever you chose) on the fly while you were recording. The little soundcard just couldn't keep up with the other tracks as they were playing back like that though, and so the newly recorded tracks would fall out of sync with the previous ones.
Could it be there's something similar happening here with the mov files and either CS4, the video card, or the QT codec etc?
That could cause the problem. But when audio is recorded with three cameras is the same and only one clip has a EQ filter to lower midtone, and the track has a denoise filter, rendered result is out of sync only in the area where the filter is applied. Even if filter is out of there rendered result is still out of sync until file is replaced from bin.
I'm wondering if maybe some people are trying to use some output settings on a particular codec that either the codec isn't really meant to handle, or that somehow is conflicting with their video card or sound card settings. Could it be that if I took that same clip and played it back on another computer that it would stay in sync there? Has anyone tried that? If it played fine on another machine with a different video or sound card, that would tell us it was a hardware issue.
Also, most people seem to have this problem with mov files. Have they tried various bitrates of mov files to see if there are any that do play correctly?