Audio out-of-sync. iMovie --> QT export

[whizdog]

I captured video from my camcorder into iMovie 4. The video segment is nearly an hour long. I did some editing of the video, and then exported it to a Quicktime movie (full quality DV export). When I play the movie (in Quicktime player) I noticed that by the end of the video, the audio portion is several seconds out-of-sync. Why would this happen?

I also noticed there is a Quicktime document inside the iMovie project folder. It is a very small file...and references the media inside the iMovie project. If I play this file (with Quicktime player), the audio is not out of sync. However, the (roughly) 20 GB Quicktime exported file does have the audio out of sync.

[The reason I noticed this problem......I created a VCD from the iMovie project. It wasn't until I was done that I noticed the audio was out of sync. So I started working backwards.....assuming that it was the MPEG encoding that caused the problem. I used ffmpegx to do the encoding....but as I researched the problem, I discovered it was the iMovie export that caused the problem...and not the VCD authoring or MPEG encoding.]

OS 10.3.3
iMovie 4.0.1
PowerMac 1.3GHZ, 1.25G RAM, 120GB HD
Quicktime 6.5.1

[icoty]

When you capture video with your camcorder, make sure you are recording at 16 bit not 12 bit. I used to have the same problems that your are experiencing but once I switched to 16 bit recording my problems were solved.

Try exporting your existing iMovie video back to your camcorder at 16 bit and then import it back into iMovie. and then export into quicktime/iDVD/etc. The sync problem should then be resolved.

[whizdog]

>When you capture video with your camcorder, make sure you are recording at 16 bit not 12 bit.

Hmmm.....I searched all through iMovie and can't find any setting to switch between 16 & 12 bit.
(I'm using iMovie 4.0.1)

[icoty]

No, make sure your camcorder is set for 16 bit recording. My default setting on my MiniDV camcorcer was 12 bit and I needed to change it to 16 bit.

[whizdog]

>No, make sure your camcorder is set for 16 bit recording.

Doh! Pardon my ignorance! Thanks for the tip. I'll have to try it.
BTW, what are the implications of using 16 vs 12 bit recording?
It's not like it's going to use any more tape......so is it a compatibility issue?

[whizdog]

>BTW, what are the implications of using 16 vs 12 bit recording?

OK, I just Googled it. Sounds like using 12 bit recording allows a second 12 bit track to be dubbed later. Recording in 16 bit mode doesn't allow a 2nd track to be dubbed.

[whizdog]

icoty, not that I didn't believe you before....but your words are now "golden". I did find the exact advice you gave me on an Apple Tech Note at:
http://docs.info.apple.com/article.html?artnum=61636
(Use 16-bit. If necessary, export 12-bit project to tape [16-bit] and re-import.)

Another tech note:
http://docs.info.apple.com/article.html?artnum=42974
Suggests that the sync problem can be remedied by extracting the audio to a separate audio track. I'm going to tinker with this and see if it works. I have an awful lot of tapes I need to process, and they are all in 12-bit audio. I'd like to avoid dubbing these tapes all over again, if possible.

[icoty]

No problem whizdog...what works best, works best...good luck and keep us posted as to whether or not your problems get solved.

[whizdog]

Extracting the audio to a separate track in iMovie before exporting to Quicktime solved the sync problem for me.