Pro Tools Bounce to Disk, Import to Final Cut - bizarre sync issue

Question

Hi all,
I've been having so much fun agonizing over this issue I thought I'd let some other people join in the fun. Okay, really, I've got a bounced AIFF file from Pro Tools that doesn't stay in sync when it goes to FCP.
There's a lot of information to cover here, so bear with me.
1) The project is a 123-minute feature. It's made up of 9 separate sequences (which correspond to nine different Pro Tools projects). This problem only occurs on 1 of these 9 sequences. Over the course of about 14 minutes, the audio is about 20 frames shorter than the video. (I know what you're thinking, but there's no pulldown or pullup anywhere. I've checked this extensively.)
2) When I export the video for this sequence from FCP and import it into the Pro Tools project, it syncs perfectly with the Pro Tools audio. No problems whatsoever.
3) This sequence worked fine until recently. It may be worth noting that I had more or less finished this project and left it for a period of a couple months before revisiting it to make the finishing touches, and it's only after revisiting it that the problem has occurred. It may also be worth noting that I had actually done a quick add-on record/edit on this particular sequence at some point during the down period (I needed the sound of footsteps in the snow, so I went and got the sound one day when it snowed, positioned it in the project, mixed it, etc. but then held off bouncing until now).
4) The source is film, and everything - EVERYTHING! - is in 24fps (true 24fps, not 23.98). I've checked the settings in FCP and Pro Tools a million times to confirm that I'm not crazy. It's 24, 24, 24, 24 all the way through. It's also 48K, 48K, 48K, 48K everywhere as well (again, no pulldown or pullup).
5) Something bizarre I noticed that I thought would be the source of the problem, but changing it ended up doing nothing. All the sequences were set to internal clock source. Somehow or another, when I looked at the Session settings for this particular sequence, the clock source had been set to SPDIF. I have no idea how this happened. I don't have any external clock source. At any rate, I changed it back to internal, but that didn't change anything. Still drifts by the same amount.
6) Like I said everything is 24fps/48K. Except that this AIFF file, when it goes to FCP, FCP thinks it's 30fps drop-frame. All the other bounced AIFF files go into FCP as pure 24. This one, despite the fact that I'm doing nothing difference, shows up as 30fps drop-frame in FCP. (Again, this is despite the fact that it's in pure 24fps in Pro Tools.)
7) Okay, here's where it gets really bizarre. The info on this AIFF file, shows the correct duration both in Finder and in FCP. The duration in 24fps is 13:51:15. FCP shows 13:51;19 in 30fps which matches up pretty much perfectly in terms of actual length. It's when I drop it into the sequence that it's off. I suspect this has something to do with putting audio with drop-frame TC into a pure 24fps sequence, but I have no idea how it happens. (How would FCP change the rate of the file for the 24fps sequence without any rendering involved?) Furthermore, I opened the file in peak and it shows all the proper parameters: 24fps, 48K. Only FCP doesn't understand this, and only for this one file out of the nine. (I know I keep saying "the file," but I assure you I've bounced many, many, many of them by now in my troubleshooting.)
Naturally, I suspect it's an issue with FCP. What I really don't understand is why this issue would occur with only this one sequence while the others work perfectly. Like I said, there are a couple things unique about this particular sequence (having worked on it a little in the interim and discovering the clock source to have been set to SPDIF), but I don't see how that could lead to this all of a sudden. At any rate, I'd say it's pretty clear that whatever is making FCP read the file as 30fps drop-frame is what's causing the problem, and that if it understood the file as a 24fps file, the problem would almost certainly go away.
For what it's worth, it appears that I can bounce to a Quicktime movie, and that audio will sync up fine, but, well, I'm just not satisfied with using that workaround permanently. Any help is greatly appreciated. Thanks.

Answer 1

smack5099 wrote:
6) Like I said everything is 24fps/48K. Except that this AIFF file, when it goes to FCP, FCP thinks it's 30fps drop-frame. All the other bounced AIFF files go into FCP as pure 24. This one, despite the fact that I'm doing nothing difference, shows up as 30fps drop-frame in FCP. (Again, this is despite the fact that it's in pure 24fps in Pro Tools.)
I don't know why FCP does this, but it does consider all audio-only clips to be 30fps.
For what it's worth, it appears that I can bounce to a Quicktime movie, and that audio will sync up fine, but, well, I'm just not satisfied with using that workaround permanently.
Why? Seems like a perfect solution for you.