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Old 05-13-2010, 08:11 AM
anthony b anthony b is offline
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Question AV sync problem in delivery due to Pro Tools changing frame rate of video

Hello, I literally just joined this forum to ask this question so please bear with me.

I just finished a mix for a student film and bounced the audio to a 24/48 WAV. They tried to place the audio in Final Cut but it would gradually lose sync. I took that to mean it's a frame rate issue, and when I looked into it I noticed that in my session Pro Tools changed the frame rate of the video from 29.97 to 23.97. However, in the session window, the time code rate is still 29.97.

The 23.97 shown in the edit window was also in red, which I've gathered means the frame rate is not set correctly. The video was a .mov and an H264 format. I've heard the H264 format can also be troublesome but am very uninformed when it comes to video.

So my reason for posting this now is that I want to know if there is any way I can save the mix I did and bounce it properly without having to redo the entire mix in a session where the video was imported correctly. Or can I time stretch the whole thing? I'm very worried that the audio is all synced to an incorrect frame rate and cannot be changed. Is that the case?

Any and all advice will be greatly appreciated!

Thanx
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Old 05-13-2010, 08:32 AM
garret garret is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

23.97 and 29.97 are essentially the same speed so that shouldn't really affect the sync. I think there is a bug in final cut when importing audio where final cut tags it as something else and does a sample rate conversion. Someone else should chime in here with more details. There are a lot of posts here and on the Gearslutz forum on this topic
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Old 05-13-2010, 08:40 AM
tom_lowe tom_lowe is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

In Final Cut 7 (maybe 6 as well) there is an option in User Preferences under the Editing tab at the bottom is a BWF import option. This may be causing your problems. Change it, restart FCP and re-import your WAV.
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Old 05-13-2010, 08:51 AM
anthony b anthony b is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

Thanks guys, I'll tell the editor to check the Final Cut settings. However, I was thinking it was a Pro Tools problem still just because the frame rate was in red in the edit window and not the same frame rate as the video. But according to what you're saying it shouldn't matter if the frame rates are different? (or at least if they're 23 97 and 29 97)

I imported the video into logic 8 as well just to see what it would do and the length of the video changed by about .05 seconds. Does that mean anything?
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Old 05-13-2010, 09:01 AM
tom_lowe tom_lowe is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

23.98 and 29.97 will be the same length, just 23.98 has had the 2:3 pull-down removed. What was it originally shot at?
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Old 05-13-2010, 09:04 AM
anthony b anthony b is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

It was shot in HD at 29.97
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Old 05-13-2010, 09:09 AM
tom_lowe tom_lowe is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

if it was shot on a P2 it might well have been 23.98 and the camera did a 2:3 pull down to 29.97. This might be why it's being interpreted as 23.98
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Old 05-13-2010, 09:40 AM
anthony b anthony b is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

It was shot on P2 cards

New development though! What you're saying is making more and more sense for this situation. The director took the original video file she gave me (pre Pro Tools import) and the soundtrack I bounced from Pro Tools syncs with that now, but its on Final Cut express on her setup at home.

It's now pointing towards the hi res color corrected video file as the source of trouble. They couldn't get it to sync last night on final cut pro with either video though (the hi res one that still doesn't work, and the lo res one that now works on her express setup). Does that confirm what you were saying about it being a final cut issue?
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Old 05-13-2010, 09:46 AM
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DigiTechSupt DigiTechSupt is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

Quote:
The video was a .mov and an H264 format.
Where did you get the movie from, exactly? Was it exported from FCP?

If so, this may be related to what you're seeing:

http://duc.digidesign.com/showthread.php?t=212057
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Old 05-13-2010, 11:02 AM
tom_lowe tom_lowe is offline
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Default Re: AV sync problem in delivery due to Pro Tools changing frame rate of video

Quote:
Originally Posted by anthony b View Post
It was shot on P2 cards

New development though! What you're saying is making more and more sense for this situation. The director took the original video file she gave me (pre Pro Tools import) and the soundtrack I bounced from Pro Tools syncs with that now, but its on Final Cut express on her setup at home.

It's now pointing towards the hi res color corrected video file as the source of trouble. They couldn't get it to sync last night on final cut pro with either video though (the hi res one that still doesn't work, and the lo res one that now works on her express setup). Does that confirm what you were saying about it being a final cut issue?
Odd that the colour graded online doesn't sync, sounds like they did a frame rate conversion. The simple rule really is make sure the sequence settings and capture settings match up. Only used Final Cut Express once and didn't like it, but guessing the same issues apply as with FCP. This whole 23.98 and 29.97 thing seems to confuse a lot of people, makes me glad we just have 25fps and 50fps (sometimes, but rare) here in the UK!
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