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Audio out of sync after export

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Dave Hall
Audio out of sync after export
on Aug 19, 2010 at 4:59:14 pm

Hey everyone, I just had a client call in with the following problem:

Client is working with FCP 6/QT 7 on a 2x 3.0 GHz Quad-Core system with 4GB RAM (10.4.11). They are trying to export a project using quicktime conversion (audio format set to AAC, everything else default). The sequence's easy setup is set to AJA Kona 3-1080psf 23.98 Apple ProRes 422 (HQ).

He is saying that whenever they export the project, the audio on the final file is a few frames out of sync. However, when viewing the project in the time line, everything looks fine. I had him export a similar project using the same settings and the sync issue did not appear.

Does anyone have any thoughts on where the issue may be? Let me know if you need any more information about their setup. Thanks.

-Dave Hall

ACMT
ACTC 10.6


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Jeremy Garchow
Re: Audio out of sync after export
on Aug 19, 2010 at 10:36:41 pm

Why QuickTime Conversion?


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Dave Hall
Re: Audio out of sync after export
on Aug 19, 2010 at 10:51:04 pm

Not quite sure why they're going with QT Conversion.

When I called back to get more info I found out that the audio and video were recorded separately (the audio as a wav file) and that the editor had synced them off the 2 pop. He said that it looked fine during playback, but looked out of sync while he was scrubbing through the timeline. Thoughts?

-Dave Hall

ACMT
ACTC 10.6


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Jeremy Garchow
Re: Audio out of sync after export
on Aug 19, 2010 at 10:53:40 pm

[Dave Hall] "Thoughts?"

Yes. when importing double system sound, you need to set FCP to the easy setup that is the same as your footage. So if working in 1080 23.98, then setup FCP in the easy setup to match. Then Quit FCP, then reopen FCP, then import the audio.

It's a dance, but it works.

Jeremy


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Dave Hall
Re: Audio out of sync after export
on Aug 19, 2010 at 11:03:42 pm

Jeremy, I appreciate the advice. I passed it along to my client. With any luck it will solve the problem for them.

If you don't mind my asking, how is it that this works? Is it just a matter of the audio being re-encoded to the proper Easy Setup when it is imported separately?

Thanks again.

-Dave Hall

ACMT
ACTC 10.6


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Jeremy Garchow
Re: Audio out of sync after export
on Aug 19, 2010 at 11:15:08 pm

[Dave Hall] "If you don't mind my asking, how is it that this works?"

In all honesty, I don't really know. The speculation is that somehow, the audio gets 'tagged' as whatever frame rate FCP was launched in. So if you import the audio when FCP was launched and it was set to 29.97, the audio will somehow get tagged as 29.97, even if it has tc that tells it otherwise. So you have to reset the easy setup to the matching frame rate, then quit FCP, then relaunch FCP. The quitting and relaunching is crucial.

Sorry I don't have a "real" answer for why the hell this happens, but I hope it helps. It usually does with double system sound. If it doesn't work, something else may be happening.

Jeremy


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