This article was first published in the July, 2009, issue of
Larry's Final Cut Pro Newsletter. Click here to subscribe.

Audio that slowly drifts out of sync is often due to a mismatch between the sample rate at which you shot the video and the sample rate at which you captured the audio. Here's an article that describes this in more detail.

However, Matt wrote in with the following problem:

Someone shot some footage (9 minutes) and gave me an MOV that plays fine in QuickTime but when I put it in Final Cut the audio is out of sync. [It gets] progressively worse as the minutes pass. The files are 44.1 khz, I put them in a 48 kHz sequence and they are out of sync, even after rendering. I've tried converting them to 48 with STP , and putting back in timeline, didn't work.

I can get them to sync in the Final Cut Timeline by changing the speed
of the audio to about 99.6, it would look pretty good playing from timeline. But when I export to a QT MOV they are out of sync again.

I tried deleting Final Cut preferences and that didn't work. But here's what did:

• took the MOV with 44.1 Khz audio, put it in Quicktime, where it had always played fine,
• exported to 48 khz MOV.
• Put it back in final cut - still out of sync
• Imported the 48 khz from QT to Imovie - output to QT MOV
• Took that MOV and imported into FCP
• It was sync'd in final cut.
• Output to Quicktime movie and it was sync.

Maybe somebody has a better solution, this Rube Goldberg method is tedious but it worked.

UPDATE - July 21, 2009

Tom Mountford, from Norfolk, UK, adds:

I read Matt's sync problem and the Rube Goldberg solution and may be able to improve on it. I have had a similar problem with sync issues when using the ProRes HQ codec - audio imported from my sound suite drifts out of sync as the minutes pass despite the sample rates being 48KHz throughout the process - I've found other references to it online and it seems to be a bug in way the ProRes codec locks audio to video. Anyway, that aside the solution I found was to drop the QuickTime movie into Compressor and pull a 48KHz 16-bit AIFF from it and substitute that for the original track using FCP and create a new .mov from the corrected sequence.

Larry replies: Thanks, Matt and Tom!

Larry Jordan is a post-production consultant and an Apple-Certified Trainer in Digital Media with over 25 years experience as producer, director and editor with network, local and corporate credits. Based in Los Angeles, he's a member of both the Directors Guild of America and the Producers Guild of America.

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