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synced audio suddenly drifts, separately on both tracks

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Kevin Knutson
synced audio suddenly drifts, separately on both tracks
on Nov 3, 2010 at 9:34:34 pm

Hey guys, forgive the urgency, but got a project due Friday (2 days away) and just got handed a very strange issue. Allow me to overwhelm you with details:

The setup:

Interviews were recorded using a Sony EX3. Two separate audio channels were recorded directly into the cam's XLR input (one a Senn. Shotgun, and one a Audio T. lav).

FCP 6.0.6 was used for the transfer. The footage transferred fine, meaning everything in sync and looking good.

The project files and media were transferred to external harddrive, given to a contractor to go edit, he placed them on his computer (same software versions), everything still fine.

Then after a few hours of working on the project, the audio tracks suddenly had drift issues. But both tracks drift at different speeds, and begin drifting almost immediately. The RAW video files are drifted as well in finder when opened in Quicktime or preview.

Inspecting the elements, both audio tracks show as 48kHz, 16bit.

Not ALL of the video files in the project are doing this, just about half of them.

Again, note, the files WERE in sync yesterday, and played fine.

I'm at a loss. I've seen drifting before, but not like this, and not when the files WERE in sync and randomly went crazy.

Example found here:

https://files.me.com/promotionarts/bqkrp4.mov

Any idea for some solution, or has anyone heard of this before?


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Kevin Knutson
Re: synced audio suddenly drifts, separately on both tracks
on Nov 3, 2010 at 9:36:03 pm

Should probably also add, all computers used in this process (tested on three now) are using Snow Leopard, all are up to date, and all have legal software.


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Michael Gissing
Re: synced audio suddenly drifts, separately on both tracks
on Nov 3, 2010 at 9:39:37 pm

Have you moved the disk back to the original machine to see if the audio sync drift is replicated on another machine?

Also have you tried the usual maintenance tasks (Trashing preferences, repairing permissions etc)?


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Kevin Knutson
Re: synced audio suddenly drifts, separately on both tracks
on Nov 3, 2010 at 9:44:14 pm

Yes, the files were sent back to the original machine, and are experiencing the same issues.

Tried trashing FCP preferences, clearing the render manager, repairing permissions, and verifying all discs the footage is on (external and computer internals).

This of course means too that I've restarted both machines, and relaunched FCP several times.

Also tried opening the footage in Soundtrack and attempted to "resample" at 48kHz even though it already read as such.


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Michael Gissing
Re: synced audio suddenly drifts, separately on both tracks
on Nov 3, 2010 at 10:04:33 pm

Truly weird. Have you tried recapturing any of the sync issue files?


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Kevin Knutson
Re: synced audio suddenly drifts, separately on both tracks
on Nov 3, 2010 at 10:09:36 pm

Wouldn't you know, the camera went out with a videographer and the card was cleared before we archived a copy of the BPAV. Seems like that only happens when there's a problem to fix.

Oof.


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