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    Serious audio sync drift problem with FCP
    Okay, let's give this board a try. I've posted this on CreativeCow, VU, Cinema5D, Twitter, Facebook, you name it. No one can figure this out.

    I had an hour+ long clip transcoded from h.264 files into one long clip. When imported into FCP, and I play the clip in the Viewer, the audio drifts out of sync more and more as you get towards the end of the clip. Fine at the beginning, way off by the end. This is in the VIEWER. I am talking about the audio contained within the clip itself. I am NOT talking about synching the clip to a separate audio stream in the timeline (I can't tell you how many solutions people keep giving me related to the timeline.) What's weird is that the clip is absolutely fine if you play it in the Finder or open it in QuickTime. No audio drift. It's only when dropped into FCP.

    First I thought it was a codec issue. I normally transcode to xdcam. Someone suggested I do ProRes. I did for smaller selection of original h.264 clips from the original batch. That seemed to work. So, I thought that the issue related to the long GOP xdcam format.

    For my next project, I decided to encode to DVCProHD. (I don't use ProRes422 b/c they are way too big.) Anyway, I got the same problem. So, I encoded another batch of files to ProRes, just to test. Same problem. I've tried every possible combination. I'm using a batch of files that I previously transcoded on my MacBook Pro on Sept 22, and that resulting xdcam file has not drift. So I took those original h.264 files and transcoded them on my Intel iMac quad core and on my old G5. I get the audio drift. I transcoded those same files again on my MBP (but this time the h264 files were on my drobo, whereas before they were on a seagate). I got the drift again.

    It only seems to happen with 23.98 footage. No 29.97 fps footage I have experiences the drift when imported into FCP. And I have 23.98 fps footage created earlier this year that when imported into FCP don't experience the drift.

    An interesting development is that I took the set of 23.98 h264 files that I transcoded on 9/22 (the ones that seemed fine at first, but now whenever I transcode them I get the audio drift) and I transcoded them to a 29.97 fps file. When I did that and imported into FCP, there was no drift.

    Some other key points: I'm running Mac 10.6.2 on an iMac quad core i5 27.5 inch screen; the MBP and old G5 both run OS 10.5.8. I use MPEG Streamclip 1.9.2 on all three machines.

    Again, the drift only occurs in FCP. And it is within the file ITSELF, not synching to another audio stream in the timelines (so please, no suggestions to "slow the footate down to 99.9%). So, it's somehow related to how FCP is interpreting the files.

    Does ANYONE have any idea what's going on. As I've mentioned on another forum, I feel like I'm in the middle of a "House"episode as it relates to this problem. Only, there is no House who has figured this out.

    Ron Dawson

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    Vacuum Tube Member Paul Hudson's Avatar
    Join Date
    Jul 2004
    Phoenix AZ and Dallas TX USA
    It could be a drop frame non-drop frame issue. Clues: 23.98 and slow drift.
    Camera and Grip Electric Rentals in Dallas and Shreveport
    Phoenix Video Productions

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    Hi Paul,

    Can you elaborate?

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    The latest update is that I discovered that 29.97 footage does not drift when imported into FCP. I transcoded the original h.264 files (shot at 23.98) and this time transcoded them to 29.97, and the drifting does not occur. The downside is that I don't want 29.97 footage, I want 23.98.

    I would make the conclusion that 23.98 footage is the culprit, except that there are SOME 23.98 clips I have which are also fine. But, somehow the drifting seems tied to 23.98 footage. Is there some other kind of special FCP tech support out there. No one can figure this thing out. Is it just a quirky bug?

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    Major props to CreativeCOW leader Jeremy Garchow for solving my FCP audio drift issue! You can read about it in this thread. The thread was started by someone else who had a similar problem to mine.

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    Hi bladeronner - are you still around these 8 years later?

    I'm looking for solution to my problem which appears to be exactly like your problem that you sought to solve and found a solution from Jeremy of CreativeCOW - EXCEPT, my problem has same audio drift issue with 29.97 footage!
    It plays fine in Finder & QT, but then in FCP7 Viewer, the audio and video drift more and more apart as the clip goes on.
    Any chance you (or anyone else reading this) know what the solution is for my 29.97 footage?

    The CLIP is ProRes 422 HQ, 720x480, 48kHz, 29.97, 16-bit Integer (Big Endian), Stereo
    The only different setting for the Sequence is the Aud Format is "32-bit Floating Point", instead of the Clip's "16-bit Integer" - but, again, before I ever drop it into the Sequence, the audio/video drift out of sync just in the Viewer (yet stay in sync in Quicktime and Finder)

    Anybody have a solution?


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    Senior Member Alchroma's Avatar
    Join Date
    Oct 2013
    Can you double check your Sequence is set to 16 bit/48kHz?

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