Fixing Out-of-Sync Sound in a ProRes File

Posted on by Larry

[ 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!

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6 Responses to Fixing Out-of-Sync Sound in a ProRes File

  1. Frank says:

    I’m wondering if this could be related to the minor nightmare in which I suddenly find myself.

    I did a two-cam shoot of a theatrical performance running about an hour. Canon HV-20 and Canon HF M40. The HV-20 (miniDV) records in HDV 1080i, 1440×1080, with separate left and right 48/16 audio.

    The HF M40 (disc) is ProRes 422, 1920×1080, with stereo 48/16. I downsampled this in Compressor to match the HV20 specs before doing the multiclip.

    For audio, I used a Tascam DR-04 set to 96k, 24-bit, which I converted to 48/16 AIF.

    I synced everything up and edited a multiclip – hundreds of cuts – and everything seemed fine. Now I’m suddenly discovering that the Tascam audio track drifts to about a full second behind by the HV20 video (and audio) track by the time it reaches the end. Just enough to be annoying. The HF M40 remains in sync.

    Unfortunately, I can’t slip the HV20 video track, is it’s a slowly expanding drift over time. If I slip-sync the end, the beginning fall out.

    Naturally, this only happens on deadline! Any ideas? I may end up having to just use one of the camera’s audio tracks.

    Deeply indebted to you – many thanks.

  2. Two years later a faced the same issue.

    Here is how I fixed it:

    My original File is on 44.1 kHz .mov

    1. Make a copy of your original file on Apple Pro Res 422 using mpeg Streamclip. Download for free from this Website:

    2. Make shure that your copy File is set on 48 kHz .mov (This is the First Key)

    3. Make shure that your Sound File is set on 48 kHz also. My Sound file came from Logic Pro 9 exported to 48 kHz .CAF or .WAVE both works. (Second Key) My intention was to mixing it on 5.1 Surround.

    4. Open your FCP and in the “Sequence Settings” set it to 48 kHz before do something. (Third Key)

    5. Import your Video and Audio file and bring it to your Timeline.

    6. You are done.

    Sorry for my poor english but I hope it can help.

    Julián Franco Ocampo

    • Great answers – I just had one further question – my video and audio are married together – from an event. Is MPEG Streamclip still a feasible solution? The issue is the same regardless of the frequency setting – sync is lost following rendering and very tedious to re-sync.

  3. Hi!! I will tell how I solve the problem. Im working in a feature film, 78min, 2K 25fps.
    When pasting audio under video in FCP7 happens what everybody is talking about, a drift that is painful.

    I use Sound Devices Wave Agent app to set audio to 25fps. Cinema tools to set video to 25fps, despite is already 25fps its a must.

    Now audio and video have the same duration inside FCP 7 and both reports TC 25. POP is not in synch, weird, but the hole audio could be put in perfect synch and theres no more drift.

    Hope it helps!!

  4. Charles says:

    This reply is six years late to the party, however I wanted to offer my .02 cents. Could the audio drift issue be related to the fact that ProRes is a variable bit rate codec (which would explain why the camera audio is perfectly in sync, but the externally recorded audio isn’t). If so, transcoding to a constant bit rate codec should fix the issue. DNxHD or DNxHR (depending if you need HD or 4K) are both constant bit rate codecs that are comparable in quality to ProRes.

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