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FCPX BUG - Synchronize Clips

5476 Views 16 Replies Latest reply: Mar 25, 2012 3:25 PM by blimpmedia RSS Branched to a new discussion.
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blimpmedia Level 3 Level 3 (570 points)
Currently Being Moderated
Aug 21, 2011 8:43 AM

If you've been following the Final Cut Pro X debacle, you've probably come to realize that version 10.0 is far from perfect.


When Apple announced FCPX, It was exciting to hear that a synchronization tool was going to be included in the software. Though this was music to our ears, I was a little confused why the developing team didn't leave this to PluralEyes.


As a freelance editor, I was recently faced with a project where I was given material which was shot on a Canon 5D Mark II, with audio captured separately on a H4n Zoom.


Having used PluralEyes with FCP7, I was excited to see how "Synchronize Clips" would handle a similar situation. To my surprise, it didn't, I was absolutely shocked to find the following results.


Having torn my hair out for a few days, I would like to share the hurdles, and the workaround I use to overcome it.


Attention Final Cut Pro X development team, please put back the smile we once had on our face, even if it means allowing third party developers to build plugins that actually work.



FCPX Synchronize Clips BUG & Workaround:


To demonstrate how inaccurate Synchronize Clips works with native h.264 media, I've constructed the following test.


First I started a new event and imported 2x raw or un-optimized files.


  • File 1 - Approx 10min video clip, shot on a Canon 5D Mark II - 1920 x 1080 25P codec h.264
  • File 2 - Approx 10min audio file, recorded on the H4n Zoom - recorded at 44.1 kHz codec WAV


During the recoding, I created sync points by clapped my hands approximately every minute.

Screen shot 2011-08-21 at 5.16.20 PM.png

Screen shot 2011-08-21 at 5.30.55 PM.png

After importing them both into FCPX, I selected the two files, right mouse clicked and selected Synchronize Clips.

Screen shot 2011-08-21 at 5.39.33 PM.png


Screen shot 2011-08-21 at 5.44.01 PM.png

As you can see in my screen grab, the sync points are clear and should be easy to match, yet FCPX was unable to line up the peaks and synchronize the two.


Trying to brain storm what it could be, I decided to optimize the h.264 clip to ProRes 422 using the optimize media option in FCPX.


To my surprise, the results were exactly the same, the clips were still out of sync.


Further investigating, I noticed something fishy going on in the inspector panel, the meta data didn't seem to be changing. Read more here:


Not knowing what else to do, I decided to transcode outside of FCPX. Using MPEG Streamclip, I transcoded the original h.264 to ProRes 422, re-imported and re-synchronized.


Need I say more about the result.

Screen shot 2011-08-22 at 12.20.25 AM.png



FCPX Synchronize Multipal Clips BUG


In this test I set the H4n Zoom to continuously record for 5min. During that time I recorded 10-15sec clips approximately ever minute. Each clip had a different amount of claps, which should have made it very easy for FCPX to sync.


  • 5min Audio
  • 5x Clips 10-15sec each
  • Every clip had a distinct amount of claps
  • All clips converted to ProRes prior importing


Result..... There all stacked on top of each other.

Screen shot 2011-08-22 at 12.49.31 AM.png



If FCPX is unable to synchronize such an easy task like this, then I think I'm right to say synchronize clips has a BUG and needs looking at by the

development team.


Please keep in mind that these findings have been my own personal experience with FCPX, if anyone else has had a different experience, please share and don't forget to send Apple feedback.

  • Andy Neil Level 4 Level 4 (3,785 points)
    Currently Being Moderated
    Aug 21, 2011 11:38 AM (in response to blimpmedia)

    From what I could see by the pics, it looks like there was sync drift in the audio file.  The first peak looked sync'ed, but the following peaks were more and more out of sync.  Could that have something to do with the 44.1 kHz recording of audio instead of the likely 48kHz of the video clip audio?



  • Andy Neil Level 4 Level 4 (3,785 points)
    Currently Being Moderated
    Aug 21, 2011 5:16 PM (in response to blimpmedia)

    Unfortunately, writing FCP X from an FCP 7 starting point wouldn't help in this situation, as FCP 7 can neither work properly with H.264, nor automatically synchronize audio to video.


    Have you tried importing the H264 with the setting, "Create Optimized Media" so that FCP X makes a ProRes file and swaps it out?  How does that fare in the synching process?



  • Andy Neil Level 4 Level 4 (3,785 points)
    Currently Being Moderated
    Aug 21, 2011 5:55 PM (in response to blimpmedia)

    Sorry, didn't catch that from your previous post.  I think the problem is based on the Long GOP structure of H264.  It's also possible that H264 from one source might sync, while H264 from another source won't.  I hope you're sending reports to Apple.  Hopefully this is an issue that can be addressed quickly.  Did you try Plural Eyes with that footage in H264 inside FCP 7?



  • Andreas Kiel Calculating status...
    Currently Being Moderated
    Aug 23, 2011 6:00 AM (in response to blimpmedia)

    I do think there is a bug.


    We normally use TC to sync AV and do create synced movies outside FCP. This is working fast, reliable and makes editing faster as the NLE doesn't have to care about this.


    Just for a matter of testing I used several short audio clips (each with four tracks from a 744T) and tried to sync them with the FCPX sync feature. None of them were in sync.

  • VoodooM Calculating status...
    Currently Being Moderated
    Aug 23, 2011 10:59 AM (in response to blimpmedia)

    Hi there, I'm having exactly the same problem, but I've noticed it goes a little deeper. I have tried this with H.264 files, transcoded to ProRes 422 by FCPX. Audio from a Zoom H1, 48khz, 24bit. Camera sound (should be) 48Khz. 1080p, 25fps.


    These can be synced just fine manually, but the auto-sync feature is way out. But when I looked a little closer, I realised that FCP had actually slowed the camera clip! Try it yourself (I filmed a stopwatch and the zoom at the same time). So even if it's in sync at the beginning, it's out by a couple of seconds for every minute it runs. It's almost as if the camera sound was 44, and FCP was stretching it out to 48 (which can't be right!!!). Totally weird, and I'm pretty sure it's a bug.

  • Andy Neil Level 4 Level 4 (3,785 points)
    Currently Being Moderated
    Aug 23, 2011 11:22 AM (in response to VoodooM)

    That's interesting. I could tell one of the clips was being slowed or sped up, but I thought it was the audio clip.  Make sure that apple gets that info via the feedback link in the program.  They probably know about it already but it's better not to assume.

  • tedtv Level 1 Level 1 (0 points)
    Currently Being Moderated
    Jan 27, 2012 9:27 AM (in response to blimpmedia)

    Great info. Thanks. However, I"m on a new Mac Mid 2012 2.8ghz running 10 gigs of RAM. Is the synchronize function a RAM intensive process, because FCPX 10.0 that I have stalls when synchronizing. On another note, I didn't put in any marks.

  • jonron239 Calculating status...
    Currently Being Moderated
    Feb 13, 2012 1:07 AM (in response to blimpmedia)

    lol - read through this thinking I experienced all of this last August then noticed the date of your original post - good to get everything confirmed though - I liked 10.0.1, quite a lot of stuff got fixed, still running it on my main editing machine - 10.0.3 on my back up 2008 MBP with projects copied onto different hard drives whilst I test it thoroughly

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