10 Replies Latest reply: Jun 17, 2013 3:22 PM by Studio X
FCP WIDESCREEN PROBLEMS Level 1 Level 1 (0 points)

So this is an issue that's been presisting regardless of the equipment i get.

 

I film live bands and I record my audio separatly from the video then synk it in FCP. The issue is that withing 3 to 4 minutes it starts to become slightly obvious that it's out of sync and by the end of a 30 min or 1 hour set, It's noticably out of sync.

 

What's going on and how do i stop it.

 

for audio I'm using a H1 Zoom. Lo cut is OFF, Auto level is OFF, and Rec format is WAV not MP3.

 

For video I use a T3i, shot at 1920 X 1080 at 23.98 FPS transcoded from H.264 to Apple Pro Res, also 1920 X 1080 at 23.90 and my sequince also shares that setting.


IMAC, Mac OS X (10.5.8)
  • 1. Re: "sliding audio" issue
    Jim Cookman Level 7 Level 7 (23,435 points)

    You have a couple of issues.  Is your audio being captured at 16 bit 48k?  That's one.  But your other, BIG issue is that neither of these devices records timecode.  And both those clocks are running their own merry way.  There is no common clock between the devices.

  • 2. Re: "sliding audio" issue
    Nick Holmes Level 7 Level 7 (29,835 points)

    Apart from both devices being in the same room, there is no shared reference between your camera and the audio recorder. Over time, one or both both will drift - speeding up or slowing down slightly.

     

    What you need is a peripheral known as a Gen Lock. The camera and audio recorder are synchronised through this device. Drift on one part of the system is compensated on the other.

     

    Note that not all cameras and audio recorders can drive or support being driven by a Gen Lock.

  • 3. Re: "sliding audio" issue
    FCP WIDESCREEN PROBLEMS Level 1 Level 1 (0 points)

    how do i get it from there to on my computer?

     

    Isn't there something in my Final Cut Studio 3 that can add the same timecode to both?

  • 4. Re: "sliding audio" issue
    Nick Holmes Level 7 Level 7 (29,835 points)

    The problem is occuring on your recording equipment, not in Final Cut Pro.

  • 5. Re: "sliding audio" issue
    FCP WIDESCREEN PROBLEMS Level 1 Level 1 (0 points)

    16 bit integer, that's the audio AND the video though my sequence... is 32 bit floating point.... aaaand i think THAT might be my problem.

  • 6. Re: "sliding audio" issue
    Meg The Dog Level 6 Level 6 (9,680 points)

    No. Audio is processed internally in FCP at 32bit, but your source should be 16bit, and when you export from FCP, the audio will be 16bit.

     

    MtD

  • 7. Re: "sliding audio" issue
    RatVega™ Level 4 Level 4 (1,910 points)

    Nick and Jim are both giving you strong clues...

     

    I'm guessing that the problem (and the Devil) is in the details. Your audio and video need to be exactly the same speed. Since you choose to record them separately, one or the other need to be adjusted. This is why the problem has persisted irrespective of the equipment you use.

     

    Your video isn't 23.98 fps, it's 23.976. Examination will probably show that the audio is something else.

    If it were me, I'd probably adjust the audio because video framerate is a bit more "sacred."

     

    HTH

  • 8. Re: "sliding audio" issue
    Jim Cookman Level 7 Level 7 (23,435 points)

    AND if you're REALLY lucky, the audio will be longer than the video.  Then you can find quiet spots to cut out and pull up the audio to resync.  This was common practice in the old film double system days.

  • 9. Re: "sliding audio" issue
    Michael Grenadier Level 7 Level 7 (20,115 points)

    One thing that can cause this problem is if your easy setup is not set to the correct frame rate.   Try changing your easy setup to match your Video frame rate and then try reimporting the audio files.  I haven't seen this, but I have read about it.  

  • 10. Re: "sliding audio" issue
    Studio X Level 7 Level 7 (26,940 points)

    And, the audio must be recorded at 48 khz not 44.1.

     

    Bit depth has NO effect on sync (not synk) relationships. Sample rate does. Video editing software, such as FCP, expect the audio to be 48khz. Anything else is a problem.

     

    x