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On long session, audio gradually gets out of sync with video

1504 Views 5 Replies Latest reply: Jun 9, 2010 1:01 PM by Jane Evans RSS
Jane Evans Calculating status...
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Jun 8, 2010 11:27 AM
In the past, I have done only short video segments, but am now trying to edit an hour-long audio. It is perfectly audio/video in sync at the beginning, but gradually gets horribly out of sync by the end of the hour. I am using firewire from the camcorder tape. Sequence Preset DV NTSC 48 kHz; Capture Preset DV NTSC 48 kHz; Device Control Preset FireWire NTSC. Video Playback Apple FireWrie NTSC (720x480); Audio Playback is FireWire DV. The tape audio was set to 48 kHz.

In User Preferences, I have checked Sync audio capture to video source, Abort ETT?PTV on dropped frames, Warn when importing non-optimized media.

I thought it might have something to do with the supposed 30 fps of FCP and the actual 29.95 fps on the tape, but can find no place where any adjustment can be made for capture.

Does anyone have any idea as to how I can resolve this? The klutzy and dirty way would be to capture it in something like 10 min segments, but that would be an ugly way to go.
Intel iMac 27", MacBook, iMac G4, Mac OS X (10.6.3)
  • Jim Cookman Level 7 Level 7 (23,435 points)
    Hi Jane, DV has an unfortunate "feature wherein audio can drift away from the video. Sony fixed this with their DVCAM implementation, where audio and picture are locked together. The drift can get rather tiresome, and indeed one way to alleviate it is to capture in smaller chunks.

    It's really not so ugly, and not at all time consuming. Find the first good timecode on the tape, and press "I" to make an in point. Then go to the outpoint code window and type a number 10 minutes away hit log clip. It will show up in the browser.

    Then type a number 15 frames earlier than the last out point, add 10 minutes. Rinse and repeat. Would make sense to make note of the outgoing code beforehand so you don't send the app on a wild goose chase looking for an outpoint. But tapes come back from the field tails out, so no biggie.

    I've found with drifting tapes you can VERY safely do 15 to 20 mins. Anything else is problematic.

    Wasn't a Canon camera, by any chance?

    Message was edited by: Jim Cookman, who can't type for sh*t
    G5 quad, 6 gigs, 2x500, nvidia 7800, 2.5TB Brian Conner Special, couple g-raids,, Mac OS X (10.4.5), 4 other macs, various. 2 minute walk to the beach elitist..
  • Meg The Dog Level 6 Level 6 (9,395 points)
    Hi -
    The source video is one long take, with no camera stops or interruptions of any kind?


    Mac OS X (10.6.3)
  • Vic Owen Calculating status...
    Breaking it into chunks should do the trick, as Jim described. I used to experience the same problem with my XL-1 until I started capturing the extended recording sessions on a Firestore, using the tape just for back-up. These kind of captures are common when recording single camera theater productions.

    Mac Pro Dual 2.6 Xeon, Mac OS X (10.6.3), 5 GB Ram, FCS-2


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