Synching footage from three cameras

Discussion in 'Amateur Video Production' started by tomededtom, Apr 6, 2006.

  1. tomededtom

    tomededtom Guest


    I have been editing with Premiere on a PC running XP for years. I use
    Matrox capture card. I shoot with a couple of Canon GL1s and a
    Canon XL1s. I mainly shoot orchestra and band performances in
    performance halls.

    I have noticed over the years that the footage of the precise same
    event from the three cameras doesn't stay synched over long clips.
    For instance, I am currently editing a clip of a performance shot with
    two cameras ( a GL1 and the X.) One camera reports clip length at
    7:19:05 and the other camera reports it as 7:24:19. Same performance,
    cameras were ten feet apart. I trimmed the tape and marked the first
    frame of the opening note on both tapes and lined up my markers
    perfectly. Both clips start at precisely the same time, down to the
    frame, on the timeline. They start together, but they don't end
    together. By the end of the tape, the audio (and obviously, the
    linked video) is out of synch by almost five and a half seconds.

    Does anyone have an explanation for this? Obviously, the cameras are
    not rolling tape at the same speed. Is something out of adjustment or
    is this normal variance between prosumer cameras?

    The more important question for me right now is this: Is there a tool
    in Premiere 6.5 to remedy this, other than resynching the two tapes
    every thirty seconds or so by cutting and moving clips on the time
    line? I tried to change the clip speed both by typing it into the
    clip:speed dialogue box, and also by using the rate stretch tool. The
    rate stretch tool did in fact change the clip speed, but the clips
    still don't end at the same time.

    Your advice is greatly appreciated.
    tomededtom, Apr 6, 2006
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  2. tomededtom

    nappy Guest

    yes.. the timebase for cameras is a crystal. The tolerance is such that
    these errors will acrue between two devices.
    nappy, Apr 6, 2006
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  3. tomededtom wrote ...
    If that is 7 hours, then 5.5 sec of slip between the two is remarkably
    good. If that is 7 minutes, then one of your camcorders is rather
    far out of spec for speed.
    5.5 seconds in a 7 minute shot is pretty bad. I just finished editing
    a 20 minute video that was shot with three Sony DV camcorders
    (all different, but similar models). By the end of the 20 minute time
    line, there was no visible slip between the three tracks. I was
    prepared to slide the video at the edit points to bring the audio back
    into sync, but never had to. I was mildly surprised at how good the
    tracking was.
    IMHO, 1~3 seconds in an hour is "normal" for random consumer
    camcorders. Your particular example seems significantly worse
    than I would expect. All cameras, even professional ones that
    cost more than your home+car will show this kind of "slip"
    Professionals connect cables between cameras to "genlock"
    them together to run in exact lock-step synchronization. Consumer
    video equipment does not have this "genlock" capability.
    Don't bother trying to "stretch" or "compress" anything. The
    artifacts from doing this are worst than what you are trying
    to fix.

    Presumably, you shot with two cameras so that you can "switch"
    between them via editing. The simple fix is to just go ahead and
    select your edit points, and then wherever you see a problem
    between the video and the audio, simply slip the video clip to
    match the audio. It actually takes more time to describe here than
    it takes to just do it. It is no big deal. Don't obsess about it.
    I am presuming that one of the cameras was getting the "master"
    version of the audio track (some common reference to sync the
    video to).
    Richard Crowley, Apr 6, 2006
  4. tomededtom

    tomededtom Guest

    Thank you so much for your reply.
    Is there any relatively painless way to synch long clips in Premiere
    At this point I'm guessing the method of marking a distinct audio event
    on each audio bed and lining up markers is the only way.
    tomededtom, Apr 6, 2006
  5. tomededtom wrote ...
    Why did you shoot with 2 cameras if you are going to use
    "long clips"? Every edit point is a prime opportunity to pull
    the video back into sync with the audio track. It is easier to do
    than it is to describe.
    Works like a charm. If you look at both waveforms on the
    timeline, it is quite easy.
    Richard Crowley, Apr 6, 2006
  6. tomededtom

    tomededtom Guest

    "The simple fix is to just go ahead and
    select your edit points, and then wherever you see a problem
    between the video and the audio, simply slip the video clip to
    match the audio."

    That's pretty much what I have been doing. I just wondered if there
    was a miracle cure for the problem ( besides live switching, which I
    just can't afford right now)

    Thank you so much for your replies.
    tomededtom, Apr 6, 2006
  7. <SNIP>

    Careful! This is either 5 minutes in 7 hours (quite a long tape) or 5
    seconds in 7 minutes. In either case the percentage difference (nearly
    1.2%) is the same. And *huge* for a crystal controlled device.

    You seem to be in time zone -7, same as me. Looks like you posted at
    21:22:45, by which time my brain is usually fried worse than that...

    I used to say "No coding after two AM or two beers, whichever comes
    first", but I'm older now :)

    Gene E. Bloch, Apr 6, 2006
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