Lip Sync on Long Mini DV Recordings

Discussion in 'Amateur Video Production' started by BrianEWilliams, Jan 5, 2004.

  1. I have been capturing 3 hour home movies to disk via my Sony TRV-120
    camcorder pass-thru. After about two hours, the lip sync is noticably
    off. Is this a product of the pass-thru? I would imagine that if I
    were to record onto a 3 hour miniDV tape, that the lip sync would be
    fine since it is all recorded in real-time to a linear medium. Then
    transfering the tape to disk either would or would not have the lip
    sync problem.

    Since I obviously can't try this experiment, does anyone have
    experience or thoughts about this? Maybe it's my computer system
    that's causing the problem. It is pretty low-powered (P3-450), but
    it's worked like a champ for many years without an issue until now.
    It's running XP Pro with a dedicated 120 GB NTFS video drive.
     
    BrianEWilliams, Jan 5, 2004
    #1
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  2. BrianEWilliams

    Jay Rose CAS Guest

    I assume you're saying sync is off when you play back the file, not as
    you're capturing. (The latter would require manipulation of the space-time
    continuum.)

    A couple of things can be causing what you see:

    Single dropped frames aren't usually visible in pix, but they stand out in
    track, so most programs give priority to the sound. If something is
    distracting your computer (network services, TSRs, whatever), you could be
    getting occasional dropped video frames that add up after a while.

    Many low-cost DV cameras cheat slightly on the audio sample rate, to take
    advantage of easier ways to derive it from the main crystal. It doesn't
    cause a problem when you play a tape*, but when you capture, your NLE
    assumes a constant 48 kHz. Over time, the slight error adds up.

    Some NLEs have a 'compensate for audio sample rate' checkbox.
     
    Jay Rose CAS, Jan 5, 2004
    #2
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  3. Thanks. Didn't even consider the camera as a source of the problem.
    Any other TRV-120 users notice this on long captures?

    Premiere 6.0 only reported 2 dropped frames so I don't think dropped
    frames are the issue. Does either Premiere or Vegas 3 have the
    'compensate for audio sample rate' option? I am at work right now,
    but when I get home, I will see if I can find it.

    BTW, Google Groups wouldn't let me start the subject with "Re:",
    saying this was not a follow up. Strange.
     
    BrianEWilliams, Jan 5, 2004
    #3
  4. BrianEWilliams

    ctrl-z Guest

    Thanks. Didn't even consider the camera as a source of the problem.


    We have to capture in 5 minute batches to compensate for this. You
    only have to make a batch capture template once.


    I'd be tempted to edit around only 2 dropped frames, but you really
    shouldn't have any.
     
    ctrl-z, Jan 5, 2004
    #4
  5. Three hour home movies? Mini DV tape? Would you mind telling me what
    Mini DV camera can do three hours? What home movie could possibly be
    that long?

    Gary Eickmeier
     
    Gary Eickmeier, Jan 6, 2004
    #5
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