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  #1  
Old 10-03-2007, 01:34 AM
DJ Robby Rabbit DJ Robby Rabbit is offline
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Default Video is out of Synch issue. Totally perplexed!


I am running PT LE on a Mac Mini with two external HDs. I am using iMovie.
This should be quick and painless but for some reason my audio is out of synch with my video.

I take my video from iMovie and exrtract the audio. I import the audio into Pro Tools. I add gain here and there, mess around with the awesome Sci-Fi plugin, consolidate the audio, and bounce to disk.

I import the audio back into iMovie and it's out of synch.

Now, there was no time code break and more important there was no destruction of any audio in Pro Tools. I kept the video one long cut and the audio one long cut. They are both the same time duration.

But no matter what they don't synch up. They seem to drift out of synch the further along.
In Pro Tools the original audio matches perfect with the Pro Tools emhanced audio.

What could cause such a synch issue?

Please advie. I am already late with this project.
Thanks in advance!
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  #2  
Old 10-03-2007, 01:56 AM
C C is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

What frame rates; sample rates etc are you using in each program?

Is this NTSC in iMovie being pulled into a PAL project on pro tools etc?
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  #3  
Old 10-03-2007, 06:48 AM
DJ Robby Rabbit DJ Robby Rabbit is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

I think it went out of synch somewhere because the frame rates were dropped or changed. How do I check what you asked about?
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Old 10-03-2007, 07:46 AM
C C is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

In Pro Tools

open the session set up window (+2) then check the frame rate on the right hand side.

Open both the disclosure arrows as well and see if there is any pulldown on at all

In iMovie

Not too familiar with it but it's default set up is as a DV NTSC project.

Let us know what these settings are and we may be able to help
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Old 10-03-2007, 08:33 AM
DJ Robby Rabbit DJ Robby Rabbit is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

Thank you so much. I will look tonight! I really appreciate it. I have a monthly commitment to putting up a web episode and now I am a few days late which is never a good thing.
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  #6  
Old 10-03-2007, 12:44 PM
Noiz2 Noiz2 is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

Frame rates are probably not the problem since your syncing to DV inside PT. I suspect you have a sample rate issue. iMovie is I'm sure at the DV rate of 48, I suspect your PT session is at 44.1 and iMovie is doing some not so great SR conversion. If your just plain out and not drifting then I would suspect the latency in the plugins. Many AS plugins have latency that will cause the audio to shift later in the time line. This would effect only the processed portions and is consistent.
So check the SR of your PT session and make sure it's 48 or bounce your track out at 48 when your done.
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Old 10-03-2007, 01:29 PM
StaticStudios StaticStudios is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

If it's drifting gradually, I'd bet it has to do with a Drop-frame vs. Non-Drop frame issue. Check the frame-rate of the quicktime you exported from imovie vs. the frame rate INSIDE iMovie. If there is a difference, that would be your problem. Again, make sure you are checking not only the frame RATE, but also whether it is Drop-frame, or non-drop frame. A non-drop quicktime will, according to time-code in pro-tools, be the same length, but in REAL TIME, it's actually longer. If you cut your audio to the longer picture and re-import it into iMovie the audio will appear longer and out of synch. To correct this without re-doing ALL of your work, re-export a new quicktime (at the correct frame rate) from iMovie, place it in a new protools session then import your out of synch audio using "Sample Rate Conversion" (SRC) (at 0.1% pull-down I believe) and line it back up to the picture. That's how I've fixed it when faced with a similar situation.
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Old 10-03-2007, 03:34 PM
cmaynes cmaynes is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

Scott's answer is the one I think is correct-

the way to check it is to repeat your process- If the Import audio window asks if you want to convert, your sample rates are not the same-

When you do import audio, check the sample rate that is listed for the incoming file.

the resulting output would then cause the speed problem you are noticing.


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Old 10-03-2007, 05:18 PM
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Default Re: Video is out of Synch issue. Totally perplexed!

Quote:
If it's drifting gradually, I'd bet it has to do with a Drop-frame vs. Non-Drop frame issue. Check the frame-rate of the quicktime you exported from imovie vs. the frame rate INSIDE iMovie. If there is a difference, that would be your problem. Again, make sure you are checking not only the frame RATE, but also whether it is Drop-frame, or non-drop frame. A non-drop quicktime will, according to time-code in pro-tools, be the same length, but in REAL TIME, it's actually longer. If you cut your audio to the longer picture and re-import it into iMovie the audio will appear longer and out of synch. To correct this without re-doing ALL of your work, re-export a new quicktime (at the correct frame rate) from iMovie, place it in a new protools session then import your out of synch audio using "Sample Rate Conversion" (SRC) (at 0.1% pull-down I believe) and line it back up to the picture. That's how I've fixed it when faced with a similar situation.
Hi StaticStudios,

sorry, but, this is not correct. audio speed in digital is governed by Sample Rate, not by Frame Rate.

Furthermore, the difference between Non Drop and Drop Frame is not .1%. the SRC trick will not help you here. Pull Down is for Frame Rate conversions, like FIlm to NTSC (or 24 to 23.976). Non-Drop and Drop are the same "speed' but counted differently. though when you feed Non-Drop code into a VTR via LTC or MTC to a DF tape, you will get problems and drift. but it is not .1%

iMovie is notoriously AWFUL with SYNC. i worked on a film that the director cut in iMovie about 6 years ago and it was a nightmare. make sure you have the latest version and a decently fast computer. once the audio is attached to the QT and is in sync, and you do no SRC, then you should be in sync. might i sugest exporting your QT from iMovie, doing your audio work in PT and use QT Pro and the 'add to movie" feature to attache the audio to the QT. (or perhaps the 'bounce to movie in PT).
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Old 10-04-2007, 12:05 PM
Noiz2 Noiz2 is offline
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Default Re: Video is out of Synch issue. Totally perplexed!

I think folks are getting confused over the differences between digital video files and tape based work flows. When your working with video files (on the same computer, VVTR is a VTR) you are not syncing with TC so the TC doesn't really matter. Video frame rate should not make a difference (unless it changes). What usually causes problems is sample rate, because that often changes and isn't always noted or documented. This is likely to be a bigger issue in the future now that both major NLE's support "multi format timelines". One of my questions to them was what happens to the audio? I mean if your getting a project that mixes and matches 35mm, 23.98, 29.97, PAL etc. what is happening to the audio, and how do you use original sources if the editor trashed things??? I don't think anyone has a real good answer right now.

Anyway. In theory a QT video plays back based on it's frame rate and PT plays back based on the session Sample Rate. Both are resolved to the computer or interface. Assuming a decently accurate clock both are self resolved and will stay in sync for a long time. The problem comes if for some reason either the SR or FR change down the line and the other doesn't follow.

In the "good old days" TC was a big issue and still is IF your syncing to tape or virtual tape. But even then TC issue is more of a warning than the problem. TC is not used as a clocking source generally except for analog tape decks and you don't see too many of those around these days. Video will be locked to black burst and audio to word clock (prob referenced off black burst). Drifting TC is an indication something is off but is not often the source. Of course some times things have the wrong TC and that is why the #'s are drifting. But if the audio is drifting it's a clocking problem somewhere.

And as Tom said Drop and Non Drop are the same frame rate, one is just counted by someone with a few missing digits.
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