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Old January 11th, 2004, 01:44 AM   #1
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Help!! Audio Drift!!! Why????

Dag Nabbit!

Can we talk about !@#$%^&*-ing audio drift for couple of minutes?

From recording to post, what are all of the possible causes of this hideous disease?, and how best to keep it from bloody well happening! Please list.

My thoughts/questions:

Can microphone distance have anything to do with it? I'm talking 20 feet, at most.

I shoot with a PDX10. Does DVCAM lessen the chance of audio drift? I've read that it insures "locked audio". Can I continue to use Sony Premium, and just record in DVCAM mode to gain this benefit, or do I have to use the DVCAM tapes too?

Is it dropouts?
Is it breach of timecode?

Help!

Shawn
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Old January 11th, 2004, 02:48 AM   #2
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Well, Shawn, I think you're the first person who has ever used "dag nabbit" in a post!

Where are you observing the drift? After capture, presumably? What editing platform are you using?

This is not entirely uncommon, especially on longer clips. Some editing systems have settings that help compensate for audio drift.
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Old January 11th, 2004, 03:40 AM   #3
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Yes, Ken, the English language is a veritable treasure trove full of gems waiting to be discovered and rediscovered. Just doing my part. :-)

Drift seems to be happening nearer to the middle of an hour long recording/capture.

I'm editing on Final Cut Express, on a desktop G4. I'm away from it right now, so I'll have to get other system stats later on, if needed.

I tried looking up the words Audio Drift in both the manual and a guide book for Dummys, to no avail. Will get out a finer comb in case the sacred third party wisdom escaped my narrow eyes the first time around.

Thanks for the assist, Ken. I know it's common, maybe that's why it irks me so. As great blundering adventures into the jungles of NLE go, well, "audio drift" doesn't exactly ooze with style.

FCE had a host of things to say at different points along the way, post capture. In trying to play the clip from the browser, before being dropped into the timeline, I was met with metronome-like beeping, telling me, according to the books, that the audio needed to be rendered...

Before I go on, is this turning out to be an issue that ought to be taken up in the Mac NLE/Editing forum? I would hate for this to turn into a Forum Drift issue on top of it all....(ba dum bump)
Just thought I'd ask.
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Old January 11th, 2004, 10:37 AM   #4
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You might post there also.

You can record DVCAM on your current tape stock.

Often the monitoring of NLEs is out of sync unless you adjust an "offset", but if you lay back to tape and check that it could be fine.

But if your tapes are starting in sync and then drifting out, the offset wouldn't be the issue. Distance can make a difference, but 20ft would be hard to see. 20ft might be a frame, I'll have to check.
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Old January 11th, 2004, 12:01 PM   #5
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I have moved this thread to this forum for best response. It's strictly an issue concerning FCE.
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Old January 11th, 2004, 02:06 PM   #6
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DVCAM uses locked audio, which kind of helps. Locked audio implies that the sampling rate of the audio is a constant 48.000khz (because the audio clocks are good), not 48.009khz like some older Canons. 48.009khz sampling rate can cause sync issues and "sync adjust movies" is supposed to fix it. Try disabling SAM.

Your camera might also be able to record in 12bit mode (4 channels, 32khz 16-bit depth) instead of 16bit mode (2channels, 48khz 16-bit depth). You should nearly always shoot in 16bit mode to avoid problems.

Final Cut doesn't seem to handle empty audio well (can cause sync issues). This can come from unplugging or turning off mics, or using your camera as a VCR to record analog sources.

Also check that your capture settings match your sequence settings. This is easiest done by using the canned presets.

Right click your clips and check their properties. What's the sampling rate?

If you capture twice the audio offset is different on the second capture.

Ok that's all I know. There might be other causes for lost sync.
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Old January 12th, 2004, 12:55 PM   #7
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Shawn,

Do you have Norton Anti-virus installed and enabled? That has been known to cause problems during capture. Since I started disabling NAV before capture I haven't had a single problem capturing. I was having drift issues with an XL1s.

HTH,

Bill
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Old January 12th, 2004, 01:22 PM   #8
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Shawn,
I don't know if you have solved this problem yet. But, if not, here's the Apple (FCP4) article on this problem which basically recites much of what Glenn noted.
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Old January 12th, 2004, 03:30 PM   #9
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Disabling NAV before capturing, will check it out, Bill.
Thank you for the article, Ken. I really want to try everything that might be connected to drift, so lay it on me, if anything else.

The real trouble, right now, however, is getting FCE to open in the first place, as maybe you have or will have gathered by my other current thread, "FCE wil not open!"

Will let us know how it pans (and tilts) out.
Thank you very much.

Shawn
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