Audio Drift Issue (47.962 khz & 29.96 fps???)
by Richard Lowe
on
Nov 3, 2009 at 8:27:25 pm
Hi everyone,
I captured some footage at DV50 through Final Cut Pro using Capture Now (because there were timecode breaks). I did two passes because the dailies tape has four channels of audio--I did one pass to capture channels 1 & 2 and one pass to capture channels 3 & 4, both with video.
In FCP, however, when I cut either or both clips into a sequence, the audio drifts very badly. I checked the original QT file (clip with channels 1 & 2) in my Capture Scratch and the audio drifts there, as well. So it's definitely a capture problem. In the QT Inspector, it says the FPS is 29.96 and the audio is 47.962. Has anyone ever seen this before? This seems totally weird to me.
Here's where it gets weirder: the clip where I captured channels 3 & 4 have an audio rate at 47.963, .001 higher than the other clip.
Any advice would be much appreciated!
Unfortunately, I don't have the deck any longer, though acquiring it again probably won't be a problem. I'm just trying to make sense of what's going on!
Re: Audio Drift Issue (47.962 khz & 29.96 fps???) by Richard Lowe on Nov 3, 2009 at 10:36:36 pm
Hi Dave,
The FCP Item Properties window shows 47962.4hz, which I imagine translates to 47.962 khz for the clip with channels 1 & 2 and 47.963.1hz for the clip with channels 3 & 4. (I am not an audio guy, unfortunately.)
Re: Audio Drift Issue (47.962 khz & 29.96 fps???) by David Roth Weiss on Nov 3, 2009 at 10:05:15 pm
[Richard Lowe]"Here's where it gets weirder: the clip where I captured channels 3 & 4 have an audio rate at 47.963, .001 higher than the other clip. "
Some time back I also experienced that same strange audio sampling issue with a rented Panasonic deck. Every tape and every capture attempt reported a different sample rate in the 47.xxx range.
As I recall there was no easy solution for that one. It cost me days and days to sort out. I think we ended up having to use the camera on which the material was shot.
David Roth Weiss
Director/Editor
David Weiss Productions, Inc.
Los Angeles
POST-PRODUCTION WITHOUT THE USUAL INSANITY ™
A forum host of Creative COW's Apple Final Cut Pro, Business & Marketing, Indie Film & Documentary, and Film History & Appreciations forums.
Re: Audio Drift Issue (47.962 khz & 29.96 fps???) by Matt Lyon on Nov 4, 2009 at 4:40:19 pm
How was the footage originated? Was it shot on a DV camera? It's been a while, but I recall early generation consumer DV cameras had issues with audio drift due to some vagaries of the format. Didn't the first gen XL-1 have issues with creating materials with strange audio sampling rates. At any rate, David Weiss' advice is probably the surest fix: capture from the same camera that shot the material.
Re: Audio Drift Issue (47.962 khz & 29.96 fps???) by Richard Lowe on Nov 4, 2009 at 5:53:06 pm
Yeah, it was via Firewire.
I don't know what the deck settings were. I didn't set them, unfortunately, and I didn't know it needed specific settings. The company we rented from didn't mention it, either, when we told them we were capturing DV50.
So you're feeling is it's a deck setting? What should the AJ-SD930 be set to for DV50?
Re: Audio Drift Issue (47.962 khz & 29.96 fps???) by Richard Lowe on Nov 4, 2009 at 7:08:38 pm
Okay, well, I definitely didn't set the deck (or change the configuration when I got it), so that may be it.
As for the Firewire connections, I had the deck connected to my Powerbook's Firewire 400 and a hard drive connected to my Firewire 800. Could that cause the problem? (I wasn't sharing a hub or daisy-chain.)
