Audio out of Sync with Video?

whiskey3 wrote on 11/2/2004, 9:10 PM
I have a live concert fotage I encoded from DVCPro to Microsoft's DV Encoder. The client gave me 6 channels of 5.1 .aiff's at 48khz. My DV audio is also at 48khz. When I sync up their audio to the video the audio does not stay in sync at all? I even converted the audio to 44.1 and it didn't work either? Is it because MS DV Encoder is type 1 not Type 2? Or does it matter?

Comments

farss wrote on 11/2/2004, 9:25 PM
It's most likely that the clocking rate on the audio kit doesn't match that of the cameras, a not uncommon problem. You can expend a lot of effort assuming the audio gear was recording TC which I much doubt or you easily fix this in Vegas.
Firstly avoid multiple sample rate and bit depth conversions, doesn't help the quality. All you need to do is sync something at the beginning, find a suitable event at the end and ctl+drag the end of the audio event till the end event lines up with the vision.
If the clock in the audio gear is all over the place then you might have to do this in shorter segments but that's no big drama either. Just split the audio event, maybe drop alterante segements down to new tracks and sync / stretch to match.
If you're strecthing the audio under 5% you shouldn't have any issues. If it's out more than that, in fact if its out more than 1% you might need to look further into just what went wrong.

Bob.
johnmeyer wrote on 11/2/2004, 10:24 PM
farss, as usual, is exactly correct. Just to emphasize: Do not change the sample rate. It has nothing to do with your problem.
whiskey3 wrote on 11/2/2004, 11:13 PM
The video is 1:20:58 and the audio is 1:22:41 so should I slide audio or video?

Thanks....
johnmeyer wrote on 11/3/2004, 7:46 AM
Change the audio.
MJhig wrote on 11/3/2004, 7:55 AM
Why change the audio? Every process performed on audio introduces degradation especially time stretching/shrinking and or pitch changes.

Our eyes are much more easily fooled than our ears, I can see no negatives associated with stretching/shrinking the video.



MJ
musicvid10 wrote on 11/3/2004, 8:19 AM
I do this a lot, and agree with johnmeyer. Squeezing the audio a little bit is less problem-prone and less time consuming than changing all that video. The effects of a 2-3% audio squeeze are barely noticeable. If, on the other hand, he was looking at a big audio stretch, I might consider operating on the video instead.
MJhig wrote on 11/4/2004, 5:13 PM
I respectfully disagree. What "all that video"? He's doing surround, 6 audio tracks.

Video suffers no degradation time stretching/shrinking, audio does from this process then add all the other necessary audio processes on top of that which of course will involve compression and EQ at the very least.

Stretching/shrinking the video is a no brainer, select all the video > group > Ctl + drag... no harm done.

This is a concert, the audio is the focal point is it not? Unfortunately we are visual creatures at the worst of times. Musicvid, I've done this "a lot" also, I've made my living the last 30 years as a musician, if you squeezed/stretched my/our audio I'd definitely notice as a drummer/keyboardist, myself and band mates would be very unhappy with that.

MJ