Neoscene audio synch issues (Canon 5D Mk II) at DVinfo.net

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Old April 29th, 2009, 07:23 AM   #1
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Neoscene audio synch issues (Canon 5D Mk II)

I was curious if anybody else is seeing any issues with the audio sync on 5D MK II files that have been converted with NeoScene. I first noticed this a month or two ago but didn't have time to fully track down the issue. This week I've started cutting some of the footage I've been shooting (all of it converted with the latest Neo Scene build) and I am seeing that on longer clips the (conformed by neo scene) audio track is losing synch with the video track. In this case, I'm talking about the audio track from the built-in mic on the 5D. Just for kicks, I tried "unconforming" the audio (time stretching it to 99.90% of the original rate)and it seems to be back in sync. Very strange.

The first time I noticed something was amiss was a month or so ago when I was working on a project where I was trying to synch with some offboard audio. This was a clip that was 14 minutes. Theoretically, assuming the original 5d video footage really was 30.00fps, and neoscene was simply changing the header to 29.97 (as cineform claims), the offboard audio track needed to be stretched by 0.1% (1001/1000=100.1%). At first I thought this factor was working well, but even several minutes into the clip you could see it was still losing synch. I found that the synch was nearly perfect (to my eyes/ears, at least) if I time stretched the audio by another 0.1% (basically 100.1% of 100.1%= 100.201%).


Has anybody else observed this? I'm using Vegas 8.0c and the built-in "Time Stretch" audio FX plugin.
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Old April 29th, 2009, 09:36 AM   #2
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to add a little bit to my findings, here are a few observations.

source 5D Mk 2 file: video and audio duration 14:03;28, file size: 4.14GB
cineform file: video duration: 14:04;21, audio duration: 14:05;16, file size 11.40GB

It seems as though the audio stretch factor that neo scene is using is being applied twice, causing the loss of synch. The difference appears to be roughly 0.1%, which means I think we need another new build of neoscene.
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Old April 29th, 2009, 10:09 AM   #3
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Fixed about a month ago. You can reconvert with Neo Scene 1.2.1
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Old April 29th, 2009, 01:15 PM   #4
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Quote:
Originally Posted by David Newman View Post
Fixed about a month ago. You can reconvert with Neo Scene 1.2.1
hmm, I was pretty sure already had that version with the fix installed when i transcoded these files. I guess I will try again.
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Old April 29th, 2009, 03:29 PM   #5
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Ok, I can now confirm 100% that this problem occured with the latest version. Also, I confirmed that the previous batch of files were also converted with version 1.2.1 build 113.
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Old April 29th, 2009, 03:46 PM   #6
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i have had loss of sync issues with my last import and i was using the latest version as well.
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