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Audio sync problem digitizing from 3/4" deck

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Scott Ogle
Audio sync problem digitizing from 3/4" deck
on Sep 23, 2011 at 7:51:43 pm

Recently, I borrowed a U-Matic 3/4" deck to capture a bunch of ancient clips. However, after trying every setting I can find, I still have a major audio sync issue that I can't resolve. Captured video is leading audio by roughly 4 seconds! It looks/sounds fine while capturing, but plays back out of sync. I just completed a similar project using a BetacamSP source deck with no problems.

Here's my setup:
Sony VP5000 playback deck is hooked up composite video and 2 channels of audio to
AJA ioLA which moves everything via Firewire 400 onto the system drive of my
iMac

Hoping somebody can assist before I have to return the deck. Thanks.
-Scott Ogle


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Chris Tompkins
Re: Audio sync problem digitizing from 3/4" deck
on Sep 23, 2011 at 9:44:13 pm

Check your offset in FCP prefs.

Chris Tompkins
Video Atlanta LLC


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Scott Ogle
Re: Audio sync problem digitizing from 3/4" deck
on Sep 23, 2011 at 10:37:02 pm

Thanks for the tip, Chris. Audio Offset was set to 4 frames, which obviously doesn't help a 4 second issue (not sure how it got that way, though). So I continued drilling down into the problem and now believe I have it solved. I'm going to post my results in case some other poor soul searches for this problem in the future.

First of all, the source tapes are 25 years old and have lots of dropouts and other issues. I couldn't get a clean capture until I unchecked the User Setting to "abort capture on dropped frames". I did keep the setting to "notify of time code breaks". - - Not sure if that had anything to do with audio sync, since AJA says dropped frames would mean audio would LEAD video instead of the reverse, which was my problem.

The primary problem appears to be that capturing uncompressed video onto the iMac's system drive is asking too much of the drive. Accepting a compressed capture (either DV50 or ProRes422) seems to work just fine. AJA tech support just sort of clucks at you for using an iMac, and says it is an unsupported use, but a Mac Pro is massive overkill for everything I do except a minor amount of editing, so I've developed lots of workarounds and this is just another example of one that's needed.


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