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RRLech
Analog Audio /Video Sync
on Feb 28, 2003 at 4:16:36 am

I'm capturing analog A/V using a DV500 and I'm having sync problems. They start out matched up but after 15 minutes they are off by about 1 full second - with the audio lagging behind. I get no dropped frames. I'm capturing to a U/W fast SCSI drive (that tests fine using DVExpert). I have the latest drivers, and I've implemented the XP tweaks listed on this site.

Can anyone enlighten me?


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RRLech
Re: Analog Audio /Video Sync
on Feb 28, 2003 at 7:18:57 pm

I may have answered my own question, and I thought it might help others...

After posting, I tried to re-capture an analog tape that had previously been captured without incident. The re-captured AVI file had no sync problems which prompted me to examine the tape that was giving me problems. It turns out that the tape had a number of points at which there was either static or a patch of new video recorded in the middle of old video. My guess is that those points confuse the DV500's synchronization algorithm.

Basically, I've decided to live with the out of sync audio and correct it in the editing process.

Of course, I'd still be interested if anyone else has feedback.


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Gary Bettan
Re: Analog Audio /Video Sync
on Mar 2, 2003 at 2:36:32 pm

Excellent popint and one that we've kinda forgaotten around here. DV is such a large section of our customer base, that we've forgotten some very important analog lessons from the past.

What you describe can be a very big problem for analog capture. I know we all like to go back and look at our video tapes, then shoot some more. Thhis can cause you all kinds of problems.

- Gaps between the footage can create capture errors
- overlapping of your recording can result in a split second of messed up footage, just enough to mess up your sync.

One of the things you can do to avoid this in the future is get in the habit of recording some black footage at the end of each day. JUst a couple of seconds with the lens cap on. This will give you a nice 'margin of error'. Now if you go back and view the days footage, you just need to start the next day somewhere in the 'black'. Record a couple of seconds of Black at the start of each day, and you'll be worry free come editing time.

If you camcorder is prone to recording noise, take it in for service and have the heads cleaned, aligned and checked out. If you have a tape with several of these 'gaps', try rrecording black over them before you capture, or make sure you use these 'gaps' as stopping points during the capture process.

Gary

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