Quantcast Audio/video sync issue. Capturing with Virtualdub - digitalFAQ Forum
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  #1  
11-13-2016, 11:45 AM
Turok81 Turok81 is offline
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I finally got myself an NV-HS950 from ebay in good working condition. I also have the ATI 600 usb device, and I've been doing some capture tests in Virtualdub. I'm very pleased with the results. The video looks very clean and plays smoothly. However, I do have one issue I'm trying to figure out. Unless I press PLAY on the VCR before I start the capture, the audio will always lag behind the video depending on how long between the two steps. Say for instance, if I hit PLAY on the VCR 2-3 seconds after I start the capture in Virtualdub, the audio will lag behind the video for 2-3 seconds from beginning to end. If I do it the other way around, by having the tape already running when I initiate the capture, everything seems perfectly in sync.

The reason I tried capturing this way is because I want to make sure I get every single second on the tape from the beginning. Are there any settings that cause this, or is it normal?
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  #2  
11-13-2016, 12:52 PM
sanlyn sanlyn is offline
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Can't say that I've encountered that problem before. Try the link below, which has 5 successive posts dealing with AGP and USB capture devices and VirtualDub settings:
Capturing with VirtualDub [Settings Guide]
Several settings can affect audio sync., but you might want to pay special attention to timing options in the 5th section. A/V timing options for USB devices differ from those for conventional AGP/PCI cards. Don't bypass the discussion in other sections of the 5-part guide.
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11-13-2016, 03:28 PM
Turok81 Turok81 is offline
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Ok. Actually, I already have gone through the guide before. It has been a tremendous help in sorting out other issues I've had. I suppose I'll go through it again and see if tweaking the timing settings helps. Thanks
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11-13-2016, 03:55 PM
sanlyn sanlyn is offline
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USB's like the 600 connect audio and sound together within the device and maintain their own sync. You shouldn't have to use VDub's audio timing to adjust sync. Specifically, the image of the timing options in Section 5 shows one way of doing it, but the discussion under the image explains how USB's usually differ from the settings shown.
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11-13-2016, 08:08 PM
Turok81 Turok81 is offline
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Well, I tried a lot of different settings but none of them solved the issue, they only introduced other issues. Then I tried using a different VCR, a cheap consumer deck, and everything was perfectly fine and in sync. Unlike the NV-HS950, it didn't matter if I started the capture a couple of seconds before running the tape, or the other way around. The resulting video capture was perfectly in sync as far as I could tell. Weird. It appears the issue lies with the Panasonic deck itself.

By the way, I don't have an external TBC yet. I'm thinking of picking one up if I find a good deal on ebay, but for now I've been running capture tests without one. Aside from this issue I'm very pleased with the quality of the captures. The videos are very smooth and, according to virtualdub, I'm not getting dropped frames on the tapes I've tested so far. I do get a few inserted frames at the beginning of the captures, but it's perfectly stable from then on.

I stress again, that it only happens if I initiate the capture BEFORE I start running the tape, and not the other way around. It's very consistent, it doesn't seem to get progressively out of sync the longer the capture is. If the audio is out of sync by two seconds from the beginning, it stays that way until the end. When I already have the tape playing before I start the capture process, the result is perfectly fine. I'm wondering if this is one of those things a TBC would solve. I find it strange that my other crappy generic VCR works without this issue.
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11-13-2016, 08:40 PM
sanlyn sanlyn is offline
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I suspected that a frame-level tbc wasn't in use, a frequent cause of sync problems. Sometimes a cheapo outputs a more smoothly timed signal than a higher end unit that's developing tracking issues. In my own case I've had to set my high-end super-super player aside and use a mainstream layer that tracked some bad tapes better than the big guy.

Many get a used DVD recorder (Panasonic ES10 or ES15 recommended) and use it as a pass-thru tbc and frame sync, connecting it between the VCR and the capture device. Not as powerful as the heavy stuff, but it's cheaper and will usually do a surprisingly decent job. Won't defeat Macrovision, but it supplies a basic level of line and frame tbc circuitry. Not many DVD machines can be used for pass-thru.
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11-14-2016, 12:29 AM
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lordsmurf lordsmurf is offline
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Quote:
Originally Posted by Turok81 View Post
By the way, I don't have an external TBC yet.
This is very likely the issue.

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