Proper VirtualDub timing settings for best video/audio sync

[premiumcapture]

Just wanted to get a feel for the best VirtualDub sync settings. Looking over the rev. notes, it seems many of the options/features were designed with hardware limitations of the time in mind, but I am wondering if it is just better not to let VirtualDub resync anything at all.

What are your thoughts?

[Brad]

It is certainly better, if your hardware will do it without needing frames dropped/inserted to keep the video synched to audio.

[premiumcapture]

Allow me to rephrase the question for clarity:

If I have good hardware, will it actually hurt the capture to leave sync settings on rather than turn them all off? I just tested with all sync settings off and the tape was still in sync at the end. Would this mean there is no need for correction?

[davexnet]

Some of the sync settings apply more to scenarios where the audio is captured through a different
input (eg. the soundcard) Vs. the video+audio going through the same capture device.

[premiumcapture]

I am using a Diamond VC500 with an AVT 8710, which I have so far had decent results. I did some research, and while I can't tell whether the VC500 has integrated sync, I have tested both with sync audio to video and turning off all settings. I haven't had any noticeable sync issues with either.

I realize that a part of the sync correction is frame timing due to the variable rate of VHS, but I am concerned that it will either retime a correct stream or not retime an incorrect stream.

What settings should I be going for?

[Brad]

It's possible leaving the sync settings on can hurt the capture; otherwise the author wouldn't have bothered to include the option of disabling resync when integrated AV is detected. (The VC500 is integrated: video and audio are both captured by it.)

I realize that a part of the sync correction is frame timing due to the variable rate of VHS

Err..?

[premiumcapture]

Just trying to figure out which is best, though I haven't really had any issues with any of the settings. One thing I picked up on was something called 'relative latency.' The rating for my last capture was 47ms, and I wasn't sure if the audio is delayed by that much or its just processing time. The integrated setting I get, but is it safe to assume that the capture is in sync because I am capturing through the same device?

Err..?

VHS has a variable frame rate, it is not a perfect 29.97 stream.

[davexnet]

This is how I set mine up, using in Avermedia PCIe capture card.

[Brad]

My settings are quite different (also using an AVerMedia PCIe card among others).



I would check the "Automatically disable" box, but I already have it manually disabled anyway and I'm apparently superstitious about messing with it when it seems to be working. I don't have any justification for setting latency to Fixed. Actually the more I look at it the more that looks wrong, but I played around with it 2 years ago and it isn't creating noticeable problems.

I found that when I unchecked the first two boxes, VDub would never drop/insert even when it was absolutely necessary to maintain sync (like if I decide to try capturing 720p60 with a slow x264vfw preset and my CPU is completely unable to compress the frames on time). The video track would just end up short.

The integrated setting I get, but is it safe to assume that the capture is in sync because I am capturing through the same device?

Sadly, no.

VHS has a variable frame rate, it is not a perfect 29.97 stream.

Can you point me to a source for this? Google Books isn't finding anything.

[premiumcapture]

Interesting, especially considering its the same piece of equipment! I tried capturing a terrible EP tape today with no sync and the result was hilarious. Sync is not bad!

As far as the VFR - I mixed up my terminology.

[davexnet]

Perhaps there is something inherently less stable about capturing through USB Vs. PCIe (just speculation).
Have you tried capturing with alternate software? Perhaps iuVCR would work.

A while back I captured a childrens tape that had a section which had been damaged by my daughter when she was very young.
Using a cheap Sony VCR and no TBC, the machine kept playing and the computer kept capturing. When I played
back the file, the thing was perfectly in sync even though at one point the picture almost disappears because
of the damage. I was either using STOIK or iuVCR at the time.

I'll post a clip if I can find it. Here's the clip of some children singing, despite the massive tape damage,
the clip synced right back up: