VirtualVCR and A/VSync
 

Hello,

Until now I have been capturing with VVCR with these
AV sync settings:

http://www.digitalfaq.com/archives/i.../2006/04/2.jpg


But after searching/reading forums/guides,I came over a
tool called AVI Offset Calculator.You find it here http://darkfalz.kiczek.com/software/

The AVI Offset Calculator calculates the av offset so we can
fix that in VDub or other editing software.

So I opened one of my captured files in AVI Offset Calculator
and the results youll see on the next picture

http://www.digitalfaq.com/archives/i.../2006/04/3.jpg

As far as I can understand from that result,the video and audio
is -40ms out of sync.

So I picked up a tips from VDub forums,adjust stream offset
in VVCR until AVI Offset Calculator shows 0ms when opening
the captured file.

So I did some tests captures,and the next picture shows
the final settings

http://www.digitalfaq.com/archives/i.../2006/04/4.jpg

When opening the file in AVI Offset Calculator,the results
are this:

http://www.digitalfaq.com/archives/error.gif


So as far as I can see,the captured video is now
perfectly in sync.?
I read that the -40ms offset was caused by the system,
bus speed,bus "bottleneck"etc.

Anyone have any comments to this?

thanks

-------------------------------------

I don't see how this tool can determine how much the audio/video was unsynch but be carefull that is you set "40 ms" in vdub, this delayis just a muxing delay. That means that once you will demux the video and audio stream, then you will have again the synch problem.

oops,forgot to say that,I read somewhere that VVCR
writes the desync/offset in the AVI file header,that
way software avi players corrects the desync when playing the file.
I guess the AVI Offset Calculator reads the offset that way to.

But editing software and MPEG encoders doesnt read the avi file header,
so after converting to mpeg,Ill have the desync.

So adjusting stream offset in VVCR until the offset in avi file header
says 0 ms,should,at least theoretically,solve this problem.

Right. I did confuse VVCR with Vdub.

I've got something like 120-160ms of offset, I've not used the calculator but VDub always inserts 3-4 frames at the beginning of my captures.

So if you'd like to make sure you have a good a/v sync, use the latest VDub :wink:

Do you use the default timing settings in latest VDub?

I got 0 inserted frames at the beginning but some frames
inserted during capturing with VDub.(default settings.)

Read at VDub forums that Inserted frames in VDub
and Dropped frames in VVCR is the same,the last good
frame is inserted instead.

anyway I captured a 7 minute clip earlier today
with the offset 40 ms setting checked in VVCR,
ran it through CCEBasic,and uploaded it herehttp://www.yourfilelink.com/get.php?fid=69156
48MB

To me it seems to be in sync.if you have time,download,
I like to hear your opinions.

Yes, except that "Correct video timing.." is disabled, it might be enabled by default, I'm not sure. I actually think that if it's enabled, you get zero inserted frames at the beginning but I only got problems during capture with it.

I think that inserted frames means in VDub that a new frame is inserted to compensate the timing error which occurs even if you have resampling enabled. This inserted frame is created like you suspected. A dropped frame means that the frame is lost and it is compensated by copying the last good frame. So the difference is that inserted frame means you do not lose anything from the original stream but a copied frame is added, dropped frame means you lost those frames.

You probably won't notice a 40ms delay anyway, I think it's closer to 100ms before it gets noticable.

Sounds good too me also.

Yes, correct video timing is enabled by default.
If I disable it I got a inserted frame every 5 second.
After what I read at the VDub forums,if it is enabled,both
audio and video is resampled. Reason :"Beacuse two is better than one".

But I guess different hardware need different settings.
Im running a AMD Athlon XP 2,1GHz with 1,25GB RAM,PCI Sound Card,
Terratec PCI TV Card.

Anyway it seems that the VDub author has done a great job
improving the capture part of VDub.

VirtualDub-Sync
 

@the viking,

Have you tried capturing with "VirtualDub-Sync": http://www-user.rhrk.uni-kl.de/~dittrich/sync/

-kwag

It's obsolete now that the VDub 1.6-branch does the same thing. The good thing about VDub 1.6.x is that it'll work with WDM drivers as well whereas the 1.5-based programs need VfW.

I didn't know that 8O
Are you sure they commited the same code mods :?: Thanks Boulder :cool:

-kwag

VirtualDub-sync is based on some VDub 1.5-build. The same resampling code is found in VDubMod as well, which is based on VDub 1.5.10 I think.

There's no reason to use any 1.5-based programs, v1.6 has proven to be very stable and troublefree. And in case of problems, Avery Lee has often come up with a fix :D