Adjusting audio stream delay ?? produces, through, stream, frame

andy

My WDM capping app produces AVI files which have audio delayed.

I use AVI Offset CAlculator to measure the delay and this is one of the results:

Video Stream Offset: 6 frames
Audio Stream Offset: 1465 samples

This equals to audio skew: 170ms

Now if I run this through an MPEG Enc the result is out of sync MPEG file.
How can I use AVISynth to fix this ?

Also, what does 6 frame delay mean ? Does it mean that there are no frames or what ?

If you have an audio skew of 170ms, then use:

DelayAudio(-0.170)

Perfect Sync!

jim

why minus-sign? shouldn't it be DelayAudio(0.17) ?

In this case the audio starts after the video.  To move the audio back we use the Minus sign.  

I take it that VirtualVCR created this file - i get exactly the sae problem.

Jim

Yes, it's from Virtual VCR. Do you know why there is a delay ?

WHy can't MPEG encoders be smart enough to fix it as they encode.

I've emailed the author a few times about the problem, but he's not sure how it occurs or how to fix it.  It only seems to be Windows Media Player which plays the file correctly, everything else (virtualdub, avisynth etc) includes the delay.

Mpeg encoders are only endoing what they see in the file, and they see the delay.  Its VirtualVCR which makes the file wrong. However, if you use delayaudio in your scripts, you'll get perfect Audio sync in your encodes!

Jim

Originally posted by numlock
Yes, it's from Virtual VCR. Do you know why there is a delay ?

WHy can't MPEG encoders be smart enough to fix it as they encode.
Heh..I use VirtualVCR too and I have always wondered why there is this delay when software shows 0 dropped frames. I have used -150ms.

Nice too see that I dont have to think there is something wrong with my HD

Btw, do you use Dynamic audio resample in AV/synch tab or something else?

What about if I put this -170 in that offset audio window in addittion to that dynamic audio resample..have you tried that?

Originally posted by Valky What about if I put this -170 in that offset audio window in addittion to that dynamic audio resample..have you tried that?

I've never got that to work.  I do use Resample Audio Dynamically.  

Jim