[wdmaudiodev] Re: Audio Video Sincronization

  • From: Bipin Mistry <bpnmistry@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Wed, 1 Feb 2006 19:15:27 +0530

Hello all
Pls go through my comments...

On 1/27/06, Tim Roberts <timr@xxxxxxxxx> wrote:
> Bipin Mistry wrote:
> > Hello All,
> > Please do help me out,
> >
> > Currently I am doing Video Audio recording and facing problems of
> > sincronization.
> >
> > I am not able to sincronize the Audio with Video after merging.
> > I mean to say if recording of 5 minutes is done then  Audio turns out
> > to be of 4:52 minutes... means some thing less then Video.
> That's a significant difference -- 3%.  Is it possible the audio simply
> started late, or is the audio really running faster than the video?
> What is the capture device?  A television capture graph should never
> encounter this problem.  Both streams should be timestamped.

Audio is not starting late...
As that was one of the issue I have solved quite back. this is regarding end
time difference.

> I worked on one camera where the designers used the wrong audio crystal
> -- 24.000 MHz instead of 24.576.  That resulted in a very similar effect.

I am working with 8000 samples per second & 16000 Avg. bites per second

> > How can I streach the Audio or Shrink the video at merging. without
> > loosing any data.
> If audio just starts late, that's an easy problem to solve.  If audio is
> really running fast, your best bet is to drop a video frame.  The eye
> will not notice.

How can I drop the video fram while recording.. this is not allowed from
Windows Media Encoder...?

If this is coming from a TV source, you can count the number of video
> frames to see if the video is really running too slow.  At the NTSC
> frequency, 29.97 Hz, you should see 8,991 frames in exactly 5 minutes.

More over please note that
1. I am working on Video Conference done via PC. (similer to yahoo, MSN)
2. My Video File's playtime is exectly as I need.
3. Only the Audio is showing issue... (less then video playtime)

More over I have worked with AUDIO JITTERs... which has given me some
improvements like instead of 4:52 minutes it is giving me 4:57...
But the issue remains same...
As My project requirements is minimum 2 Hrs of recording.
That means I am having difference of 360(3x120) seconds against 120
minutes.. now that is really big one... and notisable too..

Pls help me out for the same...
I have added question in the Google groups as well

I have gone through various groups and discussions...
Where by "Time Stretching" technic was supposed to be the solution.
But no such Logic or the Algo.. or the Source Code that explains how it can
be executed was found on the net till yet.

Any help towards any of these areas will be gr8 help to me..

Bipin Mistry

> --
> Tim Roberts, timr@xxxxxxxxx
> Providenza & Boekelheide, Inc.
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