[wdmaudiodev] Re: Audio Video Sincronization

  • From: Tim Roberts <timr@xxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Wed, 01 Feb 2006 10:27:41 -0800

Bipin Mistry wrote:

> Now when STOP is triggered
> 1. I have to mix all the WAV files generated by DLL and then
> 2. mix it with Video file I have created using Windows Media encoder
> and create FINAL VIDEO file.
> In such case I can not get all users audio syncronized with video file
> as for example
> User A audio Play time is 5:00 minutes
> User B audio Play time is 4:57 minutes
> User C audio Play time is 4:53 minutes
> User D audio Play time is 4:55 minutes
> Then in the MIX file I can here A till 5:00 B till 4:57, C till 4:53 &
> D till 4:55 in 5:00 minutes of MIX audio file.
> Where my problem resides.... if this is solved then my all worries are
> over...

There is simply no solution to this problem.  You're talking about
synchronizing files created on different computers, with varying amounts
of latency and network delay.  You have no idea what causes the
difference.  It could be the recordings started at different times, or
stopped at different times, or run at different speeds, although I would
guess the latter is the LEAST likely of the possibilities.  Audio board
clocks are way more accurate than 3%.  Given that, stretching all the
files to 5 minutes is clearly *not* the best solution.

Fortunately, in a video conference, it doesn't matter very much.  People
rarely talk over the top of one another.  If I were doing it, I'd split
the difference and put half as silence at the start, and half as silence
at the end.

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

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