[wdmaudiodev] DS Audio Filters on WDM driver

  • From: Steve Thorpe <steve@xxxxxxxxxxxxx>
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Thu, 7 Jul 2005 18:53:17 -0700 (PDT)

I have a WDM audio driver for our USB Video Capture
chip.
It seems to work okay on most systems but we have the 
following problem: 
When the driver is inserted it into a capture graph
using one of the DirectShow filters on some systems 
the sample frequency is 44100hz and on others it is
48000hz. 

This makes no discernable difference to audio preview
but our clients report that when capturing to file 
(using their proprietory USB Video Recording 
application) if the audio filter has a sample rate of 
44100hz after one or two hours of recording the audio 
is dropping out of sync with the video.

We need to understand :

1) Why do some systems insert the same audio filter 
with a different sample frequency ?


2) why, if it selcts 44100hz instead of 48000hz would 
it cause audio/video capture to go out of sync? Is
this
likely to be a driver, DS filter or application 
problem? 

Any insights would be appreciated.
Thanks

Steve T
 

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