[wdmaudiodev] supporting MuLaw in WDM audio

  • From: "Larry Cawley" <lcawley@xxxxxxxxxxxxx>
  • To: <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Thu, 29 Aug 2002 13:34:24 -0500

Hello,
I have a simple WDM Audio driver that is managing a piece of hardware
that does NOT produce linear PCM audio data (it's MuLaw encoded).  The
driver does a simple conversion between MuLaw and PCM audio and
everything works well.
 
I wanted to let the Windows kernel components (KMixer, ACM, whatever) do
this conversion for me so I changed the WDM audio driver to present
MuLaw as the native audio format.  Now when I use Windows Sound Recorder
it records a MuLaw file.  That would be expected since the application
supports MuLaw.
 
I tried running CoolEdit (which apparently only supports linear PCM) and
it fails to allow me to record now (says the driver does not support the
right format).    
 
Why would Windows NOT do this conversion for me?  I was expecting
Windows to see that CoolEdit wants linear PCM and the driver only
supports MuLaw and to do the conversion for me.  Is there something I
have to do from the WDM driver's perspective to get this to happen ?
 
Thanks in advance for your help.
 

---

Larry Cawley
CreativeMedia Software Solutions, Inc.
www.CreativeMediaSoftware.com <http://www.creativemediasoftware.com/> 
lcawley@xxxxxxxxxxxxxxxxxxxxxxxxx
(636) 458 1462
Yahoo! IM: lcawley 

 


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