[wdmaudiodev] Re: newbie questions about filter drivers

  • From: dprado@xxxxxxxxxxxxxx
  • To: wdmaudiodev@xxxxxxxxxxxxx
  • Date: Mon, 18 Oct 2004 16:26:12 -0200

Ok, I guess it is time to do more reading on the subject :) . Thank you all for
the informmation on the subject. Slowly I will fill in the gaps and have a
better understanding of wdm audio drivers.

> I think you misunderstand the way driver stacks work.  No one talks 
> directly to an audio function driver.  There are a vast number of 
> drivers in between XYZ and user-mode: sysaudio.sys, wdmaud.sys, 
> stream.sys, etc.  API requests always go into the top of the driver 
> stack, not into the middle.
> The combination of XYZ+ABC (plus the upper layers) is only going to be a 
> single audio device, no matter how you filter it, and even if both of 
> them are function drivers.  How had you planned to switch the filtering 
> on and off?  You could have a magic registry entry somewhere that your 
> filter driver reads on a regular basis, but that will just alter the 
> behavior of your one audio device.  You won't create a second device 
> that way.
> You could possibly create a second PDO, making your filter into a bus 
> driver, but then you'd be talking about mixing.
> -- 
> - Tim Roberts, timr@xxxxxxxxx
>   Providenza & Boekelheide, Inc.


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