[wdmaudiodev] Re: Audio AGC?

  • From: Matthew van Eerde <Matthew.van.Eerde@xxxxxxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Wed, 19 Dec 2012 23:06:36 +0000

Yes, that would cause Windows to use your KSPROPERTY_AUDIO_VOLUMELEVEL instead 
of injecting a software volume APO, yes.  You would then control the default 
volume, as well as the min/max/step size.  This is usually used to control a 
hardware amplifier below the driver; it is not meant to enable kernel-mode 
digital signal processing, which is risky and entails floating-point state 
recovery etc.

Perhaps a simpler option is to change your pin category to something 

The article says “Of course, the INF file that installs an audio adapter driver 
can override the operating system's default volume settings with its own 
default settings” but I don’t know details, or even whether that is still true.

From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Roberts
Sent: Wednesday, December 19, 2012 2:51 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] Re: Audio AGC?

Matthew van Eerde wrote:
What version of Windows are you running on?

See the chart here: 

That's the key reference point I was missing -- enormous thanks for that.

I'm currently testing on Win 7, as is the client.  I do advertise myself as a 
microphone, so the system is applying a +30dB boost.  So, am I right in 
thinking I can solve my problem by supporting KSPROPERTY_AUDIO_VOLUMELEVEL?


Tim Roberts, timr@xxxxxxxxx<mailto:timr@xxxxxxxxx>

Providenza & Boekelheide, Inc.

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