[wdmaudiodev] Re: LFX APOs

  • From: Matthew van Eerde <Matthew.van.Eerde@xxxxxxxxxxxxx>
  • To: "wdmaudiodev@xxxxxxxxxxxxx" <wdmaudiodev@xxxxxxxxxxxxx>
  • Date: Wed, 5 Feb 2014 00:31:31 +0000

AudioEndpointBuilder does the migration from the KSCATEGORY_AUDIO registry 
store to the MMDevices registry store. It does this when it notices a new 
Kernel Streaming filter factory and decides to make an MMDevice or two out of 

Hacking the registry after the endpoints have been built has no effect.

If you want to continue to pursue a hacky solution, you could:

1. Uninstall the device from Device Manager; this should cause both sections of 
the registry to go away
2. sc stop audioendpointbuilder (and its dependent service audiosrv)
3. Reinstall the device
4. Hack the registry under KSCATEGORY_AUDIO
5. sc start audioendpointbuilder (and audiosrv)

AudioEndpointBuilder should pick up your hacked version of KSCATEGORY_AUDIO and 
migrate it to MMDevices.

-----Original Message-----
From: wdmaudiodev-bounce@xxxxxxxxxxxxx 
[mailto:wdmaudiodev-bounce@xxxxxxxxxxxxx] On Behalf Of Tim Roberts
Sent: Tuesday, February 4, 2014 4:24 PM
To: wdmaudiodev@xxxxxxxxxxxxx
Subject: [wdmaudiodev] LFX APOs

I'm trying to understand the fine points for installing an LFX APO.

The "Custom Audio Effects in Windows Vista" white paper describes the INF 
entries necessary to set up the registry for an APO.  I'm trying to install an 
LFX APO on an existing microphone for testing purposes before I get real 
hardware.  I'd rather not take the time to construct an INF file for this quick 
test, so I'm hacking the registry.  I can add the
FX\0 registry key, and I've checked the spelling of every GUID 20 times, but 
the APO is never loaded.

Now, the white paper says that the Control\DeviceClasses registry keys are 
"migrated" to Windows\CurrentVersion\MMDevices\Audio, and I can see that's been 
done for my motherboard audio device, but there is no hint about how or when 
that migration magically happens.  My suspicion is that the MMDevices\Audio key 
is the one that audiodg actually pays attention to, and my keys are not being 
migrated there.

So, who does that migration?  Is it the Media class installer?  That would 
imply that the INF method is absolutely, positively required to enable an APO 
(unless I want to change the registry permissions, which I really don't).

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


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