CODEWITHSUNDEEP
windowsaudiocomoleregsvr32
karl-police
karl-police

Reputation: 1055

How to use a compiled Audio Processing Object (APO) .DLL?

I have compiled some test APO. Yet, I am not sure if it will even work.

When you compile an APO, you'll end up with a .DLL which usually has these methods exposed.

EXPORTS
    DllCanUnloadNow       PRIVATE
    DllGetClassObject     PRIVATE
    DllRegisterServer     PRIVATE
    DllUnregisterServer   PRIVATE

DllGetClassObject often have a ClassFactory and the ClassFactory:CreateInstance method, would return that APO. Though, I am not sure what invokes ClassFactory:CreateInstance in the first place.

DllRegisterServer and DllUnregisterServer are used with regsvr32.exe

But I don't understand the purpose of all this.

e.g. if you're familiar with an application called Soundpad, apparently it uses an APO that they call "UniteFX" to do exactly all of this. It's an application that can play sound files through any Microphone, aslong DRM is disabled. But not by default. I think the APO is attaching onto the chain of these devices, somehow through the WASAPI.

 

How does an APO run at the end? How will I be able to intercept Microphone Drivers to alter their input and output? How can I tell an APO to connect and bridge an actual running Audio Device on the Windows System?

 

All that I understood is that :APOProcess is the main thing that will do the actual audio processing, as of https://learn.microsoft.com/en-us/windows-hardware/drivers/audio/implementing-audio-processing-objects.

I don't get how regsvr32 will do all the magic.

Upvotes: 1

Views: 36

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