Changing the system-wide default input and output audio devices
WARNING: This feature is not designed to be accessible to programs and uses a COM interface that is undocumented and unsupported by Microsoft. As such, it may not function in future versions of Windows.
Several times I've come across people asking how to change the default input/output devices through code, and usually the reply is that it isn't possible. Changing the device per-app is well documented, but many people want to be able to set the system-wide default like the Sound control panel applet does. Tonight I was looking into that a little deeper, and the applet does it through an undocumented private COM interface called IPolicyConfig. So naturally I immediately found the definition and added it to oleexp.
There's two versions of the interface included, one for Windows Vista (IPolicyConfigVista / CPolicyConfigVistaClient) and one for Windows 7 and higher (IPolicyConfig / PolicyConfigClient).
Using this interface to set the defaults is very easy:
Code:
Private pPolicyCfg As PolicyConfigClient
If (pPolicyCfg Is Nothing) Then
Set pPolicyCfg = New PolicyConfigClient
End If
pPolicyCfg.SetDefaultEndpoint StrPtr(sDeviceID), eMultimedia
pPolicyCfg.SetDefaultEndpoint StrPtr(sDeviceID), eCommunicationsRequirements
-Windows Vista or higher
-oleexp.tlb v4.11 or higher (new release for this demo)
-oleexp addon mIID.bas (included in oleexp download)
-oleexp addon mCoreAudio.bas (included in oleexp download)
-oleexp addon mPKEY.bas (included in oleexp download)