@DmitrijB Use this code to get the plugin ID to access custom provider properties.
CFStringRef plugInBundleID = CFStringCreateWithCString(NULL, "com.example.apple-CustomCamera.CameraExtension", kCFStringEncodingUTF8);
CMIOObjectID plugInID = kCMIOObjectUnknown;
AudioValueTranslation value;
value.mInputData = &plugInBundleID;
value.mInputDataSize = sizeof(CFStringRef);
value.mOutputData = &plugInID;
value.mOutputDataSize = sizeof(CMIOObjectID);
UInt32 used;
CMIOObjectPropertyAddress address;
address.mSelector = kCMIOHardwarePropertyPlugInForBundleID;
address.mScope = kCMIOObjectPropertyScopeGlobal;
address.mElement = kCMIOObjectPropertyElementMain;
CMIOObjectGetPropertyData(kCMIOObjectSystemObject, &address, 0, NULL, sizeof(AudioValueTranslation), &used, &value);