The right way to do this is to add custom KS properties. MSVAD is a miniport to the Port Class port driver, and the port driver is doing all of the IRP dispatching. To catch DeviceIoControl, you have to go in and override the dispatching that Port Class has already set up. It's possible, but it's ugly, especially since there is already a well-defined mechanism for sending custom requests to KS drivers. You can use the SetupDi APIs to enumerate the devices with the device interface of KSCATEGORY_AUDIO. One of those will be your device. Check the friendly name to find the right one. -- Tim Roberts, timr@xxxxxxxxx Providenza & Boekelheide, Inc. ****************** WDMAUDIODEV addresses: Post message: mailto:wdmaudiodev@xxxxxxxxxxxxx Subscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=subscribe Unsubscribe: mailto:wdmaudiodev-request@xxxxxxxxxxxxx?subject=unsubscribe Moderator: mailto:wdmaudiodev-moderators@xxxxxxxxxxxxx URL to WDMAUDIODEV page: http://www.wdmaudiodev.com/