MMDevice can only be used on the thread they were created on.

There seems to be an issue with using MMDevice in a multithreaded scenario.

main thread:

var device = (MMDevice) comboWasapiDevices.SelectedItem;

background processing thread:

IWaveIn newWaveIn;

Task task = new Task(() => {
    newWaveIn = new WasapiCapture(device) // <----------------- THROWS EXCEPTION
});
task.start();

Exception Thrown Message: An exception of type ‘System.InvalidCastException’ occurred in NAudio.dll but was not handled in user code

{“Unable to cast COM object of type ‘System.__ComObject’ to interface type ‘NAudio.CoreAudioApi.Interfaces.IMMDevice’. This operation failed because the QueryInterface call on the COM component for the interface with IID ‘{D666063F-1587-4E43-81F1-B948E807363F}’ failed due to the following error: No such interface supported (Exception from HRESULT: 0x80004002 (E_NOINTERFACE)).”}

[markheath]

I think the code for that is in the WPF demo app. It’s not made it into the main NAudio library, but you can easily copy the code and adapt it to the number of bands you want, and frequencies you would like

[krugg]

IMO “every” object created by a thread is owned by it. So if you really want to use these devices within a thread (here Task) easily you have to create it within. Yes, there are other ways to do it, but I want to keep it simple here.

The following code do select the device by index given to the task:

            WasapiCapture device = null;
            Task task = Task.Factory.StartNew((object devIndex) =>
            {
                var index = (int)devIndex;

                var deviceEnum = new MMDeviceEnumerator();
                var threadDeviceList = deviceEnum.EnumerateAudioEndPoints(DataFlow.Capture, DeviceState.Active).ToList();

                var threadDevice = threadDeviceList[index];
                device = new WasapiCapture(threadDevice); // <----------------- SHOULD NOT THROW EXCEPTION
            }, this.DevColIn.IndexOf(this.SelectedInputDevice));
            //task.Start();

this.DevColIn is the device list created by UI thread. Hope this helps.