Default Audio Output - Getting Device Changed Notification? (CoreAudio, Mac OS X, AudioHardwareAddPropertyListener)

Question

I am trying to write a listener using the CoreAudio API for when the default audio output is changed (e.g.: a headphone jack is plugged in). I found sample code, although a bit old and using deprecated functions (http://developer.apple.com/mac/library/samplecode/AudioDeviceNotify/Introduction/Intro.html, but it didn't work. Re-wrote the code in the 'correct' way using AudioHardwareAddPropertyListener method, but still it doesn't seem to work. When I plug in a headphone the function that I registered is not triggered. I'm a bit of a loss here... I suspect the problem may lay some where else, but I can't figure out where...

The Listener Registration Code:

OSStatus err = noErr;
AudioObjectPropertyAddress audioDevicesAddress = { kAudioHardwarePropertyDefaultOutputDevice, KAudioObjectPropertyScopeGlobal, KAudioObjectPropertyElementMaster };
err = AudioObjectAddPropertyListener ( KAudioObjectAudioSystemObject, &AudioDevicesAddress, coreaudio_property_listener, NULL);
if (err) trace ("error on AudioObjectAddPropertyListener");

Answer 1

After a search in sourceforge for projects that used the CoreAudio API, I found the rtaudio project, and more importantly these lines:

// This is a largely undocumented but absolutely necessary
// requirement starting with OS-X 10.6.  If not called, queries and
// updates to various audio device properties are not handled
// correctly.

CFRunLoopRef theRunLoop = NULL;
AudioObjectPropertyAddress property = { kAudioHardwarePropertyRunLoop,
                                    kAudioObjectPropertyScopeGlobal,
                                    kAudioObjectPropertyElementMaster };
OSStatus result = AudioObjectSetPropertyData( kAudioObjectSystemObject, &property, 0, NULL, sizeof(CFRunLoopRef), &theRunLoop);
if ( result != noErr ) {
errorText_ = "RtApiCore::RtApiCore: error setting run loop property!";
error( RtError::WARNING );
}

After adding this code I didn't even need to register a listener myself.