/*!
    @function       AudioUnitAddPropertyListener
    @abstract       registration call to receive notifications for when a property changes
    @discussion     When an audio unit property value changes, a notification callback can be called by the
                    audio unit to  inform interested parties that this event has occurred. The notification is
                    defined by the tuple of inProc and inProcUserData as paired to the specified property ID,
                    so the previously defined AudioUnitRemovePropertyListener is dperecated because it didn't
                    allow for the provision of the inProcUserData to remove a given listener (so, you should
                    use AudioUnitRemovePropertyListenerWithUserData).

    @param          inUnit
                    the audio unit
    @param          inID
                    the proeprty identifier
    @param          inProc
                    the proceedure to call when the property changes (on any scope or element)
    @param          inProcUserData
                    the user data to provide with the callback

    @result         noErr, or various audio unit errors related to properties
*/
extern OSStatus
AudioUnitAddPropertyListener(AudioUnit                     inUnit,
                             AudioUnitPropertyID           inID,
                             AudioUnitPropertyListenerProc inProc,
                             void *                        inProcUserData)
                             __OSX_AVAILABLE_STARTING(__MAC_10_0,__IPHONE_2_0);

/*!
    @function       AudioUnitRemovePropertyListenerWithUserData
    @abstract       remove a previously registered property listener
    @discussion     Removes a previously registered property listener as specified by the inProc and 
                    inProcUser data as paired to the property identifier

    @param          inUnit
                    the audio unit
    @param          inID
                    the proeprty identifier
    @param          inProc
                    the proceedure previously registered
    @param          inProcUserData
                    the user data paired with the provided inProc

    @result         noErr, or various audio unit errors related to properties
*/
extern OSStatus
AudioUnitRemovePropertyListenerWithUserData(AudioUnit                     inUnit,
                                            AudioUnitPropertyID           inID,
                                            AudioUnitPropertyListenerProc inProc,
                                            void *                        inProcUserData)
                                            __OSX_AVAILABLE_STARTING(__MAC_10_5,__IPHONE_2_0);