IAudioEndpointVolumeCallback::OnNotify method (endpointvolume.h)

The OnNotify method notifies the client that the volume level or muting state of the audio endpoint device has changed.

Syntax

HRESULT OnNotify(
  [in] PAUDIO_VOLUME_NOTIFICATION_DATA pNotify
);

Parameters

[in] pNotify

Pointer to the volume-notification data. This parameter points to a structure of type AUDIO_VOLUME_NOTIFICATION_DATA.

Return value

If the method succeeds, it returns S_OK. If it fails, it returns an error code.

Remarks

The pNotify parameter points to a structure that describes the volume change event that initiated the call to OnNotify. This structure contains an event-context GUID. This GUID enables a client to distinguish between a volume (or muting) change that it initiated and one that some other client initiated. When calling an IAudioEndpointVolume method that changes the volume level of the stream, a client passes in a pointer to an event-context GUID that its implementation of the OnNotify method can recognize. The structure pointed to by pNotify contains this context GUID. If the client that changes the volume level supplies a NULL pointer value for the pointer to the event-context GUID, the value of the event-context GUID in the structure pointed to by pNotify is GUID_NULL.

The Windows 7, the system's volume user interface does not specify GUID_NULL when it changes the volume in the system. A third-party OSD application can differentiate between master volume control changes that result from the system's volume user interface, and other volume changes such as changes from the built-in volume control handler.

For a code example that implements the OnNotify method, see Endpoint Volume Controls.

Requirements

See also

AUDIO_VOLUME_NOTIFICATION_DATA

IAudioEndpointVolume Interface

IAudioEndpointVolumeCallback Interface