The VolumeStepDown method decrements, by one step, the volume level of the audio stream that enters or leaves the audio endpoint device.
HRESULT VolumeStepDown( LPCGUID pguidEventContext );
[in] Context value for the IAudioEndpointVolumeCallback::OnNotify method. This parameter points to an event-context GUID. If the VolumeStepDown call changes the volume level of the endpoint, all clients that have registered IAudioEndpointVolumeCallback interfaces with that endpoint will receive notifications. In its implementation of the OnNotify method, a client can inspect the event-context GUID to discover whether it or another client is the source of the volume-change event. If the caller supplies a NULL pointer for this parameter, the client's notification method receives a NULL context pointer.
If the method succeeds, it returns S_OK. If it fails, possible return codes include, but are not limited to, the values shown in the following table.
|E_OUTOFMEMORY||Out of memory.|
To obtain the current volume step and the total number of steps in the volume range, call the IAudioEndpointVolume::GetVolumeStepInfo method.
If the volume level is already at the lowest step in the volume range, the call to VolumeStepDown has no effect and returns status code S_OK.
Successive intervals between adjacent steps do not necessarily represent uniform volume increments in either linear signal amplitude or decibels. In Windows Vista, VolumeStepDown defines the relationship of step index to volume level (signal amplitude) to be an audio-tapered curve. Note that the shape of the curve might change in future versions of Windows. For more information about audio-tapered curves, see Audio-Tapered Volume Controls.
Client: Windows Vista
Header: Include Endpointvolume.h.
- IAudioEndpointVolume Interface
- IAudioEndpointVolumeCallback Interface