Changing the Volume of Waveform-Audio Playback

Windows provides the following functions to query and set the volume level of waveform-audio output devices.

Function	Description
waveOutGetVolume	Retrieves the current volume level of the specified waveform-audio output device.
waveOutSetVolume	Sets the volume level of the specified waveform-audio output device.

Not all waveform-audio devices support volume changes. Some devices support individual volume control on both the left and right channels. For information about how to determine the volume-control capabilities of waveform-audio devices, see Devices and Data Types.

Some applications allow the user to control the volume for all audio devices in a system. (Many applications of this type use the audio mixer services; for more information, see Audio Mixers.) Unless your application is capable of this kind of master volume control, you should open an audio device before changing its volume. You should also query the volume level before changing it and restore the volume level to its previous level as soon as possible.

Volume is specified in a doubleword value. When the audio format is stereo, the upper 16 bits specify the relative volume of the right channel and the lower 16 bits specify the relative volume of the left channel. For devices that do not support left- and right-channel volume control, the lower 16 bits specify the volume level, and the upper 16 bits are ignored.

Volume-level values range from 0x0 (silence) to 0xFFFF (maximum volume) and are interpreted logarithmically. The perceived volume increase is the same when increasing the volume level from 0x5000 to 0x6000 as it is from 0x4000 to 0x5000.