AUXDM_SETVOLUME

The AUXDM_SETVOLUME message requests a user-mode driver to set the volume level for the specified auxiliary audio device.

Parameters

uDeviceId

Device identifier (0, 1, 2, and so on) for the target device.

uMsg

AUXDM_SETVOLUME

dwUser

Not used.

dwParam1

A DWORD containing the volume setting.

dwParam2

Not used.

Return Value

The driver should return MMSYSERR_NOERROR if the operation succeeds. Otherwise it should return one of the MMSYSERR error codes defined in mmsystem.h.

Comments

A client sends the AUXDM_SETVOLUME message by calling the user-mode driver’s auxMessage entry point, passing the specified parameters.

Support for this message by user-mode drivers is optional. If the driver supports AUXDM_SETVOLUME, it must support AUXDM_GETVOLUME.

The volume value is specified by dwParam1 as follows.

Channel	Portion of dwParam1 Used
Left channel	Low word
Right channel	High word
Single channel	Low word

A value of zero is silence, and a value of 0xFFFF is full volume.

The kernel-mode driver might not support the full 16 bits of volume control and can truncate the lower bits. However, the original value requested with AUXDM_SETVOLUME should be returned with AUXDM_GETVOLUME.

Typically, the user-mode driver calls DeviceIoControl to send the kernel-mode driver an IOCTL_AUX_SET_VOLUME control code.