WODM_SETPLAYBACKRATE

This message is used in an MMDRV_MESSAGE_PARAMS structure passed to the WAV_IOControl function to request a waveform output driver to set the playback rate multiplier value for the specified device.

Parameters

uDeviceId

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

uMsg

Specifies this message.

dwUser

Specifies a device instance identifier.

dwParam1

A DWORD containing the playback rate multiplier value. This is specified as a fixed-point value, where the high-order WORD of the DWORD contains the signed integer part of the number and the low-order WORD contains the fractional part. The fraction consists of a WORD value, for which 0x8000 represents one-half and 0x4000 represents one-fourth. For example, the value 0x00010000 specifies a multiplier of 1.0, with no rate change, and a value of 0x000F8000 specifies a multiplier of 15.5.

dwParam2

Not used.

Return Values

MMSYSERR_NOERROR indicates success. Otherwise, the driver returns one of the MMSYSERR or WAVEERR error values declared in the Mmsystem.h header file.

Remarks

The ACM sends this message by calling the audio driver’s WAV_IOControl entry point through the DeviceIoControl function.

Support for this message by drivers is optional. However, if a driver supports this message, it must support WODM_GETPLAYBACKRATE. Additionally, in response to the WODM_GETDEVCAPS message, it must set WAVECAPS_PLAYBACKRATE in the dwSupport member of the WAVEOUTCAPS structure.