WODM_UNPREPARE (Compact 2013)
3/26/2014
This message is used in an MMDRV_MESSAGE_PARAMS structure passed to the WAV_IOControl function to request a waveform output driver to remove the buffer preparation performed in response to WODM_PREPARE.
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
Specifies a pointer to a WAVEHDR structure identifying the buffer.
- dwParam2
Specifies the size, in bytes, of WAVEHDR.
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 waveform API manager sends this message by calling the audio driver's WAV_IOControl entry point through the DeviceIoControl function.
Support for this message by user-mode drivers is optional. However, if the driver supports WODM_PREPARE, it must support this message.
If the driver returns MMSYSERR_NOTSUPPORTED, the waveform API manager removes the buffer preparation. For most drivers, this behavior is sufficient. If the driver does support this message, it must clear WHDR_PREPARED in the dwFlags member of WAVEHDR and return MMSYSERR_NOERROR.
Requirements
Header |
mmddk.h |
See Also
Reference
Waveform Output Driver Messages
MMDRV_MESSAGE_PARAMS
WAV_IOControl