WIDM_PREPARE (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 input driver to prepare a system-exclusive data buffer for input.
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 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 the driver supports this message, it must support WIDM_UNPREPARE.
If the driver returns MMSYSERR_NOTSUPPORTED, Waveapi.dll prepares the buffer for use. For most drivers, this behavior is sufficient. If the driver performs buffer preparation, it must set WHDR_PREPARED in the dwFlags member of WAVEHDR and return MMSYSERR_NOERROR.
Requirements
Header |
mmddk.h |
See Also
Reference
Waveform Input Driver Messages
WAV_IOControl
MMDRV_MESSAGE_PARAMS