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This message is used in an MMDRV_MESSAGE_PARAMS structure passed to the WAV_IOControl function to request a waveform input driver to add an empty input buffer to its input buffer queue.
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
Pointer to a WAVEHDR structure identifying the buffer. - dwParam2
Size, in bytes, of WAVEHDR.
Return Values
MMSYSERR_NOERROR indicates success. Otherwise, the driver returns one of the MMSYSERR or WAVERR error values declared in the Mmsystem.h header file.
Remarks
The ACM (Waveapi.dll) sends the WIDM_ADDBUFFER message by calling the audio driver's WAV_IOControl entry point through the DeviceIoControl function.
If the WHDR_PREPARED flag is not set in the dwFlags member of WAVEHDR, the driver returns WAVERR_UNPREPARED. If the flag is set, the driver performs the following actions:
- Clears the WHDR_DONE flag.
- Sets the WHDR_INQUEUE flag.
- Places the empty buffer in its input queue.
- Returns with a value of MMSYSERR_NOERROR.
The driver starts recording when it receives a WIDM_START message. If the driver has already received a WIDM_START message and the input queue is empty, recording starts immediately.
Requirements
OS Versions: Windows CE 1.0 and later.
Header: Mmddk.h.
See Also
Waveform Input Driver Messages | WAV_IOControl | WAVEHDR | MMDRV_MESSAGE_PARAMS
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