The WIDM_ADDBUFFER requests a user-mode waveform input driver to add an empty input buffer to its input buffer queue.
The driver should return MMSYSERR_NOERROR if the operation succeeds. Otherwise it should return one of the MMSYSERR or WAVERR error codes defined in mmsystem.h. See waveInAddBuffer return values in the Win32 SDK.
A client sends the message by calling the user-mode driver’s widMessage entry point, passing the specified parameters.
If the WHDR_PREPARED flag is not set in the dwFlags member of the WAVEHDR structure, the driver should return WAVERR_UNPREPARED. If the flag is set, the driver should:
The user-mode driver starts recording when it receives a WIDM_START message.
For additional information, see Transferring Waveform Input Data.