WIDM_ADDBUFFER

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 (Wavedev.dll) 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.