waveOutUnprepareHeader function (mmeapi.h)
The waveOutUnprepareHeader function cleans up the preparation performed by the waveOutPrepareHeader function. This function must be called after the device driver is finished with a data block. You must call this function before freeing the buffer.
Syntax
MMRESULT waveOutUnprepareHeader(
HWAVEOUT hwo,
LPWAVEHDR pwh,
UINT cbwh
);
Parameters
hwo
Handle to the waveform-audio output device.
pwh
Pointer to a WAVEHDR structure identifying the data block to be cleaned up.
cbwh
Size, in bytes, of the WAVEHDR structure.
Return value
Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.
| Return code | Description |
|---|---|
|
Specified device handle is invalid. |
|
No device driver is present. |
|
Unable to allocate or lock memory. |
|
The data block pointed to by the pwh parameter is still in the queue. |
Remarks
This function complements waveOutPrepareHeader. You must call this function before freeing the buffer. After passing a buffer to the device driver with the waveOutWrite function, you must wait until the driver is finished with the buffer before calling waveOutUnprepareHeader.
Unpreparing a buffer that has not been prepared has no effect, and the function returns zero.
Requirements
| Requirement | Value |
|---|---|
| Minimum supported client | Windows 2000 Professional [desktop apps only] |
| Minimum supported server | Windows 2000 Server [desktop apps only] |
| Target Platform | Windows |
| Header | mmeapi.h (include Windows.h) |
| Library | Winmm.lib |
| DLL | Winmm.dll |