waveOutUnprepareHeader function (mmeapi.h)

Article
02/22/2024

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
MMSYSERR_INVALHANDLE	Specified device handle is invalid.
MMSYSERR_NODRIVER	No device driver is present.
MMSYSERR_NOMEM	Unable to allocate or lock memory.
WAVERR_STILLPLAYING	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