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midiOutUnprepareHeader

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The midiOutUnprepareHeader function cleans up the preparation performed by the midiOutPrepareHeader function.

MMRESULT midiOutUnprepareHeader(
  HMIDIOUT hmo,            
  LPMIDIHDR lpMidiOutHdr,  
  UINT cbMidiOutHdr        
);

Parameters

hmo

Handle to the MIDI output device. This parameter can also be the handle of a MIDI stream cast to HMIDIOUT.

lpMidiOutHdr

Pointer to a MIDIHDR structure identifying the buffer to be cleaned up.

cbMidiOutHdr

Size, in bytes, of the MIDIHDR structure.

Return Values

Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.

Value Description
MIDIERR_STILLPLAYING The buffer pointed to by lpMidiOutHdr is still in the queue.
MMSYSERR_INVALHANDLE The specified device handle is invalid.
MMSYSERR_INVALPARAM The specified pointer or structure is invalid.

Remarks

This function is complementary to the midiOutPrepareHeader function. You must call midiOutUnprepareHeader before freeing the buffer. After passing a buffer to the device driver with the midiOutLongMsg function, you must wait until the device driver is finished with the buffer before calling midiOutUnprepareHeader.

Unpreparing a buffer that has not been prepared has no effect, and the function returns MMSYSERR_NOERROR.

Requirements

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Mmsystem.h; include Windows.h.
**  Library:** Use Winmm.lib.

See Also

Musical Instrument Digital Interface (MIDI), MIDI Functions, midiOutPrepareHeader, MIDIHDR, midiOutLongMsg