midiOutUnprepareHeader function (mmeapi.h)
The midiOutUnprepareHeader function cleans up the preparation performed by the midiOutPrepareHeader function.
Syntax
MMRESULT midiOutUnprepareHeader(
HMIDIOUT hmo,
LPMIDIHDR pmh,
UINT cbmh
);
Parameters
hmo
Handle to the MIDI output device. This parameter can also be the handle of a MIDI stream cast to HMIDIOUT.
pmh
Pointer to a MIDIHDR structure identifying the buffer to be cleaned up.
cbmh
Size, in bytes, of the MIDIHDR structure.
Return value
Returns MMSYSERR_NOERROR if successful or an error otherwise. Possible error values include the following.
| Return code | Description |
|---|---|
|
The buffer pointed to by lpMidiOutHdr is still in the queue. |
|
The specified device handle is invalid. |
|
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
| 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 |