midiOutUnprepareHeader

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

MMRESULT midiOutUnprepareHeader(

HMIDIOUT hmo,
LPMIDIHDR lpMidiOutHdr,
UINT cbMidiOutHdr
);

Parameters

hmo

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

lpMidiOutHdr

Address of 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:

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.

See Also

midiOutPrepareHeader, MIDIHDR, midiOutLongMsg

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