midiOutUnprepareHeader function

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
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

   
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

See Also

Allocating and Preparing MIDI Data Blocks

MIDI Functions