midiOutPrepareHeader

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The midiOutPrepareHeader function prepares a MIDI system-exclusive or stream buffer for output.

MMRESULT midiOutPrepareHeader(

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 that identifies the buffer to be prepared.

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:

MMSYSERR_INVALHANDLE	The specified device handle is invalid.
MMSYSERR_INVALPARAM	The specified address is invalid or the given stream buffer is greater than 64K.
MMSYSERR_NOMEM	The system is unable to allocate or lock memory.

Remarks
A stream buffer cannot be larger than 64K.

Preparing a header that has already been prepared has no effect, and the function returns MMSYSERR_NOERROR.

Before using this function, you must set the lpData, dwBufferLength, and dwFlags members of the MIDIHDR structure. The dwFlags member must be set to zero.