midiOutOpen 37TIML

The midiOutOpen function opens a MIDI output device for playback.

UINT midiOutOpen(

LPHMIDIOUT lphmo,
UINT uDeviceID,
DWORD dwCallback,
DWORD dwCallbackInstance,
DWORD dwFlags
);

Parameters

lphmo

Address of an HMIDIOUT handle. This location is filled with a handle identifying the opened MIDI output device. The handle is used to identify the device in calls to other MIDI output functions.

uDeviceID

Identifier of the MIDI output device that is to be opened.

dwCallback

Address of a callback function, an event handle, a thread identifier, or a handle of a window or thread called during MIDI playback to process messages related to the progress of the playback. If no callback is desired, specify NULL for this parameter. For more information on the callback function, see MidiOutProc1UBLE3H.

dwCallbackInstance

User instance data passed to the callback. This parameter is not used with window callbacks or threads.

dwFlags

Callback flag for opening the device. It can be the following values:

CALLBACK_EVENT

The dwCallback parameter is an event handle. This callback mechanism is for output only.

CALLBACK_FUNCTION

The dwCallback parameter is a callback function address.

CALLBACK_NULL

There is no callback mechanism. This value is the default setting.

CALLBACK_THREAD

The dwCallback parameter is a thread identifier.

CALLBACK_WINDOW

The dwCallback parameter is a window handle.

Return Values

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

MIDIERR_NODEVICE	No MIDI port was found. This error occurs only when the mapper is opened.
MMSYSERR_ALLOCATED	The specified resource is already allocated.
MMSYSERR_BADDEVICEID	The specified device identifier is out of range.
MMSYSERR_INVALPARAM	The specified pointer or structure is invalid.
MMSYSERR_NOMEM	The system is unable to allocate or lock memory.

Remarks

To determine the number of MIDI output devices present in the system, use the midiOutGetNumDevs18YY8W6 function. The device identifier specified by wDeviceID varies from zero to one less than the number of devices present. MIDI_MAPPER can also be used as the device identifier.

If a window or thread is chosen to receive callback information, the following messages are sent to the window procedure or thread to indicate the progress of MIDI output: MM_MOM_OPEN, MM_MOM_CLOSE, and MM_MOM_DONE.

If a function is chosen to receive callback information, the following messages are sent to the function to indicate the progress of MIDI output: MOM_OPEN, MOM_CLOSE, and MOM_DONE.