| MMRESULT midiOutOpen(lphMidiOut, wDeviceID, dwCallback, dwCallbackInstance, dwFlags) | |||
| LPHMIDIOUT lphMidiOut; | |||
| UINT wDeviceID; | |||
| DWORD dwCallback; | |||
| DWORD dwCallbackInstance; | |||
| DWORD dwFlags; |
The midiOutOpen function opens a specified MIDI output device for playback.
lphMidiOut
Specifies a far pointer to an HMIDIOUT handle. This location is filled with a handle identifying the opened MIDI output device. Use the handle to identify the device when calling other MIDI output functions.
wDeviceID
Identifies the MIDI output device that is to be opened.
dwCallback
Specifies the address of a fixed callback function or a handle to a window called during MIDI playback to process messages related to the progress of the playback. Specify NULL for this parameter if no callback is desired.
dwCallbackInstance
Specifies user instance data passed to the callback. This parameter is not used with window callbacks.
dwFlags
Specifies a callback flag for opening the device.
| Value | Meaning |
| CALLBACK_WINDOW | ||
| dwCallback is assumed to be a window handle. | ||
| CALLBACK_FUNCTION | ||
| dwCallback is assumed to be a callback procedure address. | ||
Returns zero if the function was successful. Otherwise, it returns an error number. Possible error returns are as follows:
| Value | Meaning |
| MMSYSERR_BADDEVICEID | Specified device ID is out of range. |
| MMSYSERR_ALLOCATED | Specified resource is already allocated. |
| MMSYSERR_NOMEM | Unable to allocate or lock memory. |
| MIDIERR_NOMAP | There is no current MIDI map. This occurs only when opening the mapper. |
| MIDIERR_NODEVICE | A port in the current MIDI map doesn't exist. This occurs only when opening the mapper. |
Use midiOutGetNumDevs to determine the number of MIDI output devices present in the system. The device ID specified by wDeviceID varies from zero to one less than the number of devices present. You may also specify MIDI_MAPPER as the device ID to open the MIDI mapper.
If a window is chosen to receive callback information, the following messages are sent to the window procedure function to indicate the progress of MIDI output: MM_MOM_OPEN, MM_MOM_CLOSE,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, MOM_DONE. The callback function must reside in a DLL. You do not have to use MakeProcInstance to get a procedure-instance address for the callback function.
void CALLBACK MidiOutFunc(hMidiOut, wMsg, dwInstance,
dwParam1, dwParam2)
HMIDIOUT hMidiOut;
UINT wMsg;
DWORD dwInstance;
DWORD dwParam1;
DWORD dwParam2;
MidiOutFunc is a placeholder for the application-supplied function name. The actual name must be exported by including it in an EXPORTS statement in the DLL's module-definition file.
hMidiOut
Specifies a handle to the MIDI device associated with the callback.
wMsg
Specifies a MIDI output message.
dwInstance
Specifies the instance data supplied with midiOutOpen.
dwParam1
Specifies a parameter for the message.
dwParam2
Specifies a parameter for the message.
Because the callback is accessed at interrupt time, it must reside in a DLL and its code segment must be specified as FIXED in the module-definition file for the DLL. Any data that the callback accesses must be in a FIXED data segment as well. The callback may not make any system calls except for PostMessage, timeGetSystemTime,timeGetTime, timeSetEvent, timeKillEvent,midiOutShortMsg, midiOutLongMsg, and OutputDebugStr.
midiOutClose