midiInOpen function

Article
06/06/2016

The midiInOpen function opens a specified MIDI input device.

Syntax

MMRESULT midiInOpen(
   LPHMIDIIN lphMidiIn,
   UINT      uDeviceID,
   DWORD_PTR dwCallback,
   DWORD_PTR dwCallbackInstance,
   DWORD     dwFlags
);

Parameters

lphMidiIn
Pointer to an HMIDIIN handle. This location is filled with a handle identifying the opened MIDI input device. The handle is used to identify the device in calls to other MIDI input functions.
uDeviceID
Identifier of the MIDI input device to be opened.
dwCallback
Pointer to a callback function, a thread identifier, or a handle of a window called with information about incoming MIDI messages. For more information on the callback function, see MidiInProc.
dwCallbackInstance
User instance data passed to the callback function. This parameter is not used with window callback functions or threads.

dwFlags
Callback flag for opening the device and, optionally, a status flag that helps regulate rapid data transfers. It can be the following values.

Value	Meaning
CALLBACK_FUNCTION	The dwCallback parameter is a callback procedure 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.
MIDI_IO_STATUS	When this parameter also specifies CALLBACK_FUNCTION, MIM_MOREDATA messages are sent to the callback function as well as MIM_DATA messages. Or, if this parameter also specifies CALLBACK_WINDOW, MM_MIM_MOREDATA messages are sent to the window as well as MM_MIM_DATA messages. This flag does not affect event or thread callbacks.

Most applications that use a callback mechanism will specify CALLBACK_FUNCTION for this parameter.

Return value

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

Return code	Description
MMSYSERR_ALLOCATED	The specified resource is already allocated.
MMSYSERR_BADDEVICEID	The specified device identifier is out of range.
MMSYSERR_INVALFLAG	The flags specified by dwFlags are invalid.
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 input devices present in the system, use the midiInGetNumDevs function. The device identifier specified by wDeviceID varies from zero to one less than the number of devices present.

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 input: MM_MIM_OPEN, MM_MIM_CLOSE, MM_MIM_DATA, MM_MIM_LONGDATA, MM_MIM_ERROR, MM_MIM_LONGERROR, and MM_MIM_MOREDATA.

If a function is chosen to receive callback information, the following messages are sent to the function to indicate the progress of MIDI input: MIM_OPEN, MIM_CLOSE, MIM_DATA, MIM_LONGDATA, MIM_ERROR, MIM_LONGERROR, and MIM_MOREDATA.

Requirements

Minimum supported client	Windows 2000 Professional [desktop apps only]
Minimum supported server	Windows 2000 Server [desktop apps only]
Header	Mmsystem.h (include Windows.h)
Library	Winmm.lib
DLL	Winmm.dll

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