midiInOpen

Article
12/10/2007

The midiInOpen function opens a specified MIDI input device.

MMRESULT midiInOpen(
  LPHMIDIIN lphMidiIn,          
  UINT_PTR  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 Values

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

Value	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

**  Windows NT/2000/XP:** Included in Windows NT 3.1 and later.
**  Windows 95/98/Me:** Included in Windows 95 and later.
**  Header:** Declared in Mmsystem.h; include Windows.h.
**  Library:** Use Winmm.lib.

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