I found the header used by the MidiPort library:
http://doc.ddart.net/msdn/header/includ ... tem.h.html
#define MMSYSERR_BASE 0#define WAVERR_BASE 32
#define MIDIERR_BASE 64
#define TIMERR_BASE 96
#define JOYERR_BASE 160
#define MCIERR_BASE 256
#define MIXERR_BASE 1024
/* general error return values */
#define MMSYSERR_NOERROR 0 /* no error */
#define MMSYSERR_ERROR (MMSYSERR_BASE + 1) /* unspecified error */
#define MMSYSERR_BADDEVICEID (MMSYSERR_BASE + 2) /* device ID out of range */
#define MMSYSERR_NOTENABLED (MMSYSERR_BASE + 3) /* driver failed enable */
#define MMSYSERR_ALLOCATED (MMSYSERR_BASE + 4) /* device already allocated */#define MMSYSERR_INVALHANDLE (MMSYSERR_BASE + 5) /* device handle is invalid */
#define MMSYSERR_NODRIVER (MMSYSERR_BASE + 6) /* no device driver present */
#define MMSYSERR_NOMEM (MMSYSERR_BASE + 7) /* memory allocation error */
#define MMSYSERR_NOTSUPPORTED (MMSYSERR_BASE + 8) /* function isn't supported */
#define MMSYSERR_BADERRNUM (MMSYSERR_BASE + 9) /* error value out of range */
#define MMSYSERR_INVALFLAG (MMSYSERR_BASE + 10) /* invalid flag passed */
#define MMSYSERR_INVALPARAM (MMSYSERR_BASE + 11) /* invalid parameter passed */
This is what I have found in the mmsystem.h file, used by MidiPort. Not 100% sure, but the error returned corresponds to this list, so if you get error code 4, then the error is
device already allocated.
But I don+t know what it means. Maybe some MIDI connection is opened.