mfread ()
int (*Mf_getc) (); int (*Mf_putc) (); int (*Mf_error) (char *msg); int (*Mf_header) (int format, int ntrks, int division); int (*Mf_trackstart) (); int (*Mf_trackend) (); int (*Mf_noteon) (int chan, int pitch, int vol); int (*Mf_noteoff) (int chan, int pitch, int vol); int (*Mf_pressure) (int chan, int pitch, int pressure); int (*Mf_parameter) (int chan, int control, int value); int (*Mf_pitchbend) (int chan, int msb, int lsb); int (*Mf_program) (int chan, int program); int (*Mf_chanpressure) (int chan, int pressure); int (*Mf_sysex) (int leng, char *msg); int (*Mf_metamisc) (int type, int leng, int msg); int (*Mf_seqspecific) (int type, int leng, int msg); int (*Mf_seqnum) (int num); int (*Mf_text) (int type, int leng, int msg); int (*Mf_eot) (); int (*Mf_timesig) (int numer, int denom, int clocks, int qnotes); int (*Mf_smpte) (int hour, int min, int sec, int frame, int fract); int (*Mf_tempo) (int microsecs); int (*Mf_keysig) (int sharpflat, int minor); int (*Mf_arbitrary) (int leng, int msg); int Mf_nomerge; long Mf_currtime;
mfwrite(int format, int ntracks, int division, FILE *fp)
int (*Mf_writetrack)(int track); int (*Mf_writetempotrack)(); void mf_write_midi_event(delta, type, chan, data, size) unsigned long delta; unsigned int type,chan,size; char *data; void mf_write_meta_event(delta, type, data, size) unsigned long delta; unsigned int type,chan,size; char *data; void mf_write_tempo(tempo) unsigned long tempo; unsigned long mf_sec2ticks(float seconds, int division, int tempo) float seconds; int division; unsigned int tempo; float mf_ticks2sec(ticks, division, tempo) unsigned long ticks; int division; unsigned int tempo;
The mfwrite function writes a standard MIDI file making use of user-defined functions that access the program's data structure. To use it you need to define your own Mf_writetrack routine and then make use of the write_* family of routines to write out the MIDI data. The mfwrite routine takes care of the file format and writing the file and track chunk headers.
#include <stdio.h>
#include "midifile.h"
mygetc()
{
/* use standard input */
return(getchar());
}
main()
{
Mf_getc = mygetc;
mfread();
exit(0);
}
This takes advantage of the default action when an error is detected, which is to exit silently with a return code of 1. An error function of your own can be used by giving a value to Mf_error; the function will be called with the error message as an argument. The other Mf_* variables can similarly be used to call arbitrary functions while parsing the MIDI file. The descriptions below of the information passed to these functions is sparse; refer to the MIDI file standard for the complete descriptions.
Mf_header is the first function to be called, and its arguments contain information from the MIDI file's header; the format (0,1, or 2), the number of tracks, and the division of a quarter-note that defines the times units. Mf_trackstart and Mf_trackend are called at the beginning and end of each track.
Once inside a track, each separate message causes a function to be called. For example, each note-on message causes Mf_noteon to be called with the channel, pitch, and volume as arguments. The time at which the message occurred is stored in Mf_currtime - one of the few external variables that isn't a function pointer. The other channel messages are handled in a similar and obvious fashion - Mf_noteoff, Mf_pressure, Mf_parameter, Mf_pitchbend, Mf_program, and Mf_chanpressure. See the declarations above for the arguments that are passed to each.
System exclusive messages are handled by calling Mf_sysex, passing as arguments the message length and a pointer to a static buffer containing the entire message. The buffer is expanded when necessary; memory availability is the only limit to its size. Normally, 'continued' system exclusives are automatically merged, and Mf_sysex is only called once. It you want to disable this you can set Mf_nomerge to 1, causing Mf_sysex to be called once for each part of the message.
Mf_seqnum is called by the meta message that provides a sequence number, which if present must appear at the beginning of a track. The tempo meta message causes Mf_tempo to be called; its argument is the number of microseconds per MIDI quarter-note (24 MIDI clocks). The end-of-track meta message causes Mf_eot to be called. The key signature meta message causes Mf_keysig to be called; the first argument conveys the number of sharps or flats, the second argument is 1 if the key is minor.
The Mf_timesig and Mf_smpte functions are called when the corresponding meta messages are seen. See the MIDI file standard for a description of their arguments.
The text messages in the MIDI file standard are of the following types:
0x01 Text Event 0x02 Copyright 0x03 Sequence/Track Name 0x04 Instrument 0x05 Lyric 0x06 Marker 0x07 Cue Point 0x08-0x0F Reserverd but Undefined
Mf_text is called for each of these; the arguments are the type number, the message length, and a pointer to the message buffer.
Misceallaneous meta messages are handled by Mf_metamisc, sequencer-specific messages are handled by Mf_seqspecific, and arbitrary "escape" messages (started with 0xF7) are handled by Mf_arbitrary.
#include <stdio.h>
#include <ctype.h>
#include "midifile.h"
FILE *F;
mygetc() { return(getc(F)); }
mytext(type,leng,msg)
char *msg;
{
char *p;
char *ep = msg + leng;
for ( p=msg; p<ep ; p++ )
putchar( isprint(*p) ? *p : '?' );
putchar(');
}
main(argc,argv)
char **argv;
{
if ( argc > 1 )
F = fopen(argv[1],"r");
else
F = stdin;
Mf_getc = mygetc;
Mf_text = mytext;
mfread();
exit(0);
}
mf_write_midi_event and mf_write_meta_event are routines that should be called from your Mf_writetrack routine to write out MIDI events. The delta time param is the number of ticks since the last event. The int "type" is the type of MIDI message. The int "chan" is the MIDI channel, which can be between 1 and 16. The char pointer "data" points to an array containing the data bytes, if any exist. The int "size" is the number of data bytes.
mf_sec2ticks and mf_ticks2sec are utility routines to help you convert between the MIDI file parameter of ticks and the more standard seconds. The int "division" is the same division parameter from the file header, and tempo is expressed in microseconds per MIDI quarter-note, or "24ths of a microsecond per MIDI clock". The division has two meanings, depending on whether bit 15 is set or not. If bit 15 of division is zero, bits 14 through 0 represent the number of delta-time "ticks" which make up a quarter note. If bit 15 of division is a one, delta-times in a file correspond to subdivisions of a second similiar to SMPTE and MIDI time code. In this format bits 14 through 8 contain one of four values - 24, -25, -29, or -30, corresponding to the four standard SMPTE and MIDI time code frame per second formats, where -29 represents 30 drop frame. The second byte consisting of bits 7 through 0 corresponds the the resolution within a frame. Refer the Standard MIDI Files 1.0 spec for more details.
#include <stdio.h>
#include <ctype.h>
#include "midifile.h"
FILE *fp;
myputc(c) { return(putc(c,fp));}
int mywritetrack(track)
int track;
{
int i;
char data[2];
/* 120 beats/per/second */
mf_write_tempo((long)500000);
for(i = 1 ; i < 128; i++){
data[0] = i; /* note number */
data[1] = 64; /* velocity */
if(!mf_write_midi_event(480,note_on,1,data,2))
return(-1);
if(!mf_write_midi_event(480,note_off,1,data,2))
return(-1);
}
return(1);
} /* end of write_track() */
main(argc,argv)
char **argv;
{
if((fp = fopen(argv[1],"w")) == 0L)
exit(1);
Mf_putc = myputc;
Mf_writetrack = mywritetrack;
/* write a single track */
mfwrite(0,1,480,fp);
}