smf2seq.js

/*
 *	SMF to SEQ
 *
 *	Convert Standard MIDI file to event array
 *	Output file as sequence.h: to be compiled with ino files
 *
 *	This program uses part of jasmid to decode and parse .mid files
 *	Please refer to jasmid/LICENSE for the jasmid license
 *
 *	Run this file with node.js
 *	$ node smf2seq.js [SMF filename]
 *
 *	2016 by ilufang
 */

Midifile = require("./jasmid/midifile.js");
fs = require("fs");

// # Read and parse SMF
var filename = process.argv[2]?process.argv[2]:"song.mid";
var midi_blob = fs.readFileSync(filename);
var t = "";
for (var i=0; i<midi_blob.length; i++) {
	t += String.fromCharCode(midi_blob[i] & 255);
}
try {
	midi = Midifile(t);
} catch(e) {
	console.error("Could not parse midi.");
	process.exit(1);
}

if (midi.header.formatType != 1) {
	console.error("MIDI Type not supported. Expect 1, got "+midi.header.formatType);
	process.exit(1);
}

// fs.writeFileSync("midi.json",JSON.stringify(midi,null,'\t'));
// process.exit();

// # Process events

var ptr = []; // iteration pointer per track
seq = []; // merged result

// convert delta time to accumulative time
for (var t in midi.tracks) {
	ptr.push(0); // Irrelevant to the calculation, just initialize ptr

	var tick = 0;
	var width = 0, maxwidth = 0;
	for (var i in midi.tracks[t]) {
		tick += midi.tracks[t][i].deltaTime;
		midi.tracks[t][i].time = tick;
		midi.tracks[t][i].track = parseInt(t); // Still need to keep track of the track
	}
}

// Merge the tracks
var time = 0;
while(true) {
	// 'Pop' front
	var minTrack = 0;
	for (var t in midi.tracks) {
		if (!midi.tracks[t][ptr[t]]) {
			if (minTrack == t) {
				// In case a prior tracks are shorter, assign the default minTrack to a latter one
				minTrack++;
			}
			continue;
		}
		if (midi.tracks[t][ptr[t]].time < midi.tracks[minTrack][ptr[minTrack]].time) { minTrack = t; }
	}
	if (minTrack==midi.tracks.length) {
		// No tracks have events left
		break;
	}
	seq.push(midi.tracks[minTrack][ptr[minTrack]]);
	ptr[minTrack]++;
}

// Scan for consecutive notes
/*
time = 0;
var notes_off = {};
for (var i = 0; i < seq.length; i++) {
	if (seq[i].time != time) {
		time = seq[i].time;
		notes_off = {};
	}
	if (seq[i].type=="channel") {
		if (seq[i].subtype=="noteOff") {
			notes_off[seq[i].noteNumber] = i;
		} else if (seq[i].subtype=="noteOn") {
			if (notes_off[seq[i].noteNumber]) {
				seq[notes_off[seq[i].noteNumber]].time -= 20;
			}
		}
	}
}
*/

// Regenerate deltatime
var tempo = 0;

var notes = [], note_params = [];

for (var i=0; i<seq.length; i++) {
	if (seq[i+1]) {
		seq[i].deltaTime = seq[i+1].time - seq[i].time;
	} else {
		seq[i].deltatime = 0;
	}
	prevTime = seq[i].time;

	if (seq[i].type=="meta" && seq[i].subtype =="setTempo") {
		tempo = 1.0*seq[i].microsecondsPerBeat/1000/midi.header.ticksPerBeat;
	} else if (seq[i].type=="channel") {
		if (seq[i].subtype=="noteOff") {
			seq[i].velocity = 0;
		}
		if (seq[i].subtype=="noteOn" || seq[i].subtype=="noteOff") {
			seq[i].velocity*=128/96;
			if (seq[i].velocity > 127)
				seq[i].velocity = 127;
			notes.push(seq[i].noteNumber);
			note_params.push((seq[i].deltaTime<<4)+(seq[i].velocity>>3));
		}
	}
}

fs.writeFileSync("midi.json", JSON.stringify(seq, null, '\t'));

// # Generate sin table
var file = "// MIDI events\n// Generated by smf2seq.js\n";

var sine_sample = [], sine_sample_size = 256;
for (var i = 0; i < sine_sample_size; i++) {
	sine_sample.push(128+Math.round(128*Math.sin(2*Math.PI*i/sine_sample_size)));
}

file += "const unsigned char sine[] = {"+sine_sample.join(",")+"};\n";
file += "#define TEMPO "+tempo+"\n";
file += "#define SONG_LEN "+notes.length+"\n";
file += "PROGMEM const unsigned char notes[] = {"+notes.join(",")+"};\n";
file += "PROGMEM const int params[] = {"+note_params.join(",")+"};\n";

console.log("Using memory: "+(notes.length*3));
console.log("Total memory: 32256");

// # Write to file
fs.writeFileSync("sequence.h",file);