Spaces:
Running
Running
File size: 4,761 Bytes
4cadbaf |
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 |
const midiToSequence = (midiFile, {timeWarp = 1} = {}) => {
const trackStates = [];
let beatsPerMinute = 120;
const ticksPerBeat = midiFile.header.ticksPerBeat;
for (let i = 0; i < midiFile.tracks.length; i++) {
trackStates[i] = {
nextEventIndex: 0,
ticksToNextEvent: (
midiFile.tracks[i].length ?
midiFile.tracks[i][0].deltaTime :
null
),
};
}
function getNextEvent () {
let ticksToNextEvent = null;
let nextEventTrack = null;
let nextEventIndex = null;
for (let i = 0; i < trackStates.length; i++) {
if (
trackStates[i].ticksToNextEvent != null
&& (ticksToNextEvent == null || trackStates[i].ticksToNextEvent < ticksToNextEvent)
) {
ticksToNextEvent = trackStates[i].ticksToNextEvent;
nextEventTrack = i;
nextEventIndex = trackStates[i].nextEventIndex;
}
}
if (nextEventTrack != null) {
/* consume event from that track */
const nextEvent = midiFile.tracks[nextEventTrack][nextEventIndex];
if (midiFile.tracks[nextEventTrack][nextEventIndex + 1])
trackStates[nextEventTrack].ticksToNextEvent += midiFile.tracks[nextEventTrack][nextEventIndex + 1].deltaTime;
else
trackStates[nextEventTrack].ticksToNextEvent = null;
trackStates[nextEventTrack].nextEventIndex += 1;
/* advance timings on all tracks by ticksToNextEvent */
for (let i = 0; i < trackStates.length; i++) {
if (trackStates[i].ticksToNextEvent != null)
trackStates[i].ticksToNextEvent -= ticksToNextEvent;
}
return {
ticksToEvent: ticksToNextEvent,
event: nextEvent,
track: nextEventTrack,
};
}
else
return null;
};
//
let midiEvent;
const events = [];
//
function processEvents () {
function processNext () {
let secondsToGenerate = 0;
if (midiEvent.ticksToEvent > 0) {
const beatsToGenerate = midiEvent.ticksToEvent / ticksPerBeat;
secondsToGenerate = beatsToGenerate / (beatsPerMinute / 60);
}
// beatsPerMinute must be changed after secondsToGenerate calculation
if ( midiEvent.event.type == "meta" && midiEvent.event.subtype == "setTempo" ) {
// tempo change events can occur anywhere in the middle and affect events that follow
beatsPerMinute = 60e+6 / midiEvent.event.microsecondsPerBeat;
}
const time = (secondsToGenerate * 1000 * timeWarp) || 0;
events.push([ midiEvent, time ]);
midiEvent = getNextEvent();
};
//
if (midiEvent = getNextEvent()) {
while (midiEvent)
processNext();
}
};
processEvents();
return events;
};
const trimSequence = seq => {
const status = new Map();
return seq.filter(([{event, ticksToEvent}]) => {
if (ticksToEvent > 0)
status.clear();
if (event.type !== "channel")
return true;
const key = `${event.subtype}|${event.channel}|${event.noteNumber}`;
if (status.get(key)) {
//console.debug("event trimmed:", event, ticksToEvent);
return false;
}
status.set(key, event);
return true;
});
};
const fixOverlapNotes = seq => {
const noteMap = new Map();
const overlapMap = new Map();
const swaps = [];
let leapIndex = -1;
seq.forEach(([{event, ticksToEvent}], index) => {
if (ticksToEvent > 0)
leapIndex = index;
if (event.type !== "channel")
return;
const key = `${event.channel}|${event.noteNumber}`;
switch (event.subtype) {
case "noteOn":
if (noteMap.get(key))
overlapMap.set(key, leapIndex);
else
noteMap.set(key, leapIndex);
break;
case "noteOff":
if (overlapMap.get(key)) {
swaps.push([overlapMap.get(key), index]);
overlapMap.delete(key);
}
else
noteMap.delete(key);
break;
}
});
// shift overlapped swaps
swaps.forEach((swap, i) => {
for (let ii = i - 1; ii >= 0; --ii) {
const pre = swaps[ii];
if (pre[1] < swap[0])
break;
if (swap[0] > pre[0])
++swap[0];
}
});
//console.debug("swaps:", swaps);
swaps.forEach(([front, back]) => {
if (back >= seq.length - 1 || front < 0)
return;
const offEvent = seq[back];
const nextEvent = seq[back + 1];
const leapEvent = seq[front];
if (!leapEvent[0].ticksToEvent) {
console.warn("invalid front index:", front, back, leapEvent);
return;
}
// ms per tick
const tempo = leapEvent[1] / leapEvent[0].ticksToEvent;
nextEvent[1] += offEvent[1];
nextEvent[0].ticksToEvent += offEvent[0].ticksToEvent;
offEvent[0].ticksToEvent = leapEvent[0].ticksToEvent - 1;
leapEvent[0].ticksToEvent = 1;
offEvent[1] = offEvent[0].ticksToEvent * tempo;
leapEvent[1] = leapEvent[0].ticksToEvent * tempo;
//console.debug("swap:", [front, back], offEvent, nextEvent, leapEvent);
seq.splice(back, 1);
seq.splice(front, 0, offEvent);
});
return seq;
};
module.exports = {
midiToSequence,
trimSequence,
fixOverlapNotes,
};
|