Standard MIDI file, typically known just as "MID", is a standard way to serialize series of MIDI events, which is a protocol used in many music synthesizers to transfer music data: notes being played, effects being applied, etc.
Internally, file consists of a header and series of tracks, every track listing MIDI events with certain header designating time these events are happening.
NOTE: Rarely, MIDI files employ certain stateful compression scheme to avoid storing certain elements of further elements, instead reusing them from events which happened earlier in the stream. Kaitai Struct (as of v0.9) is currently unable to parse these, but files employing this mechanism are relatively rare.
This page hosts a formal specification of Standard MIDI file using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for JavaScript generated by Kaitai Struct depends on the JavaScript runtime library. You have to install it before you can parse data.
The JavaScript runtime library is available at npm:
npm install kaitai-structSee the usage examples in the JavaScript notes.
Parse structure from an ArrayBuffer:
var arrayBuffer = ...;
var data = new StandardMidiFile(new KaitaiStream(arrayBuffer));
After that, one can get various attributes from the structure by accessing fields or properties like:
data.hdr // => get hdr
// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
(function (root, factory) {
if (typeof define === 'function' && define.amd) {
define(['exports', 'kaitai-struct/KaitaiStream', './VlqBase128Be'], factory);
} else if (typeof exports === 'object' && exports !== null && typeof exports.nodeType !== 'number') {
factory(exports, require('kaitai-struct/KaitaiStream'), require('./VlqBase128Be'));
} else {
factory(root.StandardMidiFile || (root.StandardMidiFile = {}), root.KaitaiStream, root.VlqBase128Be || (root.VlqBase128Be = {}));
}
})(typeof self !== 'undefined' ? self : this, function (StandardMidiFile_, KaitaiStream, VlqBase128Be_) {
/**
* Standard MIDI file, typically known just as "MID", is a standard way
* to serialize series of MIDI events, which is a protocol used in many
* music synthesizers to transfer music data: notes being played,
* effects being applied, etc.
*
* Internally, file consists of a header and series of tracks, every
* track listing MIDI events with certain header designating time these
* events are happening.
*
* NOTE: Rarely, MIDI files employ certain stateful compression scheme
* to avoid storing certain elements of further elements, instead
* reusing them from events which happened earlier in the
* stream. Kaitai Struct (as of v0.9) is currently unable to parse
* these, but files employing this mechanism are relatively rare.
*/
var StandardMidiFile = (function() {
function StandardMidiFile(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root || this;
this._read();
}
StandardMidiFile.prototype._read = function() {
this.hdr = new Header(this._io, this, this._root);
this.tracks = [];
for (var i = 0; i < this.hdr.numTracks; i++) {
this.tracks.push(new Track(this._io, this, this._root));
}
}
var ChannelPressureEvent = StandardMidiFile.ChannelPressureEvent = (function() {
function ChannelPressureEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
ChannelPressureEvent.prototype._read = function() {
this.pressure = this._io.readU1();
}
return ChannelPressureEvent;
})();
var ControllerEvent = StandardMidiFile.ControllerEvent = (function() {
function ControllerEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
ControllerEvent.prototype._read = function() {
this.controller = this._io.readU1();
this.value = this._io.readU1();
}
return ControllerEvent;
})();
var Header = StandardMidiFile.Header = (function() {
function Header(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
Header.prototype._read = function() {
this.magic = this._io.readBytes(4);
if (!((KaitaiStream.byteArrayCompare(this.magic, new Uint8Array([77, 84, 104, 100])) == 0))) {
throw new KaitaiStream.ValidationNotEqualError(new Uint8Array([77, 84, 104, 100]), this.magic, this._io, "/types/header/seq/0");
}
this.lenHeader = this._io.readU4be();
this.format = this._io.readU2be();
this.numTracks = this._io.readU2be();
this.division = this._io.readS2be();
}
return Header;
})();
var MetaEventBody = StandardMidiFile.MetaEventBody = (function() {
MetaEventBody.MetaTypeEnum = Object.freeze({
SEQUENCE_NUMBER: 0,
TEXT_EVENT: 1,
COPYRIGHT: 2,
SEQUENCE_TRACK_NAME: 3,
INSTRUMENT_NAME: 4,
LYRIC_TEXT: 5,
MARKER_TEXT: 6,
CUE_POINT: 7,
MIDI_CHANNEL_PREFIX_ASSIGNMENT: 32,
END_OF_TRACK: 47,
TEMPO: 81,
SMPTE_OFFSET: 84,
TIME_SIGNATURE: 88,
KEY_SIGNATURE: 89,
SEQUENCER_SPECIFIC_EVENT: 127,
0: "SEQUENCE_NUMBER",
1: "TEXT_EVENT",
2: "COPYRIGHT",
3: "SEQUENCE_TRACK_NAME",
4: "INSTRUMENT_NAME",
5: "LYRIC_TEXT",
6: "MARKER_TEXT",
7: "CUE_POINT",
32: "MIDI_CHANNEL_PREFIX_ASSIGNMENT",
47: "END_OF_TRACK",
81: "TEMPO",
84: "SMPTE_OFFSET",
88: "TIME_SIGNATURE",
89: "KEY_SIGNATURE",
127: "SEQUENCER_SPECIFIC_EVENT",
});
function MetaEventBody(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
MetaEventBody.prototype._read = function() {
this.metaType = this._io.readU1();
this.len = new VlqBase128Be_.VlqBase128Be(this._io, null, null);
this.body = this._io.readBytes(this.len.value);
}
return MetaEventBody;
})();
var NoteOffEvent = StandardMidiFile.NoteOffEvent = (function() {
function NoteOffEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
NoteOffEvent.prototype._read = function() {
this.note = this._io.readU1();
this.velocity = this._io.readU1();
}
return NoteOffEvent;
})();
var NoteOnEvent = StandardMidiFile.NoteOnEvent = (function() {
function NoteOnEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
NoteOnEvent.prototype._read = function() {
this.note = this._io.readU1();
this.velocity = this._io.readU1();
}
return NoteOnEvent;
})();
var PitchBendEvent = StandardMidiFile.PitchBendEvent = (function() {
function PitchBendEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
PitchBendEvent.prototype._read = function() {
this.b1 = this._io.readU1();
this.b2 = this._io.readU1();
}
Object.defineProperty(PitchBendEvent.prototype, 'adjBendValue', {
get: function() {
if (this._m_adjBendValue !== undefined)
return this._m_adjBendValue;
this._m_adjBendValue = this.bendValue - 16384;
return this._m_adjBendValue;
}
});
Object.defineProperty(PitchBendEvent.prototype, 'bendValue', {
get: function() {
if (this._m_bendValue !== undefined)
return this._m_bendValue;
this._m_bendValue = ((this.b2 << 7) + this.b1) - 16384;
return this._m_bendValue;
}
});
return PitchBendEvent;
})();
var PolyphonicPressureEvent = StandardMidiFile.PolyphonicPressureEvent = (function() {
function PolyphonicPressureEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
PolyphonicPressureEvent.prototype._read = function() {
this.note = this._io.readU1();
this.pressure = this._io.readU1();
}
return PolyphonicPressureEvent;
})();
var ProgramChangeEvent = StandardMidiFile.ProgramChangeEvent = (function() {
function ProgramChangeEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
ProgramChangeEvent.prototype._read = function() {
this.program = this._io.readU1();
}
return ProgramChangeEvent;
})();
var SysexEventBody = StandardMidiFile.SysexEventBody = (function() {
function SysexEventBody(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
SysexEventBody.prototype._read = function() {
this.len = new VlqBase128Be_.VlqBase128Be(this._io, null, null);
this.data = this._io.readBytes(this.len.value);
}
return SysexEventBody;
})();
var Track = StandardMidiFile.Track = (function() {
function Track(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
Track.prototype._read = function() {
this.magic = this._io.readBytes(4);
if (!((KaitaiStream.byteArrayCompare(this.magic, new Uint8Array([77, 84, 114, 107])) == 0))) {
throw new KaitaiStream.ValidationNotEqualError(new Uint8Array([77, 84, 114, 107]), this.magic, this._io, "/types/track/seq/0");
}
this.lenEvents = this._io.readU4be();
this._raw_events = this._io.readBytes(this.lenEvents);
var _io__raw_events = new KaitaiStream(this._raw_events);
this.events = new TrackEvents(_io__raw_events, this, this._root);
}
return Track;
})();
var TrackEvent = StandardMidiFile.TrackEvent = (function() {
function TrackEvent(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
TrackEvent.prototype._read = function() {
this.vTime = new VlqBase128Be_.VlqBase128Be(this._io, null, null);
this.eventHeader = this._io.readU1();
if (this.eventHeader == 255) {
this.metaEventBody = new MetaEventBody(this._io, this, this._root);
}
if (this.eventHeader == 240) {
this.sysexBody = new SysexEventBody(this._io, this, this._root);
}
switch (this.eventType) {
case 128:
this.eventBody = new NoteOffEvent(this._io, this, this._root);
break;
case 144:
this.eventBody = new NoteOnEvent(this._io, this, this._root);
break;
case 160:
this.eventBody = new PolyphonicPressureEvent(this._io, this, this._root);
break;
case 176:
this.eventBody = new ControllerEvent(this._io, this, this._root);
break;
case 192:
this.eventBody = new ProgramChangeEvent(this._io, this, this._root);
break;
case 208:
this.eventBody = new ChannelPressureEvent(this._io, this, this._root);
break;
case 224:
this.eventBody = new PitchBendEvent(this._io, this, this._root);
break;
}
}
Object.defineProperty(TrackEvent.prototype, 'channel', {
get: function() {
if (this._m_channel !== undefined)
return this._m_channel;
if (this.eventType != 240) {
this._m_channel = this.eventHeader & 15;
}
return this._m_channel;
}
});
Object.defineProperty(TrackEvent.prototype, 'eventType', {
get: function() {
if (this._m_eventType !== undefined)
return this._m_eventType;
this._m_eventType = this.eventHeader & 240;
return this._m_eventType;
}
});
return TrackEvent;
})();
var TrackEvents = StandardMidiFile.TrackEvents = (function() {
function TrackEvents(_io, _parent, _root) {
this._io = _io;
this._parent = _parent;
this._root = _root;
this._read();
}
TrackEvents.prototype._read = function() {
this.event = [];
var i = 0;
while (!this._io.isEof()) {
this.event.push(new TrackEvent(this._io, this, this._root));
i++;
}
}
return TrackEvents;
})();
return StandardMidiFile;
})();
StandardMidiFile_.StandardMidiFile = StandardMidiFile;
});