https://beatscratch.io/app/MIDI.js/js/midi/plugin.audiotag.js

1/*
2	----------------------------------------------------------------------
3	AudioTag <audio> - OGG or MPEG Soundbank
4	----------------------------------------------------------------------
5	http://dev.w3.org/html5/spec/Overview.html#the-audio-element
6	----------------------------------------------------------------------
7*/
8
9(function(root) { 'use strict';
10
11	window.Audio && (function() {
12		var midi = root.AudioTag = { api: 'audiotag' };
13		var noteToKey = {};
14		var volume = 127; // floating point 
15		var buffer_nid = -1; // current channel
16		var audioBuffers = []; // the audio channels
17		var notesOn = []; // instrumentId + noteId that is currently playing in each 'channel', for routing noteOff/chordOff calls
18		var notes = {}; // the piano keys
19		for (var nid = 0; nid < 12; nid ++) {
20			audioBuffers[nid] = new Audio();
21		}
22
23		var playChannel = function(channel, note) {
24			if (!root.channels[channel]) return;
25			var instrument = root.channels[channel].instrument;
26			var instrumentId = root.GM.byId[instrument].id;
27			var note = notes[note];
28			if (note) {
29				var instrumentNoteId = instrumentId + '' + note.id;
30				var nid = (buffer_nid + 1) % audioBuffers.length;
31				var audio = audioBuffers[nid];
32				notesOn[ nid ] = instrumentNoteId;
33				if (!root.Soundfont[instrumentId]) {
34					if (root.DEBUG) {
35						console.log('404', instrumentId);
36					}
37					return;
38				}
39				audio.src = root.Soundfont[instrumentId][note.id];
40				audio.volume = volume / 127;
41				audio.play();
42				buffer_nid = nid;
43			}
44		};
45
46		var stopChannel = function(channel, note) {
47			if (!root.channels[channel]) return;
48			var instrument = root.channels[channel].instrument;
49			var instrumentId = root.GM.byId[instrument].id;
50			var note = notes[note];
51			if (note) {
52				var instrumentNoteId = instrumentId + '' + note.id;
53				for (var i = 0, len = audioBuffers.length; i < len; i++) {
54				    var nid = (i + buffer_nid + 1) % len;
55				    var cId = notesOn[nid];
56				    if (cId && cId == instrumentNoteId) {
57				        audioBuffers[nid].pause();
58				        notesOn[nid] = null;
59				        return;
60				    }
61				}
62			}
63		};
64	
65		midi.audioBuffers = audioBuffers;
66		midi.send = function(data, delay) { };
67		midi.setController = function(channel, type, value, delay) { };
68		midi.setVolume = function(channel, n) {
69			volume = n; //- should be channel specific volume
70		};
71
72		midi.programChange = function(channel, program) {
73			root.channels[channel].instrument = program;
74		};
75
76		midi.pitchBend = function(channel, program, delay) { };
77
78		midi.noteOn = function(channel, note, velocity, delay) {
79			var id = noteToKey[note];
80			if (!notes[id]) return;
81			if (delay) {
82				return setTimeout(function() {
83					playChannel(channel, id);
84				}, delay * 1000);
85			} else {
86				playChannel(channel, id);
87			}
88		};
89	
90		midi.noteOff = function(channel, note, delay) {
91// 			var id = noteToKey[note];
92// 			if (!notes[id]) return;
93// 			if (delay) {
94// 				return setTimeout(function() {
95// 					stopChannel(channel, id);
96// 				}, delay * 1000)
97// 			} else {
98// 				stopChannel(channel, id);
99// 			}
100		};
101	
102		midi.chordOn = function(channel, chord, velocity, delay) {
103			for (var idx = 0; idx < chord.length; idx ++) {
104				var n = chord[idx];
105				var id = noteToKey[n];
106				if (!notes[id]) continue;
107				if (delay) {
108					return setTimeout(function() {
109						playChannel(channel, id);
110					}, delay * 1000);
111				} else {
112					playChannel(channel, id);
113				}
114			}
115		};
116	
117		midi.chordOff = function(channel, chord, delay) {
118			for (var idx = 0; idx < chord.length; idx ++) {
119				var n = chord[idx];
120				var id = noteToKey[n];
121				if (!notes[id]) continue;
122				if (delay) {
123					return setTimeout(function() {
124						stopChannel(channel, id);
125					}, delay * 1000);
126				} else {
127					stopChannel(channel, id);
128				}
129			}
130		};
131	
132		midi.stopAllNotes = function() {
133			for (var nid = 0, length = audioBuffers.length; nid < length; nid++) {
134				audioBuffers[nid].pause();
135			}
136		};
137	
138		midi.connect = function(opts) {
139			root.setDefaultPlugin(midi);
140			///
141			for (var key in root.keyToNote) {
142				noteToKey[root.keyToNote[key]] = key;
143				notes[key] = {id: key};
144			}
145			///
146			opts.onsuccess && opts.onsuccess();
147		};
148	})();
149
150})(MIDI);