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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,107 @@ | ||
| var audio = (function() { | ||
| "use strict"; | ||
|
|
||
| var Note = function(ctx, type, frequency, attack, release, output) { | ||
| this.oscillator = ctx.createOscillator(); | ||
| this.oscillator.type = type; | ||
| this.oscillator.frequency.value = frequency; | ||
| this.gain = ctx.createGain(); | ||
| this.gain.gain.value = 0; | ||
|
|
||
| this.oscillator.connect(this.gain); | ||
| this.gain.connect(output); | ||
|
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||
| this.ctx = ctx; | ||
| this.attack = attack; | ||
| this.release = release; | ||
| }; | ||
|
|
||
| Note.prototype.start = function() { | ||
| this.oscillator.start(); | ||
| this.gain.gain.setValueAtTime(0, this.ctx.currentTime); | ||
| this.gain.gain.linearRampToValueAtTime(1, this.ctx.currentTime + this.attack); | ||
| }; | ||
|
|
||
| Note.prototype.stop = function() { | ||
| this.gain.gain.setValueAtTime(this.gain.gain.value, this.ctx.currentTime); | ||
| this.gain.gain.linearRampToValueAtTime(0, this.ctx.currentTime + this.release); | ||
| var self = this; | ||
| setTimeout(function() { | ||
| self.gain.disconnect(); | ||
| self.oscillator.stop(); | ||
| self.oscillator.disconnect(); | ||
| }, Math.floor(this.release * 1000)); | ||
| }; | ||
|
|
||
|
|
||
| var module = {}; | ||
|
|
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| var audioCtx, notes, gain; | ||
| var enabled = false; | ||
| var synthType; | ||
|
|
||
| var CHANNELS = 17; | ||
| var ATTACK = 0.05; | ||
| var RELEASE = 0.1; | ||
|
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|
|
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| module.init = function() { | ||
| var AudioContext = window.AudioContext || window.webkitAudioContext; | ||
| if (AudioContext) { | ||
| audioCtx = new AudioContext(); | ||
| gain = audioCtx.createGain(); | ||
| gain.connect(audioCtx.destination); | ||
| } else { | ||
| // display an alert | ||
| } | ||
|
|
||
| notes = $.map(Array(CHANNELS), function() { return {}; }); | ||
|
|
||
| $('#sound-on').click(function() { | ||
| enabled = !enabled; | ||
| $(this).next('i').toggleClass('fa-volume-off fa-volume-up'); | ||
| }); | ||
|
|
||
| $('#synth-type').change(function() { | ||
| synthType = $(this).val(); | ||
| }).change(); | ||
|
|
||
| $('#gain').on('input change propertychange paste', function() { | ||
| gain.gain.value = Math.min(1, Math.max(Number($(this).val()), 0)); | ||
| }).change(); | ||
| }; | ||
|
|
||
| module.noteOn = function(channel, pitch) { | ||
| if (!audioCtx || !enabled) return; | ||
|
|
||
| if (!(pitch in notes[channel])) { | ||
| notes[channel][pitch] = | ||
| new Note(audioCtx, synthType, pitchToFrequency(pitch), | ||
| ATTACK, RELEASE, gain); | ||
| notes[channel][pitch].start(); | ||
| } | ||
| }; | ||
|
|
||
| module.noteOff = function(channel, pitch) { | ||
| if (!audioCtx) return; | ||
|
|
||
| if (pitch in notes[channel]) { | ||
| notes[channel][pitch].stop(); | ||
| delete notes[channel][pitch]; | ||
| } | ||
| }; | ||
|
|
||
| module.allNotesOff = function(channel) { | ||
| for (var i=0; i<CHANNELS; i++) { | ||
| for (var pitch in notes[channel]) { | ||
| module.noteOff(channel, pitch); | ||
| } | ||
| } | ||
| }; | ||
|
|
||
| var pitchToFrequency = function(pitch) { | ||
| return Math.pow(2, (pitch - 69)/12) * 440; | ||
| }; | ||
|
|
||
| return module; | ||
| })(); |
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