Created
February 27, 2018 07:35
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Code snippet to load a couple of wave files (from disc) and play em in a sequence
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window.onload = init; | |
var context; | |
var bufferLoader; | |
function BufferLoader(context, urlList, callback) { | |
this.context = context; | |
this.urlList = urlList; | |
this.onload = callback; | |
this.bufferList = new Array(); | |
this.loadCount = 0; | |
} | |
BufferLoader.prototype.loadBuffer = function(url, index) { | |
// Load buffer asynchronously | |
var request = new XMLHttpRequest(); | |
request.open("GET", url, true); | |
request.responseType = "arraybuffer"; | |
var loader = this; | |
request.onload = function() { | |
// Asynchronously decode the audio file data in request.response | |
loader.context.decodeAudioData( | |
request.response, | |
function(buffer) { | |
if (!buffer) { | |
alert('error decoding file data: ' + url); | |
return; | |
} | |
loader.bufferList[index] = buffer; | |
if (++loader.loadCount == loader.urlList.length) | |
loader.onload(loader.bufferList); | |
}, | |
function(error) { | |
console.error('decodeAudioData error', error); | |
} | |
); | |
} | |
request.onerror = function() { | |
alert('BufferLoader: XHR error'); | |
} | |
request.send(); | |
} | |
BufferLoader.prototype.load = function() { | |
for (var i = 0; i < this.urlList.length; ++i) | |
this.loadBuffer(this.urlList[i], i); | |
} | |
function init() { | |
// Fix up prefixing | |
window.AudioContext = window.AudioContext || window.webkitAudioContext; | |
context = new AudioContext(); | |
bufferLoader = new BufferLoader( | |
context, | |
[ | |
'techno-kit1.wav', | |
'Bass09.wav', | |
], | |
finishedLoading | |
); | |
bufferLoader.load(); | |
} | |
function playSound(buffer, time) { | |
var source = context.createBufferSource(); | |
source.buffer = buffer; | |
source.connect(context.destination); | |
source.start(time); | |
} | |
function finishedLoading(bufferList) { | |
// Create two sources and play them both together. | |
var kick = context.createBufferSource(); | |
var bass = context.createBufferSource(); | |
kick = bufferList[0]; | |
bass = bufferList[1]; | |
var eighthNoteTime = 1/8; | |
var startTime = 0; | |
for (var bar = 0; bar < 2; bar++) { | |
var time = startTime + bar * 8 * eighthNoteTime; | |
// Play the bass (kick) drum on beats 1, 5 | |
playSound(kick, time); | |
playSound(kick, time + 4 * eighthNoteTime); | |
// Play the bass drum on beats 3, 7 | |
playSound(bass, time + 2 * eighthNoteTime); | |
playSound(bass, time + 6 * eighthNoteTime); | |
} | |
} |
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