Simple Web Audio Wrapper

Seen this question asked numerous times, how to set up and use the Web Audio API, so I ripped some code out of my engine Booty5 and slimmed it down a bit and here it is, I have also pushed it to Github here.

[sourcecode language=”js”]
/**
* A Sound represents a sound effect object and can be used to play back audio
*
* Generally a sound should be added to either a {@link b5.Scene} or the global {@link b5.App}’s resources so that it can be managed by them.
*
* Example showing how to load and play a sound effect
*
* var sound = new b5.Sound("explosion", "sounds/explosion.mp3", true);
* var instance = sound.play();
*
* For a complete overview of Resources see {@link http://booty5.com/html5-game-engine/booty5-html5-game-engine-introduction/resources-the-stuff-that-games-are-made-of/ Booty5 Resources Overview}
*
* @class b5.Sound
* @constructor
* @returns {b5.Sound} The created sound
* @param name {string} Name of sound resource
* @param location {string} The sound file location
*
* @property {b5.App|b5.Scene} parent – Parent resource manager (internal)
* @property {object} snd – Sound instance (re-usable sound only) (internal). For Web Audio stores a {source:AudioBufferSourceNode, gain:GainNode} object for auto play sounds
* @property {object} buffer – AudioBufferSourceNode containing decoded audio data (Web Audio only)
* @property {string} name – Name of this sound resource
* @property {string} location – The location of the sound file that is used to create the audio object
* @property {boolean} loop – If set to true then sound will be looped
* @property {boolean} preload – If set to true then this sound will be preloaded
* @property {boolean} auto_play – If set to true then this sound will be preloaded
* @property {boolean} loaded – If true then this resource has finished loading
*/

var loadFile = function(filename, blocking, callback, binary)
{
var req = new XMLHttpRequest();
req.open("GET", filename, !blocking);
req.overrideMimeType("application/json");
if (binary)
req.responseType = "arraybuffer";
if (!blocking)
{
req.onreadystatechange = function()
{
if (req.readyState === 4)
{
if (req.status === 200 || req.status === 0) // 0 for node-webkit
{
if (binary)
callback(req.response);
else
callback(req.responseText);
}
else
callback(null);
}
};
}
try
{
req.send();
}
catch(e)
{
return false;
}

if (blocking)
{
if (req.status === 200)
{
if (binary)
callback(req.response);
else
callback(req.responseText);
}
else
callback(null);
}

return true;
};

b5.Sound = function(name, location)
{
// internal variables
this.parent = null; // Parent container
this.snd = null; // Sound instance (re-usable sound only). For Web Audio stores a {AudioBufferSourceNode, GainNode } object for auto play sounds
this.buffer = null; // AudioBufferSourceNode containing decoded audio data (Web Audio only)

// Public variables
this.name = name; // The sound name
this.location = location; // Location of the sound
this.loop = false; // If set to true the this sound will replay continuously
this.preload = false; // Set to true to preload sound
this.loaded = false; // Set to true once audio cam be played
this.auto_play = false; // Set to true to auto play sound when loaded
this.load_retry = 0;
};

/**
* AudioContext used by Web Audio API
* @type {object}
*/
b5.Sound.context = null;
b5.Sound.muted = false;

/**
* Initialises the sound system
* @parm app {b5.App} The App that will manage the audio engine
* @returns {boolean} true for success or false if error
*/
b5.Sound.init = function(app)
{
if (app.use_web_audio)
{
try
{
window.AudioContext = window.AudioContext || window.webkitAudioContext;
if (window.AudioContext === undefined)
return false;
b5.Sound.context = new AudioContext();
}
catch(e)
{
return false;
}
return true;
}
return false;
};

/**
* Loads the sound
*/
b5.Sound.prototype.load = function(force)
{
var debug = b5.app.debug;
//var snd;
var that = this;
var filename = this.location;
var auto_play = this.auto_play;
if (!loadFile(filename, false, function(data) {
if (data !== null)
{
b5.Sound.context.decodeAudioData(data, function(buffer) {
that.buffer = buffer;
if (auto_play)
that.play(force);
}, function(e)
{
console.log(e)
});
}
else
{
that.load_retry++;
if (that.load_retry < 3)
that.load();
}
}, true))
{
that.load_retry++;
if (that.load_retry < 3)
that.load();
}
};

/**
* Starts playback of the sound
* @returns {object} An Audio object representing the playing sound or a {source, gain} object if using Web Audio API
*/
b5.Sound.prototype.play = function(force)
{
if (force != true && b5.Sound.muted)
return null;
if (this.buffer === null)
return null;
var context = b5.Sound.context;
var source = context.createBufferSource();
var gain = context.createGain();
source.buffer = this.buffer;
source.loop = this.loop;
source.connect(gain);
gain.connect(context.destination);
gain.gain.value = 1;
source.start(0);
if (this.auto_play)
this.snd = { source: source, gain: gain };
return { source: source, gain: gain };
};

/**
* Stops playback of thr sound (re-usable sound only)
*/
b5.Sound.prototype.stop = function()
{
var snd = this.snd;
if (snd === null || snd === undefined)
return;
snd = snd.source;
snd.stop();
};
[/sourcecode]

Happy coding!