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Load and play sounds easily. A lightweight high level wrapper for WebAudio API.
<!doctype html>
<meta charset="utf-8">
<title>Basic WebAudio API sound sprite</title>
<p>Press 1 to play the sound</p>
<script>
//Define the audio context
window.AudioContext = window.AudioContext || window.webkitAudioContext;
var actx = new AudioContext();
//Create the sound
var shoot = makeSound("sounds/shoot.wav", actx, soundLoadHandler);
//An optional callback that runs when the sound is loaded
function soundLoadHandler() {
console.log("sound loaded");
}
//A keyboard event listener that plays the sound when
//the `1` key is pressed is pressed
window.addEventListener("keydown", function(event) {
if(event.keyCode === 49) {
//Play the sound
shoot.play();
}
}, false);
/*
#makeSound
`makeSound` creates and returns and WebAudio sound sprite. It's
After the sound is loaded you can access and use it like this:
var anySound = g.sound("anySound.wav", audioContext, optionalLoadHandler);
anySound.loop = true;
anySound.pan = 0.8;
anySound.volume = 0.5;
anySound.play();
anySound.pause();
anySound.playFrom(second);
anySound.restart();
*/
function makeSound(source, actx, loadHandler) {
var o = {};
//Set the default properties.
o.volumeNode = actx.createGain();
o.panNode = actx.createPanner();
o.panNode.panningModel = "equalpower";
o.soundNode = undefined;
o.buffer = undefined;
o.source = undefined;
o.loop = false;
o.isPlaying = false;
//The function that should run when the sound is loaded.
o.loadHandler = undefined;
//Values for the `pan` and `volume` getters/setters.
o.panValue = 0;
o.volumeValue = 1;
//Values to help track and set the start and pause times.
o.startTime = 0;
o.startOffset = 0;
//The sound object's methods.
o.play = function() {
//Set the start time (it will be `0` when the sound
//first starts.
o.startTime = actx.currentTime;
//Create a sound node.
o.soundNode = actx.createBufferSource();
//Set the sound node's buffer property to the loaded sound.
o.soundNode.buffer = o.buffer;
//Connect the sound to the pan, connect the pan to the
//volume, and connect the volume to the destination.
o.soundNode.connect(o.panNode);
o.panNode.connect(o.volumeNode);
o.volumeNode.connect(actx.destination);
//Will the sound loop? This can be `true` or `false`.
o.soundNode.loop = o.loop;
//Finally, use the `start` method to play the sound.
//The start time will either be `0`,
//or a later time if the sound was paused.
o.soundNode.start(
0, o.startOffset % o.buffer.duration
);
//Set `isPlaying` to `true` to help control the
//`pause` and `restart` methods.
o.isPlaying = true;
};
o.pause = function() {
//Pause the sound if it's playing, and calculate the
//`startOffset` to save the current position.
if (o.isPlaying) {
o.soundNode.stop(0);
o.startOffset += actx.currentTime - o.startTime;
o.isPlaying = false;
}
};
o.restart = function() {
//Stop the sound if it's playing, reset the start and offset times,
//then call the `play` method again.
if (o.isPlaying) {
o.soundNode.stop(0);
}
o.startOffset = 0;
o.play();
};
o.playFrom = function(value) {
if (o.isPlaying) {
o.soundNode.stop(0);
}
o.startOffset = value;
o.play();
};
//Volume and pan getters/setters.
Object.defineProperties(o, {
volume: {
get: function() {
return o.volumeValue;
},
set: function(value) {
o.volumeNode.gain.value = value;
o.volumeValue = value;
},
enumerable: true, configurable: true
},
pan: {
get: function() {
return o.panValue;
},
set: function(value) {
//Panner objects accept x, y and z coordinates for 3D
//sound. However, because we're only doing 2D left/right
//panning we're only interested in the x coordinate,
//the first one. However, for a natural effect, the z
//value also has to be set proportionately.
var x = value,
y = 0,
z = 1 - Math.abs(x);
o.panNode.setPosition(x, y, z);
o.panValue = value;
},
enumerable: true, configurable: true
}
});
//The `load` method. It will call the `loadHandler` passed
//that was passed as an argument when the sound has loaded.
o.load = function() {
var xhr = new XMLHttpRequest();
//Use xhr to load the sound file.
xhr.open("GET", source, true);
xhr.responseType = "arraybuffer";
xhr.addEventListener("load", function() {
//Decode the sound and store a reference to the buffer.
actx.decodeAudioData(
xhr.response,
function(buffer) {
o.buffer = buffer;
o.hasLoaded = true;
//This next bit is optional, but important.
//If you have a load manager in your game, call it here so that
//the sound is registered as having loaded.
if (loadHandler) {
loadHandler();
}
},
//Throw an error if the sound can't be decoded.
function(error) {
throw new Error("Audio could not be decoded: " + error);
}
);
});
//Send the request to load the file.
xhr.send();
};
//Load the sound.
o.load();
//Return the sound object.
return o;
};
</script>
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