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An example of how an audio sprite can be used (includes fixes for iOS)
function Track(src, spriteLength, audioLead) {
var track = this,
audio = document.createElement('audio');
audio.src = src;
audio.autobuffer = true;
audio.load();
audio.muted = true; // makes no difference on iOS :(
/* This is the magic. Since we can't preload, and loading requires a user's
input. So we bind a touch event to the body, and fingers crossed, the
user taps. This means we can call play() and immediate pause - which will
start the download process - so it's effectively preloaded.
This logic is pretty insane, but forces iOS devices to successfully
skip an unload audio to a specific point in time.
first we play, when the play event fires we pause, allowing the asset
to be downloaded, once the progress event fires, we should have enough
to skip the currentTime head to a specific point. */
var force = function () {
audio.pause();
audio.removeEventListener('play', force, false);
};
var progress = function () {
audio.removeEventListener('progress', progress, false);
if (track.updateCallback !== null) track.updateCallback();
};
audio.addEventListener('play', force, false);
audio.addEventListener('progress', progress, false);
var kickoff = function () {
audio.play();
document.documentElement.removeEventListener(click, kickoff, true);
};
document.documentElement.addEventListener(click, kickoff, true);
this.updateCallback = null;
this.audio = audio;
this.playing = false;
this.lastUsed = 0;
this.spriteLength = spriteLength;
this.audioLead = audioLead;
}
Track.prototype.play = function (position) {
var track = this,
audio = this.audio,
lead = this.audioLead,
length = this.spriteLength,
time = lead + position * length,
nextTime = time + length;
clearInterval(track.timer);
track.playing = true;
track.lastUsed = +new Date;
audio.muted = false;
audio.pause();
try {
if (time == 0) time = 0.01; // yay hacks. Sometimes setting time to 0 doesn't play back
audio.currentTime = time;
audio.play();
} catch (e) {
this.updateCallback = function () {
track.updateCallback = null;
audio.currentTime = time;
audio.play();
};
audio.play();
}
track.timer = setInterval(function () {
if (audio.currentTime >= nextTime) {
audio.pause();
audio.muted = true;
clearInterval(track.timer);
player.playing = false;
}
}, 10);
};
var player = (function (src, n, spriteLength, audioLead) {
var tracks = [],
total = n,
i;
while (n--) {
tracks.push(new Track(src, spriteLength, audioLead));
}
return {
tracks: tracks,
play: function (position) {
var i = total,
track = null;
while (i--) {
if (tracks[i].playing === false) {
track = tracks[i];
break;
} else if (track === null || tracks[i].lastUsed < track.lastUsed) {
track = tracks[i];
}
}
if (track) {
track.play(position);
} else {
// console.log('could not find a track to play :(');
}
}
};
})('myaudiosprite.mp3', 1, 1, 0.25);
// myaudiosprite.mp3 is the complete audio sprite
// 1 = the number of tracks, increase this for the desktop
// 1 = the length of the individual audio clip
// 0.25 = the lead on the audio - hopefully zero, but in case any junk is added
// Usage: player.play(position)
@jlongster

This is missing the line to declare the click variable:

var click = document.ontouchstart === undefined ? 'click' : 'touchstart';

@raldred

Thanks for sharing your findings! So frustrating trying to build games with audio on the web. I think html5 audio has a long way to go before it's acceptable.

I'm sure you know, but the junk at the beginning is because you're using MP3, it's caused by encoder & decoder delay. You have to manipulate the audio before presenting it to the encoder.

There's an app for windows to do this automatically.
If you're interested in the theory (and the app), checkout this:
http://www.compuphase.com/mp3/mp3loops.htm

The easier way... use ogg :)

@FelloDuarte

Hello! first: thank you very much for this!!!

I have a question though...
How can i make he system switch between the mp3 and ogg files automatically?

greetings !

@CoolOppo

@raldred The better "easier way": use Opus.

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