Develop Reference

Javascript - Audio elements not playing on iOS

I'm trying to have audio elements play whenever I turn the page of a book. The audio element only plays for the first page of the book, but when I turn the page and fire a function bookTurned() the audio doesn't play on the rest of the other pages turned. This issue is only happening on iOS as on every other web browser the audio is played accordingly. I've already seen that this is quite a common problem on iOS, but I haven't been able to figure out what I need to do to loop around this issue and make it work. Can someone kindly explain what would need to be done in order to have this work on iOS?
EDIT: On iOS I'm getting the following error:
NotAllowedError: The request is not allowed by the user agent or the platform in the current context, possibly because the user denied permission.
async bookTurned(event, page, pageObject) {
// Set first page turn
if (!bookTimer) {
bookTimer = new Timer();
}
// Determine direction
const direction = page > prevPage ? DIRECTION.RIGHT : DIRECTION.LEFT;
// Update turn index
currTurnIndex = convertPageNumberToTurnIdx(page);
// Play audio corresponding to the two pages we just turned to.
await BOOK_AUDIO_PLAYER.play(currTurnIndex + 1);
// Recalc max pages since turn js dynamically renders pages
const currMaxPages = calcMaxPages();
if (currMaxPages > maxPages) {
maxPages = currMaxPages;
}
}
BOOK_AUDIO_PLAYER handles the audio

Web Audio Api precise looping in different browsers

So what I want is to have constant looping interchanging from different audio sources. For demo purpose I made a little puzzle game - you align numbers in order from 0 to 8 and depending on how you align them different loops are playing. I managed to get the result I want on Chrome Browser, but not on Safari or Firefox. I tried adding a different audio destination or multiple audio contexts but no matter what loop just stops after one iteration in Safari and other browsers except for Chrome.
Here is a link to the demo on code-pen Demo Puzzle with music
please turn down your sound as music might be a little too loud, I didn't master it. And here is basic code I have for Web Audio Api manipulation.
Thanks
*Also it does not work for mobile at all.
const AudioContext = window.AudioContext || window.webkitAudioContext;
var audioContext = new AudioContext();
const audio1 = document.getElementById("aud1");
const audio2 = document.getElementById("aud2");
const audio3 = document.getElementById("aud3");
const audio4 = document.getElementById("aud4");
var chosenTrack = audio2;
let gameStarted = false;
function startGame() {
document.getElementById("sHold").style.display = "none";
document.getElementById("container").style.display = "block";
gameStarted = true;
audioContext.resume();
audioContext = new AudioContext();
audio1.pause();
audio1.play();
audio1.currentTime = 0;
}
setInterval(function() {
if (gameStarted) {
//console.log(audioContext.currentTime );
if (audioContext.currentTime >= 6.4) {
audioContext = new AudioContext();
chosenTrack.pause();
chosenTrack.play();
chosenTrack.currentTime = 0;
}
}
}, 5);

Some thoughts:
You're not really using Web Audio this way, you're still using audio elements as the source which doesn't help if you want to be able to achieve precise timing. You should load them into AudioBuffers and play them using an AudioBufferSourceNode.
If you absolutely want to use audio elements (because the files you use are really massive and you want to stream them) you probably want to use the loop property on it although i doubt if that ends up being precise and gapless.
Never use setInterval to get a callback every frame, use requestAnimationFrame
Don't use setInterval OR requestAnimationFrame to be able to achieve precise audio looping, the javascript thread is not precise enough to do that AND can be held up when other things take a bit more time, too many enemies in screen for example. You should be scheduling ahead of time now and then: https://www.html5rocks.com/en/tutorials/audio/scheduling/
AudioBufferSourceNodes have a loop boolean property which will loop them as precise as possible
Do realise that different audio-decoders (so: different browsers) MIGHT decode audiofiles slightly differently: some may have a few more ms on the start for example. This might become an issue when using multiple looping AudioBufferSourceNodes, which may all be running out of sync after an x amount of time. I always reschedule something on the exact time needed instead of using the loop property.

poor quality audio playback in javascript windows store app

I'm programming a Windows Store app using javascript and having trouble playing audio without poor quality. Usually when a sound plays it sounds as if it is skipping the first few hundred milliseconds of the sound (and sometimes more), resulting in clicks and sometimes almost no sound (because the sound files are short). I have 8 short files (27kb .mp3). The weirdest thing is that the volume of the playback also seems to randomly vary between a quiet and loud level. I'm using a Windows 8.1 tablet with a 1.6GHz processor.
//I declare like this:
var playList = new Array("chord1.mp3", "chord2.mp3", "chord3.mp3", "chord4.mp3", "chord5.mp3", "chord6.mp3", "chord7.mp3", "chord8.mp3" );
var playListIndex = 0;
var players = new Array();
//I initialise like this:
for (var i = 0; i < playList.length; i++) {
players[i] = new Audio();
players[i].src = playList[i];
}
//When it's time to play (listening for pointerdown events) I do this:
players[playListIndex].play();
//I have tried this but it just introduces latency without solving the problem
//new Audio(playList[playListIndex]).play();
//This happens after playing to make the sounds play sequentially.
//The problems occur even when there is no overlap of playback
playListIndex++;
if (playListIndex >= playList.length) {
playListIndex = 0;
}
There is almost nothing else going on in the app. Suggestions much appreciated.

Why isn't my audio rewinding?

I'm having a bit of trouble rewinding audio in Javascript. I basically have a countdown that beeps each second as it gets towards the end of the countdown.
I tried using;
var bip = new Audio("http://www.soundjay.com/button/beep-7.wav");
bip.play();
but it didn't beep every second which I'm guessing has something to do withit having to load a new sound every second. I then tried loading the sound externally and triggering it with the following code.
bip.pause();
bip.currentTime = 0;
console.log(bip.currentTime);
bip.play();
but this only plays the sound once then completely fails to rewind it (this is shown by the console logging a time of 0.19 seconds after the first playthrough).
Is there something I'm missing here?

In google chrome I noticed that it only works if you have the audio file in same domain. I have no problems if the audio file is in same domain. Event setting .currentTime works.
Cross-domain:
var bip = new Audio("http://www.soundjay.com/button/beep-7.wav");
bip.play();
bip.currentTime; //0.10950099676847458
bip.currentTime = 0;
bip.currentTime; //0.10950099676847458
Same-domain:
var bip = new Audio("beep-7.wav");
bip.play();
bip.currentTime; //0.10950099676847458
bip.currentTime = 0;
bip.currentTime; //0
I tried googling for a while and could find nothing in specs about this or even any discussion.

when I want rewind I simply load the audio again:
my_audio.load()
*btw, I also use a eventlistener for 'canplay' to trigger the my_audio.play(). It seems that this is necessary in android, and maybe other devices also*

To further dsdsdsdsd's answer with a bit of paint-by-numbers for the "whole shebang"
NOTE: In my app, loc1 is a dummy that refers to the song's stored location
// ... code before ...
tune = new Audio(loc1); // First, create audio event using js
// set up "song's over' event listener & action
tune.addEventListener('ended', function(){
tune.load(); //reload audio event (and reset currentTime!)
tune.play(); //play audio event for subsequent 'ended' events
},false);
tune.play(); // plays it the first time thru
// ... code after ...
I spent days and days trying to figure out what I was doing wrong, but it all works fine now... at least on the desktop browsers...

As of Chrome version 37.0.2062.120 m, the behaviour described by #Esailija has not changed.
I workaround this issue by encoding the audio data in base64 encoding and feed the data to Audio() using data: URL.
Test code:
snd = new Audio('data:audio/ogg;base64,[...base64 encoded data...]');
snd.onloadeddata = function() {
snd.currentTime = 0;
snd.play();
setTimeout(function() {
snd.currentTime = 0;
snd.play();
}, 200);
};
(I am surprised that there are no bug reports or references on this matter... or maybe my Google-fu is not strong enough.)

Problems preloading audio in Javascript

I'm trying to make a cross-device/browser image and audio preloading scheme for a GameAPI I'm working on. An audio file will preload, and issue a callback once it completes.
The problem is, audio will not start to load on slow page loads, but will usually work on the second try, probably because it cached it and knows it exists.
I've narrowed it down to the audio.load() function. Getting rid of it solves the problem, but interestingly, my motorola droid needs that function.
What are some experiences you've had with HTML5 audio preloading?
Here's my code. Yes, I know loading images in a separate function could cause a race condition :)
var resourcesLoading = 0;
function loadImage(imgSrc) {
//alert("Starting to load an image");
resourcesLoading++;
var image = new Image();
image.src = imgSrc;
image.onload = function() {
//CODE GOES HERE
//alert("A image has been loaded");
resourcesLoading--;
onResourceLoad();
}
}
function loadSound(soundSrc) {
//alert("Starting to load a sound");
resourcesLoading++;
var loaded = false;
//var soundFile = document.createElement("audio");
var soundFile = document.createElement("audio");
console.log(soundFile);
soundFile.autoplay = false;
soundFile.preload = false;
var src = document.createElement("source");
src.src = soundSrc + ".mp3";
soundFile.appendChild(src);
function onLoad() {
loaded = true;
soundFile.removeEventListener("canplaythrough", onLoad, true);
soundFile.removeEventListener("error", onError, true);
//CODE GOES HERE
//alert("A sound has been loaded");
resourcesLoading--;
onResourceLoad();
}
//Attempt to reload the resource 5 times
var retrys = 4;
function onError(e) {
retrys--;
if(retrys > 0) {
soundFile.load();
} else {
loaded = true;
soundFile.removeEventListener("canplaythrough", onLoad, true);
soundFile.removeEventListener("error", onError, true);
alert("A sound has failed to loaded");
resourcesLoading--;
onResourceLoad();
}
}
soundFile.addEventListener("canplaythrough", onLoad, true);
soundFile.addEventListener("error", onError, true);
}
function onResourceLoad() {
if(resourcesLoading == 0)
onLoaded();
}
It's hard to diagnose the problem because it shows no errors and only fails occasionally.

I got it working. The solution was fairly simple actually:
Basically, it works like this:
channel.load();
channel.volume = 0.00000001;
channel.play();
If it isn't obvious, the load function tells browsers and devices that support it to start loading, and then the sound immediately tries to play with the volume virtually at zero. So, if the load function isn't enough, the fact that the sound 'needs' to be played is enough to trigger a load on all the devices I tested.
The load function may actually be redundant now, but based off the inconsistiency with audio implementation, it probably doesn't hurt to have it.
Edit: After testing this on Opera, Safari, Firefox, and Chrome, it looks like setting the volume to 0 will still preload the resource.

canplaythrough fires when enough data has buffered that it probably could play non-stop to the end if you started playing on that event. The HTML Audio element is designed for streaming, so the file may not have completely finished downloading by the time this event fires.
Contrast this to images which only fire their event once they are completely downloaded.
If you navigate away from the page and the audio has not finished completely downloading, the browser probably doesn't cache it at all. However, if it has finished completely downloading, it probably gets cached, which explains the behavior you've seen.
I'd recommend the HTML5 AppCache to make sure the images and audio are certainly cached.

The AppCache, as suggested above, might be your only solution to keep the audio cached from one browser-session to another (that's not what you asked for, right?). but keep in mind the limited amount of space, some browsers offer. Safari for instance allows the user to change this value in the settings but the default is 5MB - hardly enough to save a bunch of songs, especially if other websites that are frequented by your users use AppCache as well. Also IE <10 does not support AppCache.

Alright so I ran into the same problem recently, and my trick was to use a simple ajax request to load the file entirely once (which end into the cache), and then by loading the sound again directly from the cache and use the event binding canplaythrough.
Using Buzz.js as my HTML5 audio library, my code is basically something like that:
var self = this;
$.get(this.file_name+".mp3", function(data) {
self.sound = new buzz.sound(self.file_name, {formats: [ "mp3" ], preload: true});
self.sound.bind("error", function(e) {
console.log("Music Error: " + this.getErrorMessage());
});
self.sound.decreaseVolume(20);
self.sound.bind("canplaythrough",function(){ self.onSoundLoaded(self); });
});