IE9 can only (pre)load max. 41 audio files; maybe also iPad affected

[netmills]

Undocumented IE behavior

IE9 (and IE10?) has an internal limit of 41 simultaneous audio and video elements/objects. The 42nd won't be loaded.

It seems to me (without having tested it enough) that this is a "global" limit, affecting all open tabs, and not only a single html document. So it might be that one can load less than 41 audio/videos.

SoundJS/PreloadJS bug

PreloadJS with the SoundJS plugin creates an audio object for each loaded file. So if you load to many audio files, some will will not load - and the error event will be raised containing an valid HTMLAudioElement, which won't play.

The sound will play at random on your site (depending which loaded first). Also videos won't play after preloading sounds.

I reckon that even without preloading SoundJS will not be able to play more than 41 sounds.
I am not sure, but it seems that HTMLAudioPlugin keeps the played audio elements in memory.

Possible solution

• Don't create HTMLAudioElements when preloading (at least in IE). This would affect existing code of developers using the library.
• Reuse the max. 41 "slots" when playing sound on IE.

Further information

It took me almost a day to find this piece of information - more or less by accident :(
This is the only information i could find:

• See the comment of Kevin Gadd
• Or Barry Dormans answer on stackoverflow
• Sam might have the same issue

If you find an official documentation of this limit, I would be glad if you let me know.

iPad bug?

We also found a very weird behavior on the iPad (with WebAudioPlugin). At some point our sounds sounded completely distorted and also played to slow. (The sound files are fine, it also occurs with sound files from you demos.) At the beginning of the project everything was ok (we used less sounds them).

I also assume that we are preloading to many sound files, but I don't have the time to isolate the error. (If one sound is distorted, subsequently sound may also be - even in other tabs. You must then quit (not only close) Mobile Safari and delete the cache to have a "clean" state for testing.)

Sorry, but currently I have no time to create a test page. If you need one it will take some time.

[OJayRobinson]

Hi, thanks for the report.

Undocumented IE behavior

We are aware of the maximum audio tag instance limitation, which previously applied to other browsers but now seems primarily limited to IE9. We have a property in place to inform developers of a safe limit to the number of sounds, but after seeing the confusion we will add more information to the documentation. The limit is not always the same, it seems to depend on hardware and browser settings, but we generally found most systems set the limit around 42 . Here is a quick spike that can determine the limit for a browser:

<script type="text/javascript">
    var readyCount = 0;
    var countElement = document.getElementById('loadcount');
    function readyTest() {
        //var a0 = new Audio('../examples/assets/Thunder1.mp3');
        var a0 = document.createElement("audio");
        a0.oncanplaythrough = function () {
            readyCount++;
            countElement.innerHTML = readyCount;
            readyTest();
        }
        /*a0.onreadystatechange = function () {
            readyCount++;
            countElement.innerHTML = readyCount;
            readyTest();
        }*/
        a0.src = "../examples/assets/Thunder1.mp3";
        a0.load();
    }
    readyTest();
</script>

iPad bug

We encountered similar behavior when loading just 2 sounds while also loading videos on demand via VideoJS. We have not had a chance to fully explore the issue, but at the time thought it may be related to the amount of data we were trying to load at once or a problem with the two libraries conflicting in some way. Any further information about what libraries you are using and how you were using the sound may be helpful in us tracking down and resolving this issue. Thanks.

[OJayRobinson]

iPad bug

It turns out there is an iPad bug, if you have a video tag in html and web audio, the web audio will distort. The timing of when it will distort is unpredictable, but it will distort at some point. A bug has been reported to Apple.

[djboeren]

I'm currently running into the same problems as the OP, and am wondering why this issue has been closed?

Testing this in IE9, I notice the bug unfortunately still exists. So, I looked into your suggestion, the MAX_INSTANCES property. This is indeed present in the code, but it does nothing? When I search for it I only see a declaration in HTMLAudioPlugin, but that is completely unused. I find 3 other occurences in the same file and one in Sound.js but all these are comments.

Has this problem been fixed in an unreleased version? If not, shouldn't the issue be reopened?

[OJayRobinson]

MAX_INSTANCES is meant to give developers a safe guideline, but is not currently used by SoundJS as it does not make sense to limit the number of audio instances in browsers that don't have a limit. My suggestion would be that you reduce the number of instances you have, either by reducing the total number of sounds and/or by reducing the number of instances of each sound by setting the data property to 1 in registerSound.

Hope that helps.

[djboeren]

Hey OJay,

thanks for your answer. Unfortunately, for the application I'm working on, we cannot reduce the amount of sound effects (that would defeat its purpose). Even with a max of 1 instance per sound, we would go well over 90 sound instances. I've tested using sound sprites but this leads to many problems as well (mainly on mobile devices).

For IE9, I have chosen to write a custom version of sound loader/player for devices that cannot handle too many audio tags - this way we can control the maximum number of audio tags depending on the platform and reuse these instead of recreating them (even cloning seems to cause problems).

Thanks for the help, your suggestion gave me the idea to re-use the tags and that worked wonders, IE hasn't crashed yet and tested with over 350 sounds played (~100 different).

[Tolmark12]

Does anyone know if this affects IE 11?

[NuclearCookie]

Hello.
I found no concrete answers if this was still an issue in IE 11.
I created a JSFiddle to test it out.
Turns out it's still there, but 41 does not seem to be a magic number. I get inconsistent numbers of failures. ( but always failures )
http://jsfiddle.net/NuclearCookie/6c1dps3b/

[themoonrat]

This still affects IE11, yes. And there isn't a magic number for it at all, it seems rather arbitrary. In testing (getting the whole office involved!) I found that I was always definitely safe at 20, and, apart from very rare cases, almost certainly safe at 25. The higher the amount after that, the greater the risk of some not loading.

So for my games, I tended to list first 25 sounds in the manifest as the most important ones, and any after that being spot effects that, if they didn't load and play, wouldn't be the end of the world.

For more recent games, I've been able to take advantage of the sound sprite feature within SoundJS, to get more sound samples within the same amount of audio files.