W3C home > Mailing lists > Public > public-html-a11y@w3.org > April 2011

Re: [media] adding autoplay requirements to requirements doc

From: Philip Jägenstedt <philipj@opera.com>
Date: Wed, 20 Apr 2011 09:41:30 +0200
To: public-html-a11y@w3.org
Message-ID: <op.vt77ngrksr6mfa@localhost.localdomain>
On Wed, 20 Apr 2011 04:52:08 +0200, Silvia Pfeiffer  
<silviapfeiffer1@gmail.com> wrote:

> On Tue, Apr 19, 2011 at 8:58 PM, Philip Jägenstedt <philipj@opera.com>  
> wrote:
>> On Tue, 19 Apr 2011 12:00:38 +0200, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>>> On Tue, Apr 19, 2011 at 6:29 PM, Philip Jägenstedt <philipj@opera.com>
>>> wrote:
>>>> Possible solutions here are:
>>>> 1. Requiring explicit approval for all media playback, with the
>>>> possibility
>>>> of remembering approval per domain.
>>>> 2. Exposing a list of all media elements associated with a document to
>>>> scripts so that extensions could find and pause all media elements.
>>>> Currently this is not possible because elements can be created by  
>>>> scripts
>>>> and set to play without being inserted into a document, so e.g.
>>>> document.querySelector('audio,video') does not find them.
>>> These are both good ideas. Would it be possible to get them through
>>> plugins? Or do they need a JS API?
>> I think the first really needs to be a browser feature to be effective,
>> similar to pop-up blockers. Extensions could emulate it to some extent,  
>> but
>> could not create a UI to list all of the blocked sites, for example.
>> The second should be possible using scripts, but it takes some effort to
>> intercept everything that could possibly create new media element. For
>> createElement, one would have to do something like this:
>> (function() {
>>  var cE = document.createElement;
>>  document.createElement = function() {
>>    var elm = cE.apply(document, arguments);
>>    if (elm instanceof HTMLMediaElement) {
>>      /* keep track of this element */
>>    }
>>    return elm;
>>  };
>> })();
>> Similar things would have to be done to innerHTML, outerHTML and any  
>> other
>> properties that can create new elements.
>> A very serious downside of this approach is that just by keeping track  
>> of
>> the elements, they can never be garbage collected, so all media elements
>> would be kept alive as long as the creating document is alive.  
>> (ECMAScript
>> doesn't have weak references.)
>> In summary, this is something best done as a browser feature.
> In either case, none of this influences the HTML spec, right?
> Also, all these solutions can do is catch any call of play()? So it
> they would be general control of playback rather than just the initial
> autoplay? Is this really something we want to require for
> accessibility reasons? It may be going just a tad too far IMHO.

If it's a problem that media starts playing without user consent then it's  
not enough to disable autoplay, as there will certainly be sites that use  
scripts to start playing. The spec doesn't need to change for it to be  
possible to do option 1. For option 2 it would have to expose a list of  
all live media elements, but I think that's not such a great idea after  

Philip Jägenstedt
Core Developer
Opera Software
Received on Wednesday, 20 April 2011 07:42:00 UTC

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