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Re: Survey ready on Media Text Associations proposal

From: Philip Jägenstedt <philipj@opera.com>
Date: Fri, 05 Mar 2010 14:36:12 +0800
To: "Silvia Pfeiffer" <silviapfeiffer1@gmail.com>
Cc: "Michael Smith" <mike@w3.org>, "Eric Carlson" <eric.carlson@apple.com>, "HTML Accessibility Task Force" <public-html-a11y@w3.org>
Message-ID: <op.u820mmnsatwj1d@philip-pc>
On Fri, 05 Mar 2010 13:21:11 +0800, Silvia Pfeiffer  
<silviapfeiffer1@gmail.com> wrote:

> On Fri, Mar 5, 2010 at 2:38 PM, Philip Jägenstedt <philipj@opera.com>  
> wrote:
>> On Fri, 05 Mar 2010 01:36:23 +0800, Eric Carlson  
>> <eric.carlson@apple.com>
>> wrote:
>>
>>>
>>> On Mar 2, 2010, at 10:48 PM, Michael(tm) Smith wrote:
>>>
>>>> A survey is ready on the "Media Text Associations" draft change
>>>> proposal.
>>>>
>>>>  http://www.w3.org/2002/09/wbs/44061/text-associations/
>>>>
>>>
>>> I generally agree with this proposal, but would like to see the  
>>> following
>>> changes before we submit it to the WG:
>>>
>>> + We should not mandate DFXP at this time. It has many features that  
>>> will
>>> complicate implementation significantly which are not needed for this
>>> proposal. I think we should help define a DFXP profile that is more  
>>> suitable
>>> for our needs.
>>
>> For the record, I still agree.
>>
>>> + The 'enabled' attribute on a <track> in a <trackgroup> should be
>>> invalid, as the UA is responsible for selecting the most appropriate  
>>> track
>>> from the alternates.
>>
>> What should the track selection algorithm be?
>
> I thought the spec explained that fairly well, see
> http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations#Resource_selection_algorithm
> .
>
> Do you think something is missing?

That algorithm seems to conflict with what Eric is saying as it relies on  
the enabled attribute on <track>, so I was asking how Eric thinks it  
should work. That was more or less answered in subsequent mails though.

Personally, I think the track selection should be something like this:

For each group:
   If there exists tracks with the enabled attribute:
     Select the first such track.
   Else:
     Do nothing

Server-side solutions can look at Accept-Language to add enabled="" on the  
appropriate <track>. I think Accept-Language is quite useless and see no  
reason why the same or a new language setting for captions/subtitles would  
be any better. Therefore, I suggest not inventing a new solution at all.

For role="" I don't have much of an opinion at all, but am not optimistic  
about browser settings being very helpful -- since users don't change  
their settings sites will rely on other methods anyway.

I don't think we need to resolve this before going to the HTML WG as I'm  
sure everything will get discussed all over again anyway.

>> Do you still want to keep the
>> enabled *property* so that scripts can switch between different tracks  
>> of a
>> group, just like the browser context menu?
>
> I assume you are referring to the JavaScript API with *property*? If
> so, yes, I think a Web Developer should be able to set a default
> through the @enable attribute, and ask the track about its state
> through the enabled property, then be allowed to react accordingly.
>
>> I am not very optimistic about UA
>> track selection being very useful being applying the 'media' attribute.
>
> Those media queries that apply to this (as well as the video element)
> actually still need to be defined. As with the JavaScript API, we
> could decide to leave the media attribute out for the moment and add
> it at a later state when we are sure that we actually have media
> queries that help in the resource selection process.
>
> Incidentally - have any browser vendors implemented support for the
> @media attribute on the video and audio elements? I'd be curious about
> test cases there and whether they apply to external text associations.

Opera supports it and it would be easy to support it on whichever of the  
new elements we decide should use it as well.

There are some examples in  
http://my.opera.com/core/blog/2010/03/03/everything-you-need-to-know-about-html5-video-and-audio-2

Search for 'media=' to find the examples.

>> I
>> also have a feeling we haven't completely thought through what kind of
>> selection belong on the <trackgroup><track> level and what belongs in
>> <track><source> (assuming we'll go with that, just like for <audio> and
>> <video>).
>
> If you have any suggestions of what needs to be added to
> http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations#Resource_selection_algorithm
> let us know.

I'm inclined to say that the media="" attribute should be relegated to the  
<source> attribute, just like for <audio> and <video>.

Again, I don't think we need to resolve any of this before going to the  
HTML WG. Also, I assume this (and the other suggestion) will be presented  
to the HTML WG as a rough draft for further discussion rather than as a  
complete solution with consensus and all.

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Friday, 5 March 2010 06:37:15 GMT

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