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

Re: ISSUE-163 navigating-tracks: Chairs Solicit Change Proposals

From: Philip Jägenstedt <philipj@opera.com>
Date: Wed, 06 Jul 2011 13:50:43 +0200
To: public-html@w3.org
Message-ID: <op.vx64itp3sr6mfa@kirk>
On Wed, 06 Jul 2011 12:47:35 +0200, Silvia Pfeiffer  
<silviapfeiffer1@gmail.com> wrote:

> On Wed, Jul 6, 2011 at 6:33 PM, Philip Jägenstedt <philipj@opera.com>  
> wrote:
>> On Fri, 01 Jul 2011 16:29:23 +0200, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>>
>>> Hi Paul, all,
>>>
>>> after analyzing this problem thoroughly, which I have documented [1],
>>> I have come to the conclusion that there is no need for introduction
>>> of any normative text into the specification to satisfy this use case.
>>>
>>> Right now, we have a linear navigation means through text tracks of
>>> kind chapter.
>>>
>>> IMO the best means to provide hierarchical navigation, which is
>>> particularly useful to vision-impaired users, is to make it possible
>>> to provide navigation lists inside the cues that make up
>>> kind="chapters" track. As such cues are handed to AT, their markup is
>>> interpreted and made available to AT, including any associated lists.
>>>
>>> My only suggestion would be to potentially add a recommendation to the
>>> specification underneath where "chapters" are introduced [2]
>>> which essentially states that subnaviation within chapter cues should
>>> be provided through list elements (ul,li) inside a chapter's cue.
>>
>> There are no list elements in WebVTT, are you suggesting they be added?
>
> Yes,  am. If you look at the examples, I added a <nav> element and am
> using the <time> elements as list elements, since the time markers
> provide the navigation points.

Oops, I didn't notice you'd linked to  
http://www.w3.org/WAI/PF/HTML/wiki/Media_Navigation until now.

>> To
>> provide a chapter tree, would it not be better to have dedicated syntax  
>> for
>> it? Perhaps:
>>
>> 00:00.000 --> 01:00.000
>> 1. Foo
>>
>> 00:00.000 --> 00:30.000
>> 1.1. Foo, Part 1
>>
>> 00:30.000 --> 01:00.000
>> 1.2. Foo, Part 2
>>
>> The spec would need to add some parsing for kind=chapters, to deduce the
>> level of nesting from the leading x.y.z...
>
> I've considered this, but with this kind of markup you cannot
> guarantee that the sublevels are temporally within the main level and
> you have to deconstruct the hierarchy. I think parsing something like
> this into a navigation tree is much harder.
>
> Also, navigation currently works in accessibility technology very
> easily through lists, so if we can map whatever we do in WebVTT into a
> list markup, that makes it simple. Therefore, I came up with the list
> markup as given in the wiki page:
>
> <ul>
>         <li><? target='timestamp' data='00:00:03.450'>Subchapter 1</li>
>         <li><? target='timestamp' data='00:00:04.000'>Subchapter 2</li>
>         <ul>
>           <li><? target='timestamp' data='00:00:04.000'>Paragraph 1</li>
>           <li><? target='timestamp' data='00:00:04.500'>Paragraph 2</li>
>           <li><? target='timestamp' data='00:00:05.000'>Paragraph 3</li>
>         </li>
>         <li><? target='timestamp' data='00:00:06.000'>Subchapter 3</li>
>       </ul>
>
> That is using the mapped timestamps from WebVTT to provide the
> navigation points and the list markup to allow making use of
> screenreaders' hierarchical navigation capabilities.

OK, so the idea is that markup as in  
http://www.w3.org/WAI/PF/HTML/wiki/Media_Navigation#Possible_Markup_for_WebVTT  
should get converted into a list for getCueAsHTML? That seems a bit funky,  
how about just letting it be a HTML <nav> element?

The syntax here doesn't seem very important though, so let's discuss that  
when the times actually comes to include this in the spec.

>> I'm not convinced this should be added to the spec right away,
>
> Are we talking about adding something to the WebVTT spec or the HTML  
> spec?
>
> For HTML, we don't have to add anything, because IIUC the above markup
> (with <ul> etc) would already be supported. We might add an example,
> if/when we think this is the right way forward.

I don't understand, HTML doesn't seem involved here except for  
getCueAsHTML, right?

> For WebVTT I am expecting a discussion in the WHATWG, since it's not
> specified in this WG. There is bugs that track this, see
> http://www.w3.org/Bugs/Public/show_bug.cgi?id=12662 .

OK, thanks.

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Wednesday, 6 July 2011 11:51:16 GMT

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