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

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Wed, 6 Jul 2011 20:47:35 +1000
Message-ID: <CAHp8n2mfbgAFx8A1z4W5AmkpY9WBtAkcsMxPNSUS=AVZ1wGmYQ@mail.gmail.com>
To: Philip Jägenstedt <philipj@opera.com>
Cc: public-html@w3.org
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.

> 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:

        <li><? target='timestamp' data='00:00:03.450'>Subchapter 1</li>
        <li><? target='timestamp' data='00:00:04.000'>Subchapter 2</li>
          <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><? target='timestamp' data='00:00:06.000'>Subchapter 3</li>

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.

> 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.

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 .

> some
> experimentation with chapters using JavaScript would be a good first step.

Yes, I agree.

Received on Wednesday, 6 July 2011 10:48:22 UTC

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