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

RE: [media] Navigation of media by content structure (Issue-163)

From: John Foliot <jfoliot@stanford.edu>
Date: Wed, 29 Jun 2011 12:20:22 -0700 (PDT)
To: "'Silvia Pfeiffer'" <silviapfeiffer1@gmail.com>, "'HTML Accessibility Task Force'" <public-html-a11y@w3.org>
Cc: "'Sean Hayes'" <Sean.Hayes@microsoft.com>
Message-ID: <011a01cc3691$974c9c80$c5e5d580$@edu>
Silvia Pfeiffer wrote:
> 
> This is to address Issue-163, which is due by 1st July, see
> http://lists.w3.org/Archives/Public/public-html/2011May/0428.html.
> 
> I've put together some thoughts in the wiki page at
> http://www.w3.org/WAI/PF/HTML/wiki/Media_Navigation on how navigation
> of media could be addressed.
> 
> There are basically two approaches, each with their own advantages and
> disadvantages. They together provide quite some flexibility and
> neither really needs any changes made to HTML5, unless I'm missing
> something. They may, however, need changes to other technologies along
> the solution chain, including screen readers and file formats.
> 
> Please share any ideas for different solutions that I may have missed.

Hi Silvia,

Thank you for putting together this wiki page.  

I'm looking at this, and I'm perhaps just not catching this right, but
your proposed code sample seems to only include one level of navigation.
In the first example, could it also be replicated like this?:

...
     <nav>
       <00:00:47.600>Impact of Captions on the Web
       <00:01:50.100>Requirements of a Video text format
	 <00:02:30.000>The Web VTT Format
       	<00:03:33.000>Simple WebVTT file
       	<00:04:57.766>Styled WebVTT file
       	<00:06:16.666>Internationalized WebVTT file
     </nav>",
  getCueAsHTML(): "Talk on WebVTT
      <ul>
        <li><? target='timestamp' data='00:00:47.600'>Impact of Captions
on the Web</li>
        <li><? target='timestamp' data='00:01:50.100'>Requirements of a
Video text format</li>
        <li><? Target='timestamp' data='00:02:30.000'>The Web VTT Format
		<ul>
			<li><? target='timestamp'
data='00:03:33.000'>Simple WebVTT file</li>
        		<li><? target='timestamp'
data='00:04:57.766'>Styled WebVTT file</li>
        		<li><? target='timestamp'
data='00:06:16.666'>Internationalized WebVTT file</li>
		</ul>
	  </li>
      </ul>"
...

To create a multi-level navigation scheme? (Realizing that indentation is
of course for reading clarity only)
How would this map back to TTML? The code example for TTML does not show
any Human readable chapter/subchapter names.

*************

As I continue through your proposals, you then suggest spreading the
chapter and timings over 2 files:

  <video src="video.ogv" controls>
    <track src="webvtt1.vtt" kind="chapter" label="level 1 navigation">
    <track src="webvtt2.vtt" kind="chapter" label="level 2 navigation">
  </video>

... where you illustrate chapter <nav> in WebVTT, but not for TTML. I'd
like to hear what Sean might suggest.



But then, I got to thinking...

If you can suggest mixing both <nav> time markers and <ul><li> structure
in one WebVTT file, and/or reference 2 WebVTT files to carry different
levels of navigation, then why not just go the distance and create a
navigation file using getCueAsHTML() and list markup, at which point you
have abstracted the human readable hierarchy to a document that maps back
it's time-stamps to the relevant and reported (albeit different reporting
scheme) time markers in the transcript file(s).

In other words, it's the getCueAsHTML() that is the key (I think). Simply
put something like this (not sure of syntax):  

<!DOCTYPE html>
  getCueAsHTML(): "Talk on WebVTT
      <ul>
        <li><? target='timestamp' data='00:00:47.600'>Impact of Captions
on the Web</li>
        <li><? target='timestamp' data='00:01:50.100'>Requirements of a
Video text format</li>
        <li><? Target='timestamp' data='00:02:30.000'>The Web VTT Format
		<ul>
			<li><? target='timestamp'
data='00:03:33.000'>Simple WebVTT file</li>
        		<li><? target='timestamp'
data='00:04:57.766'>Styled WebVTT file</li>
        		<li><? target='timestamp'
data='00:06:16.666'>Internationalized WebVTT file</li>
		</ul>
	  </li>
      </ul>
</html>

...save as nav.html, then write:

  <video src="video.ogv" controls>
    <track src="webvtt1.vtt" kind="chapter">
    <track src="nav.html" kind="navigation" label="Chapter Navigation">
  </video>

I know, I know, I hear somebody screaming SMIL.... (Argghhh), but...

JF
Received on Wednesday, 29 June 2011 19:20:50 GMT

This archive was generated by hypermail 2.2.0+W3C-0.50 : Friday, 27 April 2012 04:42:41 GMT