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Re: [media] Moving forward with captions / subtitles

From: Philip Jägenstedt <philipj@opera.com>
Date: Wed, 17 Feb 2010 21:15:53 +0800
To: "Geoff Freed" <geoff_freed@wgbh.org>, "Silvia Pfeiffer" <silviapfeiffer1@gmail.com>
Cc: "Eric Carlson" <eric.carlson@apple.com>, "HTML Accessibility Task Force" <public-html-a11y@w3.org>
Message-ID: <op.u79wgrqiatwj1d@philip-pc>
On Wed, 17 Feb 2010 21:04:37 +0800, Geoff Freed <geoff_freed@wgbh.org>  
wrote:

>
> ________________________________________
> From: Silvia Pfeiffer [silviapfeiffer1@gmail.com]
> Sent: Wednesday, February 17, 2010 6:56 AM
> To: Philip Jägenstedt
> Cc: Geoff Freed; Eric Carlson; HTML Accessibility Task Force
> Subject: Re: [media] Moving forward with captions / subtitles
>
> On Wed, Feb 17, 2010 at 7:00 PM, Philip Jägenstedt <philipj@opera.com>  
> wrote:
>> On Wed, 17 Feb 2010 15:10:06 +0800, Silvia Pfeiffer
>> <silviapfeiffer1@gmail.com> wrote:
>>
>>> Maybe we have converged?
>>
>> Yes, and for the record this is what I think we agree on:
>>
>> <track> is used to reference an external text track.
>
> GF:  Agreed.
>
>>
>> <trackgroup> is used to group several tracks which are mutually  
>> exclusive.
>> Often they will have the same role="", but this isn't necessarily so.
>
> GF:  So role is *not* a requirement for <trackgroup>, correct?

Correct.

>> Your example with active changed to enabled:
>>
>> <video src="video.ogv">
>>  <track src="cc.en.srt" srclang="en" role="CC" enabled>
>>  <track src="tad.en.srt" srclang="en" role="TAD">
>>  <trackgroup role="SUB">
>>    <track src="subs.de.srt" srclang="de">
>>    <track src="subs.sv.srt" srclang="sv">
>>    <track src="subs.jp.srt" srclang="jp">
>>  </trackgroup>
>> </video>
>>
>> <track> is a void element (no end tag), if there any reason to think  
>> that it
>> would ever need child elements then now is the time to give it an end  
>> tag.
>
> GF:  I can't think of a reason today, but there may be reasons in the  
> future.  Is it a big deal to require an end tag?  If not, I think we  
> should require one now.

I'm not a fan of void elements and wouldn't mind <track> having an  
end-tag. The case that might happen is that <track> is used for external  
additional audio/video tracks (e.g. sign language overlays) and we need  
<source> to provide fallback because we don't have a baseline audio/video  
codec (just like for <audio>/<video>, not in the sense that we've been  
using <source> in this discussion).

> Re enabling/disabling:  in the example above, the CC track is enabled by  
> default while the others are enabled at the user's discretion.  Would it  
> not be more logical, and more consistent with other attribute  
> structures, to use markup to make this explicit?  That would require the  
> use of enable="on" or enable="off" on each track.  Hmmm.  This is akin  
> to SMIL's systemCaptions="on/off".  And that brings up the SMIL argument  
> again.

Boolean attributes are a pretty standard thing in HTML, where the only way  
to express false is to not have the attribute at all. This is consistent  
with e.g. the attributes "selected", "autoplay", etc.

-- 
Philip Jägenstedt
Core Developer
Opera Software
Received on Wednesday, 17 February 2010 13:16:33 GMT

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