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Re: Survey ready on Media Text Associations proposal

From: Dick Bulterman <Dick.Bulterman@cwi.nl>
Date: Fri, 05 Mar 2010 13:10:58 +0100
Message-ID: <4B90F4D2.1020000@cwi.nl>
To: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
CC: Eric Carlson <eric.carlson@apple.com>, Michael Smith <mike@w3.org>, HTML Accessibility Task Force <public-html-a11y@w3.org>
On the track proposal, just to make sure I'm not missing something:
Is there an implied preference order in the statements:
> <trackgroup media="accessibility(captions:yes") >
>>  <track src="en.srt" lang="en" enabled >
>>  <track src="fr.srt" lang="fr" >
>>  <track src="de.srt" lang="de" >
>> </trackgroup>

(In other words, the implied preference order is English, French, German.)

Compare this to the SMIL way of doing the same thing:
     <video src="..." />
     <switch systemCaptions="on" allowReorder="yes">
       <textstream src="en.xxx" systemLanguage="en" />
       <textstream src="fr.xxx" systemLanguage="de" />
       <textstream src="de.xxx" systemLanguage="de" />
The default behavior is that the first candidate matching a set language 
preference is used. The 'allowReorder' attribute explicitly allows a 
user agent the reorder the order of options if the user (via the UA) has 
determined that he/she prefers German over French.

Note also that in this example, the entire <switch> is only evaluated if 
the user (agent) has determined that captions are required. Note finally 
that if the user has the language preference Dutch, no captions will 
play (since he presumably can't understand them anyway). Having a final 
statement in a <switch> without a predicate determines a result that 
will allows play if no earlier option (reodered or not) do not provide a 
preference match.

Are the semantics of <trackgroup> similar? (If so, why invent something 
new; if not, are at least the SMIL semantics supported?)

Received on Friday, 5 March 2010 12:18:33 UTC

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