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Re: [css3-speech] :media-overlay-active

From: Daniel Weck <daniel.weck@gmail.com>
Date: Mon, 27 Jun 2011 20:55:48 +0100
Message-Id: <5236B679-4D1E-4CDC-AA90-B95D81F69DA1@gmail.com>
To: www-style@w3.org
Note that the associated EPUB3 issue was recently closed [1] due to  
the EPUB Working Group reaching consensus on a proposed alternative  
solution.

In a nutshell: EPUB3 content authors can now define the CSS class name  
applicable to "active" elements in the context of Media Overlays  
synchronization of pre-recorded audio and document elements (text,  
image, video, etc.). This author-defined CSS class name is exposed in  
the publication manifest (via well-defined metadata vocabulary) and  
can therefore be unambiguously discovered by EPUB3 reading systems.

The solution based on a CSS pseudo-class was rejected on the basis  
that it was impractical for reading system implementors. Reserving a  
particular class name was obviously wrong from a standardization  
perspective, so this solution was rejected too.

I still believe (as per my original reply to Fantasai's email) that  
the CSS3 Speech Module is not the right place to define a pseudo-class  
similar to (the now defunct) ":-epub-media-overlay-active". There  
needs to be a concerted effort with the HTML-Speech activity and other  
working groups focused on multimedia synchronization, in order to  
better understand the functional requirements and scope of such  
feature. For example, this feature is not actually directly related to  
speech synthesis: EPUB3 Media Overlays is based entirely on pre- 
recorded audio narration (TTS being handled separately, but not  
necessarily in a mutually-exclusive fashion), and text/video  
synchronization in the context of sign-language interpretation doesn't  
rely on speech at all (furthermore, it requires support for  
simultaneous non-adjoining "active" document elements). As you can  
see, there is more to it than what initially seems like a trivial  
feature, with implications beyond the CSS3 Speech Module.

I believe that we should focus on moving the CSS3 Speech Module  
towards Last Call Working Draft, and discuss the ":active" CSS class  
topic in a separate track.

Regards, Daniel

[1]
http://code.google.com/p/epub-revision/issues/detail?id=140
Received on Monday, 27 June 2011 19:56:20 GMT

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