W3C home > Mailing lists > Public > public-html-a11y@w3.org > November 2009

Re: timing model of the media resource in HTML5

From: Frank Olivier <franko@microsoft.com>
Date: Fri, 27 Nov 2009 22:37:42 +0000
To: Eric Carlson <eric.carlson@apple.com>
CC: Philip J├Ągenstedt <philipj@opera.com>, Silvia Pfeiffer <silviapfeiffer1@gmail.com>, HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-ID: <E2646595-C284-4947-9978-228DCC7F6110@microsoft.com>
After discussing it on our side - we agree that not having multiple  
element synchronization in this version of the spec is a good idea.

As for captions: if captions are stylable via page css, what happens  
if the caption format itself specifies styling? Also, imo the user  
should be able to override page-specified styling, as they might  
prefer their own styling.

On Nov 25, 2009, at 8:04, "Eric Carlson" <eric.carlson@apple.com> wrote:

> On Nov 25, 2009, at 4:24 AM, Philip J├Ągenstedt wrote:
>> I agree that syncing separate video and audio files is a big  
>> challenge. I'd prefer leaving this kind of complexity either to  
>> scripting or an external manifest like SMIL.
>  +1 to keeping multiple element synchronization out of our spec!
>> Below I focus on the HTML-specific parts:
>> Captions/subtitles... The main problem of reusing <source> is that  
>> it doesn't work with the resource selection algorithm.[1] However,  
>> that algorithm only considers direct children of the media element,  
>> so adding a wrapping element would solve this problem and allow us  
>> to spec different rules for selecting timed-text sources. Example:
>> <video>
>> <source src="video.ogg" type="video/ogg">
>> <source src="video.mp4" type="video/mp4">
>> <overlay>
>>   <source src="en.srt" lang="en-US">
>>   <source src="hans.srt" lang="zh-CN">
>> </overlay>
>> </video>
>> We could possibly allow <overlay src="english.srt"></overlay> as a  
>> shorthand when there is only one captions file, just like the video  
>> <video src=""></video> shorthand.
>> I'm suggesting <overlay> instead of e.g. <itext> because I have  
>> some special behavior in mind: when no (usable) source is found in  
>> <overlay>, the content of the element should be displayed overlayed  
>> on top of the video element as if it were inside a CSS box of the  
>> same size as the video. This gives authors a simple way to display  
>> overlay content such as custom controls and complex "subtitles"  
>> like animated karaoke to work the same both in normal rendering and  
>> in fullscreen mode. (I don't know what kind of CSS spec magic would  
>> be needed to allow such rendering, but I don't believe overlaying  
>> the content is very difficult implementation-wise.)
>  I like the idea of an <overlay> element, but I don't understand  
> what you are proposing for when no usable source is found. Can you  
> elaborate please?
>> If there is a use case, displaying several captions/subtitles at  
>> once could be allowed as such:
>> <video src="video.ogg">
>> <overlay src="en.srt" class="centerTop"></overlay>
>> <overlay src="hans.srt" class="centerBottom"></overlay>
>> </video>
>  I also like this idea. I don't think it will be difficult to find  
> legitimate use cases, eg. displaying closed captions and subtitles  
> simultaneously.
> eric
Received on Friday, 27 November 2009 22:38:18 UTC

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