Re: CEA-608/708 and WebVTT

On Thu, Aug 30, 2012 at 2:39 AM, David Singer <singer@apple.com> wrote:
> The biggest issue I see is that 708 has the concept of 'windows' -- rectangular areas into which text gets painted.  We can land text in the right place, I think, but 708 has *3* colors -- the window, the text background, and the text foreground.  I don't see a way to identify the rectangular region to paint with the window color, in WebVTT, right now.  The 'size' and 'position' on a cue effectively define the left/right extent, but we don't have a line-range, just a line number.  (I am researching when the window gets painted with that color in 708.)

I would add, to all these, the anchor point concept that describes the
direction in which the windows expand as content is being added and
which point within the window lies on top of the video. This is
something impossible to achieve with the existing WebVTT spec.

There are some pages in the CEA 708-B/D document that describe in
detail how the painting is done when using anchor points. I also
registered a bug a while ago:
https://www.w3.org/Bugs/Public/show_bug.cgi?id=15859

Victor

> On Aug 27, 2012, at 7:12 , Silvia Pfeiffer <silviapfeiffer1@gmail.com> wrote:
>
>> Hi all,
>>
>> I've moved the CEA-608/708 conversion document out of the wiki into a
>> proper W3C document and updated the spec.
>> This will also go towards satisfying the FCC needs for captions for
>> online video.
>>
>> For now the document is an unofficial draft, available at:
>> https://dvcs.w3.org/hg/text-tracks/raw-file/669f6b95a488/608toVTT/608toVTT.html
>>
>> I propose to make it a CG document.
>>
>> Accepting it as a CG document puts it into Editor Draft status - it
>> wouldn't meant that this document is finished, of course.
>> There are still a number of open issues.
>>
>> To summarize my approach:
>> * I've gone through the CEA-608/708 feature set and replicated them as
>> WebVTT features.
>> * This required making use of file-wide metadata. [1]
>> * This also required making use of CSS features.
>>  Since it's a limited set of CSS features, it's quite simple to
>> provide a "default CSS file" for CEA-608/708 features. [2]
>> * I've not been able to replicate the roll-up feature [3] since we
>> don't have a recommended solution for this yet [4].
>> * Probably need to dig more into 708 features and provide more CSS
>> solutions for them.
>>
>> I would welcome technical input.
>>
>> Best Regards,
>> Silvia.
>>
>>
>> [1] https://www.w3.org/Bugs/Public/show_bug.cgi?id=15851
>> [2] http://dvcs.w3.org/hg/text-tracks/raw-file/fe5cd9afb9c7/608toVTT/608toVTT.html#rendering-in-web-browsers
>> [3] http://dvcs.w3.org/hg/text-tracks/raw-file/fe5cd9afb9c7/608toVTT/608toVTT.html#roll-up-captions
>> [4] https://www.w3.org/Bugs/Public/show_bug.cgi?id=16706
>>
>
> David Singer
> Multimedia and Software Standards, Apple Inc.
>
>

Received on Thursday, 30 August 2012 08:03:20 UTC