Re: CEA-608/708 and WebVTT

Silvia

thanks for taking the lead on starting this.  I think making it a CG document makes a lot of sense, and unless someone objects (I can't think why), we should take it on.  You should also indicate when you're ready to have others contribute and help.

Some points:

Suggest we define some styles that are clearly 608/708 specific with names that clue us in to that (e.g. s708 for Style from 708, or CEAx08, or somesuch).

In that vein, how about s708cXYZ, where X, Y and Z are 0 thru 3, for the CEA 708 64 standard colors?  We should also have names for the 8 named colors (R G B, C M Y and L, and White).

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.)

Your example of metadata in the file header uses key=value, and though I originally suggested key=value, Ian and you both proposed key: value, and that's what's in the most recent write-ups.  Suggest we change the example to use colons.

More as I see it, but thanks for catalyzing this important work!


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 Wednesday, 29 August 2012 23:40:07 UTC