[webvtt] support custom cue settings

alexdean has just created a new issue for 
https://github.com/w3c/webvtt:

== support custom cue settings ==
I would like the WebVTT spec to define a method for publishers to 
include custom cue settings.

I would like to be able to mark some cues as the beginning of a 
paragraph. At [TED Conferences](http://www.ted.com), we use data like 
this to construct a readable transcript from the subtitles created by 
[our volunteer 
translators](http://www.ted.com/about/programs-initiatives/ted-open-translation-project).
 You can see an example in [the English transcript of Shonda Rhimes'
TEDTalk](http://www.ted.com/talks/shonda_rhimes_my_year_of_saying_yes_to_everything/transcript?language=en).

We currently use a custom JSON format to transmit this data. We would 
like to switch to a more standard format, but need support for this 
additional per-caption metadata.

Something like [HTML's data-* 
attributes](https://www.w3.org/TR/2011/WD-html5-20110525/elements.html#embedding-custom-non-visible-data-with-the-data-attributes)
 would serve our purposes nicely.

For example:

```
WEBVTT

00:00:00.960 --> 00:00:04.616 data-paragraph:true
So a while ago, I tried an experiment.

00:00:04.640 --> 00:00:08.080
For one year, I would say yes
to all the things that scared me.
```

cc @zcorpan @jwarchol @bendk

Please view or discuss this issue at 
https://github.com/w3c/webvtt/issues/286 using your GitHub account

Received on Friday, 19 February 2016 21:38:55 UTC