Add full support for WebVTT

[terrill]

Add support for the following markup within VTT files:

• Cue settings
• Cue payload span tags

Resources:

• https://developer.mozilla.org/en-US/docs/HTML/WebVTT
• http://dev.w3.org/html5/webvtt/

[terrill]

In Commit e14f76e I added filters to the WebVTT parser so it ignores specialized markup for now. Actually handling the additional tags will be no small chore.

In Commit dd55d99 I added both cue settings and cue payload span tags to the sample caption file so folks can play with it (feel free to add more).

[coreystaten]

Cue settings and payload span tags are supported by the new parser; code has not been added for any special rendering based on them though.

[terrill]

We might be able to learn from, or use, C Giffard's Captionator parser: https://github.com/cgiffard/Captionator

[terrill]

Just dropping in a note that any effort to more fully support the WebVTT spec should include support for nested cues:
https://w3c.github.io/webvtt/#file-using-only-nested-cues

This would involve significant updates to the WebVTT parser (in webvtt.js, maybe also some work in track.js) but it's needed particularly in chapter tracks, in order to build a chapter structure or outline that has depth.

[jessehall3]

@terrill Is this something that can or should be worked on presently? I saw your mention in #237 that you had reservations because of the evolving standard? I'd be interested in looking into this.

[KimPatch]

Hi Jesse, it's great that you're interested in increasing WebVTT support. I'm working on a website that uses Able Player and makes use of existing WebVTT support (http://livinghistory.sanford.duke.edu/). We are eager to have better support for paragraphs and subheads in transcripts. There's a programmer from Code Alliance who has also expressed interest in helping with this. I'll encourage him to connect with you here.

[jessehall3]

@KimPatch That sounds great. I'll be sending you an e-mail with my info, I'm interested in communicating with the programmer from Code Alliance.

[MIsmailKhan]

Hi Jesse, I am the programmer from Code Alliance. My name is Ismail. I am definitely up for collaboration. Perhaps we can set up a chat for this purpose?

[jessehall3]

@MIsmailKhan Sounds good. Please send me an e-mail to jessehall3@gmail.com and we can set one up, thanks.

[terrill]

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