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Re: {minutes} Geneva F2F day 1 16/09/2014

From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
Date: Sun, 21 Sep 2014 10:41:47 +1000
Message-ID: <CAHp8n2n5czK=FCxn-bkbXt56XCSw5_G4XLDuaBQwc5qfyXAX6Q@mail.gmail.com>
To: Glenn Adams <glenn@skynav.com>
Cc: Nigel Megitt <nigel.megitt@bbc.co.uk>, TTWG <public-tt@w3.org>, "public-texttracks@w3.org" <public-texttracks@w3.org>
On Sun, Sep 21, 2014 at 12:42 AM, Glenn Adams <glenn@skynav.com> wrote:
> On Sat, Sep 20, 2014 at 7:30 AM, Silvia Pfeiffer <silviapfeiffer1@gmail.com>
> wrote:
>> Most interesting read. Seems like there is not that much that doesn't
>> map in either direction.
>> A few additions / corrections about WebVTT that relate to this
>> discussion and that were missed (though Simon caught most):
>> 1.) Mapping WebVTT - 608/708
>> This wasn't mentioned, but I wanted to make sure people are aware that
>> there is already a spec that provides a basic mapping between WebVTT
>> and 608 and 708 captions at
>> https://dvcs.w3.org/hg/text-tracks/raw-file/default/608toVTT/608toVTT.html
>> .
>> It does indeed require some CSS.
>> 2.) Repetition of cue settings:
>> There's a plan to allow for some file metadata to set different
>> default values for settings, so repetition is not necessary.
>> 3.) CSS works by using ::cue and ::cue-region - the first for cues and
>> the second for regions.
>> These selectors work from a Web page (wherever CSS is specified there)
>> and override default styling of WebVTT cues.
>> 4.) cue overalpping:
>> It's actually not true that cues cannot overlap in time. They can and
>> are expected to. In fact, chapter cues are specifically defined as a
>> particular kind of overlapping cues that are hierarchically
>> structured, or in your words: are nested.
>> 5.) cue ids:
>> I think it might be possible to map numeric identifiers to XML
>> identifiers - at least it's possible to use them like this for CSS:
>> ::cue(#\31) { color: green; }
>> This references a cue with id=1. That might work for mapping to TTML
>> xml:id too.
> it would be necessary to prefix a numeric identifer with at least one alpha
> to use with xml:id

Interesting. How does this work in the context of browsers?

For comparison, I'm looking at SVG, though I'm wondering if that's
applicable to TTML.

Here's how they define ID in SVG:

<!ENTITY % SVG.id.attrib
    "id ID #IMPLIED"

(so, it's "id" and not "xml:id")

It works, e.g. in an example document like this, the element is identifyable:

<svg xmlns='http://www.w3.org/2000/svg' id='1'>
      alert(document.getElementById('1') == document.documentElement);

It seems to me that SVG have moved away from xml:id, since the #myRect
reference in the example below doesn't work

<svg xmlns="http://www.w3.org/2000/svg"
     version="1.2" baseProfile="tiny" viewBox="0 0 480 360">

  <desc>Forward reference of use element</desc>

  <use xlink:href="#myRect" x="200" fill="green"/>
  <circle cx="450" cy="50" r="50" fill="yellow"/>

  <g fill="red">
    <rect xml:id="myRect" width="100" height="100"/>

but starts working if you add id="myRect" on the <rect> element. It
continues to work even when replacing the "myRect" string with merely
a number such as "1".

Is there any intention to move to that approach in TTML, too? If so,
then maybe the WebVTT identifiers should be mapped into an "id"
attribute rather than the "xml:id" attribute?

Just some thoughts...

Received on Sunday, 21 September 2014 00:42:34 UTC

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