[Webkit-unassigned] [Bug 110479] [Meta] Implement support for TTML

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=110479





--- Comment #6 from Glenn Adams <glenn at skynav.com>  2013-02-21 14:51:51 PST ---
(In reply to comment #5)
> Do you have a link to the rules for rendering TTML in browsers? HTML requires these:  http://www.w3.org/TR/html5/single-page.html#replaced-elements

I guess you are asking if I could provide a reference to rules for TTML that are equivalent to the following found in 10.4.1 Embedded content:

<quote>
Any subtitles or captions are expected to be overlayed directly on top of their video element, as defined by the relevant rendering rules; for WebVTT, those are the WebVTT cue text rendering rules. [WEBVTT]

When the user agent starts exposing a user interface for a video element, the user agent should run the rules for updating the text track rendering of each of the text tracks in the video element's list of text tracks that are showing (e.g., for text tracks based on WebVTT, the rules for updating the display of WebVTT text tracks). [WEBVTT]
</quote>

Is that what you are asking? At present, TTML leaves the decision about where to display the "root container region" up to the external authoring or presentation context (see [1], with a minor clarifying edit "[or presentation]"):

<quote>
If the tts:extent attribute is specified on the tt element, then it must adhere to 8.2.7 tts:extent, in which case it specifies the spatial extent of the root container region in which content regions are located and presented. If no tts:extent attribute is specified, then the spatial extent of the root container region is considered to be determined by the external authoring or presentation context. The root container origin is determined by the external authoring [or presentation] context.
</quote>

So the language you cite in HTML5 10.4.1 can certainly apply as the "external presentation context" rules. However, there is a recent thread [2] related to this matter, the resolution of which I expect will add further clarifying language, and possibly new mechanisms to permit the author to express intentions about the relation between the root container region and the related media object display region.

If you need something more specific, let me know and I'll raise an issue with the TTWG.

[1] https://dvcs.w3.org/hg/ttml/raw-file/default/ttml10/spec/ttaf1-dfxp.html#document-structure-vocabulary-tt
[2] http://lists.w3.org/Archives/Public/public-tt/2013Jan/0027.html

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