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ISSUE-286 (rowPadding): Extend the background area behind rendered text to improve readability [TTML2]

From: Timed Text Working Group Issue Tracker <sysbot+tracker@w3.org>
Date: Wed, 23 Oct 2013 10:24:41 +0000
Message-Id: <E1VYvcH-0004pj-D1@shauna.w3.org>
To: public-tt@w3.org
ISSUE-286 (rowPadding): Extend the background area behind rendered text to improve readability [TTML2]

http://www.w3.org/AudioVideo/TT/tracker/issues/286

Raised by: Nigel Megitt
On product: TTML2

The current rendering rules for TTML allow for a background colour to be specified, to be painted behind rendered text. However the edges of this background area are coincident with the foreground text boundary, or with the entire region, neither of which meets all use cases. A common practice in rendering subtitles against video is to extend slightly the background area painted behind the foreground text, e.g. by the width of one space character [1].

[1] https://industry.youview.com/resources/YouView_Core_Technical_Specification_1.0.pdf section 4.4.4.4

No proposed solution is available to address the general case of this, which has some complexity e.g. what to do if a <span> has a different background colour from its parent <p> and the text in the span is wrapped over a line. However the specific use case can be addressed either by specifying a generic rendering rule to cover all text in a region or even a document, e.g. a tts:rowPadding attribute with a length value. Alternative proposals for indicating the requirement for presentation processors to use this rendering behaviour are welcomed!
Received on Wednesday, 23 October 2013 10:24:42 UTC

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