ISSUE-439: #length-pixel forbidden

#length-pixel forbidden

TTML WebVTT mapping note
Raised by:
Pierre-Anthony Lemieux
Opened on:
Although specifying lengths in pixels should generally be discouraged, I have seen many TTML documents use them.

As long as tts:extent is specified on <tt> using "px" metric, can't "px" coordinates be converted to percentage coordinates by merely dividing the horizontal (vertical) component by the number of tts:extent pixels in the horizontal (vertical) direction?
Related Actions Items:
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Related emails:
  1. {agenda} TTWG Meeting 2015-09-24 (from on 2015-09-23)
  2. ISSUE-439: #length-pixel forbidden [TTML WebVTT mapping note] (from on 2015-09-23)

Related notes:

This is related to the general mapping approach taken in the document to make an "intermediate" document type as close as possible to WebVTT. WebVTT does not support "absolute" positioning with pixel. But you may allow pixel as length metric for font-size (this is supported in CSS).

Andreas Tai, 27 Oct 2015, 21:53:01

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