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[imsc] Requirement to support certain Code Point

From: Andreas Tai via GitHub <sysbot+gh@w3.org>
Date: Fri, 02 Jun 2017 13:09:12 +0000
To: public-tt@w3.org
Message-ID: <issues.opened-233178041-1496408951-sysbot+gh@w3.org>
tairt has just created a new issue for https://github.com/w3c/imsc:

== Requirement to support certain Code Point ==
As there is a discussion recently about Reference Fonts in IMSC1, I would like to clarify, if a presentation processor **SHALL** have a font available for all codepoints listed in Annex B (https://www.w3.org/TR/ttml-imsc1/#recommended-unicode-code-points-per-language).

Section 7.3 states:

> When rendering codepoints matching one of the combinations of computed font family and codepoints listed in A. Reference Fonts, a processor **shall** use a font that generates a glyph sequence whose dimension is substantially identical to the glyph sequence that would have been generated by one of the specified reference fonts.

Regarding codepoints Annex A. points to Annex B (without making an exception). 

My reading is that implicitly there must be font support for all codepoints in Annex B. It is the minimum condition to generate an identical glyph sequence as in the reference fonts.

I could also see why there may be other interpretations (e.g. because ANNEX B has only "recommended" in the title). But from my interpretation the normative text is clear. 

One other observation: people may also have problems in reading the statements for table 2.

> Table 2 specifies supplementary character set that have proven useful in captioning and subtitling applications for a number of selected languages. Table 2 is non-exhaustive, and will be extended as needs arise.

Especially the addition that this table may be extended could lead to the conclusion that support for table 2 characters is more a recommendation then a strict normative requirement.

Please view or discuss this issue at https://github.com/w3c/imsc/issues/241 using your GitHub account
Received on Friday, 2 June 2017 13:09:18 UTC

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