[imsc] [WR/ARIB] Compatibility with ARIB-TTML / 2. Font handling (#547)

himorin has just created a new issue for https://github.com/w3c/imsc:

== [WR/ARIB] Compatibility with ARIB-TTML / 2. Font handling ==
Per: https://github.com/w3c/ttwg/issues/116
Comment 3 (https://github.com/w3c/imsc/issues/545), 2

In Japanese language, Kanji is one of essential characters. More than 10,000 Kanji (repertoire) are standardized for Japanese broadcast environment. But still characters not listed in the standard are still required in some cases. In ARIB STD-B62 based environment, two approaches are prepared against such cases.

## Ideographic Variation Selector (IVS)

Some required Kanji characters can be considered as variants of existing characters. IVS is the mechanism to identify and handle this case as defined in clause 16.6 of ISO/IEC 10646:2017 or Unicode Technical Standard #37. With the Moji_Joho collection, 19 cases are included in ARIB TR-B39 which is the operational guideline for ARIB STD-B62. It is required for ARIB STD-B62 compliant environment to handle IVS properly.

## Gaiji

When a non-standardized Kanji character is needed, “Gaiji” that is to place a glyph image of such a character is the way to support it. Use of code points in Private Use Area. (PUA) for such characters is common approach to avoid duplicated character assignment. For this purpose, “arib-tt:font-face” element is defined to allow additional characters packed in different fonts. The font is supposed to be delivered on the fly with the TTML document. SVG and WOFF can be used as available font formats. The “unicode-range” attribute is also available in the element so that the characters included in the font can be easily handled by a TTML processor. This element can also be used to handle inline graphics by rendering the graphic encoded as a glyph image. It can be achieved by a combination of a glyph image and PUA assigned code value, and/or a use of GSUB in WOFF if a processor is capable to handle it properly.

Please view or discuss this issue at https://github.com/w3c/imsc/issues/547 using your GitHub account

Received on Friday, 8 May 2020 10:06:06 UTC