OpenType is an victor-based font format developed by Microsoft and Adobe.

It is the successor to both TrueType and Adobe Type 1 font formats. An OpenType font is a single file, which can be used on any digital platform without conversion and it is an international standard commonly used on many devices.

OpenType is used for Text-subtitle streams and BD-J Text rendering for Java applications. (Text-subtitles are not available on Ultra HD Blu-ray). The available fonts can be listed in a font index file dvb.fontindex that is shared with all BD-J applications in the disc, located in the AUX directory.

 

Limitations

The BDMV application format has its own font memory with a size of 4 MB. It should have a minimum font rendering performance of 50 characters per second for fonts up to 72 points in size and 25 characters per second for larger point sizes. These minimum performance recommendations have to take into account of Asian fonts and other complex fonts.

Font Compatibility
You need to ensure that your font complies with the Blu-ray profile of OpenType. Some BD players, including PC players, may not accept non-compliant fonts. On other compliant players, they might not appear at all. If there's Unicode text but without a font, it will display the BD player's default font.

Features

OpenType fonts have many advantages over previous font formats because they contain more glyphs, support more languages (OpenType uses the Unicode standard for character encoding). OpenType fonts also support rich typographic features such as small caps, old style figures, and ligatures, all in a single font. 

Fonts can have different presentation styles such as text position/flow/alignment, and font style/size/color.

 

Character Encoding

The BD specification allows OpenType to support the following character encoding formats: 

Unicode 2.0 (UTF-8 and UTF-16BE) - Created by the Unicode Consortium, it's an international standard on covering over 38,885 characters from various writing systems (modern or ancient), as well as special symbols of many types, are each given a number. It is the most commonly used text encoding format for languages and coding. It is backwards compatible with ASCII, an American standard for the English language.

Shift-JIS - A Japanese standard, a character encoding for the Japanese language, originally developed by the Japanese company ASCII Corporation in conjunction with Microsoft and standardized as JIS X 0208 Appendix 1.

KSC 5601-1987 (including KSC 5653) - A Korean coded character set standard to represent Hangul and Hanja characters on a computer. It's a South Korean national standard.

GB18030-2000 - A Chinese government standard, a  Chinese coded character set and defines the required language and character support necessary for software in China. It supports both simplified and traditional Chinese characters.

GB2312 - A legacy Chinese government standard for simplified Chinese characters for Mainland China.

BIG5 - A standard encoding for traditional Chinese characters for Taiwan, Hong Kong, and Macau. It was created by a consortium of Taiwanese computer and electronics companies Acer, MiTAC, JiaJia, ZERO ONE Technology, and First International Computer (FIC), with significant contributions from the Institute for Information Industry (III) in Taiwan.

Text Compatibility

You need to ensure that your text encoding complies with the BD specifications, Unicode 2.0 (UTF-8 and UTF-16BE), Shift-JIS, KSC 5601-1987 (including KSC 5653),GB18030-2000, GB2312, and BIG5. It does not support older or non-standard text encoding formats. It is also recommended to avoid a Mojibake, an occurrence of incorrect unreadable characters displayed when software fails to render text correctly to its associated character encoding.

Sources

• HD Cookbook - Chapter 18
• OpenType is defined in Part 3-1 of BD-ROM specification, section H.3.1

Standards

• ISO/IEC 14496-22:2019

Specifications

• OpenType specification

Sample files

• http://tug.ctan.org/tex-archive/fonts/cm-unicode/fonts/otf/
• dexvert samples — font/otf

Metaformat files

• Synalysis grammar file (for Hexinator / Synalize It!; more details)

Links

• Wikipedia article
• Adobe's OpenType FAQ
• Archive Team 

Author(s) : Æ Firestone