[MPEG-OTSPEC] Does OpenType have a one to many GSUB-like feature please?

John Hudson john at tiro.ca
Fri Dec 23 17:09:37 CET 2022

Yes, OTL GSUB has a one-to-many lookup type (GSUB lookup type 2), but I 
don’t think this is relevant to the issue of emoji in text-to-speech 

> I am wondering if a font could have a table where the codepoint (or 
> postscript name) of an emoji is substituted by the codepoints of a 
> sequence of regular text characters, with the output then routed to a 
> text to speech system.

GSUB operates at the glyph ID number level, not at the codepoint level. 
Text-to-speech and text-to-glyphs can be seen as parallel but separate 
presentation technologies, both sitting on top of Unicode encoded text, 
but presenting that text in different ways. Text-to-speech systems rely 
on natural language processing, and the reason they become clunky when 
dealing with emoji—as with other symbols and non-linguistic content—is 
that such characters do not participate in linguistic communication, so 
at best have to be named or described. But what is being named or 
described is still at the character level, not at the glyph level.



John Hudson
Tiro Typeworks Ltdwww.tiro.com

Tiro Typeworks is physically located on islands
in the Salish Sea, on the traditional territory
of the Snuneymuxw and Penelakut First Nations.


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