W3C Invites Implementations of IMSC Hypothetical Render Model

The Timed Text Working Group invites implementations of the IMSC Hypothetical Render Model Candidate Recommendation Snapshot. This specification specifies an Hypothetical Render Model (HRM) that constrains the presentation complexity of documents that conform to any of the TTML Profiles for Internet Media Subtitles and Captions ([IMSC]). 

The model is not intended as a specification of the processing requirements for implementations. For instance, while the model defines glyph cache for the purpose of modelling how the number of glyph drawing operations can be reduced, it neither requires the implementation of such a cache, nor models the sub-pixel glyph positioning and anti-aliased glyph rendering that can be used to produce text output. Furthermore, the model is not intended to constrain readability complexity.

Comments are welcome via the GitHub issues by 20 July 2023.