W3C TTWG seeks feedback on draft IMSC 1.3

W3C Timed Text Working Group (TTWG)  has begun working on a new version (1.3) of the Internet Media Subtitles and Captions (IMSC) specification and is seeking feedback.


As part of this work, we are considering removing the Image Profile in IMSC 1.3, indicating that the Image Profile has reached maturity and that no further work is planned. Organisations wanting to reference Image Profile would therefore need to continue to reference IMSC 1.2.


If future requirements for changes to Image Profile arise, the TTWG will consider whether they warrant an update and publication of a new version of Image Profile.


Some of the additional changes currently being proposed in IMSC 1.3, which may be of interest are:

  *   Addition of Japanese characters matching those specified in ARIB STD-B69 [2]
  *   Addition of superscript and subscript
  *   Removal of the normative requirement to conform to the Hypothetical Render Model (HRM) provisions, which have now been published as the IMSC-HRM Recommendation [2] so that it can be specified as a distinct requirement where needed. The IMSC-HRM Recommendation [3] does not specify an algorithm for assessing Image Profile documents, however IMSC 1.2 does so in its HRM provision.


We welcome any feedback, but in particular would like to know if the removal of Image Profile will cause any difficulties.


Kind regards,


Nigel Megitt, Chair W3C TTWG


[1] IMSC 1.2: https://www.w3.org/TR/ttml-imsc1.2/


[2] ARIB STD-B69 (English translation, PDF): https://www.arib.or.jp/english/html/overview/doc/6-STD-B69v1_1-E1.pdf

[3] IMSC-HRM: https://www.w3.org/TR/imsc-hrm/