This document captures technical requirements for [[ttml-imsc1.2]], the next revision of [[ttml-imsc1.1]].

Terms and Definitions

Deprecated. Permitted today, but expected to be prohibited in the future.



[[!ttml-imsc1.2]] SHALL retain the scope of [[!ttml-imsc1.1]] while adding the minimal set of features necessary to support current practices for worldwide subtitling and captioning delivery.

Open issues

[[!ttml-imsc1.2]] SHALL address outstanding open issues documented in the IMSC repository.

IMSC1.1 Compatibility

A valid [[!ttml-imsc1.1]] Text Profile document SHALL be a valid [[!ttml-imsc1.2]] Text Profile document, and a valid [[!ttml-imsc1.1]] Image Profile document SHALL be a valid [[!ttml-imsc1.2]] Image Profile document.

A [[!ttml-imsc1.2]] presentation processor SHALL present a valid [[!ttml-imsc1.1]] document as it would have been presented by an [[!ttml-imsc1.1]] presentation processor.

TTML2 Subset

[[!ttml-imsc1.2]] SHALL use features defined in [[!TTML2]] to satisfy each requirement specified herein, unless infeasible.

When an [[!ttml-imsc1.1]] extension is deprecated and an equivalent [[TTML2]] feature is permitted, a document instance SHALL NOT use both the deprecated extension and the equivalent [[TTML2]] feature.

HTML5 Mapping

[[!ttml-imsc1.2]] SHALL specify a mapping of each of its features to [[!HTML51]] documents including support for [[!CSS-2018]].

The fidelity of the mapping is not necessarily exact, but SHALL provide an acceptable result.

#font support

[[!ttml-imsc1.2]] Text Profile SHALL support the inclusion of inline pictorial information that is not available in (a) the font set expected to be supported natively by presentation processors or (b) not available as a [[Unicode]] character.