This document captures technical requirements for [[!ttml-imsc1.1]], the next revision of [[!ttml-imsc1.0.1]].

Terms and Definitions

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

Requirements

Overall

[[!ttml-imsc1.1]] SHALL retain the scope of [[!ttml-imsc1.0.1]] while adding the minimal set of features necessary to support current practices for worldwide subtitling and captioning delivery.

IMSC1.0.1 Compatibility

A valid [[!ttml-imsc1.0.1]] Text Profile document SHALL be a valid [[!ttml-imsc1.1]] Text Profile document, and a valid [[!ttml-imsc1.0.1]] Image Profile document SHALL be a valid [[!ttml-imsc1.1]] Image Profile document.

A [[!ttml-imsc1.1]] presentation processor SHALL present a valid [[!ttml-imsc1.0.1]] document as it would have been presented by an [[!ttml-imsc1.0.1]] presentation processor.

The #fillLineGap and #activeArea specified in [[!ttml-imsc1.0.1]] SHALL be permitted in [[!ttml-imsc1.1]].

TTML2 Subset

A valid [[!ttml-imsc1.1]] Document SHALL be a valid [[!TTML2]] document.

Any [[!ttml-imsc1.0.1]] extension that (i) is not one of the following and (ii) has an equivalent feature in [[!TTML2]] SHALL be deprecated in [[!ttml-imsc1.1]] and the corresponding [[!TTML2]] feature permitted:

  • #activeArea
  • #fillLineGap
  • #forcedDisplay
  • #linePadding
  • #multiRowAlign

When an [[!ttml-imsc1.0.1]] 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-imsc1.1]] SHALL specify a mapping of each of its features to [[!HTML51]] documents including support for [[!CSS-2017]].

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

Image and Text Profiles

While [[!ttml-imsc1.1]] defines both Image and Text Profiles, distinct Image and Text processors SHALL be defined such that an Image Processor is not required to accept Text Profile documents, and vice versa.

Profile Resolution Semantics and Signaling

The profile resolution semantics and signaling specified in [[!TTML2]] SHOULD be used whenever possible.

Japanese Text Support

To support Japanese text as used in subtitles and captions, [[!ttml-imsc1.1]] Text Profile SHALL support the following features.

Feature
Ability to apply shear transformations on line areas, as a block, where a line area includes ruby base text, ruby annotations, and emphasis marks.
#ruby, as specified in [[!TTML2]].
#rubyAlign, as specified in [[!TTML2]], where only center and spaceAround semantics are required.
#rubyPosition, as specified in [[!TTML2]].
#rubyReserve, as specified in [[!TTML2]].
#textEmphasis-minimal, as specified in [[!TTML2]].
#textCombine, as specified in [[!TTML2]].

References:

Stereoscopic Presentations

To support stereoscopic presentations, both [[!ttml-imsc1.1]] Text and Image profiles SHALL support the #disparity feature specified in [[!TTML2]].

References:

High-Dynamic Range Presentations

To support HDR presentations, both [[!ttml-imsc1.1]] Text and Image profiles SHALL support the #luminanceGain feature specified in [[!TTML2]].

References:

#position

To simplify positioning, [[!ttml-imsc1.1]] Text Profile SHALL support the #position feature specified in [[!TTML2]].

#initial

To simplify style authoring, [[!ttml-imsc1.1]] Text Profile SHALL support the #initial feature specified in [[!TTML2]].

#textShadow

To support the edge styles required by the FCC, [[!ttml-imsc1.1]] Text Profile SHALL support the #textShadow feature specified in [[!TTML2]].

References:

#length-root-container-relative

To allow straightforward sizing and length-dependent styling of fonts relative to the root container, [[!ttml-imsc1.1]] Text Profile SHOULD support the #length-root-container-relative feature specified in [[!TTML2]].

References: