This specification improves on ttml-imsc1.1 by supporting contemporary practices, while retaining compatibility with ttml-imsc1.1 documents. It provides one new feature, which permits external font files to be referenced explicitly. One existing feature has been clarified, and no features have been deprecated in this version.

This specification defines two profiles of TTML2: a text-only profile and an image-only profile. These profiles are intended to be used across subtitle and caption delivery applications worldwide, thereby simplifying interoperability, consistent rendering and conversion to other subtitling and captioning formats.

This document specifies two profiles of TTML1: a text-only profile and an image-only profile. These profiles are intended to be used across subtitle and caption delivery applications worldwide, thereby simplifying interoperability, consistent rendering and conversion to other subtitling and captioning formats.