The Timed Text Working Group has published a Candidate Recommendation of TTML Profiles for Internet Media Subtitles and Captions 1.2. 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 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.
Original source: https://www.w3.org/blog/news/archives/8420