The EBU has published a new specification for the distribution of subtitles: EBU-TT-D (Tech 3380). The XML based EBU-TT-D format is a low-complexity way to combine subtitle text, styling, timing information, and positioning details to allow implementers to provide users with a subtitle experience at least as good as that on current TVs, regardless of the platform on which they are watching the content.
EBU-TT-D was developed in less than a year, by taking into account expertise from users, distribution parties, hybrid TV organizations and CE manufacturers. The work built on the EBU XML Subtitles group’s knowledge gained when creating the EBU-TT subtitle format for production interchange and archiving (EBU Tech 3350). The specification is derived from the base W3C TTML specification. It strongly constrains the feature set of TTML to make it easier for decoder/renderer implementers to add subtitle overlays to video without the complexity that is present in TTML to support other scenarios.
EBU-TT-D was published and presented during the EBU's Production Technology Seminar 2014
Work is in progress in HbbTV and DVB to reference EBU-TT-D within the upcoming HbbTV 2.0 and DVB DASH standards. The EBU has also published the first carriage specification document for EBU-TT-D, EBU Tech 3381 v0.9, which defines how to carry EBU-TT-D in ISO BMFF, itself a necessary step for distributing EBU-TT-D via DASH. This builds on work done by MPEG, not yet published in international standard form.
Having published EBU-TT-D, the EBU Group on subtitling will shift its main attention to production again, focusing on helping users move from STL to EBU-TT and developing a solution for the creation and contribution of live subtitling. For more information, join the EBU technical group on subtitling.