The EBU has published v0.9 of its live subtitling specification EBU Tech 3370. The document is stable and is meant to encourage implementers to gain practical experience with the specification in prototype implementations. Feedback on the specification is welcome until 30 April 2016. After this date, a final release version of the specification will be created.

What is the specification for?

This document describes how the EBU-TT subtitling format can be used in a broadcasting environment to carry subtitles that are created in real time (“live” or from a prepared file) from an authoring station to an encoder prior to distribution.

What does it provide?

Tech 3370 v0.9 provides:

  • a system model consisting of processing nodes that pass streams of subtitles along a chain;
  • a content profile based on EBU-TT Part 1 specifying the data format of each document in a live subtitle stream;
  • a mechanism by which content providers can model and potentially improve synchronization between the subtitles and the audio to which they relate;
  • a mechanism for interoperable management of the handover from one subtitle to the next, to generate a single output subtitle stream;
  • conformance requirements for specifications that define the carriage of EBU-TT Part 3 data between nodes in a chain.

Reference implementation

The EBU intends to initiate an open source reference implementation project in the near future to demonstrate the practicality of EBU-TT Live subtitling and provide interoperability test points. The group invites anyone interested in contributing to this project to register their interest via

Learn more


What to learn more? Take a look at this webinar recording, in which Nigel Megitt (BBC) provides an introduction to the EBU-TT Live Subtitling specification.

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