EBU-TT Part 3 Live Subtitling

EBU Tech 3370

This document is Part 3 of the EBU-TT series. It specifies how to use EBU-TT for the production and contribution of live subtitles. This is version 1.0.

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This publication describes how EBU‑TT 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, via intermediate processing units. It does this by specifying:

  • 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 synchronisation between the subtitles and the audio to which they relate;
  • a mechanism for interoperable management of the handover from one subtitler to the next, to generate a single output subtitle stream.
  • an extension facility to allow other types of live documents to be defined in future specifications, for example for passing messages between subtitlers

See the EBU-TT-Live Interoperability Toolkit for an open source implementation of this specification.

A changelog with pointers to previous versions is available here.

Note carriage of EBU‑TT Part 3 over WebSocket is specified in EBU Tech 3370s1.


The following translations of this document are available. Please note the translations may not be based on the latest version; see the year mentioned in brackets. These translations are courtesy of the translaters and hosted by the EBU 'as is'. The official and definitive version is the EBU English version.

Russian version of EBU Tech 3370 [2015] - Special thanks to EBU Member RTR.