Subtitling

Helping Members to use subtitles in new facilities and for new distribution platforms.

Today’s distribution platforms offer a higher quality display of subtitling and more flexible positioning options than traditional analogue television. File- and IP-based production facilities demand clearly specified ways to carry subtitles during production, exchange, archiving and distribution to their customers, including the use of online services. To handle these new contexts, broadcasters need a low-complexity, but thoroughly specified subtitling format.

EBU-TT

To meet these requirements, the EBU Group 'Subtitles in XML' has created EBU-TT, which stands for EBU Timed Text. EBU-TT is the follow-up to the widely used EBU STL format (EBU Tech 3264). The EBU-TT family consists of the following specifications:

EBU-TT Part 1: Archive & Exchange

EBU-TT Part 1 (EBU Tech 3350) defines an easy-to-use XML structure for the interchange and archiving of subtitles. It builds on the W3C Timed text Markup Language (TTML) 1.0.

EBU-TT Part 2: STL mapping

EBU-TT Part 2 (EBU Tech 3360) is a mapping guide on how to map EBU STL files to EBU-TT.

EBU-TT Part M

Since May 2017, the EBU-TT metadata elements are defined in a single document (EBU Tech 3390). This makes it easier to maintain an overview and avoid duplication.

EBU-TT Part 3: Live contribution

EBU-TT Part 3 (EBU Tech 3370) provides a System Model and Content Profile for authoring and contribution of live (and prepared) subtitling. It further introduces the concept of processing 'nodes' that can help improve subtitling quality in production. This part is also known as "EBU-TT Live".

EBU-TT WebSocket Carriage Specification

EBU-TT Live does not prescribe which carrier mechanisms to use. These mechanisms can be defined in supplemental publications. EBU Tech 3370s1 is such a supplement. It describes how to carry EBU-TT-Live streams using WebSocket.

EBU-TT Live Interoperability Toolkit

This is not an official EBU spec, but an Open Source project that builds on the EBU-TT Live spec. It was used to test the specification in code and is a useful resource when adding EBU-TT Live support to products. See http://ebu.github.io/ebu-tt-live-toolkit/ for more.

EBU-TT-D

EBU-TT part 'D' (EBU Tech 3380) is the format for the distribution of subtitles over IP. There also is a document for the use of EBU-TT-D in ISO BMFF /  MPEG-DASH (EBU Tech 3381). Other specs reference EBU-TT-D, such as HbbTV 2.0, and Freeview Play. 

Related publications

The EBU has also developed a recommendation on the transport of subtitles inside and outside of MXF files (EBU R 133).

EBU Member BBC has published BBC Subtitles Guidelines. These are intended to serve as the basis for all subtitle work across the BBC (prepared and live, online and broadcast, internal and supplied)

Quality Control Tests

The EBU Quality Control Group is extending the range of QC Tests for subtitling. All published tests are available via EBU.IO/QC. To participate in the drafting work, join the QC group.

Software

Also check out this list of existing open source subtitling software and samples.

 

EBU Project Group on Subtitles in XML

Technical aspects of subtitling are being addressed by the EBU Group 'Subtitles in XML', which is part of the EBU's Strategic Programme on Video Systems.

Main activities:

  • Helps Members to use subtitles in new file-based facilities and for new distribution platforms.
  • Develops broadcast specifications based on the W3C Timed Text Markup Language (TTML).
  • Provides mappings and example files to help you use the format for subtitling.

Toolkit for Live Subtitling

The EBU has set up an open source software project to develop an Interoperability Toolkit for live subtitles. This toolkit will both validate the specification and help developers to verify that their implementations meet the specification and are interoperable. If you would like to participate in this project, please feel welcome! There is no requirement to be a member of the EBU or the Subtitles in XML Group.

​Join us

If you are interested in Subtitles in XML, join our group on this topic and participate in the discussions.

EBU Technology & Innovation Workplan

Every two years, the EBU develops a roadmap for technology and innovation activities based on the requirements and inputs given by EBU Members. The result of this roadmap is our bi-annual EBU Technology & Innovation Workplan. Strategic programmes and project groups are set up to focus on specific areas of interest. To access the latest Workplan, click here.

This document contains the formal definitions for metadata elements that can be used within EBU‑TT documents to describe characteristics of the contained subtitle data, thus facilitating interchange between users of an EBU‑TT document.

EBU Timed Text (EBU-TT) is the successor of the EBU STL subtitling format. It supports the production and archiving of subtitles, legacy STL file transcoding and tunnelling, online distribution and live subtitling.

EBU tech-i magazine, Issue 23 tells you how you can produce smarter, introduces future broadcasting architectures, dives into the use of the 700 MHz band, explains how hackers have become 'smart', and more...

Issue 17 of tech-i  looks at UHDTV, with SVT's Per Björkman on the UHD equation, Hans Hoffmann on UHD technology parameters, David Wood on high frame rates, and a report on the recent shoot of the Eurovision Young Dancers.

This article explores some of the whats and hows of Access Services – what do prepared subtitling, live subtitling, audio description, spoken subtitling and visual signing entail ... what kinds of issues emerge when offering access services ... and how can these production and delivery issues be addressed by broadcasters.

XML Files

Informative XML sample and XML Schema files can be found via:

EBU-TT example files

EBU-TT-D XML Schema

Software implementation

We are also aware of the following EBU-TT related open source projects:

More software projects

The EBU collects links to media-related open source software projects: media-related open source software

Related topics