Subtitling

Helps Members with subtitling for multiple platforms by exchanging best practice and standardizing formats

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 Timed Text Group 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, DVB TTML Subitling 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 Timed Text group, 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 EBU Timed Text Group.

​Join us

If you are interested in subtitles, 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.

We are aware of the following parties supporting EBU-TT and/or IMSC in products/tools.*

EBU-TT Part 1

EZtitles - Subtitling software that can be purchased or rented.

Subtitling Conversion Framework (SCF) - A set of open source modules for converting subtitle formats.

EBU-TT Part 2

Subtitling Conversion Framework (SCF) - A set of open source modules for converting subtitle formats.

Subito - Captioning platform from Red Bee

EBU-TT-Live (part 3)

EBU-TT Live Interoperability Toolkit - A set of components for generating, testing and distributing subtitle documents in the EBU-TT Live format.

FAB Subtitler - Supports EBU-TT-Live for the creation of (live) subtitles.

Subito - Captioning platform from Red Bee

EBU-TT-D / IMSC

(Note: With IMSC we refer to the IMSC Text-only Profile - IMSC support implies EBU-TT-D support, as it is a subset of the former.)

AppleTV and iOS - play back IMSC in fragmented MP4.

BBC's HTML Standard Media Player - plays back EBU-TT-D.

dash.js - A reference client implementation for the playback of MPEG DASH via JavaScript and compliant browsers. Suppports IMSC.

EZtitles - Subtitling software that can be purchased or rented, supports EBU-TT-D.

FAB Subtitler - Can export in EBU-TT-D and IMSC.

Flow - A product from Limecraft that can export EBU-TT-D.

GStreamer TTML subtitling package - A means for the open source GStreamer pipelines to parse and render EBU-TT-D (TTML) subtitles.

ICE reference QC player - Marquise Technologies

imscJS - A JavaScript library for rendering IMSC1 Text and Image Profile.

Subcheck - A commercial service from the IRT for validating IMSC subtitling files (beta version free for a limited period of time).

Subito - Red Bee supports EBU-TT-D using Subito's conversion & delivery engine.

Subtitling Conversion Framework (SCF) - A set of modules for converting subtitle formats.

take1 - Providing EBU-TT-D subtitles to a leading broadcaster.

VLC - The versatile media player has support for TTML, especially EBU-TT-D and IMSC.

If you are supporting EBU-TT and/or IMSC in your product(s) and would like to be added, send us an e-mail via: tech@ebu.ch Likewise, if you spot an error in the list, please let us know via tech@ebu.ch too.

* Disclaimer Above list of parties providing EBU-TT/IMSC products/tools is based on information provided by these organisations themselves, such as publicly available product specifications. Please note that the EBU does NOT verify conformance of the implementations. Inclusion in the list also does NOT mean the EBU recommends the party or its product(s)/tool(s). Users should verify the suitability of any product/tool themselves. Where tools have no clear company owner, the tool name is used.

XML Files

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

EBU-TT example files

EBU-TT-D W3C XML Schema - Informative EBU-TT-D XML Schema to support the implementation of EBU Tech 3380.

IRT EBU-TT-D Application Samples - EBU-TT-D sample files, related PNG images and mp4 videos showing how they should be rendered.

EBU launches NLE user group

See EBU-TT @ IBC

EBU-TT subtitling goes live

Subtitling Symposium "SUBTECH 1"

On 24 and 25 May 2018, the IRT is organizing a symposium on subtitling technology, where you can meet engineers and technical experts form standards organizations, studios, broadcasters, subtitling vendors, etc. More information is available here.

For Public Service Media access services such as subtitling are very important. The formats used for its creation and distribution are evolving and converging around IMSC.

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.

Related topics