Timed Text Working Group Charter

The mission of the Timed Text Working Group, part of the Video in the Web Activity, is to develop W3C Recommendations for media online captioning by maintaining and developing new versions of the Timed Text Markup Language (TTML) based on implementation experience and interoperability feedback.

Join the Timed Text Working Group.

End date 31 January 2014
Confidentiality Proceedings are public
Initial Chair Sean Hayes
Initial Team Contact
(FTE %: 10)
Philippe Le Hégaret,
Usual Meeting Schedule Teleconferences: Weekly
Face-to-face: 2-3 per year


This group is chartered to develop formats used for the representation of streamable text synchronized with other timed media, like audio and video. Such formats MUST be useable for online media captioning, described video (aka video/audio description) and should address the media accessibility user requirements. Such formats MAY also be useable for broadcast production and exchange.

The Group will:

  1. Produce a Second Edition of the Timed Text Markup Language (TTML) 1.0 Recommendation;

    In the process of producing this new edition, the Group WILL:

    1. Address known errata with the 1.0 specification
  2. Produce a simple constrained profile for delivery of closed captions for video content ("Simple Delivery of Closed Captions").
  3. Produce a technical report (Note) on the application of TTML in HTML5 (i.e. the mapping of TTML to HTML5/CSS3).
    1. Describe TTML intermediate synchronic document as HTML5.
    2. Understand how the presentation syntax and semantics relate to CSS3.
  4. Produce a technical report (Note) on the application of TTML in live production and streaming such as for video content.
  5. Publish a Recommendation for a new Timed Text Markup Language (TTML) 1.1 specification to include the Note described above.

    In the process of producing this new revision, the Group WILL:

    1. Address any issues found during the development of a Simple Delivery Profile for Closed Captions.
    2. Consider for adoption features developed by groups such as SMPTE, DECE and EBU.
    3. Produce other technical reports (Notes) on aspects of TTML processing as appropriate.
    4. Address v.next issues deferred during last call.
    5. Seek backward compatibility with TTML 1.0 whenever possible.
    6. As required, produce a test suite for the above.
    7. Produce an implementation report, based on the test suite above.

The new work is expected to be broadly available and should be provided on a timely fashion. This charter features a tightly constrained scope designed to ensure that the Working Group will meet its schedule and objectives.

Success Criteria

The Working Group is expected to demonstrate at least two interoperable implementations of all available features in the specification.


Other Deliverables

The Working Group will update the test suite intended to promote implementations of the above specification(s) and to assess interoperability between these implementations. The Group will also produce an implementation report for each deliverable.

The Working Group may also propose a new charter for follow on work on the specification.


Note: The group will document significant changes from this initial schedule on the group home page.
Deliverable LC Note CR PER PR Rec
Timed Text Markup Language (TTML) 1.0 (Second Edition) N/A N/A N/A July 2012 N/A November 2012
Simple Delivery Profile for Closed Captions Note July 2012 September 2012 N/A N/A N/A N/A
TTML in HTML 5 Note August 2012 November 2012 N/A N/A N/A N/A
TTML Live Update Note November 2012 February 2013 N/A N/A N/A N/A
Timed Text Markup Language (TTML) 1.1 February 2013 N/A May 2013 N/A August 2013 September 2013

Timeline View Summary

  • February - May 2012: Charter definition and resolve errata issues
  • May - July 2012: Incorporate errata into TTML 1.0 Second Edition Edited Recommendation.
  • May - August 2012: Develop Simple Delivery Profile for Closed Captions for video content.
  • May - August 2012: Gather requirements as needed for TTML 1.1.
  • August - November 2012: Develop HTML5 application note, produce first working draft of TTML1.1.
  • November 2012 - February 2013: Live Update TTML, produce second working draft TTML 1.1.
  • February 2013: Last Call Recommendation for TTML 1.1.
  • May 2013: Candidate Recommendation for TTML 1.1.
  • August 2013: Proposed Recommendation for TTML 1.1.
  • September 2013: Final Recommendation for TTML 1.1.


As part of the Video in the Web Activity, the Timed Text Working Group will be represented in the Hypertext Coordination Group.

Dependencies with W3C Groups

CSS Working Group
The work of the Working Group coordinates with this group on presentation and layout issues.
Protocols and Formats Working Group
The PFWG looks at the formal Web technologies (protocols, formats, etc.) from an accessibility perspective.
Web Content Accessibility Guidelines Working Group
This Group aims to make Web content accessible for people with disabilities.

Liaisons with W3C Groups

Scalable Vector Graphics (SVG) Working Group
The Scalable Vector Graphics language allows authors to describe two-dimensional vector and mixed vector/raster graphics. It includes support for multimedia: audio, video and animation.
HTML Working Group
The HTML 5 specification is intended to provide a semantic-level markup language and associated semantic-level scripting APIs for authoring accessible pages on the Web ranging from static documents to dynamic applications. It includes media elements to present audio data, or video and audio data.
Hypertext Coordination Group
The purpose of this group is to identify technical areas where different working groups may overlap, encourage discussion, and to coordinate their work.
Web Media Text Tracks Community Group
This group produces a Community report on the WebVTT format and related.

External Groups

ISO/IEC JTC-1/SC-29 WG 11 Moving Picture Experts Group (MPEG)
This group is developing standards for coded representation of digital audio and video, including MPEG-4.
Society of Motion Picture and Television Engineers (SMPTE)
This organization was founded to advance theory and development in the motion imaging field. SMPTE produced extensions to TTML 1.0 that are part of SMPTE-TT.
European Broadcasting Union (EBU)
EBU is a confederation of national broadcasting organisations, facilitate exchange of audiovisual content. This Group has developed an XML -based format for use in subtitling production and exchange, based on TTML 1.0.
Digital Entertainment Content Ecosystem (DECE)
DECE is a consortium chartered to develop standards for the digital distribution of premium content.


To be successful, the Timed Text Working Group is expected to have 5 or more active participants for its duration. Effective participation to Timed Text Working Group is expected to consume one half-day per week for each participant; one day per week for editors. The Timed Text Working Group will allocate also the necessary resources for building Test Suites for each specification.

Participants are reminded of the Good Standing requirements of the W3C Process.


This group primarily conducts its work on the public mailing list public-tt@w3.org (archive).

A Member-only mailing list, member-tt@w3.org (archive) is available for administrative purposes such as liaison with Member-only Working Groups.

Information about the group (deliverables, participants, face-to-face meetings, teleconferences, etc.) is available from the Timed Text Working Group home page.

Decision Policy

As explained in the Process Document (section 3.3), this group will seek to make decisions when there is consensus. When the Chair puts a question and observes dissent, after due consideration of different opinions, the Chair should record a decision (possibly after a formal vote) and any objections, and move on. This charter is written in accordance with Section 3.4, Votes of the W3C Process Document and includes no voting procedures beyond what the Process Document requires.

Patent Policy

This Working Group operates under the W3C Patent Policy (5 February 2004 Version). To promote the widest adoption of Web standards, W3C seeks to issue Recommendations that can be implemented, according to this policy, on a Royalty-Free basis.

For more information about disclosure obligations for this group, please see the W3C Patent Policy Implementation.

About this Charter

This charter for the Timed Text Working Group has been created according to section 6.2 of the Process Document. In the event of a conflict between this document or the provisions of any charter and the W3C Process, the W3C Process shall take precedence.

Changes from the previous charter:

Philippe Le Hégaret

$Date: 2012/07/25 16:50:04 $