**DRAFT** 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 developing and maintaining new versions of the Timed Text Markup Language (TTML) and WebVTT (Web Video Text Tracks) based on implementation experience and interoperability feedback, and the creation of semantic mappings those languages.

Join the Timed Text Working Group.

End date 30 September 2015
Confidentiality Proceedings are public
Initial Chairs Sean Hayes,
David Singer
Initial Team Contact
(FTE %: 20)
Philippe Le Hégaret,
Thierry Michel, @@tocheck
Mark Sadecki @@tocheck
Usual Meeting Schedule Teleconferences: Weekly
Face-to-face: 1-2 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. 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.
  2. Publish a Recommendation for the WebVTT language, in particular the parts that cover the syntax, semantics, and rendering of subtitles, captions, chapter markers, and textual audio descriptions for speech synthesis. The Group is expected to produce annual updates for the Recommendation with previously specified but now newly supported features by browser vendors.

    In the process of producing the specification, the Group WILL:

    1. Address any issues found in WebVTT: The Web Video Text Tracks Format produced by the Text Text Community Group. Some may be deferred to v.next.
    2. Include all features that have at least two independent and interoperable implementations
    3. Solidify the set of features through the creation of a WebVTT test suite
    4. Consider the adoption of new features
  3. Establish a semantic mapping between TTML and WebVTT in order to facilitate browser implementation and market adoption.
  4. 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
  5. Maintain a simple constrained profile for delivery of closed captions for video content ("Simple Delivery Profile for Closed Captions").
  6. 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.
  7. Produce a technical report (Note) on the application of TTML in live production and streaming such as for video content.

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 recommendations.


Other Deliverables

The Working Group will update the test suites 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.


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 May 2013 N/A July 2013
WebVTT October 2013 N/A January 2014 N/A April 2014 June 2014
TTML in HTML 5 Note August 2013 November 2013 N/A N/A N/A N/A
TTML Live Update Note November 2013 February 2014 N/A N/A N/A N/A
Timed Text Markup Language (TTML) 1.1 February 2014 N/A May 2014 N/A August 2014 September 2014


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

HTML Working Group
The HTML 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 video, audio and video text tracks and their associated APIs.
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.
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 developed the first Community report for the WebVTT format and will continue to explore new features.

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.

The previous charter is also available.

Philippe Le Hégaret, and al.

$Date: 2013-05-14 23:49:43 $