Timed Text Working Group Charter

The mission of the Timed Text Working Group, part of the Video in the Web Activity, is to produce a W3C Recommendation for media online captioning by refining the W3C specification Timed Text (TT) Authoring Format 1.0 — Distribution Format Exchange Profile (DFXP) based in implementation experience and interoperability feedback.

Join the Timed Text Working Group.

End date 31 March 2011
Confidentiality Proceedings are public
Initial Chairs Sean Hayes, David Kirby
Initial Team Contact
(FTE %: 20)
Philippe Le Hégaret
Usual Meeting Schedule Teleconferences: Weekly
Face-to-face: 3-4 per year


This Group is chartered to develop an XML based format used for the representation of streamable text synchronized with other timed media, like audio and video. Such format MUST be useable for online media captioning.

The Group will:

  1. Produce a new revision of the Timed Text (TT) Authoring Format 1.0 — Distribution Format Exchange Profile (DFXP) specification;

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

    1. Substantially modify and simplify the dynamic flow processing feature (marked at risk in the current version) in order to make it usable for roll-up captions/subtitles;
    2. Retain or remove any of the required or optional in the existing specification;
    3. Introduce different conformance levels or profiles, such as for authoring tools, user agents, or basic requirements for an online captioning format.
  2. Produce a test suite, covering all required and optional features;
  3. Produce an implementation report, based on the test suite above.

The new format 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.

Out of Scope

This Group is not chartered to develop new technologies but only to bring the existing Timed Text (TT) Authoring Format 1.0 — Distribution Format Exchange Profile (DFXP) to W3C Recommendation. Therefore, while the Group could decide to remove features based on the interoperability feedback, it is not chartered to introduce new functionalities in the specification, nor is it chartered to substantially modify the existing set of functionalities. As mentioned in the scope section, the only exception will be for the dynamic flow processing feature, which may require substantial modification.


Other Deliverables

The Working Group will produce a test suite intended to promote implementations of the specification and to assess interoperability between these implementations. The Group will also produce an implementation report.

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.
Specification LC CR PR Rec
DFXP 1.0 January 2009 March 2009 June 2009 July 2009

Timeline View Summary

  • September 2008: First teleconference
  • January 2009: Last Call for DFXP 1.0
  • March 2009: Candidate Recommendation for DFXP 1.0
  • June 2009: Proposed Recommendation for DFXP 1.0
  • July 2009: W3C Recommendation for DFXP 1.0


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

Synchronized Multimedia (SYMM) Working Group
The Synchronized Multimedia Integration Language (SMIL) allows authors to describe the temporal behavior of a multimedia presentation, associate hyperlinks with media objects and describe the layout of the presentation on a screen. This Group also defines the SMIL 3.0 smilText extension.
Protocols and Formats Working Group
The PFWG looks at the formal Web technologies (protocols, formats, etc.) from an accessibility perspective.

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.
CSS Working Group
The work of the Working Group coordinates with this group on presentation and layout issues.
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.

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.
The Society of Motion Picture and Television Engineers (SMPTE)
This organization was founded to advance theory and development in the motion imaging field.
The 3rd Generation Partnership Project (3GPP)
The scope of 3GPP is to produce globally applicable Technical Specifications and Technical Reports for a 3rd Generation Mobile System. Among others, it produced a timed text binary format (3GPP TS 26.245).
The Internet Captioning Forum (ICF)
This organization addresses the technical challenges presented by online video repurposed from broadcast or other previously captioned sources, as well as video created specifically for the Web.


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.

Please also see the previous charter for this group.

This charter was extended from end of December 2099 to end of March 2011.

Philippe Le Hégaret

$Date: 2011/03/11 15:51:38 $