**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
between those languages.
Join the Timed
Text Working Group.
|30 November 2015
|Proceedings are public
|Initial Team Contact
(FTE %: 20)
|Philippe Le Hégaret,
|Usual Meeting Schedule
|Teleconferences: Weekly for TTML, and as
needed for WebVTT
Face-to-face: 1-2 per year
This group is chartered to develop formats used for the
representation of text synchronized with other timed media, like audio
and video. Such formats MUST be useable for online media captioning,
should be useable for 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 and MUST be useable in
the context of HTML.
The Group will:
- Publish a Recommendation for a new Timed Text Markup Language
(TTML) 2 specification. In the process of producing this new
revision, the Group WILL:
- Address any issues found during the development of a Simple
Delivery Profile for Closed Captions.
- Consider for adoption features from existing formats, such as
CEA608 or CEA708, or developed by groups such as SMPTE, DECE and
- Produce other technical reports (Notes) on aspects of TTML
processing as appropriate.
- Seek backward compatibility with TTML 1 whenever possible.
- Will provide a mapping with HTML5/CSS3, including describing
TTML intermediate synchronic document as HTML5 document
fragment, and understanding how the presentation syntax and
semantics relate to CSS3.
- As required, produce a test suite for the above.
- Produce an implementation report, based on the test suite
- Publish a Recommendation for the WebVTT language, in particular
the parts that cover the syntax, semantics, and rendering of
subtitles, delivery of metadata, captions, chapter markers, and
textual audio descriptions for speech synthesis. The Group is
expected to produce annual updates for the Recommendation with
previously unspecified features from browser vendors.
In the process of producing the specification, the Group WILL:
- Address any issues found in WebVTT:
The Web Video Text Tracks Format produced by the Web Media
Text Tracks Community Group. Some may be deferred to future
- Include all features that have at least two independent and
- Solidify the set of features through the creation of a WebVTT
- Consider the adoption of new features
The group MAY decide to the use the experimental
license, developed for HTML extensions, for the VTT
Why does this ask for permission to use the experimental license?
The experimental license was approved only for
products of the HTML working group. Though VTT is
often thought of as an HTML extension (notably by the
original author), this work will be going on in the
more appropriate TTML working group, dedicated to
Timed Text, and thus it doesn’t fall automatically
into the approved category. The original version of
the VTT document was developed in a Community Group,
and CG deliverables have a fairly liberal license. The
group is keen to avoid the problem that the CG
output(s) become more used/referenced than the WG
official documents, as a consequence of their more
liberal license: in a sense, this would be encouraging
the very forking that the W3C license normally tries
to avoid. Ideally the CG output(s) are seen as, and
marked as, and understood as, precursors to the WG
output(s), and the WG Recommendation Track documents
are seen as current and are the ones used, referenced,
and so on. By using a liberal license for the WG
document(s), we can avoid having the CG documents be
apparently ‘more attractive’, and thus we can
effectively retire them.
(We note that this work is among the first to move
from Community to Working group, and this issue may
come up again.)
If problems are found with this approach, the group
will use the W3C document license, and try to handle
the transition as gracefully as it can.
- Establish a semantic mapping between TTML and WebVTT in order to
facilitate browser implementation and market adoption.
- Maintain a simple constrained profile for delivery of closed
captions for video content ("Simple Delivery Profile for Closed
Captions") for TTML.
- Maintain TTML 1.
- Publish a text and an image profile of the Timed Text Markup
Language (TTML) appropriate for worldwide subtitling applications,
including dialog language translation, content description, captions
for deaf and hard of hearing, etc., using TTML
Text and Image Profiles for Internet Media Subtitles and Captions
- Produce a technical report (Note) on the application of TTML in
live production and streaming such as for video content.
- Produce a technical report (Note) on
of CEA-608/708 data streams to WebVTT.
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.
The Working Group is expected to demonstrate at least two
interoperable implementations of all available features in the
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
|TTML Live Production and Streaming
|Timed Text Markup Language (TTML) 2
|Text and Image Profiles for Internet
Media Subtitles and Captions
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
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.
- Web and TV Interest Group
- The Web and TV Interest Group provides a forum for Web and TV
technical discussions, review existing work, as well as the
relationship between services on the Web and TV services, and
identifies requirements and potential solutions to ensure that the
Web will function well with TV.
- Web Media Text Tracks Community Group
- This group developed the first Community report for the WebVTT
format and will continue to explore new features.
- Internationalization (i18n) Working Group
The mission of the Internationalization Working Group is
to enable universal access to the World Wide Web and
provide reviews of W3C technologies for
- 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 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.
- Digital Entertainment Content Ecosystem (DECE)
- DECE is a consortium chartered to develop standards for the
digital distribution of premium content.
- DVB Project: Technical Module (DVB-TM)
The DVB Project develops specifications for digital television
systems, which are turned into standards by international standards
bodies such as ETSI or CENELEC. It provides a conduit to other
relevant standardisation activities including MPEG for the purpose
of meeting the objectives of the DVB Project.
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
A Member-only mailing list, email@example.com (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.
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
Votes of the W3C Process Document and includes no voting
procedures beyond what the Process Document requires.
This Working Group operates under the W3C
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
charter is also available.
Proposed by David Singer.
® (MIT , ERCIM , Keio,
All Rights Reserved.
$Date: 2013-12-09 14:10:37 $