W3C has published a First Public Working Draft for Timed Text (TT) Authoring Format 1.0 — Distribution Format Exchange Profile (DFXP). The draft has been produced by members of the Timed Text (TT) Working Group as part of the W3C Synchronized Multimedia Activity.

The W3C Timed Text Working Group was chartered in January 2003 to "develop an XML-based format used for the representation of streamed text synchronized with other timed media, like audio and video. A typical application is real time captioning of movies on the Web (e.g., integrated in SMIL)."

The W3C Timed Text specification is intended to cover "all necessary aspects of timed text on the Web. Typical applications of timed text are the real time subtitling of foreign-language movies on the Web, captioning for people lacking audio devices or having hearing impairments, karaoke, scrolling news items or teleprompter applications."

The Timed Text (TT) authoring format is a "content type that represents timed text media for the purpose of interchange among authoring systems." Goals for W3C design activity are presented in the second version of the Timed Text (TT) Authoring Format 1.0 Use Cases and Requirements document. Timed text is there defined as "textual information that is intrinsically or extrinsically associated with timing information." The authoring format "simplifies the creation and distribution of synchronized text for use with a multitude of devices, such as multimedia players, caption, subtitle, and teletext encoders and decoders, character generators, LED displays, and other text display devices."

The Distribution Format Exchange Profile (DFXP) Working Draft document specifies a vocabulary and semantics for a distribution format exchange profile (DFXP) of the timed text authoring format. The distribution format exchange profile is intended to be used for the purpose of transcoding or exchanging timed text information among legacy distribution content formats presently in use for subtitling and captioning functions. It provides a standardized representation for a particular subset of textual information with which stylistic, layout, and timing semantics are associated by an author or an authoring system for the purpose of interchange and potential presentation."

A posting from the WG Chair clarifies that the primary intent of the DFXP is "to support interchange among the common features of certain existing distribution formats, such as 3GPP Timed Text, QuickText (Apple), RealText (RealNetworks), SAMI (Microsoft), World Standard Teletext (WST), EIA-608, and EIA-708. Although the DFXP is designed as an authoring format, it is not precluded from being used as a distribution format in its own right, e.g., by implementing native support for the DFXP in a SMIL or other multimedia user agent."

The DFXP specification is expressly designed to meet "only a limited set of requirements established in the Use Cases and Requirements document. In particular, only those requirements which service the need of performing interchange with existing, legacy distribution systems are satisfied. It is intended that a more feature-rich profile, known presently as the Authoring Format Exchange Profile (AFXP), will be developed and published to address the full set of documented requirements."

Bibliographic Information

• Timed Text (TT) Authoring Format 1.0 — Distribution Format Exchange Profile (DFXP). Edited by Glenn Adams (Extensible Formatting Systems, Inc). W3C Working Draft. 01-November-2004. Appendix A presents the Relax NG Schema. Version URL: http://www.w3.org/TR/2004/WD-ttaf1-dfxp-20041101/. Latest version URL: http://www.w3.org/TR/ttaf1-dfxp/.

  Members of the Timed Text Working Group included Glenn Adams, Extensible Formatting Systems, Inc. (chair); Kaes Blom, CWI; Brad Botkin, WGBH; Dick Bulterman, CWI; Michael Dolan, Invited Expert; Gerry Fields, WGBH; Geoff Freed, WGBH; Markus Gylling, DAISY Consortium; Markku Hakkinen, Japanese Society for Rehabilitation of Persons with Disabilities; Sean Hayes, Microsoft; Erik Hodge, RealNetworks; Masahiko Kaneko, Microsoft; George Kerscher, DAISY Consortium; David Kirby, BBC; Thierry Michel, W3C (team contact); David Singer, Apple Computer.

• Timed Text (TT) Authoring Format 1.0 Use Cases and Requirements. Edited by Glenn Adams (Extensible Formatting Systems, Inc). W3C Working Draft. 15-September-2003. Version URL: http://www.w3.org/TR/2003/WD-tt-af-1-0-req-20030915/. Latest version URL: http://www.w3.org/TR/tt-af-1-0-req/. Previous version URL: http://www.w3.org/TR/2003/WD-tt-af-1-0-req-20030515/.