The mission of the Timed Text Working Group 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.
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 SHOULD:
- Publish a Recommendation for a new Timed Text Markup Language 2 (TTML2) specification. In the process of producing this new revision, the Group SHOULD:
- 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 EBU.
- Consider backward compatibility with TTML1 such as:
- A conforming TTML1 content document instance is a conforming TTML2 content document instance.
- A conforming TTML2 processor processes a conforming TTML1 content document instance such that the output produced by the TTML2 processor is within the variations allowed per TTML1; however, it may emit warnings if it encounters deprecated features.
- Facilitate mapping to HTML5/CSS3.
- Should address the Media Accessibility User Requirements.
- Publish Recommendations of new versions of TTML Profiles for Internet Media Subtitles and Captions 1.0.1 (IMSC1.0.1) and TTML Profiles for Internet Media Subtitles and Captions 1.1 (IMSC1.1) specifications subtitle and caption delivery applications worldwide, including dialog language translation, content description, captions for the deaf and hard of hearing, based on TTML Profiles for Internet Media Subtitles and Captions 1.0 (IMSC1), W3C Recommendation 21 April 2016.
- 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 have a maintenance process that produces new versions of WebVTT annually, potentially adding new features to the specification. In the process of producing the specification, the Group SHOULD:
- Maintain TTML1 and IMSC1 Recommendations as needed.
- Produce other technical reports (Notes) on aspects of TTML processing as appropriate.
- Liaise with other organisations including but not limited to those listed in § 3.2.
- Investigate caption format requirements for 360 Degree, AR and VR video content.