- From: Janina Sajka <janina@rednote.net>
- Date: Tue, 18 May 2010 19:22:14 -0400
- To: HTML Accessibility Task Force <public-html-a11y@w3.org>
The following is a draft. Comments, edits, etc., most welcome. These will be in the Wiki soon, so you may want to follow developments there at the following URI: http://www.w3.org/html/wg/wiki/Accessibility_Requirements_of_Media Sec. 1.10 Content Navigation by Content Structure Most people are familiar with fast forward and rewind in media content. However, fast forward and rewind, because they progress through content based only on time, are ineffective particularly when the content is being used for other than entertainment purposes. People with disabilities are also particularly disadvantaged if forced to rely solely on time-based forward and rewind to study content. Fortunately, most content is structured, and appropriate markup can expose this structure to forward and rewind controls: * Books generally have chapters and perhaps subsections within those * chapters. They also have structures such as page numbers, side-bars, * tables, footnotes, tables of contents, glossaries, etc. * Short music selections tend to have versus and repeating choruses. * Larger musical works have movements which are further dividable by * component parts such as "Exposition, Development, and Recapitulation;" * or "Theme and Variations." * Operas, theatrical plays, and movies have acts and scenes within those * acts. *Television programs generally have clear divisions, e.g. * newscasts have individual stories usually wrapped within a larger * structure called "News, Weather, and Sports." * A lecturer may first lay out the issue, then consider a series of * approaches or illustrative examples, and finally the lecturer's * conclusion. Just as the structures introduced particularly by nonfictional titles make books more usable, media is more usable when its inherent structure is exposed by markup. And, markup-based access to structure is critical for persons with disabilities who possess less ability to infer structure from purely presentational queues. Structural navigation has proven highly effective internationally in various programs of electronic book publication for persons with print disabilities. Nowadays, these programs are based on the ANSI/NISO Z39.86 specifications, (see http://www.daisy.org/daisy-standard). Z39.86 structural navigation is also supported by e-publishing industry specifications (see http://www.idpf.org/). Structural navigation markup must support both global navigation by the larger structural elements of a media work, and also the most localized atomic structures of that work, even though authors may not have marked-up all levels of navigational granularity. Structural navigation must be possible through third-party provided navigational markup files. Structural navigation must keep all content representations in sync, so that moving to any particular structural element in media content also moves to the corresponding point in all provided alternate media representations (captions, described video, transcripts, etc) associated with that work. /end 1.10 Sec. 1.11 Miscellaneous Requirements 1.11.1 Direct Device Control Multiple user devices must be directly addressable. It must be assumed that many users will have multiple video displays and/or multiple audio output devices attached to an individual computer, or addressable via LAN. It must be possible to configure certain types of media for presentation on specific devices, and these configuration settings must be readily overwritable on a case by case basis by users. 1.11.2 Time Scale Modification While all devices may not support the capability, a standard control API must support the ability to speed up or slow down content presentation without altering audio pitch. -- Janina Sajka, Phone: +1.443.300.2200 sip:janina@asterisk.rednote.net Chair, Open Accessibility janina@a11y.org Linux Foundation http://a11y.org Chair, Protocols & Formats Web Accessibility Initiative http://www.w3.org/wai/pf World Wide Web Consortium (W3C)
Received on Tuesday, 18 May 2010 23:22:46 UTC