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Media--Summary of Technical Requirements Exposed by our User Requirements

From: Janina Sajka <janina@rednote.net>
Date: Tue, 27 Jul 2010 21:13:07 -0400
To: HTML Accessibility Task Force <public-html-a11y@w3.org>
Message-ID: <20100728011307.GJ2478@sonata.rednote.net>
Colleagues:

The following is a summary of the content types and API mechanisms we
have discussed during our last two teleconferences. It is intended as a
summary of the technical requirements our user requirements expose.  As
before,it is intentionally agnostic regarding any particular technology.

Terminology:	Primary Media Resource
		The video and/or audio resource for which users with
disabilities require alternative media renditions because they are unable to
comprehend the primary resource by virtue of disability.

		Alternative Media Resource
		An alternative media rendition of a primary media resource
created to communicate aspects of the primary media resource to persons with
disabilities in a communication medium they can comprehend.

NOTE:	We have begun using these terms because our discussions have required
it. The above definitions are my own. We have not achieved consensus on them.

Alternative Media Types

	Alternative Video:	Used to provide sign translation

				NOTE: If the primary resource contains long sections WITHOUT spoken dialog, the alternative video may be of significantly shorter length than the primary resource.

				Users need to be able to position and resize primary and alternative video on the available display vis a vis one another; If additional displays are available via the host OS, this video should be directable to any of those.

Alternative audio:	Used to provide video description; Extended video description; clear audio

				NOTE: If the primary resource contains almost no sections WITHOUT spoken dialog, the alternative audio may be of significantly shorter length than the primary resource. By definition the extended audio alternative is always longer than the primary media resource.

				Users need to be able to adjust volume and pan position of primary and alternative audio independently of one another; If additional audio output devices are available via the host OS, this audio should be directable to any of those.

	Alternative Text:	Used to provide texted video description; extended texted video description; captions; extended captions; transcripts

				Users require this text be streamable; support styling, semantics, hyperlinks, and timing data (for syncronization with primary media)

				Users need to be able to position and resize text and primary video on the available display vis a vis one another; If additional displays are available via the host OS, this video should be directable to any of those. Users need to be able to choose their preferred fonts and foreground and background colors.

				By definition extended texted video description and extended captions are longer than the primary resource.

Syncronization:	Users require that the primary media resource and their selected alternative media resources remain syncronized during playback and following any navigation within content, whether by structure or time offset.

Content Navigation: Users require the ability to navigate forward and back through primary and alternative media by time or by structure. The structural navigation points may be hierarchically nested, in which case users require the ability to navigate by realtime adjustable nested level.

 
Realtime controls / menus & Configuration Settings

An API providing access to:

Stop/Start
Pause
Fast Forward and Rewind (time based)
time-scale modification control
volume (for each available audio track)
pan location (for each available audio track)
Next and Previous (structural navigation)
Granularity Adjustment Control (Structural Navigation)
Viewport content selection, on screen location and sizing control
Font selection, foreground/background color, bold, etc configuration/selection
Extended descriptions and extended captions configuration/control
Ancillary content configuration/control

Discovery and activation/deactivation of available alternative content by the user

A discovery mechanism and presentation of available alternative media options for user selection.

A discovery mechanism of available OS provided output device options for user selection.


-- 

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 Wednesday, 28 July 2010 01:13:38 GMT

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