This Wiki page is edited by participants of the HTML Accessibility Task Force. It does not necessarily represent consensus and it may have incorrect information or information that is not supported by other Task Force participants, WAI, or W3C. It may also have some very useful information.
Media Accessibility Tech Requirements
- 1 Summary of Technical Requirements Exposed by User Requirement
Summary of Technical Requirements Exposed by User Requirement
The following technical requirements are a summary of the content types and API mechanisms that were exposed as consequence of the user requirements. As before, it is intentionally agnostic regarding any particular technology.
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 by Janina. We have not achieved consensus on them.
Alternative Media Types
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.
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.
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.
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.
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.
An API providing access to:
- 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.