Change Proposal: Rely on ISO/IEC 23001-6 to Synchronize Multiple Binary Media Resources

• Author: Janina Sajka (janina at rednote dot net)

JTC1 SC29, the MPEG/JPEG Subcommittee of JTC1, has created a specification for keeping multiple binary streaming media resources in sync over HTTP. This neatly solves a major hole in HTML 5. Adopting reliance on this ISO specification to fill the HTML 5 requirement will also leverage existing standards likely to be adopted by the media industry.

Rationale

The HTML-A11Y Task Force has identified a requirement for alternative media presentations of video and audio resources. These alternative binary resources may be audio (for described video) or video (for sign language translation). This is a critical accessibility requirement currently not solved by HTML 5. Furthermore, it is a requirement internationalization also imposes on HTML 5. While the WG is certainly capable of solving this problem on its own, reusing existing emerging standards from the industry most directly responsible for publishing media over HTTP should, at the very least, be seriously considered.

Details

ISO/IEC 23001-6 provides for a Manifest to declare relevant data for the primary and alternative media resources encompassed by a particular media publication. This manifest would need to be parsed. An example from

http://www.w3.org/WAI/PF/HTML/wiki/Media_Multitrack_Media_API#.281.29_No_markup_in_HTML_-_leave_to_a_manifest_file

For example synchronizing external audio description and sign language video with main video:

<video id="v1" poster=“video.png” controls>
 <source src=“manifest_webm” type=”video/webm”>
 <source src=“manifest_mpg” type=”video/mp4”>
 <track kind=”captions” srclang=”en” src=”captions.vtt”>
</video>

Impact

Will solve the problem with minimal impact on HTML 5 specification documents.

Positive Effects

• Provides an industry consensus mechanism to synchronize media, including media fragments.

Negative Effects

• Does not provide a means for sizing and styling via CSS.

Risks

• An appropriate enumeration of resources is not guaranteed as it requires ISO to correctly meet accessibility requirements identified by the Task Force.

References