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Re: Categorization of media a11y requirements

From: Maciej Stachowiak <mjs@apple.com>
Date: Fri, 05 Nov 2010 10:25:24 +0100
Cc: Frank Olivier <Frank.Olivier@microsoft.com>, "public-html@w3.org" <public-html@w3.org>, "HTML Accessibility Task Force (public-html-a11y@w3.org)" <public-html-a11y@w3.org>
Message-id: <2401FBD9-EA3D-4ED5-98F8-198C21E3CCAC@apple.com>
To: Maciej Stachowiak <mjs@apple.com>

On Nov 5, 2010, at 8:50 AM, Maciej Stachowiak wrote:

> (1) What are the kinds of changes needed to the HTML5 spec to support this requirement?

Here is my attempt to answer this question for the following items, based on our discussions yesterday:

> On Nov 4, 2010, at 5:55 PM, Frank Olivier wrote:
>> SPECNEW, SPECCED: (SL-1) Support sign-language video either as a track as part of a media resource or as an external file.

The <track> element currently only supports textual formats; would need to support video format and an appropriate value for the kind attribute. Another possibility is a mechanism to associate two <video> elements to play in sync.

>> SPECNEW, SPECCED: (SL-2) Support the synchronized playback of the sign-language video with the media resource. 

Ditto above.

>> SPECNEW, TRACK: (CC-5) Support positioning in all parts of the screen - either inside the media viewport but also possibly in a determined space next to the media viewport. This is particularly important when multiple captions are on screen at the same time and relate to different speakers, or when in-picture text is avoided.

Timed track rendering section does not seem to have provision for positioning timed text outside the media element or its controls.

>> SPECNEW, TRACK: (CN-1) Provide a means to structure media resources so that users can navigate them by semantic content structure. 

We were not sure whether this is provided for, however, using a <track> element with kind=chapters seems to address this requirement.

>> SPECNEW, UX: (CC-25) Support edited and verbatim captions, if available. 

We thought the <track> element lacked a way to distinguish verbatim and edited captions in the same language, however, it seems like the label attribute may be sufficient to identify caption tracks as edited or verbatim.

>> SPECNEW, UX: (DV-8) Allow the author to provide fade and pan controls to be accurately synchronized with the original soundtrack.

HTML5 does have volume control, but not the ability to pan a soundtrack.

>> SPECNEW: (DAC-5) Non-synchronized alternatives (e.g., short text alternatives, long descriptions) can be rendered as replacements for the original rendered content (UAAG 2.0 3.1.3).

HTML5 spec doesn't seem to have specific provision for a textual alternative (as opposed to captions or a transcript) for a video.

Also, looking closer at the spec, I believe the following items marked SPECCED are actually *not* yet provided for:

>> SPECCED: (CA-1) Support clear audio as a separate, alternative audio track from other audio-based alternative media resources.

There is no provision for the <track> element to reference audio, nor is there an appropriate kind value for clear audio.

>> SPECCED: (DV-4) Support recordings of real human speech as a track of the media resource, or as an external file.

The HTML5 draft has no provision for a video description track in the form of audio rather than text in the <track> element.

And I believe the following 4 items may not actually have HTML5 spec impact:

>> SPECNEW: (CN-6) Support direct access to any structural element, possibly through URIs. [Media fragment-like issue]

Seems addressable through Media Fragments URI: <http://www.w3.org/TR/media-frags/>
Does HTML5 need any changes to adopt this?

>> SPECNEW: (CN-3) 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.

(I don't fully understand this requirement; sounds like maybe it should be in the UX category.)

>> SPECNEW: (CNS-1) All identified structures, including ancillary content as defined in "Content Navigation" above, must be accessible with the use of "next" and "previous," as refined by the granularity control. [May be handled with cue ranges]

(I don't recall why this is a spec requirement rather than UX)

>> SPECNEW: (DAC-2) The user has a global option to specify which types of alternative content by default and, in cases where the alternative content has different dimensions than the original content, how the layout/reflow of the document should be handled. (UAAG 2.0 3.1.2). [Probably minimal spec text required: Media queries would work nicely here; also UX issue (user sets media query to match)]

Seems like this would be an issue for a spec to extend Media Queries; not clear if there is actual HTML5 impact.

If I am correct in these assessments, this would leave us with 9 requirements that have HTML5 spec impact.

Received on Friday, 5 November 2010 09:26:03 UTC

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