Re: 48-Hour Call for Consensus (CfC): Comments on WebVTT--Quick Responses Needed

(As author of the response, do I still +1?)

JF

On Thu, Jan 25, 2018 at 3:16 PM, Janina Sajka <janina@rednote.net> wrote:

> Colleagues:
>
> This is a Call for Consensus (CfC) to the Accessible Platform
> Architectures (APA) Working Group on our review of the WebVTT
> specification as requested at:
>
> https://lists.w3.org/Archives/Member/w3c-archive/2017Dec/0107.html
>
> Please note these are comments following on work in response to PF-WB
> comments from 2015.
>
> Please note also that the draft comments below cover some similar issues
> present in our current
> CfC on TTML Profiles:
>
> http://lists.w3.org/Archives/Public/public-apa-admin/2018Jan/0000.html
>
>
> <Begin draft comments>
>
> *Item #1 Users of Magnification:*
>
> The bug-tracker indicates the following response(s):
>
>   * Snap to flag (assumption: snap-to-lines flag)
>
>      -> Concern: the concern is likely that if text is explicitly
> positioned on certain lines, there is potential that enlarging the text may
> lead to text growing outside the rendering area (e.g. text positioned in
> the top-most line), or successive lines may grow into each other.
>
>      -> Reply: First we have to understand that when content is enlarged,
> the video is typically enlarged together with the text. Therefore, the
> occurrance of this problem is rare. Secondly, there is a conflict between
> authoring requirements and rendering limitations. The browser rendering
> algorithm will [adjust?] as well as it can, but once text breaks out of the
> video rendering boundaries, there is not much it can do.
>
>      -> APA Response: APA recognizes the technical constraints noted here
> with regard to rendering limitations. Authoring Guidance recommendations
> should nonetheless indicate the potential of this problem, and urge content
> authors to strive to have captions (etc.) be no greater than 50% of the
> default width of the viewport (which would allow for a text increase of
> roughly 200% without clipping). APA notes that for low-vision users, even
> at full-screen, those users may still need to enlarge the caption text to
> meet their reading needs.
>
>
>   * Sizing of the captions rendering area
>
>      -> Concern: the concern is likely that the display area of captions is
> limited to the background area of the video element it is rendered onto and
> that with magnification the captions may go outside this rendering area.
>
>      -> Reply: The area outside the video element is no usable to render
> captions onto (think about full-screen mode, or if the video is on a Web
> page there is other content around the video element). Therefore, after
> having done all it can to try and retain visibility of all caption text,
> the browser will hit the limit of what it can do.
>
>      -> APA Response: APA again recognizes the technical constraints noted
> here with regard to rendering limitations. We once again recommend good
> authoring guidance to ensure that content authors are aware of the
> potential issue raised, so that authoring decisions regarding line-lengths
> and amount of caption text rendered on screen at any single instance can be
> made with this knowledge.
>
>
>   * Visibility of captions when text is zoomed
>
>      -> Concern: the concern is likely about what happens when the text is
> zoomed, but the video isn't.
>
>      -> Reply: If there are tools that do this, then you will hit the
> issues of overlapping text and disappearing text when hitting the
> boundaries of the rendering area faster than normal. However, it is
> unlikely that a tool would exist that zooms just the text and not the video
> element on screen. Normally, all content on a Web page is zoomed when
> magnification or zooming tools are in use.
>
>      -> APA Response: It was APA's understanding that one of the benefits
> of WebVTT was that it could be further styled by the content author using
> CSS. User stylesheets today provide the ability for users to modify and
> enlarge onscreen text, and tools and browser extensions exist today to
> accomplish this task.
>
> The presumption that video content would be zoomed to the same level of
> caption text is, from APA's perspective, unfounded and incorrect, and the
> emergent WCAG 2.1 specifically will have a new Success Criteria (Success
> Criterion 1.4.12 Text spacing -
> http://rawgit.com/w3c/wcag21/master/guidelines/index.html#text-spacing)
> which currently notes that caption files (when supplied as stand-alone
> time-stamped documents) are covered by this SC. Please also see:
> https://rawgit.com/w3c/wcag21/text-spacing/understanding/21/
> text-spacing.html
>
> > Normally, all content on a Web page is zoomed when magnification or
> zooming tools are in use.
>
> Respectfully, this is factually incorrect. Browser-based zoom traditionally
> operates like this, however other Assistive Technology tools may only zoom
> a part of the whole web page, or may only apply zoom to text (and/but not
> imagery). Some user-agents and platforms also allow for end-user font
> magnification (for example, on the Android platform, individual users can
> choose from different default font sizes, that are applied to all on-screen
> content.
>
> APA again recognizes the technical limitations noted here with regard to
> rendering limitations, and strongly recommends that appropriate authoring
> guidance to address all 3 related issues noted here be included (directly)
> in the Recommendation.
>
> ----------
>
> *Item #2: The spec should include feature explanations in plain language*
>
>      -> Reply: no change, we rely on external documents to provide an
> authoring guide.
>
>      -> APA Response: There are actually 2 responses here.
>
> The first is related to an on-going request from APA that W3C Technical
> Recommendations also include, when and where necessary, prose summaries in
> "plain english" that explain features and functions of the various parts
> of any given spec. The intent here is to explain what is happening with the
> technology in lay terms, rather than explain how to create content using
> the technology. (i.e.: don't just show an API [sic], explain it.) This
> remains an important request from APA, but is not a blocking issue.
>
> The second response is related to Authoring Guidance documents (referenced
> in your reply). Following up on the Bug Tracker, it shows a link to an
> authoring guidance document (
> https://docs.webplatform.org/wiki/concepts/VTT_Captioning), yet that URL
> returns a 404 today.
>
>    - Has this document been relocated elsewhere? If yes, can we please have
>    the reference URL. If no, does the WG plan on updating/recreating this
>    document? (This also ties-back to Item #1)
>
>    - The current WebVTT Working Draft (https://www.w3.org/TR/webvtt1)
>    currently has 'editorial guidance' as part of the normative
> specification
>    addressing privacy and security, and APA's request is that editorial
>    guidance for accessibility considerations also be provided in the same
>    fashion (i.e. directly in the Rec, as opposed to linking out.)
>
>
> APA would be please to assist in the review of any authoring guidance that
> emerges from the WebVTT WG.
>
> ----------
>
> *Item #3: Captions on the audio element*
>
>      -> Reply: fixed, explanations added.
>
>      -> APA Response: Thank you.
>
>
>
> APA trusts this meets your request, and we are happy to further elaborate
> on any of these issues as required.
>
> <End Draft Comments>
>
> *       ACTION TO TAKE
>
> This CfC is now open for objection, comment, as well as statements of
> support via email. Silence will be interpreted as support, though
> messages of support are certainly welcome.
>
> If you object to this proposed action, or have comments concerning this
> proposal, please respond by replying on list to this message no later
> than 23:59 (Midnight) Boston Time, Monday 29 January.
>
> APA Tracking Notes
>
> These comments reiterate requirements published in the W3C Note: Media
> Accessibility User Requirements (MAUR):
> http://www.w3.org/TR/media-accessibility-reqs/#captioning
>
> Inasmuch as similar comments to TTML have been Under an APA CfC, that TTML
> CfC will now be extended to expire with this CfC:
> http://lists.w3.org/Archives/Public/public-apa-admin/2018Jan/0000.html
>
> The WebVTT comments in this CfC were drafted for APA by John Foliot and
> are in sync with our
> TTML comments referenced above:
> http://www.w3.org/WAI/APA/track/actions/2162
>
> Further APA discussion is logged at:
> http://www.w3.org/2018/01/24-apa-minutes.html#item05
>
> Janina
>
>
> ------------------------------------------------------------
> ------------------
>
> Janina Sajka
>
> Linux Foundation Fellow
> Executive Chair, Accessibility Workgroup:       http://a11y.org
>
> The World Wide Web Consortium (W3C), Web Accessibility Initiative (WAI)
> Chair, Accessible Platform Architectures        http://www.w3.org/wai/apa
>
>
> Here is my proposed feedback to the Timed Text Working Group:
>
>
>
> <draft-feedback>
>
>
>
>    1. While we appreciate that TTML Profiles for Internet Media Subtitles
>    and Captions 1.1 <https://www.w3.org/TR/ttml-imsc1.1/> is depending on Timed
>    Text Markup Language 2 (TTML2) <https://www.w3.org/TR/ttml2/>, it
>    should still include an introduction that guides the reader to a better
>    understanding of its content.  Such an introduction could respond to the
>    following questions:
>       1. Why are profiles needed for text-only and image-only
>       captions/subtitles?
>       2. What are typical use cases for a image-only captions/subtitles?
>       3. What is the purpose of a presentation processor, and a
>       transformation processor?
>
>
>
>    1. There is a general issue with the way that an author specifies
>    layout characteristics of captions and subtitles, such as font size, font
>    family, line height, background and positioning.  The spec describes the
>    approach of the author specifying a “fixed layout” for captions and
>    subtitles that the user cannot change.  However, it must be possible for
>    the user to overwrite the author’s choice of font size, or background
>    color, for example. This is necessary for accessibility reasons, in the
>    same way that browsers allow the user to change font size and background
>    color.  How can we find a good solution for these conflicting interests
>    between author and user?  We would like to get into a discussion with you
>    on this issue.
>
>
>
>    1. Section 2 Documentation Conventions (applies also to Timed Text
>    Markup Language 2 (TTML2) <https://www.w3.org/TR/ttml2/> section 2.3).
>    For accessibility of the spec, information such as whether an element is
>    deprecated or obsoleted should not be indicated by color (or background
>    color) alone (cf. WCAG 2.0 SC 1.4.1
>    <https://www.w3.org/WAI/WCAG20/quickref/#visual-audio-contrast-without-color>).
>
>
>
>
>    1. Section 5.1 General. The method of associating a text profile
>    document instance with an image profile document instance should be
>    specified for interoperability reasons, and not be left open to the
>    specific implementation.  Also, the association should be in both ways,
>    i.e. also from the image profile document instance to the text profile
>    document instance.
>
>
>
>    1. Section 6 Supported Features and Extensions. All font-related
>    features are prohibited for the image profile. This seems to be an
>    unnecessary restriction if the image profile contains images in SVG format
>    which could be rendered differently based on the author’s choice of font
>    characteristics.
>
>
>
>    1. Section 7.7.3 itts:forcedDisplay. This seems like a temporary
>    solution. Wouldn’t it be better to define semantic layers of information
>    that each could be made visible and invisible at runtime as appropriate for
>    the user?  For example, the user may want to see either speech-only
>    (subtitles), narration speech only (parts of subtitles), foreign-language
>    speech-only (parts of subtitles) or any combination of them.
>
>
>
>    1. Section 7.7.4 itts:altText.  While we see this feature as useful
>    for accessibility purposes, it should be mandatory for images rather than
>    recommended only. As mentioned in the spec, one could take the pertaining
>    text passage from the text profile document instance – but (1) an
>    accompanying text profile is not required, and (2) the alternative text for
>    the image could be different from the textual caption. Therefore, the
>    itts:altText element should always be specified, but it should be empty for
>    decorative images (not clear if a “decorative image” used as a caption
>    makes sense anyway). By requiring an itts:altText for every image, but
>    allowing for an empty element in case of a decorative image, we would align
>    it with the alt attribute in HTML5 for images.
>
>
>
> </draft-feedback>
>
>
>
> Best regards,
>
> Gottfried
>
>
>
> -----Ursprüngliche Nachricht-----
> Von: Accessible Platform Architectures Working Group Issue Tracker [mailto:
> sysbot+tracker@w3.org]
> Gesendet: Mittwoch, 18. Oktober 2017 09:29
> An: public-apa@w3.org
> Betreff: apa-ACTION-2152: Review ttml profiles for internet media
> subtitles and captions 1.1 https://www.w3.org/tr/ttml-imsc1.1/
>
>
>
> apa-ACTION-2152: Review ttml profiles for internet media subtitles and
> captions 1.1 https://www.w3.org/tr/ttml-imsc1.1/
>
>
>
> http://www.w3.org/WAI/APA/track/actions/2152
>
>
>
> Assigned to: Gottfried Zimmermann
>
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-- 
John Foliot
Principal Accessibility Strategist
Deque Systems Inc.
john.foliot@deque.com

Advancing the mission of digital accessibility and inclusion