W3C home > Mailing lists > Public > public-tt@w3.org > January 2018

[imsc1.1] Comments from APA

From: Janina Sajka <janina@rednote.net>
Date: Tue, 30 Jan 2018 09:55:10 -0500
To: public-tt@w3.org
Cc: Accessible Platform Architectures Administration <public-apa-admin@w3.org>, W3C WAI Accessible Platform Architectures <public-apa@w3.org>
Message-ID: <20180130145510.GH16383@rednote.net>
Colleagues:

The Accessible Platform Architectures (APA) Working Group has reviewed
your FPWD and offers our comments below.

According to APA process, the formal APA decision on these comments is
logged at:
http://lists.w3.org/Archives/Public/public-apa-admin/2018Jan/0008.html


Janina Sajka, APA Chair

<Begin comment>

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:

a.	Why are profiles needed for text-only and image-only captions/subtitles?
b.	What are typical use cases for a image-only captions/subtitles?
c.	What is the purpose of a presentation processor, and a transformation processor?

2.	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. 

3.	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> ). 

4.	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.

5.	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.

6.	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. 

7.	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.

<End Draft Comment>

*       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, Tuesday 23 January.

Janina
 
 APA Tracking Notes

apa-ACTION-2152:
 Assigned to: Gottfried Zimmermann
https://www.w3.org/tr/ttml-imsc1.1/

Draft comments by Gottfried:
http://lists.w3.org/Archives/Public/public-apa/2017Nov/0008.html


------------------------------------------------------------------------------

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 [1]TTML Profiles for Internet Media
       Subtitles and Captions 1.1 is depending on [2]Timed Text Markup
       Language 2 (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:

    a. Why are profiles needed for text-only and image-only
       captions/subtitles?
    b. What are typical use cases for a image-only captions/subtitles?
    c. What is the purpose of a presentation processor, and a
       transformation processor?


    2. 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.


    3. Section 2 Documentation Conventions (applies also to [3]Timed Text
       Markup Language 2 (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. [4]WCAG 2.0 SC 1.4.1).


    4. 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.


    5. 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.


    6. 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.


    7. 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.

   </end comments>


-- 

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
Received on Tuesday, 30 January 2018 14:56:08 UTC

This archive was generated by hypermail 2.3.1 : Tuesday, 30 January 2018 14:56:10 UTC