[Bug 24860] New: When can user agents honor the user preferences for automatic text track selection

https://www.w3.org/Bugs/Public/show_bug.cgi?id=24860

            Bug ID: 24860
           Summary: When can user agents honor the user preferences for
                    automatic text track selection
           Product: HTML WG
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: CR HTML5 spec
          Assignee: robin@w3.org
          Reporter: hbbtvjon@gmail.com
        QA Contact: public-html-bugzilla@w3.org
                CC: public-html-admin@w3.org

This issue is raised on behalf of HbbTV - see http://www.hbbtv.org, an
organisation specifying the use of web technologies in television receivers.
HbbTV is in the process of adding the HTML5 video element to its specification.
The current HbbTV specification uses the <object> element for presenting video
in an HTML page.

The current HTML5 specification defines two circumstances under which automatic
track selection for text tracks happens.

1) "When a media element is popped off the stack of open elements of an HTML
parser or XML parser, the user agent must honor user preferences for automatic
text track selection, populate the list of pending text tracks, and set the
element's blocked-on-parser flag to false." and

2) "When a text track corresponding to a track element is added to a media
element's list of text tracks, the user agent must queue a task to run the
following steps for the media element:" ... "Honor user preferences for
automatic text track selection for this element."

This language can be interpreted as only permitting user agents to honor "the
user preferences for automatic text track selection" in these two
circumstances. It can also be interpreted as saying that, while it is required
in these two circumstances, it could happen at other times as well.

We have a use-case for user preferences to be honored at other times.
Specifically, TV receivers normally come with a remote control that includes a
subtitle button. The user can press this button at any time. When watching
normal TV, this will either 1) toggle subtitles on or off or 2) will bring up a
TV receiver specific UI to enable the user to set preferences to subtitles.
Many believe that the user should get a consistent experience when they press
the subtitle button regardless of whether the video being shown is classic
broadcast TV or video presented via an HTML5 video element. This requires that
the user agent can disable and enable text tracks on the request of the user
without the app being involved.

Given this use-case, we would appreciate your feedback about whether the HTML5
specification permits honoring the user preferences for automatic text track
selection in circumstances other than the two listed in the specification, such
as the end-user pressing a subtitle button on a TV remote control.

If it doesn't permit honoring the user preferences in other circumstances, can
it be changed to permit this?

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Received on Friday, 28 February 2014 15:49:23 UTC