- From: Silvia Pfeiffer <silviapfeiffer1@gmail.com>
- Date: Fri, 22 Apr 2011 14:12:41 +1000
- To: HTML Accessibility Task Force <public-html-a11y@w3.org>
(sending this on behalf of the accessibility task force) Dear HTML WG chairs, The undersigned members of the media subgroup of the accessibility task force have come to a consensus on ISSUE-152, which we'd like to share with the larger group through this email. We appreciate the extra time provided to us by the chairs to further discuss the submitted four change proposals and come to an agreement. There have indeed been lengthy discussions during the provided time frame and we have made great progress. The group has come to a consensus on which proposal to support. While some of our feedback on that change proposal has already been taken on board, there is still a list of 5 outstanding changes that need to be addressed for the specification text to be complete. The four proposals on the table are as follows: 1. Audio Track Selecction for Media Element submitted by: Frank Olivier http://lists.w3.org/Archives/Public/public-html/2011Feb/att-0363/CP_Issue152.htm 2. Media Multitrack Change Proposal 2: Synchronize separate media elements through attributes submitted by: Sean Hayes http://www.w3.org/WAI/PF/HTML/wiki/Media_Multitrack_Change_Proposal_2 3. Media Multitrack Change Proposal: Synchronize separate media elements through attributes submitted by: Silvia Pfeiffer and Eric Carlson http://www.w3.org/WAI/PF/HTML/wiki/Media_Multitrack_Change_Proposal 4. Proposal for Audio and Video Track Selection and Synchronisation for Media Elements submitted by: Ian Hickson http://lists.w3.org/Archives/Public/public-html/2011Mar/0436.html CONSENSUS The undersigned members of the media subgroup of the accessibility task force have agreed to withdraw proposals 1-3 in favor of proposal 4 with the following additions to be made to the proposal: (1) track kind for in-band tracks: At this point, it is also not possible to discover the functionality that a in-band track provides through script. A similar problem was solved for the TextTrack object by introduction of a kind attribute. This is also necessary for the TrackList object, in particular to introduce a standard naming scheme across different media container formats for exposing the kind of data that their tracks provide. Therefore, we request addition of a getKind(in unsigned long index) function to the TrackList object, or something of equivalent functionality. The proposed list of values that kind should understand are: for video: * sign language video (in different sign languages as provided through getLanguage()) * captions (as in: burnt-in video that may just be overlays) * different camera angles * video mosaic for audio: * audio descriptions * language dub * commentary (such as director's commentary) * clear audio (see http://www.w3.org/WAI/PF/HTML/wiki/Media_Accessibility_Requirements#Clear_audio) (2) loop attribute for grouped multitrack: The MediaController object currently does not allow for looping of the grouped resource. This is inconsistent with what is possible on individual media elements and also inconsistent with what is possible on in-band multitrack media resources. The same behavior that an in-band multitrack resource exposes on looping needs to also be possible on a grouped multitrack resource. Therefore, we request addition of a loop IDL attribute on the MediaController object. When it is set to true, playback on the grouped multitrack must restart after all slave elements have ended. It is set to true when at least one of the media elements in the group have a loop IDL attribute that is set to true, false otherwise. Alternatively, it would also be acceptable to set it to true only when all of the media elements in the group have a loop IDL attribute that is set to true, though that seems overly verbose. (3) autoplay attribute for grouped multitrack: The MediaController object currently always autoplay without a means to control this autoplay behaviour and without consistent autoplay across all the slave elements. This is inconsistent with in-band multitrack media resources. One of the main use cases for the introduction of autoplay attributes was that this allows the UA to expose a user setting that disables autoplay behaviour, which is particularly useful to vision-impaired users who cannot easily locate autoplaying media elements. Therefore, we request addition of a autoplay IDL attribute on the MediaController object. When it is set to true, playback of the grouped multitrack must start once all slave elements have reached a readyState of HAVE_ENOUGH_DATA and can play through. It is set to true when at least one of the media elements in the group have a autoplay IDL attribute that is set to true, false otherwise. Alternatively, it would also be acceptable to set it to true only when all of the media elements in the group have a autoplay IDL attribute that is set to true, though that seems overly verbose. (4) readyState for grouped multitrack: The MediaController object currently does not expose an aggregate view of the readyState of the slave media elements. It is, however, impossible for a developer to reliably aggregate the readyState from the individual slave media elements, since their states may continue to change. The media framework inside the UA is the only place where such aggregation is sensibly possible. Therefore, we request addition of a readyState IDL attribute on the MediaController object. It must represent the minimum state that all the slave media elements have achieved. (5) onended event: The MediaController object currently does not expose an onended event. This is inconsistent with in-band multitrack media resources and a convenience event that is useful when reacting to the situation of all slave elements being finished. This would for example be the case for a grouped multitrack resource with an ordinary video track and a sign language track, where the ordinary video track should get a display of further related videos once all tracks have finished playing. It would e.g. wait until the sign language track is finished before it displayed further information. Therefore, we request addition of a onended event to the MediaController object. Best Regards, Media Subgroup of the Accessibility Task force Judy Brewer Janina Sajka John Foliot Sean Hayes Frank Olivier Eric Carlson Mark Watson Bob Lund Silvia Pfeiffer
Received on Friday, 22 April 2011 04:13:28 UTC