Re: [media] proposed a11y TF letter on issue-152

Please add me to the signatories when/if this letter goes out. Thanks,
Silvia.

Janina

Silvia Pfeiffer writes:
> Hi all,
> 
> in today's call we discussed outstanding issues on the media
> multitrack change proposals, which we would like to see addressed as
> part of accepting proposal 4 on our summary list, see
> http://www.w3.org/WAI/PF/HTML/wiki/Media_Multitrack_Change_Proposals_Summary#Proposal_4:_Controller_proposal
> .
> 
> Below is a draft letter of consensus to be sent to the HTML Working
> Group to help resolve issue-152.
> 
> DEADLINE: this letter will be sent in 24 hours from now, so if you
> disagree with anything stated below, please speak up.
> 
> IMPORTANT: as part of the letter, the individual change proposals 1-3
> on issue-152 are withdrawn, so check if that is in your interest.
> 
> (Note that Ian just added a getID() function, so I was able to remove
> this from our list of discussed changes form today's call.)
> 
> Cheers,
> Silvia.
> 
> 
> Here is the proposed letter:
> 
> ---
> Subject: Accessibility Task Force consensus on Issue-152, media multitrack
> 
> 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.
> 
> However, we request 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
> (is there anyone I've missed or wants to be on that list?)

-- 

Janina Sajka,	Phone:	+1.443.300.2200
		sip:janina@asterisk.rednote.net

Chair, Open Accessibility	janina@a11y.org	
Linux Foundation		http://a11y.org

Chair, Protocols & Formats
Web Accessibility Initiative	http://www.w3.org/wai/pf
World Wide Web Consortium (W3C)

Received on Thursday, 21 April 2011 03:01:48 UTC