- From: Michael(tm) Smith <mike@w3.org>
- Date: Thu, 18 Feb 2010 19:22:39 +0900
- To: public-html@w3.org
We had a one-time telcon on 2010-02-17 to discuss some open
proposals for improving accessibility of HTML media content.
The minutes are copied in below and also available here:
http://www.w3.org/2010/02/17-html-a11y-minutes.html
Attendees
DaveSinger, John_Foliot, PhilippeLeHegaret, MikeSmith,
SilviaPfieffer, EricCarlson, JaninaSajka, FrankOlivier, GeoffFreed
* Topics
1. Multitrack JavaScript API
2. Declarative syntax for associating external text
resources
3. External caption format support
* Summary of Action Items
_________________________________________________________
<silvia> 1. Multitrack JavaScript API
<silvia> Discussion & Agreement
<silvia> Specification:
<silvia> http://www.w3.org/WAI/PF/HTML/wiki/Media_MultitrackAPI
http://www.w3.org/WAI/PF/HTML/wiki/Media_MultitrackAPI
<scribe> scribe: MikeSmith
Multitrack JavaScript API
http://www.w3.org/WAI/PF/HTML/wiki/Media_MultitrackAPI
http://www.w3.org/WAI/PF/HTML/wiki/Media_MultitrackAPI
silvia: can have multiple tracks: caption tracks, subtitle tracks,
etc.
... so far there is no API for the browser to know [how to
differentiate among the various tracks]
... we discussed a declarative way for exposing the tracks to
browsers
... but after discussion, came to conclusion that we need an API
eric: nothing in this API is specific to a11y
... instead it is a general-purpose API [for accessing multiple
tracks]
... so it brings additional value in general, not just for
accessibility
JF: we have an issue in that, e.g., section 508, still have a
requirement that no critical accessibility require Javascript to be
enabled
eric: the accessibility features are in no way dependent on this API
JF: OK, I want to make sure that it's not misconstrued
eric: one of my goals is to make sure that any feature we add inside
the UA -- anything the UA can put into its UI (controller) -- should
also be exposable to script -- so that developers can create
alternative UIs
silvia: agreed about the need for this to be exposable through
script
<silvia> interface MediaTrack {
<silvia> readonly attribute DOMString name;
<silvia> readonly attribute DOMString role;
<silvia> readonly attribute DOMString type;
<silvia> readonly attribute DOMString lang;
<silvia> attribute boolean enabled;
<silvia> ...
<silvia> };
silvia: role = caption, subtitle, etc.
... type=media type
... lang = an IANA language tag
... so we want to get opinions about the propose API
JF: role values are predefined?
silvia: we are, btw, doing some similar work in Ogg along these
lines
<dsinger> how does this intersect with Richard's idea of basing the
media queries on access-for-all ?
eric: I think it does need to be a predefined [enumerated] list of
roles
<dsinger> no, the bus is too noisy
janina: These are synchronized tracks?
silvia: yes
janina: what about structural navigation? is it just FF and rewind?
JF: you thinking about something along the Daisy model?
silvia: chapter-marking mechanism.. that is a meta-structural
mechanism [that would reside on top of this]
eric: QT movies and MPEG4 files do have a chapter-track mechanism to
find named sections of a file
silvia: but the mechanism of moving among [those is outside of the
work we are doing here]
... I think we need to do some more experimentation with this and
then eventually propose it to the HTML WG as an addition to the spec
eric: essentially what we want to do is provide script-level access
to the same set of information that the UA already has
<silvia> 2. Declarative syntax for associating external text
resources
<silvia> Discussion & Agreement
<silvia> Specification:
<silvia>
http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations
http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations
Declarative syntax for associating external text resources
http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations
http://www.w3.org/WAI/PF/HTML/wiki/Media_TextAssociations
[Geoff summarizes the state of current discussion]
silvia: we have to schemes, one that Philip is currently defending,
and one that is based on the wiki link above
<silvia> <video src="video.ogg">
<silvia> <track role="subtitle">
<silvia> <source src="video_sub_en.srt" type="text/srt;
charset='Windows-1252'" lang="en">
<silvia> <source src="video_sub_de.srt" type="text/srt;
charset='ISO-8859-1'" lang="de">
<silvia> <source src="video_sub_ja.srt" type="text/srt;
charset='EUC-JP'" lang="ja">
<silvia> </track>
<silvia> </video>
plh: so how does the track element get exposed to the multitrack
API?
eric: we are in the midst of having a discussion about that now
<silvia> <video src="video.ogv">
<silvia> <track src="subs.de.srt" srclang="de" role="SUB">
<silvia> <track src="subs.sv.srt" srclang="sv" role="SUB">
<silvia> <track src="subs.jp.srt" srclang="jp" role="SUB">
<silvia> </video>
silvia: the above is an alternative that has been proposed
... [the semantics of that would need to be determined and
specified]
eric: clearly the UA would need to have a heuristic for making
choices [among the roles provided]
silvia: If I have my browser prefs set to always display subtitles
in German if they are available, then the UA would play the first
one above
gfreed: what Silvia has described is almost exactly what Real Player
did -- that the user can state a preference of, being able to state
that they want to see captions and in what lang they want to see
those captions
<dsinger> is there an access-for-all spec that uses media queries
already? I know Richard is working on one
janina: the Media Queries through CSS in implemented [in Canada]
through the access-for-all [project? application?]
... the point is the we need a cascading set of choices
eric: Dave Singer and I have started to have a discussion with RichS
about this
janina: I think it's important that we don't want to end up having
multiple [redundant] ways of doing the same thing
<silvia> <video src="video.ogv">
<silvia> <track src="cc.en.srt" srclang="en" role="CC" active>
<silvia> <track src="tad.en.srt" srclang="en" role="TAD">
<silvia> <trackgroup role="SUB">
<silvia> <track src="subs.de.srt" srclang="de">
<silvia> <track src="subs.sv.srt" srclang="sv">
<silvia> <track src="subs.jp.srt" srclang="jp">
<silvia> </trackgroup>
<silvia> </video>
silvia: above is yet another proposal under discussion
... I think within the next week or so we will get agreement amongst
ourselves on the final proposal
gfreed: would this most recent example that you pasted into IRC
allow multiple displays of the same role?
... that is, would I be able to display to subtitle track
simultaneously?
silvia: so the way to do that now would be to take them out of the
trackgroup and just make them tracks
... [because the trackgroup semantics are that it contains
alternatives]
gfreed: my concern is just that we make sure we end up with a way
that does allow display of multiple tracks with the same role at the
same time
silvia: I am confident that we can come up with agreement
eric: I would go so far as to say that it's a requirement [nothing
we spec should prevent multiple tracks of the same role from being
displayed at the same time]
gfreed: I sent an example to the list of how iTunes deals with a
case like this (the specific menu it provides for controlling this)
eric: so what we are working on is making that all configurable
through script, so that authors/developers can provide their own UIs
<dsinger> w3c timed text?
<silvia> 3. External caption format support
<silvia> Discussion & Agreement
<silvia> Proposed:
<silvia> * srt
<silvia> * DFXP
<dsinger> what would be parsing the format? scripts or the UA?
External caption format support
gfreed: I would prefer that we lean toward DFXP, because it's been
vetted and because it's a W3C spec
<dsinger> is there a scripted implementation of DFXP?
gfreed: on the other hand, srt has not been fully vetted and is not
a spec [in the same sense]
... it is true that DFXP is too big [complex] for some
<dsinger> we could recommend both, and give reasons for them?
<frankolivier> yes, there is (at least one) scripted implementation
of dxfp (I have it in my bookmarks somewhere)
<plh> frank, yes there is :)
silvia: I think ultimately what we will end up with is a
subset/profile of DFXP
plh: I did implement DFXP in JS
... which by the way is just called "timed text" too
... I would suggest also that we subset/profile it
<dsinger> it would have to be a profile, agreed, because it needs to
be 'linear', at least
plh: DFXP is currently "stuck" due to a particular feature
<plh>
http://lists.w3.org/Archives/Public/public-tt/2010Feb/0000.html
http://lists.w3.org/Archives/Public/public-tt/2010Feb/0000.html
plh: and the group and chair seemed poised to remove that particular
feature
gfreed: for the greater percentage of captioning and subtitling use
cases, I would agree that DFXP has more features than needed, so it
would make sense to subset/profile it
janina: when we are at Stanford last year, one outcome we discussed
was documenting the list of requirements
silvia: there is in fact a page at the Wiki for that
... I think we don't need to impose a deadline on this, but let the
discussion proceed as it has been
gfreed: It might be useful to schedule a call for two weeks or three
weeks [and try to get PhilipJ on]... particularly if it seems like
we are stuck on e-mail
silvia: yeah, if it seems like we are stuck on e-mail, then would be
good to have another call
... I am not in a hurry to have another call, would suggest that we
consider having one again if/when it seems like we need to
--
Michael(tm) Smith
http://people.w3.org/mike
Received on Thursday, 18 February 2010 10:22:44 UTC