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{minutes} TTWG Meeting 21/8/2014

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 21 Aug 2014 15:05:33 +0000
To: TTWG <public-tt@w3.org>
Message-ID: <D01BC8FF.10709%nigel.megitt@bbc.co.uk>
Minutes available in HTML format at http://www.w3.org/2014/08/21-tt-minutes.html

Reminder: there will be no meeting on August 28.

In text format:


      [1] http://www.w3.org/

                               - DRAFT -

                Timed Text Working Group Teleconference

21 Aug 2014

   See also: [2]IRC log

      [2] http://www.w3.org/2014/08/21-tt-irc


          Mike, nigel, Pierre, Courtney, jdsmith, Frans_EBU





     * [3]Topics
         1. [4]This meeting
         2. [5]Geneva F2F meeting
         3. [6]Action Items
         4. [7]Issues
         5. [8]IMSC 1 issues
         6. [9]Change Proposals
     * [10]Summary of Action Items

   <trackbot> Date: 21 August 2014

This meeting

   <scribe> scribeNick: nigel

   group: no AOBs to raise

   mike: regrets for me for Sep 4 meeting

   nigel: Let's set aside 1 hour for our 4th September meeting

Geneva F2F meeting

   RESOLUTION: We will proceed with the Geneva F2F meeting as

   pal: Based on the attendees I suggest we take 2-3 hours on day
   2 morning to resolve any issues on IMSC 1 in prep for LC.

   nigel: We have more folk interested in VTT attending on day 1
   than on day 2 so that makes sense to me.

   pal: I may have to duck out on 2nd day afternoon for some SMPTE

   mike: I plan to try to be there both days. On day 2 at 1700
   local time there's a meeting I need to be at but we should have
   finished by then.

   nigel: Anything else to squeeze into the agenda as well as the
   TTML <--> WebVTT and IMSC 1 work?

   group: nothing to add.

   nigel: We need to think about the structure of the TTML <-->
   WebVTT part - I've added some thoughts, but please could all
   consider this and make any proposals first on the reflector,
   and then we can
   ... make them more concrete on the wiki page.

   frans_EBU: We're okay to use the EBU canteen on an ad hoc basis
   - it won't be a served meal.

   nigel: So the only cost for attendance is food at EBU, travel
   and accommodation - there's no other attendance fee.

Action Items


   <trackbot> action-319 -- Nigel Megitt to Draft liaisons to
   relevant organisations for imsc 1 timeline -- due 2014-08-21 --


     [11] http://www.w3.org/AudioVideo/TT/tracker/actions/319

   mike: Both SMPTE and DECE messages were transmitted. Response
   will probably be after the Geneva meeting.

   frans_EBU: I can confirm I received the EBU message and will
   forward it today.

   close action-319

   <trackbot> Closed action-319.


   <trackbot> action-323 -- Nigel Megitt to Update issue-263 to
   target product ttml2 and open a new one on sdp-us. -- due
   2014-08-21 -- PENDINGREVIEW


     [12] http://www.w3.org/AudioVideo/TT/tracker/actions/323

   nigel: I completed this.

   close action-323

   <trackbot> Closed action-323.


   <trackbot> action-320 -- Glenn Adams to Review
   [13]https://www.w3.org/wiki/ttml/codecsregistry w.r.t. recent
   ttml2 changes in profile definition mechanisms -- due
   2014-08-21 -- OPEN

     [13] https://www.w3.org/wiki/ttml/codecsregistry


     [14] http://www.w3.org/AudioVideo/TT/tracker/actions/320


   <trackbot> action-322 -- Jerry Smith to Indicate preference for
   updating sdp-us for ttml2 -- due 2014-08-21 -- OPEN


     [15] http://www.w3.org/AudioVideo/TT/tracker/actions/322

   jdsmith: Still working on that one. Hopefully will do so in the
   next few days.


   <trackbot> action-324 -- Glenn Adams to Draft a note for imsc 1
   progressivelydecodable to make concrete what authors should
   take into account -- due 2014-08-21 -- OPEN


     [16] http://www.w3.org/AudioVideo/TT/tracker/actions/324

   glenn: My email earlier was related to this.

   pal: We agreed that within <head> it is not required to
   dereference forward references while parsing?

   glenn: That's correct.
   ... The dereferencing process only occurs during the synchronic
   flow processing process as currently defined, generally done
   after the whole document has been processed.
   ... It could be done as an optimisation during processing of
   the <body> but elements spread out throughout the whole
   document may select into the same region;
   ... If they're ordered temporally then you would be able to
   perform the synchronic processing once you get to a time you
   know is later than the time of the elements
   ... currently being considered for inclusion in the synchronic
   ... So the only consideration is times.
   ... My message earlier today related to the styles portion.
   There doesn't seem to be an ordering dependency there.

   pal: If you order the style elements in order in <head> you
   don't have to wait until the end of <head> to compute your
   final style properties.

   glenn: You never do that until you process the content
   elements, and that doesn't occur until you perform the
   synchronic processing step.

   pal: So if style id="a" references style id="b" then I need to
   see both, for a parsing simplicity aspect.

   glenn: That's an optimisation but not predicated by anything in
   the spec. It doesn't matter if they're ordered or not; the
   optimisation may not be possible if they're not ordered.

   pal: The purpose of the flag is to indicate that the
   optimisation is possible.

   glenn: In that case it should be named "pre-optimised" or

   pal: yes, it's a head optimisation thing.

   glenn: It's a small optimisation.

   pal: I agree with this assessment. It's called
   progressivelyDecodable in CFF-TT but if there's a consensus on
   a different name we could consider that.

   glenn: We should keep the name but have a note that points out
   what I said about styles.

   pal: I'm happy to have that note. Is that all of the note or
   would there be other stuff?

   glenn: That's all I'd comment on.

   pal: You can move the action to me then. The note will indicate
   that the ordering of style in head is not necessary for
   progressive presentation but is an optimisation of the head

   glenn: There are only 2 types of forward referencing: 1.
   Chained styles with xml:id; 2. Temporal ordering of elements.
   Then I'd explain that dereferencing style elements is
   technically only required after <head> is fully parsed.
   ... In the case of a non-linear ordering it might prevent an
   optimisation prior to completing parsing of the head element.

   nigel: I've reassigned that action to pierre.

   pal: Just to confirm, the only xml:id referencing that impacts
   ordering is the style one - is that your conclusion?

   glenn: Yes, in TTML1. Region is the other thing that makes
   references, but only from body elements to region elements in
   the head, so the definition always precedes the usage.
   ... TTML2 will be a little more complicated due to out of line
   animation plus potential link elements.

   mike: The assumption in DECE has always been that it's after
   the parsing of head that we need to worry about most.



   <trackbot> issue-334 -- Misuse of style property
   characteristics with ttp:progressivelyDecodable -- pending


     [17] http://www.w3.org/AudioVideo/TT/tracker/issues/334

   pal: this needs review by Glenn.

   glenn: sounds good, we can close this.

   close issue-334

   <trackbot> Closed issue-334.

   glenn: Is progressivelyDecodable a parameter or a metadata

   pal: It's ittp:

   glenn: It's sort of borderline between parameter and metadata.
   It's potentially usable by a processor so I can accept it's a

   mike: Agree - it changes the decoding approach for the


   <trackbot> Issue-303 -- Permit HTML-style <a> elements to
   contain href links -- open


     [18] http://www.w3.org/AudioVideo/TT/tracker/issues/303

   nigel: This has only been discussed in relation to the WAI/PF
   Media Accessibility Requirements, which in the Enhanced
   Captions requirements state that a link mechanism should be

   glenn: I'm working on a more generic mechanism for expressing
   links and ruby rather than opening it up for everything.
   ... I'm thinking about adding an attribute to <span> which may
   work a bit like the class attribute, with a string of one or
   more tokens, that adds semantics onto span
   ... such as 'this is a ruby span', 'this is an anchor/link
   span' etc. It turns out that Apple has added support for ruby
   in TTML using a ruby token to span
   ... It seems to me that the same approach could be applied to
   link. Just thinking about that.

   Courtney: I want to clarify: we have a proposal for doing it
   that way for the iTunes Timed Text Format, derived from TTML.
   We did that
   ... because the ruby tag isn't in TTML. There are benefits to
   using it as a ruby tag - we'd have consistency with other
   ... If we could add the ruby tag into TTML2 then I think Apple
   would use that instead.

   glenn: This could be a useful side-discussion at the F2F. We
   already have a relatively complex process for translating
   ... from TTML into HTML so it wouldn't be difficult to
   translate from a marked up span to the equivalent HTML.
   ... From a specification and schema perspective it's easier not
   to define new element types, but I'm willing to consider both
   ... I actually like the way you did it - it integrates pretty
   well and has other benefits.

   Courtney: Okay, it would be good to get a decision one way or
   the other.

   nigel: I suggest this should be on the agenda for TPAC

   glenn: Yes it's an issue to resolve before LC at least.


   <trackbot> issue-310 -- Forward reference rule doesn't take
   into account child elements -- pending review


     [19] http://www.w3.org/AudioVideo/TT/tracker/issues/310

   pal: I've addressed your last comment on the reflector.

   close issue-310

   <trackbot> Closed issue-310.


   <trackbot> issue-335 -- In order to handle offsets between
   start time in TTML docs and start time in video, allow negative
   times to be used in fragment begin times. -- raised


     [20] http://www.w3.org/AudioVideo/TT/tracker/issues/335

   reopen issue-335

   <trackbot> Re-opened issue-335.

   nigel: The reflector discussion seemed to end up that by adding
   a document temporal offset we can make whole document
   adjustments most easily.

   Courtney: This may be specific to our workflow.

   glenn: When we drafted the timing section I drafted a
   referenceBegin parameter, but at that time we didn't have a
   strong driving use case.
   ... Now that we have this use from Apple for negative times it
   would resolve that. It might also be used to make it simpler
   for SMPTE-TT documents that
   ... start at 10:00:00 to change the tokens to zero based times.

   nigel: As I understand it transformations on times are not
   permitted on smpte times with discontinuous markerMode - would
   that change that?

   glenn: I'd have to have a look at that more closely.


   <trackbot> issue-336 -- Syntax definition missing from
   ittp:aspectRatio -- raised


     [21] http://www.w3.org/AudioVideo/TT/tracker/issues/336

   reopen issue-336

   <trackbot> Re-opened issue-336.

   pal: That's something I noticed - we need to make a change to
   ttp:aspectRatio along the lines of what we had to do for


   <trackbot> issue-337 -- Update SDP-US for TTML2 -- raised


     [22] http://www.w3.org/AudioVideo/TT/tracker/issues/337

   reopen issue-337

   <trackbot> Re-opened issue-337.

IMSC 1 issues

   pal: A number of the remaining open issues are related to the
   change proposal on profiles. The proposal is to refactor IMSC
   to add another profile, but
   ... that's contingent on some not-yet-completed submissions. So
   we can't really make progress on any of these.
   ... I need to wait for all the requests to be in by Sep 5
   before I can make an editorial proposal. It's not clear how
   e.g. #cellResolution will interact with other feature requests.


   <trackbot> issue-327 -- IMSC should meet W3C QA Framework Spec
   guidelines -- open


     [23] http://www.w3.org/AudioVideo/TT/tracker/issues/327

   pal: My plan is to complete the bulk of changes and then do an
   editorial pass on the whole document, so I expect to register
   that issue at the last moment.
   ... Unless you know of specific normative impact then it's only

Change Proposals

   group: no specific CPs to discuss.

   nigel: Meeting adjourned - thanks everyone, reminder there's no
   meeting next week.

Summary of Action Items

   [End of minutes]

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