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{minutes} TTWG Meeting 2015-03-12

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 12 Mar 2015 14:50:06 +0000
To: Public TTWG List <public-tt@w3.org>
Message-ID: <5941EAB8802D6745A7D363D7B37BD1F75CC155A4@BGB01XUD1012.national.core.bbc.co.uk>
Thanks all for attending today's TTWG meeting. Minutes in HTML format can be found at http://www.w3.org/2015/03/12-tt-minutes.html

In text format:


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

                Timed Text Working Group Teleconference

12 Mar 2015

   See also: [2]IRC log

      [2] http://www.w3.org/2015/03/12-tt-irc


          mike, pal, tmichel, nigel, dsinger

          glenn, Andreas, Frans, jdsmith




     * [3]Topics
         1. [4]This Meeting
         2. [5]Action Items
         3. [6]F2F
         4. [7]IMSC 1 Test Suite
     * [8]Summary of Action Items

   <trackbot> Date: 12 March 2015

   <scribe> scribe: nigel

This Meeting

   nigel: I think given those present we can best cover the SMPTE
   liaison, IMSC 1 test suite and the F2F agenda

   tmichel: We also need to mention the Sapporo TPAC opportunity
   for a F2F

   group: no other AOB

Action Items


   <trackbot> action-378 -- Pierre-Anthony Lemieux to Draft smpte
   request including dispositions from action-369 and
   backgroundcolor initial value question -- due 2015-03-05 --


      [9] http://www.w3.org/AudioVideo/TT/tracker/actions/378

   pal: I've drafted this and sent it round.

   mdolan: The initial values for the root container were neither
   defined nor specified as
   ... implementation dependent. So SMPTE went about setting
   initial values. It's unfortunate
   ... that they're not the same as what's in TTML1SE.
   ... Timing wise, SMPTE 2052 was originally drafted before TTML1
   was published as a Rec.
   ... I don't recall what the reasoning was, but that's the
   ... More importantly, IMSC 1 came about from a request from
   DECE, based on TTML1 plus
   ... some constrained extensions from SMPTE. SMPTE also added
   for the image handling
   ... to be added to TTML2 and IMSC 1. So I think there could be
   a misunderstanding that either
   ... SMPTE or DECE wanted IMSC 1 to match identically. That may
   not have been the intent.

   nigel: Are you saying that we could just make the IMSC 1
   initial values the same as TTML1 and be done with it?

   mdolan: That would be my proposal, to remove the initial values
   text from IMSC 1.
   ... I'd like to validate this back with DECE and report back
   next week.

   nigel: Does this mean we don't need to bother sending this to

   mdolan: Depending on the answer, yes. It may be better to go to
   DECE because SMPTE
   ... would be going back 10 years and the history is probably
   not well remembered, and is complex.
   ... Even if we got an answer it may not be helpful.
   ... I propose that I'll investigate and get back and we may
   need to ask DECE, or nobody.

   pal: I like that plan, because I've certainly heard that not
   aligning with TTML1 is a bad idea.

   nigel: +1
   ... I'll leave action-378 open in that case.

   mdolan: If I get an answer back sooner I'll post it to the


   nigel: There's been some offlist discussion. It's looking
   likely that there'll be an agenda item
   ... to talk about the plan for creating the TTML<-->WebVTT
   mapping document, rather than
   ... to talk about the substance of it.
   ... It's good news that there's enthusiasm for it, and we need
   to open that up to the right
   ... community.

   pal: One quick request: I may not be able to be there all day
   Friday, so I'd appreciate it if
   ... we can cover IMSC 1 topics on the Thursday and TTML2 also.


     [10] https://www.w3.org/wiki/TimedText/F2F-april-2015

   nigel: Since last week Courtney has added her name to the
   ... She's likely to be interested in VTT topics and only be
   there on the Thursday too.
   ... Given that we're not talking about substance with the
   mapping, but planning, it should
   ... be maximum 30 minutes.
   ... I'm also wondering if we should explore inviting the TTCG
   to that agenda item, since
   ... they have a lot of expertise in WebVTT.

   pal: Thanks for the prompt - I've just added my name to the
   attendee list.

   nigel: Thierry, do you want to mention some details about

   tmichel: It's worth noting the dates of TPAC, which will be in
   Sapporo, Japan at the end of October.
   ... We've been asked if we plan to meet there. The question is
   do we want to meet or not?

   nigel: We have a deadline for responding to that survey too.
   ... The dates of TPAC are 26-30 October 2015.
   ... I need to respond on the questionnaire by 30th April.

   tmichel: If we plan to meet, the earlier we plan it the better
   choice of dates we will have
   ... available.

IMSC 1 Test Suite

   nigel: I eventually managed to complete my promised analysis
   and send it round.
   ... Pierre, you responded on the reflector that there were some
   points you thought we should discuss.

   pal: Thank you nigel for putting that report together. I
   concentrated on the ones with No
   ... under 'In Test suite?'
   ... For the first row I created a test.
   ... For the second one, I'm not sure how a test can be written.
   You'd probably offer a TTML
   ... file and a video file and identify that it is not a legal
   combination but the spec does not
   ... say what processor behaviour is in that case. Also this
   made me look at how TTML1SE
   ... has been modified to say how to generate media time from
   timing expressions, and I'm
   ... not even sure this is really needed. I've been casually
   asking DECE folks about this.
   ... So I suggest doing nothing right now - there might be a
   suggestion to remove that clause.

   nigel: So we may need to signal that this statement is 'at

   pal: Give me a week - that could be one outcome.
   ... The fourth row in the table (the third red one) is
   something I'd like glenn's thoughts on.
   ... TTML1SE has some clear text on rounding and positioning. In
   the DECE member submission
   ... this text was there to try to create consistency across
   implementations for aligning
   ... regions on the pixel grid. That was specific text about
   pixel position on related video.
   ... In the scope of DECE that's a clearly defined thing. In
   TTML1SE there's no mention of
   ... pixels - it says that if a value of extent is not available
   to the implementation then what
   ... the fallback is. I'm not sure what the interaction is
   between the IMSC 1 statement and that
   ... in TTML1SE. It needs more study. I'll ask at DECE there
   too. Again it might be a situation
   ... where we remove this text or add a note or do some other
   ... That's my report.

   nigel: There are also two actions to get/generate PNGs.

   pal: They're already linked in via the EBU docs.

   nigel: Are they clear enough to use as test criteria?

   pal: I think there is enough precision there already. The EBU
   spec is pretty clear in what
   ... the output should look like.

   <mike> need to drop. cheers until next week

   nigel: I think it's not clear that the images in the EBU specs
   are generated by exactly these
   ... test case TTML documents.

   <scribe> ACTION: nigel Obtain PNG images for #linePadding and
   #multiRowAlign test cases. [recorded in

   <trackbot> Created ACTION-379 - Obtain png images for
   #linepadding and #multirowalign test cases. [on Nigel Megitt -
   due 2015-03-19].

   nigel: I haven't seen any other comments on the tests. Have

   pal: No.
   ... I think we're good, so I'll report hopefully next week on
   those two items.

   <inserted> dsinger joins the call

   nigel: I was earlier talking about inviting the CG for an
   agenda item at the F2F to talk about the TTML <--> WebVTT

   dsinger: Sure, that's a good idea. I'll send an email to the CG
   saying that the TTWG invites them to join at the F2F for that.

   nigel: Thanks. We're out of agenda for the folk present so I'll
   adjourn now. See you next week. Thanks all. [adjourns meeting]

Summary of Action Items

   [NEW] ACTION: nigel Obtain PNG images for #linePadding and
   #multiRowAlign test cases. [recorded in

   [End of minutes]

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