{Minutes} TTWG Meeting 2020-09-03

Thanks all for attending today's TTWG meeting. Minutes can be found in HTML format at https://www.w3.org/2020/09/03-tt-minutes.html


In text format:

   [1]W3C

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


                Timed Text Working Group Teleconference

03 September 2020

   [2]Previous meeting. [3]Agenda. [4]IRC log.

      [2] https://www.w3.org/2020/08/27-tt-minutes.html

      [3] https://github.com/w3c/ttwg/issues/143

      [4] https://www.w3.org/2020/09/03-tt-irc


Attendees

   Present
          Andreas, Atsushi, Cyril, Gary, Mike, Nigel, Pierre

   Regrets
          -

   Chair
          Gary, Nigel

   Scribe
          nigel

Contents

    1. [5]This meeting
    2. [6]Interaction between tts:writingMode and tts:direction on
       paragraph element. w3c/ttml2#1211
    3. [7]Virtual TPAC 2020 Planning.
    4. [8]Add syntax of codecs parameter
       w3c/tt-profile-registry#78
    5. [9]MIME parameters ("codecs") for bucket ISO BMFF-wrapped
       TTML versus "application/ttml+xml"
       w3c/tt-profile-registry#76
    6. [10]Meeting Close

Meeting minutes

  This meeting

   Nigel: Today I've put TTML2 #1211 back on the agenda in case we
   want to discuss more.
   … Also Virtual TPAC planning, and TTML Profiles Registry
   … AOB?

   group: [no AOB]

  Interaction between tts:writingMode and tts:direction on paragraph
  element. w3c/ttml2#1211

   Pierre: I'd like to discuss how we get to a resolution on this;
   it is blocking resolution of an
   … issue on imsc.js
   … What about if we pick a time and date and say "we're going to
   solve this on this time and date"
   … and ask everyone to come in with all the input needed etc.
   Then at the end we'll pick
   … something.

   Nigel: Would it make sense to gather our best knowledge and
   then raise it in the joint meeting
   … with the CSS WG?

   Pierre: The answer should be yes, I'm hesitating because I am
   not a specialist in Arabic, Hebrew etc
   … and there's a limitation on CSS; if that would be helpful I'm
   happy to ask the question on
   … the CSS mailing list: explaining that direction in CSS sets
   the direction and writing mode,
   … which Elika has already told me it is not a limitation but a
   feature.

   Nigel: Also something we should ask internationalisation?

   Pierre: We're unlikely to change CSS on this, there's a lot
   more international content in
   … CSS than in TTML, so I doubt that we would change their mind
   without a compelling set
   … of examples, which we don't. Glenn might be the best person
   to provide that, but he has
   … not. I would tend to saying "do what CSS does" in the absence
   of the test content and
   … examples to have a definitive opinion.

   Andreas: Which specification can we target for a change here?

   Pierre: TTML2, ultimately.

   Andreas: OK, there was also the idea to constrain IMSC.
   … The second thing is more a concern, from the current
   discussion, I think I understand
   … how it was meant and how it should work, which may already
   help IMSC, and it should
   … be possible to implement, but my concern is about how
   everything works together and
   … that it is not explained enough in TTML. It is only in the
   reference implementation of TTPE
   … and not in the spec.

   Pierre: To make things worse it is broken in TTPE too.

   github: [11]https://github.com/w3c/ttml2/issues/1211


     [11] https://github.com/w3c/ttml2/issues/1211


   Pierre: So I am not super excited to consult CSS, we should use
   what's in browsers today
   … and only ask for a change if we find a fatal flaw.

   Nigel: Are you making a specific proposal to remove the
   application of direction to p?

   Pierre: Yes, but I think it is not sufficient because setting
   it on span also changes the
   … definition of start and end as Gary pointed out.
   … I'm suggesting we pick a time, aim to solve within an hour
   and reach consensus.
   … That gives everybody an opportunity to prepare.
   … After or at TPAC, for example.

   <atsushi> [12]https://www.w3.org/wiki/TPAC/2020/GroupMeetings


     [12] https://www.w3.org/wiki/TPAC/2020/GroupMeetings


   Nigel: OK, TPAC dates are a little unclear, the obvious date
   range is 19-24 October.
   … How about making it the main topic of our call on 8th
   October, the regular weekly call?

   Andreas: We may need to extend the call

   Nigel: I've created [13]https://github.com/w3c/ttwg/issues/151

   for that meeting.

     [13] https://github.com/w3c/ttwg/issues/151


   Nigel: Any specific points about this issue to raise while
   we're here?

   Cyril: Small point to clarify. Many times in our discussions we
   mentioned the semantic
   … derivation and hinted that we could use the direction as a
   way to interpret the edge
   … for padding and textAlign, and Glenn never responded to that
   part.
   … My understanding is that they are not normative and that may
   be why he did not consider
   … them at all. Is that true that they are not normative?

   Nigel: I think so, need to check.

   Cyril: Then we should be careful - it may mean the CSS writing
   mode reference is not normative.

   Nigel: Yes, it's in Appendix N which Non-Normative.

   Andreas: I think this is really the point. You say that it is
   semantically derived from those
   … specs, but don't explain a lot in the spec itself, and then
   make the derivation informative.
   … TTML has not sufficient text to explain the layout in
   general. It leans on XSL-FO but a lot
   … of it is informative not normative so it is really hard to
   understand how this works together.
   … For an implementer what should they do? Where should they
   check how it should work?
   … Even if it is not normative, but there is a semantic
   derivation, there is some kind of dependency.

   Nigel: N.2.1 says that it can be used for mapping to CSS or
   XSL, or to other things like SVG.
   … I think the informative nature of these derivations is
   supposed to be a strength in that way,
   … but sometimes it appears to be a weakness as well.

   Cyril: I just wanted to alert the group about that.

   Nigel: Thank you.

  Virtual TPAC 2020 Planning.

   Nigel: I think Gary, we haven't done our action, so let's slap
   our wrists and get on with it!

   Gary: I haven't done it, no

   Nigel: And Gary, you added the viewport issue to the list of
   CSS issues.

   Gary: Yes

   Nigel: There is a proposal from APA to meet with synchronised
   media groups on
   … Tuesday, Oct. 13 from 14:00–15:00pm UTC (10:00 - 11:00pm EDT)
   … I will respond to say yes, assuming no objections?

  Add syntax of codecs parameter w3c/tt-profile-registry#78

   github: [14]https://github.com/w3c/tt-profile-registry/pull/78


     [14] https://github.com/w3c/tt-profile-registry/pull/78


   Mike: 4 points, a couple are editorial.

   Nigel: My plan for the concrete example was to have a separate
   pull request.

   Mike: Sure, we should add it though, as we agreed last week.

   Nigel: Yes, no problem.

   Mike: Going through my comments.
   … I thought it would be good to note that the element in
   RFC6381 prohibits "."
   … It's not clear in RFC6381 but you can't add a "."

   Nigel: I wanted only to add a constraint statement and not
   duplicate what's in 6381.
   … We could describe 6381 but not redefine it.

   Mike: I think 99% of readers won't go to 6381 so the
   prohibition of "." is worth calling out in a note.
   … 2nd one is a bit of rewording.

   Nigel: Good for me.

   Mike: The concrete example using IMSC 1.0.1 and EBU-TT-D 1.0.1
   would be valuable.
   … And the 4th one is something about the formatting.

   Nigel: The formatting looks good to me.

   Cyril: It looks good to me too.

   Nigel: That's weird, I stole the formatting from IMSC to make
   it look the same.

   Cyril: There's a typo - I'll put a note on the line.

   Nigel: OK sounds like there's a bit of work, but
   straightforward, thanks for the reviews.

   SUMMARY: @nigelmegitt to do 2nd editorial pass

  MIME parameters ("codecs") for bucket ISO BMFF-wrapped TTML versus
  "application/ttml+xml" w3c/tt-profile-registry#76

   github: [15]https://github.com/w3c/tt-profile-registry/issues/

   76

     [15] https://github.com/w3c/tt-profile-registry/issues/76


   Nigel: Looks like there's proposed wording and an amendment
   that Mike is happy with.

   Mike: I'll open a pull request.

   Nigel: I'm a little confused about what grants the ISOBMFF
   codecs value the right to use
   … our codecs parameter value as the third component.

   Cyril: It's in the RFC, which points to 14496-12 and 14496-30
   says the first term (sample entry)
   … is stpp, the second is "ttml" and the third points to the
   profiles registry.

   Nigel: That's clear, thank you. And it says specifically the
   "codecs" value?

   Mike: Yes. The practical purpose is to signal indirectly via
   the parts in the MP4 file, which
   … might be extracted into the DASH manifest to identify the
   media types.

   Nigel: Thank you that really clarifies it in my mind.

   Mike: Yes, it's the same parameter name, perhaps in hindsight
   we could have picked a different name, but it will work out.

   SUMMARY: @mikedo to raise a pull request

  Meeting Close

   Nigel: Thanks everyone, we're out of agenda, let's have 13
   minutes of our lives back! [adjourns meeting]


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