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{minutes} TTWG Meeting 2016-04-21

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 21 Apr 2016 15:17:25 +0000
To: Timed Text Working Group <public-tt@w3.org>
Message-ID: <D33EAAC1.39E54%nigel.megitt@bbc.co.uk>
Thanks all for attending today's TTWG meeting, in which we were able to celebrate the publication of the IMSC 1 Recommendation!

Minutes in HTML format are available at: https://www.w3.org/2016/04/21-tt-minutes.html


In text format:


   [1]W3C

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


                Timed Text Working Group Teleconference

21 Apr 2016

   See also: [2]IRC log

      [2] http://www.w3.org/2016/04/21-tt-irc


Attendees

   Present
          Glenn, Nigel, Plh, Pierre, Andreas, tmichel, Mike

   Regrets
          Frans

   Chair
          nigel

   Scribe
          nigel

Contents

     * [3]Topics
         1. [4]This meeting
         2. [5]Action Items
         3. [6]IMSC
         4. [7]TTML
     * [8]Summary of Action Items
     * [9]Summary of Resolutions
     __________________________________________________________

   plh: I can't stay for long but want to note that the IMSC 1 Rec
   was published today
   ... [10]https://www.w3.org/TR/ttml-imsc1/ is REC
   ...
   [11]https://lists.w3.org/Archives/Member/w3c-ac-members/2016Apr

   Jun/0012.html
   ... Karen told me this morning she still wants to do the press
   release but unfortunately
   ... it won't happen this morning due to other events.
   ... I did not put last week's stuff in, because I received it
   from Pierre too late yesterday,
   ... so it got published as is today.

     [10] https://www.w3.org/TR/ttml-imsc1/

     [11] https://lists.w3.org/Archives/Member/w3c-ac-members/2016AprJun/0012.html


   nigel: Fantastic, well done everyone, great news!

   glenn: An announcement message did go out shortly before the
   meeting.

   plh: Congratulations again, apologies I cannot stay for the
   rest of the meeting.

This meeting

   nigel: I don't think there's much to discuss on Charter, but
   there's stuff to discuss re TTML1 and TTML2

   <scribe> scribe: nigel

   nigel: AOB?

   group: no AOB

Action Items

   glenn: I need to write up some of these - some have been taken
   care of one way or another.
   ... No specific progress to report on them this week.

   action-459?

   <trackbot> action-459 -- Thierry Michel to Process the PR at
   [12]https://github.com/w3c/tt-profile-registry/pull/3 and post
   for review to the reflector -- due 2016-04-21 -- OPEN

     [12] https://github.com/w3c/tt-profile-registry/pull/3


   <trackbot>
   [13]http://www.w3.org/AudioVideo/TT/tracker/actions/459


     [13] http://www.w3.org/AudioVideo/TT/tracker/actions/459


   tmichel: Thanks to plh the pull request has been merged while I
   was away.
   ... The follow up is for the group to review the draft.
   ... Plh told me you want to split the table?

   nigel: Yes, I don't mind who does it but the table is a bit
   unwieldy now so I think it should be split.

   tmichel: Shall I do that?

   nigel: I'm happy for you to do that.

   tmichel: Okay I'll do that after the call and send around a
   call for review probably tomorrow.

   action-459: [TTWG meeting 2016-04-21] agreed to split the table
   prior to sending for review.

   <trackbot> Notes added to action-459 Process the PR at
   [14]https://github.com/w3c/tt-profile-registry/pull/3 and post
   for review to the reflector.

     [14] https://github.com/w3c/tt-profile-registry/pull/3


   mike: There's still an action to replicate the media type
   information from Annex C of
   ... TTML1 and add the codecs parameter and update the IANA
   registration. Is that still
   ... needed?

   nigel: Yes please.

   mike: So the process is to make a Pull Request and then request
   review?

   glenn: Which document?

   nigel: [15]https://w3c.github.io/tt-profile-registry/index.html

   ... Yes, we can be flexible about this, but for example making
   a pull request and discussing
   ... it in a meeting prior to merging would be fine.

     [15] https://w3c.github.io/tt-profile-registry/index.html


   mike: Okay I'll do a pull request against the profile registry
   and then we can all look at it.

   nigel: Fantastic, thank you Mike.
   ... I also propose to merge Cyril's TTML versions document into
   this too, as a separate exercise.
   ... That material is more descriptive.
   ...
   [16]https://dvcs.w3.org/hg/ttml/raw-file/5ee90ec0d897/ttml-stat

   us/index.html
   ... Looking at that, there's so little content in there that we
   maybe just add new
   ... descriptive sections and leave Cyril's where it is.

     [16] https://dvcs.w3.org/hg/ttml/raw-file/5ee90ec0d897/ttml-status/index.html


IMSC

   nigel: Following on from the Rec publication noted at the top,
   are there any other points?

   tmichel: I noticed yesterday that we don't have an
   acknowledgments section. It's nice
   ... to have so maybe we should put a placeholder for the next
   version of IMSC.

   glenn: I suggest we create an errata document to start with and
   add an ack section to
   ... that as a placeholder. I think this was probably an
   editorial oversight.

   <scribe> ACTION: tmichel Add an acknowledgment section to the
   IMSC 1 errata section. [recorded in
   [17]http://www.w3.org/2016/04/21-tt-minutes.html#action01]

     [17] http://www.w3.org/2016/04/21-tt-minutes.html#action01]

   <trackbot> Created ACTION-461 - Add an acknowledgment section
   to the imsc 1 errata section. [on Thierry Michel - due
   2016-04-28].

   pal: Philippe put the github copy of the errata in the wrong
   place on github, so I need to
   ... move it.

   <plh> wrong place?

   tmichel: Okay, move it and then I'll make a pull request.

   pal: Can we put an issue on github to add the acknowledgments?

   tmichel: Who should be acknowledged - just group members?

   glenn: Only people who have made some kind of contribution to
   the spec should be
   ... acknowledged.

   nigel: I've created [18]https://github.com/w3c/imsc/issues/177


     [18] https://github.com/w3c/imsc/issues/177


   glenn: You could also list group participants, but not random
   people who are not
   ... engaged or have not contributed something.

   tmichel: If we want other people, e.g. from the community
   group, let me know. We
   ... could also acknowledge people for filing implementation
   reports, again, not mandatory.

   glenn: If people have contributed in some way to the process or
   the spec then I think
   ... they should be acknowledged.

   nigel: +1

   pal: This work began from a DECE contribution.

   glenn: I'd acknowledge the group, unless you choose to pick
   named individuals. That would be fine too.
   ... Take a look at what we did in TTML1 - I think it's
   instructive.
   ... I made special mention to a few people who contributed more
   than the average share.

   nigel: Who's going to start work on this?

   tmichel: I will.

   nigel: Thanks.

   pal: Based on our discussion last week I sent plh too late
   yesterday a document that's
   ... a roadmap to the IMSC family of specifications, addressing
   what we discussed last week,
   ... that "latest version" might point to one of several
   possibilities. I created that document
   ... and a pull request. It did not make it to this release of
   IMSC 1, but my suggestion is
   ... still to accept the pull request and leave that document
   there. It's useful, and if we
   ... ever do a 2nd edition then it will be there ready to go.
   ... It's a really short document, that lists the current IMSC
   documents. Right now there's
   ... only one.

   glenn: Looking at TTML1, the Latest version points to TTML1,
   but it could be updated

   nigel: We discussed this last week and decided to use a
   separate document to dereference
   ... all the different possible branches that a spec can take,
   from 1st ed to 2nd ed, or v2 etc.

TTML

   nigel: We have a number of things to cover: background image,
   time expressions and audio description.
   ... Let's begin with background image

   [19]https://github.com/w3c/ttml2/issues/157


     [19] https://github.com/w3c/ttml2/issues/157


   glenn: I was in the process of implementing the semantics for
   the IMSC background image
   ... mechanism, based on SMPTE ST2052, and I realised that there
   was a discrepancy
   ... between what we ended up with in IMSC and the normal
   CSS/XSL-FO semantics.
   ... Here's the scenario: In CSS if you put a background image
   on a div element, let's say,
   ... and there's no content in that div, then you will not see
   any background image, as
   ... I demonstrated in the sample that I attached.
   ... If you manually size the content rectangle of the div or
   insert some content that causes
   ... it to be sufficiently big then the background image will
   become visible (possibly clipped).
   ... In SMPTE-TT it appears to have been dealt with by stating
   that the minimum width and
   ... height of the area of the div should be at least as large
   as the size of the background
   ... image. I didn't notice this difference to CSS before. The
   problem we have today is that
   ... now we're adding image support to TTML2 and we have IMSC 1
   published we have
   ... to deal with the effects of that variation somehow and come
   up with something that
   ... makes sense in TTML2. That's the basis of the problem.

   pal: In TTML2 images are an element, right?

   glenn: There are 2 ways to use images. One is a content image
   using the image element,
   ... which definitely has a size that's equal to its intrinsic
   image size unless it's otherwise
   ... manually sized. If you were to use the image element to map
   the SMPTE backgroundImage
   ... attribute into TTML2 then this won't be an issue.
   ... In TTML2 we also added the backgroundImage style property,
   intending it to work like
   ... CSS/XSL-FO. We could solve this by putting some language
   somewhere saying that
   ... mapping from IMSC 1 image should be via the image element.

   pal: Yes, why not?
   ... We have 2 choices. We could use exactly the same semantics
   in TTML2 as in SMPTE-TT;
   ... the other option is to map to the image element.

   glenn: The other option is to use different semantics in TTML2
   than in IMSC and adopt
   ... the CSS semantics, and require that the element is sized
   explicitly using ipd and bpd.
   ... That would work.

   pal: Ideally using TTML2 it looks like the "right" way to do
   image as content is to use
   ... the image element?

   glenn: Right, the backgroundImage isn't intended as being used
   for content.

   pal: I'm thinking that we indicate that it should be mapped to
   the image element in TTML2.

   glenn: I agree. We probably need to create a placeholder
   document to deal with such
   ... mappings.

   pal: I'm happy to start work on that, and have that as the
   first item in it.

   glenn: It could be maintained as a separate document or we
   could merge some of it
   ... into IMSC 2. We can make that choice later.

   pal: Yes.

   glenn: What I ended up deciding to do is to map
   smpte:backgroundImage to the image
   ... element because it wants to behave like that.

   pal: Ok.

   glenn: I'm tentatively using the same semantics as CSS for
   backgroundImage in TTML2.

   pal: In CSS the name is background-image, right?

   glenn: Correct.

   pal: I guess we'll have to teach people!

   glenn: Yes, it could be a source of confusion for authors.

   pal: What's the name in XSL-FO?

   glenn: backgroundImage. There's also an externalGraphic that
   works a bit like in SVG as
   ... an image. In SVG you can also apply a pattern as a fill,
   using an image, which works
   ... more like background-image.
   ... We'll continue to have both kinds of concept, a content
   image and a stylistic
   ... background image.

   mike: The discussion came as a bit of a surprise to me because
   noone has looked at this
   ... for a while. I think we need to sort this out. The
   overloading on the name is unfortunate
   ... but it really was intended for content. I'm not really
   happy with any of the options but
   ... this is the least bad.

   glenn: IMSC doesn't say anything about this right now, but the
   reference to SMPTE suggests
   ... that the normative language in SMPTE-TT applies.

   pal: Yes.

   glenn: You might want an errata for IMSC 1 that notes that
   applicability.

   pal: Also note that it's not just the backgroundImage attribute
   but also the semantics
   ... that surround it.

   glenn: Absolutely. One has to assume that that's true otherwise
   there's insufficient text to describe it.

   pal: Do you want to file a quick issue?

   glenn: Okay I'll do that.

   pal: I think we're going to have to deal with this in the next
   version of IMSC. We have
   ... two possibilities. We can create a document where we track
   these - that's probably best.
   ... I'll refactor the repo to include an IMSC 2 draft, and note
   this in there.

   glenn: Or do what we did in TTML and add a new repo.

   pal: Then you can't easily move bugs from one to another. I'm
   thinking of having
   ... multiple subdirectories, one per big version.

   glenn: You're the Editor!

   nigel: Yes, that's fine.

   pal: What about also adding a note to TTML2 for users of
   backgroundImage, warning
   ... about the mapping from smpte:backgroundImage?
   ... That might be helpful for IMSC and everyone else to
   reference.

   glenn: Okay, it doesn't hurt to add that as a comment. Or add
   an informative mapping
   ... section.

   pal: That would be great.

   glenn: For mapping from other versions or profiles of TTML.

   <scribe> ACTION: gadams create issue on TTML2 to add "Mapping
   from other Versions and Profiles of TTML" [recorded in
   [20]http://www.w3.org/2016/04/21-tt-minutes.html#action02]

     [20] http://www.w3.org/2016/04/21-tt-minutes.html#action02]

   <trackbot> Created ACTION-462 - Create issue on ttml2 to add
   "mapping from other versions and profiles of ttml" [on Glenn
   Adams - due 2016-04-28].

   nigel: I'd also like to raise
   [21]https://github.com/w3c/ttml1/issues/210

   ... This came about from implementation work where it appears
   that leap second
   ... syntax is permitted even when it has no meaning.

     [21] https://github.com/w3c/ttml1/issues/210


   glenn: I propose in TTML1 to add a section to ยง10.3.1 matching
   Nigel's proposal, and
   ... in TTML2 then we can strengthen that.

   nigel: That sounds good.

   glenn: When I process it on TTML1 I'll do it on TTML2.

   nigel: I'll add an issue on TTML2 pointing to the TTML1 issue
   then.

   <scribe> ACTION: nigel Add an issue on TTML2 regarding 60
   second minutes to point to the TTML1 one. [recorded in
   [22]http://www.w3.org/2016/04/21-tt-minutes.html#action03]

     [22] http://www.w3.org/2016/04/21-tt-minutes.html#action03]

   <trackbot> Created ACTION-463 - Add an issue on ttml2 regarding
   60 second minutes to point to the ttml1 one. [on Nigel Megitt -
   due 2016-04-28].

   nigel: I'd also like to signal my intent to specify and
   implement audio description in TTML2.
   ... The idea is to add some audio style attributes that could
   be subject to animation
   ... and use included or referenced audio files to generate an
   audio description

   <glenn> [23]https://www.w3.org/TR/REC-CSS2/aural.html


     [23] https://www.w3.org/TR/REC-CSS2/aural.html


   nigel: presentation experience that aligns with current
   practice. We also intend to
   ... implement a prototype of this using web audio.
   ... Thanks for that link Glenn, I'll check if that includes
   useful semantics I'll reference them.

   glenn: That spec probably covers a lot of what you want to do
   already.

   nigel: I may need to cross-check that with Web Audio as well.
   ... Apologies I've taken us 4 minutes over. Thanks all
   [adjourns meeting]

Summary of Action Items

   [NEW] ACTION: gadams create issue on TTML2 to add "Mapping from
   other Versions and Profiles of TTML" [recorded in
   [24]http://www.w3.org/2016/04/21-tt-minutes.html#action02]
   [NEW] ACTION: nigel Add an issue on TTML2 regarding 60 second
   minutes to point to the TTML1 one. [recorded in
   [25]http://www.w3.org/2016/04/21-tt-minutes.html#action03]
   [NEW] ACTION: tmichel Add an acknowledgment section to the IMSC
   1 errata section. [recorded in
   [26]http://www.w3.org/2016/04/21-tt-minutes.html#action01]

     [24] http://www.w3.org/2016/04/21-tt-minutes.html#action02

     [25] http://www.w3.org/2016/04/21-tt-minutes.html#action03

     [26] http://www.w3.org/2016/04/21-tt-minutes.html#action01


Summary of Resolutions

   [End of minutes]
     __________________________________________________________


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