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{minutes} TTWG Meeting 2017-07-13

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 13 Jul 2017 15:24:44 +0000
To: TTWG <public-tt@w3.org>
Message-ID: <D58D4F13.44407%nigel.megitt@bbc.co.uk>
Thanks all for attending today's TTWG meeting. Minutes can be found in HTML format at: https://www.w3.org/2017/07/13-tt-minutes.html

In text format:


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

                Timed Text Working Group Teleconference

13 Jul 2017

   See also: [2]IRC log

      [2] http://www.w3.org/2017/07/13-tt-irc


          Glenn, Thierry, Nigel, Pierre, Dae, Andreas





     * [3]Topics
         1. [4]This meeting
         2. [5]TPAC / CSS
         3. [6]IMSC
         4. [7]TTML
         5. [8]WebVTT
         6. [9]HDR in PNG
         7. [10]IMSC Tests
     * [11]Summary of Action Items
     * [12]Summary of Resolutions

   <scribe> scribe: nigel

This meeting

   Glenn: [needs to leave after 45 minutes]

   Nigel: Today we have a bit on TPAC/CSS, IMSC, TTML, HDR in PNG,
   ... Any other business or specific items to cover?

   group: [no other business]



   <trackbot> action-497 -- Nigel Megitt to Invite csswg to joint
   meeting at tpac 2017, with list of topics. -- due 2017-06-15 --


     [13] http://www.w3.org/AudioVideo/TT/tracker/actions/497

   Nigel: I've begun to pull together the list of CSS features,

   [14]CSS Requirements wiki

     [14] https://www.w3.org/wiki/TTML/CSSRequirements

   Nigel: That's a work in progress - input very much welcome.
   ... I've lifted the existing points - I don't know all the
   information. For example with
   ... fontShear do we need it in CSS?

   Glenn: fontShear is frequently used in Japanese subtitling,
   with more than one angle being
   ... used in the same document. CSS does not support that at the
   moment, though you
   ... could support it in SVG with 2D transforms.

   Nigel: Let's keep this scoped to CSS, since that's this
   document's purpose.

   Dae: "Ignore" means that's the fallback, in this case CSS can't
   do it at all.

   Nigel: Thanks for the explanation.
   ... Please could I ask everyone with an interest in this to add
   detail where they know it, and
   ... if there are any missing features, add them.
   ... Some more context here - when TAG reviewed TTML2 they
   offered to facilitate a
   ... joint meeting with CSSWG, and we invited CSSWG to our
   meeting at TPAC. In advance of
   ... that TAG has invited me to discuss these issues with them
   around 26th July so there's a
   ... deadline for sorting this document out so we can share it
   with TAG. I suggest getting
   ... this to a shareable state by Friday 21st July.

   Pierre: We need to add multiRowAlign too.

   Nigel: Thanks I wasn't sure about that. Also you have some
   codepens too? It would be
   ... useful to add those in please.

   Pierre: Ok

   Nigel: Regarding TPAC, Thierry created a wiki page for it

   [15]TPAC2017 TTWG page

     [15] https://www.w3.org/wiki/TimedText/tpac2017

   Thierry: The dates are 6-10 November, and we are meeting on 9th
   and 10th.

   Nigel: Plus we are meeting jointly with the Media and
   Entertainment IG on Monday 6th.


   Thierry: We have published the IMSC 1.0.1 CR today
   ... This has triggered the Call for Exclusion of 60 days until
   Sep 11.
   ... I think we should target, if we have enough
   implementations, a PR publication by Sep 15.

   Nigel: Can we do a PR earlier and just delay Rec until the end
   of the CfE?

   Thierry: If we want to go fast track we could ask for this - I
   have to check in the Process
   ... how to do that. When do you think we can do that? In terms
   of implementation.

   Nigel: Now we have published the CR I will go through the BBC
   processes to add our
   ... implementation.

   Glenn: I could add the new features to TTV as a second

   Thierry: I'll send you the exact procedure if we want to go
   into PR review earlier than the
   ... 60 days in case we meet the exit criteria earlier. Then
   it's another 4 week to Rec, so we
   ... can envision a Rec before end of October if we keep to that

   Nigel: Well done getting here, thank you everyone!

   Thierry: We've been using the 2017 Process and therefore this
   allows AC review starting
   ... after CR publication (it used to be PR) but now your AC Rep
   can from today review the
   ... document and agree to Rec publication.
   ... If we publish a new CR then it might trigger a new review.
   Your AC Rep will have
   ... received a review form.


   Glenn: I did a bit of administrative work after last week's
   meeting to organise the TTML1
   ... issues into milestones, with the test related ones in a
   separate milestone.
   ... I made sure that every issue had a milestone.

   Nigel: On Tuesday I found 2 open issues with no milestone.

   Glenn: I'll check that.
   ... In TTML2 I'm soon going to ramp up work to resolve existing
   issues, hopefully in a week
   ... or so.

   Nigel: Last week I opened a pull request to address some
   formatting and a "silly" mistake
   ... about the HDR thing.

   Glenn: I'll look at that and merge it today.

   Nigel: I also raised an issue for supporting font variation
   settings, with the use case of
   ... number presentation.


     [16] https://github.com/w3c/ttml2/issues/400

   Glenn: Now that you've raised that I'm keen to go ahead with it
   using the syntax in the
   ... CSS fonts module. One of the criticisms of this feature is
   that it is tied to TrueType and
   ... OpenType, but practically pretty much all, or anyway most,
   fonts in use fit this category. If an
   ... implementation provides a semantic mapping for other font
   formats then it can still be
   ... used so I'm not concerned about that.
   ... Just in case we get similar comments in the future.
   ... One more thing: since it is a kind of open-ended
   extensibility mechanism for directing
   ... the font and layout system to do something special we may
   want to create a registry
   ... to give guidance to authors and implementors about which
   features are supported,
   ... otherwise there will be no expectations for specific
   support, unless we define profile
   ... feature designator.

   Nigel: So in my case I would want the tnum value to be
   variable, so there would be a
   ... feature designator for that?

   Glenn: Right, though we would likely not publish a new
   designator for every individual
   ... feature. It could be that we put them in the extensions
   space for designators. It is
   ... something to think about.

   Nigel: Any other TTML comments right now?

   Glenn: There's been some reflector conversation initiated by
   ... I would suggest Nigel points the commenter towards your
   work on live contribution of TTML.

   Nigel: Good idea.

   Glenn: It doesn't make much sense to do roll-up for pre-canned
   ... There are two features that I've considered adding in the
   past but never done so:
   ... end="indefinite" and begin="now" for the live use case.

   Nigel: The EBU-TT Live spec works around their absence okay.

   Glenn: mediaOffset could be used for the begin="now" case.

   Nigel: Actually I think it can't, but that is very similar to
   the reason I wanted to introduce
   ... a tt element attribute "clipBegin" to carry the same

   Thierry: The Wide Review of TTML2 started when the publication
   was released around 10 days ago.
   ... I have sent calls for review to all the W3C groups and the
   external bodies, with one
   ... remaining for the Japanese IPTV Forum. I need to send that
   and also I need to work on the
   ... TAG questionnaire. So now I will be tracking those comments
   also for TTML2.

   Nigel: Fantastic, thank you for doing that (and reminding me
   about it!).

   Thierry: The review ends Sep 30.


   Thierry: Silvia has done a lot of work on editing the WebVTT
   draft of the CG mainly fixing
   ... broken links and linking to W3C HTML spec instead of
   ... The draft was published today on TR as an ordinary draft.
   My understanding is we should
   ... trigger another draft soon for wide review.

   Nigel: It's also worth noting that Silvia has now joined the WG
   and has effectively taken on
   ... shared Editing role with Simon.

   Pierre: Who does Silvia represent?

   Nigel: It's CSIRO in Australia.
   ... Any progress on looking at the Dispositions for the
   previous Wide Review?

   group: [silence]


   Pierre: All the comments filed on GitHub have been resolved.
   The only outstanding question
   ... I know of is related to the supported bit depth of PNG. PNG
   supports only 8 and 16 bits,
   ... and nothing in between. Some folk have pointed out that 8
   is too little and 16 is too much.
   ... 8 is too little for general use, but it's okay for
   subtitles and captions. Possibly we should
   ... extend the note on bit depth to say that. I'm reluctant to
   state that until someone has
   ... a concrete issue filed. I think this would impact only the
   informative note. I think this
   ... is ready to be published.

   [17]Feedback on HDR compositing #400

     [17] https://github.com/w3c/ttml2/issues/400

   Nigel: I forwarded some feedback to TTML2 that may be relevant
   ... I think the overall comment is that in PQ both narrow and
   full range are in use so the
   ... spec should support that. I am not sure if that also
   applies back to the PQ in PNG note.

   Pierre: The note only deals with full range quantisation. We
   could conceivably add a row
   ... for narrow range - technically that is easy to add to the
   document. I suggest that we
   ... keep this a living document, and address that point if and
   when it is raised.

   Nigel: OK - the point raised on TTML2 was about the range of
   the video rather than the
   ... range of the image.

   Pierre: Yes, though in a simple implementation a copy or blit
   of full range subtitle pixels
   ... to narrow range video you would not get what you expected.
   That is less of an issue for
   ... subtitles and captions.

   Nigel: Why is that?

   Pierre: If you get the luminance a bit off then it is not
   orders of magnitude difference.

   Nigel: Great, shall we do one final review pass of the document
   and the comments before
   ... proposing to publish it next week?

   Pierre: Sure. And Thierry if you could look at it and check its
   suitability for publishing then
   ... that would be useful.

   Thierry: Okay I will look at it today or tomorrow.

   Nigel: Thank you.

IMSC Tests

   Pierre: I've been updating the tests and have just pushed a
   pull request to address the
   ... spaces before line breaks issue we discussed last week.
   ... There are 15 issues against the IMSC tests, all but that
   one being cosmetic, but that one
   ... is important to get right. It affects only a few tests, but
   as you know Chrome, which is
   ... used to generate the renders, seems not to suppress spaces
   before explicit line breaks
   ... if those spaces are within a span. That's also something
   I've added to the wiki about CSS
   ... and TTML compatibility. We really should understand if it
   is a Chrome bug or a divergence
   ... between CSS and XSL-FO behaviour. To me it looks like a
   Chrome bug.

   Nigel: Me too.

   Pierre: It means that any implementation using CSS needs to
   include some extra manual work.

   Nigel: Will you add the IMSC 1.0.1 exit criteria tests into the

   Pierre: Yes when I have confirmation from implementations that
   they're right.
   ... It would be just a copy and paste since the format of the
   tests is the same in both
   ... imsc-tests and the IMSC 1.0.1 exit criteria tests.

   Nigel: We seem to have completed our agenda in an hour, which
   was secretly my plan all along, so thanks everyone! [adjourns

Summary of Action Items

Summary of Resolutions

   [End of minutes]

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