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{minutes} TTWG Meeting 2016-07-21

From: Nigel Megitt <nigel.megitt@bbc.co.uk>
Date: Thu, 21 Jul 2016 15:12:43 +0000
To: W3C Public TTWG <public-tt@w3.org>
Message-ID: <D3B6A468.3FD5A%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/2016/07/21-tt-minutes.html

In text format:


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

                Timed Text Working Group Teleconference

21 Jul 2016

   See also: [2]IRC log

      [2] http://www.w3.org/2016/07/21-tt-irc


          Nigel, Mike, Andreas, David_Ronca, Philippe

          Thierry, Frans, Pierre, Glenn




     * [3]Topics
         1. [4]This meeting
         2. [5]TPAC 2016
         3. [6]Profiles registry and TTML IANA registration
         4. [7]TTML issues
         5. [8]Profiles registry and TTML IANA registration
         6. [9]TTML issues (continued)
     * [10]Summary of Action Items
     * [11]Summary of Resolutions

   <scribe> scribe: nigel

This meeting

   nigel: We are low on numbers today for various reasons. What
   are we quorate to discuss?

   mike: Perhaps a brief update on the IANA registration

   Andreas: TPAC
   ... Also the lineHeight, background height issue and the need
   for a solution.

   nigel: Okay, I'd also maybe like to come back to the Safe Crop
   Area proposal.

TPAC 2016

   nigel: Note that the hotel closest to the venue is getting low
   on availability: I just tried booking and failed!
   ... So it's worth booking accommodation soon.

   Andreas: Regarding the conflict (for some) with the Web & TV IG
   meeting on the Monday
   ... and the TTWG meeting on the Monday and Tuesday. There is
   some overlap of interest
   ... so this is unfortunate. It may be difficult to change this,
   but we should ask the Web & TV IG
   ... at least about their agenda so we can have a basis for
   setting our agenda topics.
   ... Also we thought about a combined meeting with the Web & TV
   IG. I'm not sure if this
   ... is still of interest for others. There's clearly an overlap
   in what they are working on,
   ... and also the members are I think interested in progress on
   the subtitle front. It could
   ... be a possibility to discuss the issues about WebVTT and
   TTML and the adoption of
   ... IMSC.

   nigel: For the last few years we have provided an update to the
   Web & TV IG who are
   ... indeed interested in our progress, so I think it makes
   sense to ask for some joint time
   ... with them so that we can do the same this year. I'll give
   myself an action.

   <scribe> ACTION: nigel Contact the chair of the Web & TV IG to
   ask about schedule and joint meeting time. [recorded in

     [12] http://www.w3.org/2016/07/21-tt-minutes.html#action01]

   <trackbot> Created ACTION-475 - Contact the chair of the web &
   tv ig to ask about schedule and joint meeting time. [on Nigel
   Megitt - due 2016-07-28].

   mike: That's a good idea - I won't be there by the way.

   davidr: Dae will be there for Netflix - I don't really have an
   opinion on it.

Profiles registry and TTML IANA registration

   mike: If you go to the interaction with IANA link, there's the
   old one a year or two ago,
   ... but nothing in there that indicates that we have any open
   engagement with IANA. I
   ... thought plh had done that but it looks like not. We've had
   no response from IANA either.

   nigel: Okay, it looks like something's "stuck". I have prompted
   plh but it's unclear what's happening.
   ... Ideally he'd be on the call...
   ... I've sent him a message to see if he is available to join.
   If he can let's come back to this.

TTML issues

   nigel: Andreas, I think you wanted to mention lineHeight etc?

   andreas: We discussed this for 3 weeks with a lot of discussion
   and comments, then
   ... other discussions took over. I think it's important that we
   look for a solution because
   ... HbbTV has now published an update to their spec and they
   have some normative
   ... text that clarifies this issue and I think they also are
   waiting for clear guidance from
   ... W3C or EBU that they could reference, but because they have
   to publish sooner they
   ... needed to include some text. I think it's important for us
   to check this change and
   ... also to work on the solution and decide if there's an
   errata needed for TTML1 or an
   ... update to IMSC 1 and how in general this should be solved
   for TTML2.
   ... It may also be important but out of scope for W3C that
   HbbTV starts a liaison with W3C
   ... on this issue.

   nigel: Can you recall what HbbTV did?

   andreas: They made a lightweight addition, based on a request
   that a transparent gap
   ... should not appear between line backgrounds. So the solution
   is that for lineHeight <= 125%
   ... when the background is set on consecutive rows there should
   not be a gap between
   ... the line backgrounds, without explaining how the renderer
   should make that happen.
   ... The solution for how this conceptually and theoretically
   would be done in TTML is still
   ... outstanding and the task of this group.

   nigel: Even this group may not be the best place to fix it -
   sometimes we have to do so
   ... when nobody else will fix it, but it seems like it should
   be fixed in CSS and then we should
   ... align with that, otherwise it's a bit backwards.

   andreas: It would be good to have a pragmatic solution as soon
   as possible so that the
   ... different standards are compatible with us, e.g. by an
   errata with TTML1. Going back
   ... to the discussion we had there was I think not a really
   clear view of the group how this
   ... case should be handled so there seems to be a gap in TTML1
   how it should be handled.
   ... If this is the case that there is some room for
   interpretation then there can be an errata
   ... in TTML1. If this is not the case then it would be good to
   have a solution in the next
   ... upcoming spec, which could be an update to IMSC 1.

   davidr: I've seen that separation between backgrounds of
   multiple lines of text is a problem
   ... on iOS with WebVTT.
   ... For our TTML clients we don't specify backgrounds.

   nigel: Our BBC subtitle guidelines take the opposite approach -
   a black background is
   ... required and there must not be gaps between lines, so this
   is a real issue for us.
   ... Thank you for raising the profile of this once again.

Profiles registry and TTML IANA registration (continued)

   plh: I started the review - IETF says we have to start the
   review on their TIES mailing list
   ... first. You have to do a complete submission every time.
   ... Once we're done we send the request to IANA.

   nigel: Is the IETF review period open ended or will it close?

   plh: It is open ended; it's been more than a month but I would
   think that is enough.
   ... I would not worry about the time period. But I would ask if
   we addressed the comments?

   mike: The status is: we received 2 comments from W3S; one was
   rejected by the WG

   plh: I'm not aware of W3S comments on the IETF list.

   mike: I'm not aware of any comments from the IETF list.
   ... There was a comment from Eric Prud'hommeaux and Paul
   Libbrecht who posted to the public TTWG reflector
   ... and those are the only two comments.

   plh: [looks on the IETF list] If the comments are not on the
   IETF list then they are not a concern.



     [13] https://lists.w3.org/Archives/Public/public-tt/2016Jun/0012.html

   plh: That's my request on June 16, which I sent to the IANA
   media types list, as required.



     [14] https://lists.w3.org/Archives/Public/public-tt/2016Jun/0014.html



     [15] https://lists.w3.org/Archives/Public/public-tt/2016Jun/0015.html

   plh: So one comment was rejected?

   mike: We decided not to proceed with the Mac clipboard type

   <plh> answer to Paul:


     [16] https://lists.w3.org/Archives/Public/public-tt/2016Jun/0018.html

   mike: Nobody expressed any interest or practice that we could

   plh: So did you do what is needed to address the comments?

   mike: Eric's comment was editorial, but I didn't want to edit
   the document until the review
   ... period is over.

   plh: At this point I need the document to be updated so I can
   submit the registration to
   ... IANA itself.

   mike: Okay I'll make the changes via issues and PRs and send
   you an email when I'm done.

   plh: Then let me know when you're done and email me until I've
   sent it to IANA!
   ... The form I will fill is at:

   <plh> [17]http://www.iana.org/form/media-types

     [17] http://www.iana.org/form/media-types

   plh: Sometimes the hardest question to answer is "encoding
   consideration" so if you think
   ... it is perfectly answered in your document then you're fine.

   <plh> "Encoding Considerations"

   mike: All the comments are on the note not the media type
   registration. We didn't touch
   ... that aside from adding a codecs parameter.
   ... I can't understand why the same answer would be a concern
   now when it wasn't before.

   plh: Understood. When I send the form to IANA then, according
   to my most recent experience,
   ... they're pretty fast in processing it.

   mike: I understand the steps - I'll make the edits and send you
   an email later.

   plh: Thank you.

   nigel: Thanks both - great to unlock that.

TTML issues (continued)

   nigel: I'd like to come back the BBC's Safe Crop Area proposal
   - noting that the people
   ... present today are a mutually exclusive set relative to
   those present last week when we
   ... discussed it.
   ... I don't know if anyone has had a chance to look through it.
   Mike, thank you for
   ... sending through the links to smpte documents.
   ... I think they help to explain how the problem arises but do
   not solve it.
   ... [outlines problem of trying to maintain positional
   registration and complete display]

   mike: There's both a display problem and an authoring problem.
   ... There used to be something like a safe area in the video,
   not directly solving the
   ... problem for subtitles and captions. The active format
   descriptor and bar data help
   ... to describe the status for video, and SMPTE is in the
   process of updating those.
   ... It helps solve the video problem and may provide a
   framework for how we want to fix
   ... it for TTML. There's also ISO/IEC 14496-30 corrigendum 1,
   which tries to provide
   ... some signalling outside the document, which we should look

   nigel: It was unclear to me what that corrigendum actually
   means for the decoder.

   mike: It's about the aspect ratio of the TTML and the active
   format descriptors describe
   ... how to ignore deliberately black areas even though they're
   encoded in the video.

   nigel: What this proposal does is to defer some of the solution
   space but provide extra
   ... information to allow decoders to do a better job.

   davidr: At this point we don't deal with the use case of
   subtitle registration differing from how it is authored.

   nigel: Okay, well I encourage everyone to look at the proposal

   ... direct link to PDF:

   ... If there are no adverse comments then I intend to raise
   this as an issue and possibly a PR on
   ... IMSC 1 for a future update, because that is where it would
   be most useful for uptake.
   ... Thanks all [adjourns meeting]

     [18] https://lists.w3.org/Archives/Public/public-tt/2016Jun/0003.html

     [19] https://lists.w3.org/Archives/Public/public-tt/2016Jun/att-0003/Subtitle_Safe_Crop_Area_BBC_submission_2016-06-09.pdf

Summary of Action Items

   [NEW] ACTION: nigel Contact the chair of the Web & TV IG to ask
   about schedule and joint meeting time. [recorded in

     [20] http://www.w3.org/2016/07/21-tt-minutes.html#action01

Summary of Resolutions

   [End of minutes]

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     [21] http://dev.w3.org/cvsweb/~checkout~/2002/scribe/scribedoc.htm

     [22] http://dev.w3.org/cvsweb/2002/scribe/



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Received on Thursday, 21 July 2016 15:13:10 UTC

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