{Minutes} TTWG Meeting 2019-07-18

Thanks all for attending today’s TTWG meeting. Minutes can be found in HTML format at https://www.w3.org/2019/07/18-tt-minutes.html

Please note I will not be able to attend and Chair next week’s meeting – please let me know by 1600 UTC tomorrow if you would like to step in and chair, otherwise I will cancel the call next week.

Those minutes in text format:


   [1]W3C

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

                Timed Text Working Group Teleconference

18 July 2019

   [2]Agenda. [3]IRC log.

      [2] https://github.com/w3c/ttwg/issues/48
      [3] https://www.w3.org/2019/07/18-tt-irc

Attendees

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

   Regrets
          none

   Chair
          Nigel

   Scribe
          cyril

Contents

     * [4]Meeting minutes
         1. [5]this meeting
         2. [6]WebVTT
         3. [7]TTML2
         4. [8]Improve interoperability of non-negative-real and
            xs:decimal. ttml2#943
         5. [9]Remove xml:base and @condition from chunk.
            ttml2#961
         6. [10]TPAC Planning
     * [11]Summary of resolutions

Meeting minutes

this meeting

   nigel: we are still missing Mike so we cannot talk about
   profile registry

   cyril: but I don't think we need to discuss it, I have an
   action

   glenn: I prefer to have a proposal and then discuss based on it

   nigel: we will discuss progress towards CR for WebVTT

   gkatsev: yes, there is some progress

   nigel: 2 issues on TTML 2 that I think need discussion
   … we can discuss the region-timing test
   … I put charter status update if he joins
   … TPAC planning also is on the agenda
   … any other business ?

   glenn: I'd like to go over PR 1096

   nigel: I'm aware that you are waiting for feedback
   … ok if we have time

   nigel: the review of PR is a bit difficult and we are working
   on that

WebVTT

   gkatsev: the big thing that we last discussed was interop in
   parsing of region lines
   … spec says integer, Safari and Firefox do different things
   … I spoke with FF and they are fine with rounding
   … so I have a change for that
   … borrowed from the HTML spec
   … Silvia approved it
   … if any body has feedback
   … I have updated the snapshot for at-risk
   … it should be reviewed

   <gkatsev> [12]update region line parsing

     [12] https://github.com/w3c/webvtt/pull/470

   <gkatsev> [13]new snapshot

     [13] https://github.com/w3c/webvtt/pull/460

   nigel: PR preview does not seem to work
   … but there is a link in 460

   gkatsev: maybe because it's a change to the archive

   <plh> 45211

   nigel: process-wise we will review those and when there is
   consensus, merge them and propose new CR
   … is that the plan?

   gkatsev: yes
   … the CR stuff is in the snapshot #460 but because there are
   changes that we want to make permanently, I created a separate
   PR for the main spec

   nigel: those changes from 470 are also in 460 ?

   gkatsev: yes

TTML2

   nigel: we'll cover the issues first
   … 943 ?

Improve interoperability of non-negative-real and xs:decimal.
ttml2#943

   <nigel> github: [14]https://github.com/w3c/ttml2/issues/943

     [14] https://github.com/w3c/ttml2/issues/943

   nigel: this issue is about allowing zero point to be valid
   … it is not at the moment
   … glenn's proposal is to permit it
   … there is a PR for this

   glenn: I restarted the original PR that had been done last year
   … I updated based on the current master

   nigel: this means that a previous non-conformant document would
   become conformant

   glenn: technically yes
   … but it was never the intention to make that non-conformant

   <nigel> [15]xs:decimal definition

     [15] https://www.w3.org/TR/xmlschema-2/#decimal

   cyril: is '0.' allowed in xs:decimal?

   cyril: it seems that it is allowed according to section
   "3.2.3.1 Lexical representation"

   nigel: but the fact that the . is the last character is a bit
   confusing

   gkatsev: but it says that trailing 0 are optional

   glenn: we changed the schema since then to use xs:string
   … that change was based on the comment of July 21, last year
   … we just need to widen the expression for non negative real

   nigel: this change makes non negative real, the + becomes a *?

   glenn: no it adds a new line
   … you need the full stop to denote it's a real number

   nigel: ok, it makes sense
   … the idea of making non negative real coincident with
   xs:decimal makes sense
   … it makes it easier to write the schema
   … seems like a good change to me

   cyril: is it affecting only gain and pan?

   nigel: a lot of things
   … lengths, gain, pan, ...
   … pitch, percentage uses number
   … a lot of things would be affected by this

   pal: I'm looking at ttval
   … so now non-negative real always has a dot
   … but not a dot by itself

   nigel: it's good to look at implementation
   … just checking EBU-TT impl, 1. would not match, but 1.0 would

   pal: it seems ttval would reject 0. but I need to check

   nigel: it might make some existing implementations non
   conformant
   … I'm beginning to think it's a problem

   glenn: there is no requirement to backport it to TTML1
   … it would potentially make validation tools not implementing
   2nd ed more restrictive
   … not sure what the roll out status of TTML2 in the industry
   … but that would improve the status of interop

   nigel: that would be a change for IMSC 1.1 also

   cyril: I would say we shouldn't do syntactic changes unless
   it's broken

   pal: if we have several such changes, we could accumulate them
   and wait
   … it would make it easier to include this one

   glenn: I'm not sure I agree that it's a breaking change

   nigel: it's not a document breaking change, but an
   implementation breaking change

   cyril: I think people should look at their implementations and
   we can take a decision based on that

   nigel: if this would be the only syntactical change, then it
   might not be worth

   glenn: we already approved some changes

   cyril: it would be good to have a list of those

   glenn: we changed the content body to add audio

   nigel: summary: group to study implementation impact and add
   review comments

   pal: and if we do it, we should have a test for that

Remove xml:base and @condition from chunk. ttml2#961

   <nigel> github: [16]https://github.com/w3c/ttml2/issues/961

     [16] https://github.com/w3c/ttml2/issues/961

   nigel: a year ago, we discussed xml:base on the chunk element
   … with no apparent use
   … actually, xml:base is used to process condition
   … so it was proposed to remove condition
   … assuming positions haven't changed, it's to remove both, on
   the purpose that they do not serve any purpose

   glenn: the PR that I raised is a resurrection of the one last
   year
   … there is a significant difference in putting condition on
   chunk vs. source

   cyril: would there be an interop problem if I used them?

   glenn: it's quite dangerous, and you should not do that
   … I think that was an error when we authored it

   nigel: is it safe to say that there are other ways to do the
   same thing?
   … like putting condition on something else

   glenn: yes
   … you could have a multi-entry source
   … I could dream-up use cases, not obvious that might use that
   … but I'm pretty convinced that it's dangerous, security impact
   … because you cannot decode the bytes until presentation time
   … and so cannot determine that you have a valid resource

   cyril: I don't have a strong opinion on this, as we have not
   implemented it
   … but we should refrain from making changes unless it's broken
   … we could add a note without making changes

   glenn: my claim is that it is broken

   nigel: despite my comment in the issue, I think I've changed my
   mind and agree with Glenn
   … if you are worried of buffer overflow, that can happen with
   chunks or sources, regardless of whether condition is used

   pal: I don't have a strong opinion on this

   cyril: chances that people have authored documents with this
   feature is low
   … and it would not require people to change their
   implementation
   … so I'm fine with it

   pal: we really need tests
   … maybe that will limit us

   nigel: right, we should have tests with PR asking changes
   … because it will speed up CR processing

   pal: and helps people testing their implementation

   nigel: I'm hearing consensus to approve it and write tests for
   it

   pal: please include a test before merging the PR

   nigel: yes, good rule

   glenn: tests are not in the same repo

   pal: we could link PRs

   glenn: I have no problem creating tests for these

   Resolved: we approve the PR and write tests for it

TPAC Planning

   nigel: in the past, our team contact had prepared a wiki page
   … with draft agenda topics
   … there is also a proposal to have a joint meeting with CSS WG
   … and there is an issue on the TTWG repo #52

   <nigel> [17]Discussion points for CSS WG at TPAC 2019

     [17] https://github.com/w3c/ttwg/issues/52

   nigel: gathering discussion points for CSS WG at TPAC 2019
   … Atsushi could you create a similar looking wiki page

   atsushi: we should have a page for last year
   … is it ok to do something like that?

   nigel: yes

   <atsushi> [18]2018

     [18] https://www.w3.org/wiki/TimedText/tpac2018

   <nigel> [19]Action for Atushi to Create a TPAC 2019 wiki page

     [19] https://github.com/w3c/ttwg/issues/58

   pal: I'll be there only tuesday to thursday

   nigel: I'm not here next week
   … unless someone wants to chair, i'll cancel next week

   <nigel> log: [20]https://www.w3.org/2019/07/18-tt-irc

     [20] https://www.w3.org/2019/07/18-tt-irc

Summary of resolutions

    1. [21]we approve the PR and write tests for it


    Minutes manually created (not a transcript), formatted by
    Bert Bos's [22]scribe.perl version Mon Apr 15 13:11:59 2019
    UTC, a reimplementation of David Booth's [23]scribe.perl. See
    [24]history.

     [22] https://w3c.github.io/scribe2/scribedoc.html
     [23] https://dev.w3.org/2002/scribe/scribedoc.htm
     [24] https://github.com/w3c/scribe2/commits/master/scribe.perl