{minutes} TTWG Meeting 2015-10-30

Thanks all for another productive day. Minutes for today's meeting can be found at http://www.w3.org/2015/10/29-tt-minutes.html

In text format:


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

                               - DRAFT -

                Timed Text Working Group Teleconference

29 Oct 2015

   See also: [2]IRC log

      [2] http://www.w3.org/2015/10/29-tt-irc


          Andreas, Dae, Glenn, Nigel, Phillipe, Pierre, jcdufourd




     * [3]Topics
         1. [4]Charter
         2. [5]IMSC & TTML industry feedback, profiles etc.
         3. [6]IMSC Issues - proposals review
         4. [7]Agenda
         5. [8]Joint meeting with Multimodal Interaction Group
         6. [9]Charter (revisited)
         7. [10]IMSC issues proposals review (continued)
         8. [11]IMSC 2 and TTML2
         9. [12]TTML2
     * [13]Summary of Action Items

   <trackbot> Date: 29 October 2015

   <scribe> scribe: nigel


   nigel: Our charter runs out at the end of March 2016.
   ... So we have an opportunity to revise the charter in whatever
   way we see fit.
   ... As a result of the Web & TV IG meeting on Monday I put a
   call out for input.
   ... I received two comments. One was that HTMLCue might be
   related to the TimingCue
   ... being proposed by the Multi-Device Timing CG.
   ... The other was that we need to include other timing event
   models such as SMPTE
   ... timecode, MIDI etc. which I think we already do in TTML.
   ... Possibly there's an exception for external event based


     [14] http://www.w3.org/2014/03/timed-text-charter.html

   scribe: Since we have no concrete proposal for HTMLCue to be
   defined in this group I think
   ... we can discount the first comment, and the second comment I
   think is also already
   ... handled by our existing work.
   ... I haven't had any other proposals for change.

   pal: IMSC 2?

   nigel: We can already do that with the existing wording, which
   is vague enough to
   ... allow for multiple versions of a spec.

   plh: You can keep it as vague as it is now and still do IMSC 2.

   pal: We need to update the links from Mercurial to git - that's
   ... The links are in the Deliverables section.

   nigel: We should just update them to point to /TR.

   pal: And the milestones need to change.

   glenn: Can we eliminate the Milestones section?

   pal: +1

   plh: You'll probably get an objection from the W3C EO.

   nigel: Can we rename it "Forecast"?

   glenn: That would work.

   pal: If we have IMSC 2 do we need a new line in the milestone
   section for it?

   plh: The goal for milestone is to indicate the likely resource

   atai2: It's important for industry to know this information

   plh: You don't need milestones for every deliverable, but
   having none would be worrying.

   nigel: Can we make the milestones a link to something else that
   we maintain?

   plh: I believe so, I'd have to double check.

   <plh-web> [15]https://w3c.github.io/charter-timed-text/

     [15] https://w3c.github.io/charter-timed-text/

   plh: That's a link to the online version to your draft charter.

   <plh> [16]https://github.com/w3c/charter-timed-text

     [16] https://github.com/w3c/charter-timed-text

   plh: You have write access to it.
   ... When we are ready to submit it to the AC I will remove the
   write access to it.

   nigel: Why not create a branch?

   plh: True, I could do that or create a dated version that only
   Thierry and I can change.
   ... At some point I just need a guarantee of stability.

   nigel: For the process, when do we need to have this ready?

   plh: You need to give me a charter at the end of January.
   ... Then I take your draft, go to W3C management, and make the
   case for spending the
   ... resources on this WG. That takes ~2 weeks to get approval.
   ... Then once we secure management approval it is submitted to
   the AC for review.
   ... That takes 4 weeks, per process. Then after that the
   Director has 2 weeks to follow up.
   ... Additional delays could be introduced by review feedback,
   if the charter is controversial.
   ... One strategy for dealing with that is to give the draft
   sooner. The other is to indicate
   ... that it will take a while, and request a ~3 month extension
   to the current charter
   ... while the potential objections are resolved.
   ... If you don't have a charter ready by the end of January
   please let me know because
   ... you will need an extension to cover the gap.
   ... One consideration to have, which I can raise as an issue on
   github, is which
   ... license do you want to use for the documents? You can use
   the W3C document licence
   ... that is the one you are currently using, which doesn't
   permit document forking and reuse.
   ... There's another licence available that permits forking as
   long as you give attributions.
   ... It's called the W3C Software and Document licence. It's an
   OSI approved licence that
   ... was modified to include documents.
   ... You can use whichever one you want. WebVTT will want to use
   the Software and Document
   ... Licence.

   glenn: Do we have to choose one for the group?

   plh: Only two working groups are using it so far. Other groups
   decided not to use the

   <scribe> ... new licence. I don't know any reason why you
   shouldn't use different licences for

   UNKNOWN_SPEAKER: different documents. If you want to do more
   complex stuff but not put it in the charter,
   ... then you could look at the HTML WG charter, which allows
   for a discussion during the
   ... course of the WG to decide later.
   ... I don't recommend one way in particular.

   nigel: Is there a licence specified in the current charter?

   plh: No - we only had one licence at the time, so there was no



     [17] http://www.w3.org/2015/10/webplatform-charter.html#licensing

   plh: I recommend that you look at the wording of the above web
   platform charter as a
   ... source of inspiration. For example for wording about where
   most of the work happens.
   ... The Decision Policy is an example. Also look at the
   Milestones section, which is
   ... very vague. That WG has 40-50 documents, but only 5 are
   listed. That's another example.
   ... That includes a link to the Specification Status as a
   pointer for accurate current data.

   nigel: Can we use the same stylesheet for the Charter as the
   new one for /TR?

   plh: I'll ask but it may not seem important enough to spend a
   lot of time on.
   ... Now that you mention it there was a thread on the AC forum
   about a new style for charters.



     [18] https://lists.w3.org/Archives/Member/w3c-ac-forum/2015OctDec/0006.html

   pal: So what's our process for developing this?

   nigel: Do you want to treat me as the Editor and send PRs?

   pal: Okay.

   plh: I can do a first pass at changing the links etc.

   nigel: The most important thing is the End Date!

   plh: Your maximum is 2 years.

   nigel: Everyone happy with 2 years?

   all: yes

   glenn: By the way, 2018 will be the 15th anniversary of this

   plh: The start date will be whenever the Director approves the

   nigel: Right now the only substantive change we have on the
   table is the end date.
   ... Apart from that we're just looking at polishing and

   plh: In that case you might just want an extension.

   nigel: Is there a maximum duration of extension?

   plh: I'm not sure - we need to check what the AB is comfortable
   with nowadays.
   ... By the way if you change the document licence for WebVTT
   that would be a substantive
   ... change.
   ... Although it may not matter because the CG version is
   published under the CLA anyway.
   ... I'll ask Simon what he thinks.

   atai2: I wonder about adding deliverables that ease adoption of
   our specs like primers etc.

   plh: We haven't got enough resources for Recommendations - if
   you know someone
   ... who is willing to do the work on Primers (which I like)
   then you can add it.

   nigel: We don't need new Notes to be in the Charter.

   plh: We got objections in the past when Primers were excluded
   from the charter.
   ... For example the Web Performance Group charter - the absence
   of a primer there
   ... generated a formal objection.

   nigel: It's a shame we had to swap the agenda around today to
   bring this discussion
   ... ahead of the industry feedback section. One thing on my
   mind is if we should publish
   ... a document that explains how to stream TTML to avoid us
   having the same conversations
   ... over and over again.

   plh: It can be a good technique to get someone outside the WG
   to work on primers,
   ... because they have an external viewpoint. You could ask them
   to join the WG for the
   ... purpose of writing the primer.
   ... You might want to look carefully at the Scope section, for
   example to remove
   ... anything you know you will no longer need to deliver.

   nigel: Looking at Dependencies, do they now need to change?

   plh: You want HTML WG and Web Platform WG.
   ... PFWG is now called something else.
   ... Leave it to us to update the names.
   ... The groups in the Liaisons section all still exist.

   nigel: We should take Good Standing out?

   plh: Correct. Other changes will need to happen to keep up with
   the new process.
   ... Look at the Web Platform charter for Decision Policy. I
   don't think it will have a practical change on your operational

   atai2: The Web Annotations group has been considering using
   Timed Text. Members
   ... of that group have mentioned that it may be helpful to meet
   up with them. Also,
   ... the same people are in the Digital Publishing group, so it
   may be helpful to meet up
   ... with them. If there's an opportunity for collaboration then
   that would be good.

   nigel: I think one WG needs to be responsible for any single
   ... Do you think that would be a liaison or a dependency?

   atai2: Yes, one of those.

   nigel: Okay, we need further discussion on that.

IMSC & TTML industry feedback, profiles etc.

   atai2: Over the past year we've seen really good uptake of TTML
   in the EBU-TT-D profile
   ... especially because of HbbTV 2.0. For example there's a
   prototype implementation
   ... television from Samsung. I asked if they had any feedback
   for the group.
   ... First they said it is very good, and they would also like
   to implement IMSC.
   ... Also they said they had a good experience working with
   people involved in writing
   ... the specification, and they would like to work with
   ... They have implemented linePadding and multiRowAlign.
   ... Another comment is that there is no precise identification
   mechanism for IMSC and
   ... EBU-TT-D even though they are different. We should consider
   a precise identification
   ... mechanism, bearing in mind the option to add a profile
   ... I think the main message is that they need a precise
   identification mechanism when
   ... they work with different profiles. We heard this from
   others too, and on the mailing
   ... list.

   nigel: Can you explain the use case more precisely?

   atai2: No I can't. For a processor that gets a file they have
   to look at the document to see
   ... if it is EBU-TT-D or IMSC. They have to choose or decide if
   they can play it or which
   ... kind of settings they must apply. I think that's what they

   glenn: I can give a couple of use cases too for having some
   kind of profile specification
   ... that is in the document, e.g. the profile attribute. When
   landing on a client, to
   ... determine if the decoder can support it. In the absence of
   any profile specification on
   ... a generic decoder, in the absence of external knowledge,
   then it has to use the default
   ... "dfxp transform" profile. That's safe because no content
   will be rejected.
   ... Another use case is for validation and verification, where
   specifying the TTML1
   ... profile is a hint as to what may have been expected. We
   know it is not a content
   ... profile specification, but it does give some guidance.

   jcdufourd: Our use case is that TTML is one of many media that
   we want to package
   ... in MP4 for a segment, or for DASH segmentation, e.g. 2-10s
   long segments. We want
   ... to deal with TTML as with any other kind of media, like a
   video gives a precise profile
   ... indication that's commonly used. It's the same in any
   ISOBMFF version not just MP4.
   ... There's this strange thing that in audio there's the same
   problem as in TTML. There's
   ... no indication without going in deep. dsinger said a couple
   of days ago that it's good
   ... that we only use AAC Low Complexity otherwise noone would
   be able to use it.
   ... That's a similar situation where not having a correct
   indication in the stream is a problem.
   ... Cyril told me that the default profile is unhelpful and
   there are multiple ways of
   ... signalling profile. There's no easy sniffing heuristic. So
   all of that makes it difficult
   ... to use the media TTML, so from our systems point of view if
   we have a difficulty using
   ... one codec then we would use another one.
   ... Please make it easier for us!

   glenn: Of course with WebVTT we don't know which features are

   pal: There was an issue filed against IMSC 1 based on feedback
   from Cyril. Based on
   ... that issue I have a proposed resolution. Maybe we could
   look at that?

   atai2: We need to give clear guidance to implementors, and
   maybe to abstract a bit from
   ... what is correctly written in TTML and find a practical
   solution for now.


   <trackbot> issue-448 -- Add recommendation for ttp:profile and
   ebuttm:conformsToStandard -- pending review


     [19] http://www.w3.org/AudioVideo/TT/tracker/issues/448

   pal: Presents proposed edit to the #profile feature.
   ... One problem is that ttp:profile attribute only supports a
   single value in TTML1, so you
   ... cannot signal dual conformance with EBU-TT-D and IMSC 1
   Text profile.
   ... Also EBU-TT-D prohibits use of ttp:profile.
   ... So the proposal is to use ttp:profile="[imsc profile
   designator]" for IMSC 1, and
   ... omit ttp:profile but include ebuttm:conformsToStandard for

   jcdufourd: And ttp:profile element is prohibited?

   pal: Yes. The reason for that is that the element is used to
   specify a profile specification
   ... in-band, and IMSC 1 does not specify such a profile.

   jcdufourd: Why 'SHOULD' not 'SHALL'?

   pal: There will still be instances where it is not present for
   a while. It would be extreme
   ... to reject otherwise conformant documents just because they
   do not include the ttp:profile attribute.
   ... I'm happy to put SHALL though.
   ... The spec also says that if a document is not conformant
   then the behaviour is not defined.

   jcdufourd: So if neither of these things is present then what
   would you do?

   pal: If I were building an implementation then I would force
   the "user" (broadly) to tell
   ... the implementation what the file is.

   jcdufourd: That matches what nigel recommended privately.

   nigel: Yes, I said the same thing.

   glenn: In TTML1 we say that the processing environment can
   infer a profile in the absence
   ... of any information in the document, and if that fails then
   there's a default minimum profile.

   jcdufourd: The use case in which inferring is not good is in
   the live situation where you
   ... stream a presentation with live subtitles and you have no
   idea what will happen in
   ... the future so you cannot sniff ahead.

   glenn: Since TTML does not define a streaming format what
   people have done is to
   ... chunk into separate small TTML files, each of which can
   specify the profile. If they
   ... change this between documents, then that would be
   ... I would prefer 'SHALL' also. I wonder what would happen
   with CFF content. In that
   ... case I guess it would be implementation dependent since
   those existing files would
   ... not be valid.

   pal: This can't be pain-free, but we should minimise the pain!

   nigel: What about EBU-TT-D documents that don't support imsc or
   do - what should we say about ebuttm:documentConformsToStandard
   carrying one or two values?

   group: [discusses this] It's actually covered.

   atai2: The recommendation is to have both values signalled in
   ... Maybe we should clarify that if imsc is omitted from
   ...conformsToStandard then it should be considered
   non-compliant with IMSC.

   pal: If we write SHALL then it implies that implementations
   give up if they don't see
   ... exactly what's here, but the proper behaviour is that
   there's an opportunity to specify
   ... the profile externally.

   jcdufourd: What I understand is either 1) IMSC or 2) EBU-TT-D
   or 3) External profile or
   ... 4) I can trash it. The flavour is that there is a SHALL.

   pal: So an out of band specification doesn't break the SHALL?

   jcdufourd: Correct. If that's the understanding then we're

   glenn: Is there any reason you would have to trash it? You
   could just use the default default.

   jcdufourd: The thing is that our way of doing it in systems is
   to use the maximum profile.

   nigel: Actually that's the same thing.

   glenn: If you choose the maximum then you're being the most
   conservative about what
   ... you require from the profile. If you were talking about
   content profiles then you'd be
   ... saying that the document uses all the features but the
   processor does not need to.

   jcdufourd: I don't see a difference from the systems

   glenn: The difference is that you wouldn't necessarily throw
   the document out.

   pal: You can set an out of band policy for a specific profile.

   glenn: It's fair to be able to do that.

   pal: If I find a document with conformsToStandard="ebu-tt-d"
   but not Imsc1 then that's
   ... fine and the logical conclusion is that I can't assume that
   it's an IMSC 1 compliant document.

   nigel: That would handle the corner case of say an EBU-TT-D
   document that's UTF-16, say.


   <Zakim> glenn, you wanted to ask if ebu will remove the
   restriction on ttp:profile

   glenn: That goes back to my question. If you have a generic
   IMSC or TTML processor and
   ... no profile attribute is present then it can handle it, and
   if one is present than it can
   ... handle it but if it is prohibited then that introduces the
   problem of having to guess.
   ... You really want both ttp:profile and conformsToStandard to
   be present, because
   ... an IMSC processor that does not know about
   ... would not know what to do.
   ... It's hostile to interoperability to prohibit ttp:profile.
   What's the chance of EBU
   ... changing it?

   atai2: Realistically, the spec is closed apart from errata.

   glenn: In a future version?

   atai2: I agree it's better to have it all in one place, but as
   pierre said you cannot signal
   ... multiple profiles to be present. It would have to be
   discussed in EBU. At the moment
   ... we need to find a solution for current documents. This from
   my side is a good solution.

   nigel: I agree this is a proposal that will work pragmatically.
   The thing we haven't
   ... considered is adding a new thing to IMSC that could find
   its way into TTML later
   ... that permits multiple profiles to be indicated, perhaps
   using the profile registry
   ... short codes.

   pal: I'm happy that this current proposal satisfies the issue
   that's been raised.

   nigel: Agreed. Adding a new thing would give e.g. EBU something
   to discuss that may deal with their issues.

   atai2: We can also look at how the profile registry document
   can support this.

   pal: I'd like to close this issue because it addresses the use
   case and then look at that separately.

   atai2: Additionally, did we agree that it is possible to signal
   the profile externally without
   ... using this?

   pal: Yes. The profile designator can be specified out of band.

   nigel: So are we adopting this proposed #profile text unchanged
   or are we changing
   ... any of the SHOULDs to SHALLs?

   jcdufourd: If the out of band signalling is meaningful and not
   rare then you can leave the SHOULDs in.

   glenn: I'm fine with leaving it as SHOULD. I think there needs
   to be language somewhere
   ... that says if neither are present then what behaviour is
   expected or any inference should
   ... be made.

   pal: That's the implementor's problem.

   atai2: Undefined.

   nigel: We can be a bit friendlier and add a note to say that
   out of band signalling is expected
   ... if the SHOULDs are not honoured.

   glenn: So there's no inference?

   nigel: The inference is if there's no in-band and no
   out-of-band signalling then it's not
   ... related to this specification!

   pal: I would also say authoring tools should never be able to
   create documents that don't
   ... signal the profile.

   jcdufourd: +1

   pal: I don't like to add a Note here about out of band
   signalling. I don't think it's helpful to implementors.

   nigel: Okay but we haven't dealt with the feedback 'what to do
   if there's no in band signalling'?

   pal: I think that's something to add to an external usage note
   like the profile registry
   ... document.

   jcdufourd: My name is Jean-Claude Dufourd. I work at ParisTech,
   alongside my colleague Cyril who cannot be present today.

   Shingo: My name is Shingo Mine from Mitsubishi.

   atai2: I propose that in the profile registry document we add a
   recommendation on where
   ... to find profile information in-band as well as out-of-band,
   to make it clear for all
   ... implementors where they can find this information.

   <scribe> ACTION: atai2 Propose to mdolan this addition to the
   profile registry document. [recorded in

   <trackbot> Created ACTION-445 - Propose to mdolan this addition
   to the profile registry document. [on Andreas Tai - due

   nigel: Let's break - back at 1100.

   close issue-448

   <trackbot> Closed issue-448.

IMSC Issues - proposals review


   <trackbot> issue-410 -- Constraints on #linePadding and
   #multiRowAlign -- pending review


     [21] http://www.w3.org/AudioVideo/TT/tracker/issues/410

   group: reviews text on #linePadding and #multiRowAlign in the
   current ED.

   glenn: You can not use the word apply in this way.
   ebutts:linePadding has no effect on region.
   ... The only place it has an effect is on a span.

   atai2: The definition of this does describe its application
   relative to a containing block.
   ... The meaning is exactly as you describe. The apply section
   is about the semantic
   ... application of this concept to elements in TTML.

   glenn: Another example is foreground colour, which can be
   specified on any content
   ... element type but it only applies to text elements inside a
   ... Similarly extent and origin apply to region, which was
   misconstrued because we
   ... didn't say that there's no semantic when it is on an
   element from which there is no
   ... inheritance down to region.

   atai2: That's 100% the meaning we intend.

   glenn: It only applies to span though.

   atai2: But the EBU-TT-D definition is for application to parent
   ... There seem to be 2 issues. One is not related to IMSC,
   being the definition of the feature.
   ... The other is the conformance language, which is the issue
   we have to deal with here.

   nigel: We have to consider "applies" relative the feature as
   defined, which is on the block element.

   glenn: I have to consider the equivalent functionality in

   nigel: I disagree - you can treat that independently.

   glenn: Line areas are all descendants of the p element so it
   makes no sense to apply
   ... linePadding to region, body or div.
   ... [draws diagram showing block, line and inline areas] Line
   areas are only generated
   ... by block areas associated with p elements.

   nigel: Can we resolve by saying that #linePadding applies to p
   and is inherited?

   group: okay

   pal: let me add that...

   issue-410: [meeting 2015-10-30] agreed to say for #linePadding
   and #multiRowAlign that they shall be applied to p and that
   they shall be treated as inheritable.

   <trackbot> Notes added to issue-410 Constraints on #linePadding
   and #multiRowAlign.

   nigel: Also worth noting that the other raised problem was
   fixed in issue-450.

   issue-410: [meeting 2015-10-30] Also note that issue-450 was
   resolved so the conformance language problem no longer applies.

   <trackbot> Notes added to issue-410 Constraints on #linePadding
   and #multiRowAlign.


   <trackbot> issue-411 -- "shall be inherited" on #multiRowAlign
   -- pending review


     [22] http://www.w3.org/AudioVideo/TT/tracker/issues/411

   issue-411: [meeting 2015-10-30] See also notes on issue-410.

   <trackbot> Notes added to issue-411 "shall be inherited" on

   close issue-410

   <trackbot> Closed issue-410.

   close issue-411

   <trackbot> Closed issue-411.


   <trackbot> issue-423 -- Use of proprietary, non-open source
   fonts as reference fonts -- pending review


     [23] http://www.w3.org/AudioVideo/TT/tracker/issues/423

   glenn: The switch to open source fonts is acceptable to me.

   pal: I also verified that the width is equivalent.

   glenn: Is there any need to have the OR?

   pal: The reason I kept that is that if you do have the non-open
   fonts available you should
   ... not be penalised, so both should be allowed.

   glenn: I would remove the Note in Appendix A too.

   pal: I would agree with that - I don't think it is particularly
   ... I'll remove it right now.

   close issue-423

   <trackbot> Closed issue-423.


   <trackbot> issue-450 -- IMSC1 Does Not Require Any
   Feature/Extension be supported by a Processor -- pending review


     [24] http://www.w3.org/AudioVideo/TT/tracker/issues/450

   nigel: I think we covered this yesterday?

   pal: I've now done the commit based on the preview.
   ... In §4 Conformance I added an i.e. phrase to address Glenn's

   glenn: I don't like seeing "i.e." in conformance language but I
   won't object to it.

   nigel: Is there an easy quick shortcut to fix that?

   glenn: I'll compose something...

   <glenn> SHALL implement presentation semantic support for all
   features designated as "permitted" by the profile, modulo any
   additional constraints on features as specified by the profile;

   pal: Can we use "subject to" instead of "modulo"?

   <glenn> SHALL implement presentation semantic support for all
   features designated as "permitted" by the profile, subject to
   any additional constraints on features as specified by the

   group: looks good

   glenn: The same change applies to presentation processor and
   transformation processor.

   <glenn> SHALL implement transformation semantic support for all
   features designated as "permitted" by the profile, subject to
   any additional constraints on features as specified by the

   glenn: Are there any features that are not "permitted" where
   some support is required?

   pal: No we only have permitted and prohibited.

   nigel: Now that we've done that wouldn't it make sense to add
   "permitted" to #lineBreak-uax14?
   ... and add a note that it has no syntactical impact.

   group: [discusses the pros and cons of this]

   nigel: Consensus achieved on leaving #lineBreak-uax14 as is,
   noting that processor implementors may have to be extra careful
   to note
   ... that implementation of that feature is required even in the
   absence of the "permitted" keyword.

   close issue-450

   <trackbot> Closed issue-450.

   issue-450: [Meeting 2015-10-30] Change implemented above as

   <trackbot> Notes added to issue-450 IMSC1 Does Not Require Any
   Feature/Extension be supported by a Processor.


   nigel: We're visiting Multimodal Interaction in 2F. 204 at
   1300, returning here at 1315.
   ... [adjourns for lunch]

   close issue-452

   <trackbot> Closed issue-452.

   issue-452: [Meeting 2015-10-30] Change agreed as above.

   <trackbot> Notes added to issue-452 The ttp:profile element is
   permitted to conflict with the IMSC 1 profile.

Joint meeting with Multimodal Interaction Group

   nigel: [discussion of TTML example in EMMA 2.0 spec, and
   further potential use cases]

Charter (revisited)

   glenn: There may be a use case we haven't covered for HTMLCue.

   nigel: Maybe if people want us to develop something in this
   group then we need to add
   ... something to the Charter.
   ... It can be generic, like "A mechanism for displaying
   arbitrary HTML with cue timings"

   group: [general support]

IMSC issues proposals review (continued)


   <trackbot> issue-418 -- semantics of ttp:aspectRatio is
   ambiguous -- pending review


     [25] http://www.w3.org/AudioVideo/TT/tracker/issues/418

   glenn: My query is if aspect ratio and extent are both
   specified then which one applies?

   nigel: Aren't you assuming square pixels?

   glenn: No I'm not!

   pal: Let's look at the examples.

   glenn: My first question is what is the relationship between
   the aspect ratio and the
   ... storage aspect ratio implied by the extent?

   pal: None. extent describes the root container logical
   coordinates, e.g. 400px 300px.

   glenn: That can be used to derive the storage aspect ratio.
   ... I agree that it only matches the Display Aspect Ratio if
   the pixels are square.
   ... So aspectRatio tells you the display aspect ratio. And you
   can derive the pixel aspect
   ... ratio from that?

   pal: That's right.

   glenn: Can you add a note to say that aspect ratio means
   display aspect ratio?

   pal: Sure. Of the root container.

   glenn: That's right.
   ... And that you can derive a storage aspect ratio...

   pal: Can you draft that in IRC?

   <glenn> Note: The ittp:aspectRatio parameter effectively
   defines the intended display aspect ratio (DAR) of the root
   container, while the tts:extent style property on the root
   element effectively defines the intended storage aspect ratio
   (SAR) of the root container.

   issue-418: [Meeting 2015-10-30] Proposed note: Note: The
   ittp:aspectRatio parameter effectively defines the intended
   display aspect ratio (DAR) of the root container, while the
   tts:extent style property on the root element effectively
   defines the intended storage aspect ratio (SAR) of the root

   <trackbot> Notes added to issue-418 semantics of
   ttp:aspectRatio is ambiguous.

   nigel: Does that resolve it Glenn?

   glenn: Yes, that would resolve this issue.
   ... I was previously interpreting it as storage aspect ratio,
   which would have been a conflict.

   pal: I've updated the document, just adding the changelog to
   the issue.

   close issue-418

   <trackbot> Closed issue-418.


   <trackbot> issue-449 -- Needs XSD Schema for IMSC Extensions --
   pending review


     [26] http://www.w3.org/AudioVideo/TT/tracker/issues/449

   pal: I added XSDs
   ... I was inspired by Glenn's contribution but changed it. The
   end result is identical.
   ... I changed it to define types inline rather than in a new

   glenn: It turns out to be important for enumeration types when
   you generate a JAXB
   ... binding. If you don't have a top level definition then it
   won't generate a type. The
   ... code in TTV that supports IMSC has to have them as separate

   pal: But there's no enumeration here though. Just native

   glenn: I just double checked and it's fine. The only JAXB type
   generated was the alt-text element that is defined as a new
   element in this.

   nigel: Having a look at the schemas... Can't view the files.

   pal: I need to update the links to change raw-file to file so
   you can navigate the directory.

   glenn: And these are not normative so we can change the

   pal: That's right. Specifically non-normative.

   glenn: Notice that they do not include either the SMPTE or
   EBU-TT-D entities. In TTV
   ... I had to add this as well as the SMPTE and EBU-TT-D
   features, which I had to subset.

   pal: The links are relative, so I don't know how to fix them.
   This will probably go away when we switch to github.

   issue-449: [Meeting 2015-10-30] Group happy with schemas - can

   <trackbot> Notes added to issue-449 Needs XSD Schema for IMSC

   close issue-449

   <trackbot> Closed issue-449.


   <trackbot> issue-451 -- #visibility-inline should be limited to
   text profile -- pending review


     [27] http://www.w3.org/AudioVideo/TT/tracker/issues/451

   <scribe> ACTION: pal Go through every feature and make sure
   that they take into account any dependent features. [recorded
   in [28]http://www.w3.org/2015/10/29-tt-minutes.html#action02]

   <trackbot> Created ACTION-446 - Go through every feature and
   make sure that they take into account any dependent features.
   [on Pierre-Anthony Lemieux - due 2015-11-06].

   close issue-451

   <trackbot> Closed issue-451.


   <trackbot> issue-453 -- Clarify relation between forcedDisplay
   and visibility in intro statement -- pending review


     [29] http://www.w3.org/AudioVideo/TT/tracker/issues/453

   close issue-453

   <trackbot> Closed issue-453.

   pal: There are some issues still open on HRM, which are all
   ... The difference between GCpy and Ren is the performance
   improvement from glyph reuse.
   ... Based on the discussion yesterday glyphs cannot always be
   reused for a particular code point,
   ... because a code point has multiple variant glyphs. The idea
   is to reduce the performance
   ... improvement that is predicted based on script, because some
   scripts have more
   ... variant glyphs than others.
   ... The distinction for CJK is only outside the glyph buffer
   for text rendering.

   glenn: So you might have different values of GCpy based on

   pal: Right. However as you pointed out that there are different
   ratios for different scripts.

   glenn: The question is if it is worth changing the model to
   take into account Indic.
   ... In Indic there are other steps too, like reordering. I
   would say on average treat Indic
   ... the same as Arabic for the multiplier. I suggest using two
   terms, "simple" and "complex"
   ... which are commonly used in the industry. Unfortunately
   there is no Unicode term for
   ... this. There is an enumeration of scripts, and there are ISO
   script codes.


     [30] https://en.wikipedia.org/wiki/ISO_15924

   glenn: You could enumerate the script codes and enumerate them
   as simple or complex.
   ... I'd suggest varying the HRM based on those two labels, and
   I can tell you which scripts
   ... fall into which category offline.

   <scribe> ACTION: glenn Send Pierre the list of which scripts
   are simple and which are complex. [recorded in

   <trackbot> 'glenn' is an ambiguous username. Please try a
   different identifier, such as family name or username (e.g.,
   gadams, ggoldste).

   <scribe> ACTION: gadams Send Pierre the list of which scripts
   are simple and which are complex. [recorded in

   <trackbot> Created ACTION-447 - Send pierre the list of which
   scripts are simple and which are complex. [on Glenn Adams - due


   <trackbot> action-432 -- Nigel Megitt to Nigel, pal, andreas
   and frans to hook up re changing imsc 1 ebu-tt feature
   references to point to tech3350 v1.1 -- due 2015-10-15 -- OPEN


     [33] http://www.w3.org/AudioVideo/TT/tracker/actions/432

   pal: We've made a decision how to progress.

   close action-432

   <trackbot> Closed action-432.


   <trackbot> action-437 -- Nigel Megitt to [imsc1] propose new
   wording for intro sentence to itts:forceddisplay -- due
   2015-10-22 -- PENDINGREVIEW


     [34] http://www.w3.org/AudioVideo/TT/tracker/actions/437

   close action-437

   <trackbot> Closed action-437.

   pal: Can we talk about set in IMSC?
   ... I got an email asking how to express in IMSC 1 a real world
   example where a title

   <pal> pal: use case is " A real world example is when a title
   or graphic suddenly appears in the video, a good real-time
   captioner will send a command to move the existing accumulated
   captions to another part of the screen so that they don’t
   obscure the graphic. How do we represent that in IMSC? We
   thought of some options"

   pal: The two options they could think of were a) duplicate the
   text in a different region.
   ... b) use set to move the origin of the region.
   ... They asked for any other ideas.

   glenn: Are they asking for smooth scrolling?

   pal: No just a jump.

   glenn: Both of those would work.

   nigel: I want to know why they need to know if the text is the
   same text as opposed to
   ... just being interested in the appearance being correct.

   glenn: They could define some of their own metadata to identify
   the content, if they use the first solution and want to keep
   the semantic meaning.

   nigel: I'd observe that in EBU-TT-D you can't use set, but if
   they don't need that then they can use set.
   ... The usage of a content identifier is useful not just for
   spatial movement/deduplication
   ... but also temporal, in case the same text appears in
   consecutive TTML documents in
   ... a streaming scenario. If you want to push the text into a
   screen reader or TTS engine
   ... then a content identifier allows the implementation to
   avoid speaking the same words
   ... multiple times.

   pal: Has anyone solved this?

   nigel: I'm told that the streaming solutions for VTT don't have
   this effect.

   atai2: This has been discussed in other groups also.

   glenn: It turns out that Lambda cap does have an id called
   screen number but it is not
   ... consistently used, so it's hard to maintain that metadata.

   pal: So the downside of using set is that in general it would
   not deal with semantic linking
   ... temporally.

   nigel: Yes.

   atai2: Is there a requirement for an id independent from xml:id
   that makes it possible
   ... to have a linkage between content elements.

   nigel: xml:id is tightly specified to have single document
   uniqueness. If you want something
   ... that crosses documents you need to define something else.
   ... Is there a generalised ID scheme for content across and
   within XML documents?

   glenn: Not that I'm aware of.
   ... I would imagine in the Text Encoding Initiative there is
   markup that's defined
   ... for this purpose.

   pal: Okay thanks I'll respond based on that.

IMSC 2 and TTML2

   pal: I have a draft set of proposals for what to include from
   ... One worry is the condition construct.

   glenn: You could subset it to parameter based conditions only,
   to satisfy forcedDisplay.

   pal: I was hoping to have a wider session to think about the
   whole condition construct.

   glenn: The existing condition language is less complex than
   other similar languages like
   ... in CSS. I had in mind boolean expressions, but there
   doesn't seem to be any point
   ... in not having relative arithmetic too with less than or
   greater than for example.
   ... We also have media queries which I had incorporated into
   that condition language.
   ... They are commonly used in CSS and in mobile contexts.
   ... I thought it would be useful to design TTML content that
   could work on devices where
   ... it chooses different video formats and resolutions based on
   the screen aspect ratio
   ... and resolution. You could create different files for each
   context; another is to use
   ... condition.

   nigel: This is an interesting moment to show a demo of some
   work done by some of
   ... my colleagues in BBC R&D. [shows demo of text size vs time

   glenn: You could do this by duplicating content and using the
   condition system to
   ... select content based on font size range.

   nigel: My thinking was to use an earliest and latest time
   expression semantic, in other
   ... words extending the time expressions.

   pal: Why is this not purely a client feature?

   nigel: You need to have some authorial input because you may
   want to restrict the
   ... earliest or latest appearance time of e.g. words.

   pal: You could add metadata to add earliest/latest semantics.

   glenn: You could also conditionalise line breaks.

   atai2: Can we collect some more detailed use cases for this?

   glenn: If you had a tag that would clear a region and you could
   conditionalise that then
   ... it could help with this.

   pal: In general it would be better to list the use cases to
   meet here for this conditional
   ... language and to accommodate what you have shown, to see
   what more would be
   ... needed to meet these requirements, and to decide if we
   should cover those use cases.

   dae: That's called Responsive Subtitles?

   nigel: Right.

   dae: Another use case is to change the colour scheme.

   atai2: Also a request to support better customisation in TTML
   directly would be a part of it.
   ... Users often want support for customisation.

   nigel: One problem we have is how to make it possible for
   implementations to be
   ... processor spec compliant and also accessibility guidelines

   glenn: We had a thing a while ago called Dynamic Flow
   Processing Model.
   ... I spent a long time trying to come up with a rational model
   for this!



     [35] http://www.w3.org/TR/2010/CR-ttaf1-dfxp-20100223/#dynamicFlowModel

   glenn: [explains]

   nigel: I don't propose to bring that back!

   pal: I want to clarify why I don't think it's necessary for
   implementations to offer the
   ... user to change colours etc. The parallel is televisions,
   which receive a very specific
   ... coding format, with a colour space, a reference decoder
   etc. but of course the TV
   ... applies other processing like denoising, vivid mode etc.
   There's a clear parallel, where
   ... you can have a core conformant processor and yet the
   application can choose to apply
   ... additional processing like choosing fonts.

   atai2: I think possibly the author may need more influence than
   that to follow
   ... accessibility, with data in the document not just in the
   implementation. The client
   ... side does not know about the content, only the author does.

   pal: There's a regulatory regime that players have to meet
   already, in the US.

   nigel: It would be nice if implementations could meet
   regulations and be spec compliant.

   pal: They already are. The spec does not prevent customisation.

   nigel: If a user chooses a font size then except in the one
   case that they choose what is
   ... in the file then the processor can either meet regulations
   or the spec.

   atai2: Nevertheless it would be useful to provide guidance on
   how customisation could
   ... be provided.

   pal: I am not aware of inconsistencies between specification
   and regulations.

   glenn: I can't see any language in TTML1 that allows for user
   overrides, but that would
   ... have been the intention all along. We just assumed that it
   would happen. I don't
   ... think that comment has ever been raised before.
   ... We could make an errata to state that the processing
   environment can override
   ... presentation requirements as requested. We should also
   think about that in TTML2.
   ... There are a couple of pending review items on TTML...



   <trackbot> issue-224 -- Support text placement in 3D coordinate
   spaces (not zIndex compositing). -- pending review


     [36] http://www.w3.org/AudioVideo/TT/tracker/issues/224

   glenn: I applied Pierre's patch. I have since learned that some
   edits may be needed.

   pal: I corrected this in the branch.

   glenn: Unless it's ready I won't reapply it.
   ... Looking at the sentence that begins "tts:disparity" please
   could you edit it so it does not begin with a keyword?
   ... I didn't spot the latest email and just applied the
   previous patch.
   ... Maybe we can do that offline.
   ... Also I edited it a little bit to remove the reference to
   ... The changes made between 25th and 27th were just language

   pal: yes.

   glenn: Okay I'll fix that up.


   <trackbot> issue-322 -- Formula for dropNTSC time expressions
   is incorrect. -- pending review


     [37] http://www.w3.org/AudioVideo/TT/tracker/issues/322

   glenn: We had from June 2015 an email from Charles Ritchea
   pointing out an error
   ... in Appendix N.3. He points out that the floor() is in the
   wrong place.
   ... And he shows the fix for the dropPAL case also.
   ... I recently verified these numbers with some actual test
   content and looking at the
   ... exact generated timing, and these corrections produce the
   right results. I've fixed
   ... these in two places. There's an errata update for TTML1:



     [38] https://dvcs.w3.org/hg/ttml/raw-file/2cd6f1c06e57/ttml1/spec/ttml1-errata.html

   nigel: Looks like you haven't pushed the same changes to TTML2

   glenn: So I'd like approval to publish the new errata and once
   I've verified it in TTML2 to close that out.

   pal: Where did you find the formulas?

   glenn: Originally I derived them from some specifications in
   SMPTE specs that defined
   ... the drop frames very precisely, but it looks like I got it
   ... I can't remember the exact specs.

   issue-322: [Meeting 2015-10-30] Group happy with proposed
   errata text at


     [39] https://dvcs.w3.org/hg/ttml/raw-file/2cd6f1c06e57/ttml1/spec/ttml1-errata.html

   <trackbot> Notes added to issue-322 Formula for dropNTSC time
   expressions is incorrect..

   nigel: I want to use the last few minutes of Glenn's time to go
   through some timing
   ... pictures following on from what we discussed in Las Vegas.
   ... [Document time vs media time picture]
   ... [Constrained by some external process] - the constraint
   does not offset the contents.

   glenn: I need to check that Root Temporal Extent does not
   always start at zero.
   ... The constraint of active window fits the SMIL concept.

   group: moves on to the subject of media offsets

   glenn: The proposal is to move a media offset to metadata.

   nigel: Yes - I think the most useful thing is to indicate the
   beginning of the programme
   ... in the document's timeline.

   glenn: Wouldn't that have the same values as mediaOffset?

   nigel: Well maybe but I think the meaning is clearer.

   glenn: I'd also like to conditionalise based on ttm:item

   nigel: Why not do it based on any extension thing like
   myextension:myparameter attribute?

   glenn: Well you could do that too.

   group: discussion of media time and whether it begins at zero
   or not.

   pal: We discussed this in the context of IMF and the
   overwhelming consensus was not
   ... to permit negative media times.

   <scribe> ACTION: nigel put timing diagrams somewhere they can
   be reviews [recorded in

   <trackbot> Created ACTION-448 - Put timing diagrams somewhere
   they can be reviews [on Nigel Megitt - due 2015-11-06].

   nigel: Well it's time for a break, and we've done pretty much
   everything we wanted to,
   ... and some folk have to catch their flights, so let's end the
   meeting here.
   ... [adjourns meeting] Thanks everyone!

Summary of Action Items

   [NEW] ACTION: atai2 Propose to mdolan this addition to the
   profile registry document. [recorded in
   [NEW] ACTION: gadams Send Pierre the list of which scripts are
   simple and which are complex. [recorded in
   [NEW] ACTION: glenn Send Pierre the list of which scripts are
   simple and which are complex. [recorded in
   [NEW] ACTION: nigel put timing diagrams somewhere they can be
   reviews [recorded in
   [NEW] ACTION: pal Go through every feature and make sure that
   they take into account any dependent features. [recorded in

   [End of minutes]

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Received on Friday, 30 October 2015 07:17:39 UTC