- From: David Ronca <dronca@netflix.com>
- Date: Mon, 9 Oct 2017 16:45:16 -0700
- To: Nigel Megitt <nigel.megitt@bbc.co.uk>
- Cc: Timed Text Working Group <public-tt@w3.org>
- Message-ID: <CAMjV-Fh2h2h7mUiY+AvhkQzn0YzYvnp0phFtbhe7zZ8j-ZTmyg@mail.gmail.com>
> Given that we're not proposing a pure subset of TTML2 I would propose calling this > ... IMSC v1.1, especially since we seem to be targeting IMSC 1 compatibility. Adding a significant amount of TTML2 functionality into IMSC1 and mixing TTML 1 and 2 seems untenable. Will a processor have to decide feature-by-feature, whether to interpret as TTML1 or TTML2? We need an IMSCvNext profile that is a pure subset of TTML2. Giving it a version 1.1 seems to obfuscate the fact that IMSCvNext necessarily carries significant changes from V1. Especially WRT JA features. On Thu, Oct 5, 2017 at 9:20 AM, Nigel Megitt <nigel.megitt@bbc.co.uk> wrote: > Thanks everyone for attending today's TTWG meeting. Minutes can be found > in HTML format at https://www.w3.org/2017/10/05-tt-minutes.html > > Please note the proposal to publish a FPWD of IMSC v1.1 next week, and to > publish the IMSC v1.1 requirements. > > Minutes in text format: > > [1]W3C > > [1] http://www.w3.org/ > > Timed Text Working Group Teleconference > > 05 Oct 2017 > > See also: [2]IRC log > > [2] http://www.w3.org/2017/10/05-tt-irc > > Attendees > > Present > Nigel, Pierre, Andreas, Mike, Thierry, Glenn > > Regrets > Cyril > > Chair > Nigel > > Scribe > nigel > > Contents > > * [3]Topics > 1. [4]This meeting > 2. [5]IMSC vNext Issues > 3. [6]SMPTE backgroundImage deprecation > 4. [7]TTML2 Wide and Horizontal Review > 5. [8]IMSC vNext FPWD > 6. [9]TTML2 #454 Missing ruby attributes from list of > styling attributes > 7. [10]TTML2 #440 Condition attribute missing in Core > catalog. > 8. [11]Other TTML2 issues > 9. [12]Meeting close > * [13]Summary of Action Items > * [14]Summary of Resolutions > __________________________________________________________ > > <scribe> scribe: nigel > > This meeting > > Nigel: I haven't had confirmation of whether David or Silvia > will join, so we'll bump WebVTT > ... down the agenda until they join. > ... Today then we have IMSC vNext requirements, TTML2 wide > review comments, and > ... then WebVTT review comments. > ... Anything else to cover, or specific points to raise? > > Pierre: I sent an email - suggest getting to FPWD of IMSCvNext > as soon as possible, > ... hopefully by next week so that it can be in time for MPEG. > > Nigel: OK got that for the agenda, anything else? I know for > TTML2 we need to think about > ... review comment timing. > > Pierre: I'd like to cover Mike's two IMSC issues too. > > Nigel: I don't think there's anything to discuss re TPAC so > I'll drop it from today's agenda. > > IMSC vNext Issues > > Pierre: Mike brought up two issues: a) if all IMSC vNext > references should be to TTML2, > ... and if TTML2 is in fact a superset of TTML1 and processing > a TTML1 document with the > ... TTML2 processor will yield the same result. > ... b) deprecation of smpte:backgroundImage - to me that was a > good exercise to try > ... deprecating that. > > github: [15]https://github.com/w3c/imsc/issues/258 > > [15] https://github.com/w3c/imsc/issues/258 > > Mike: I was concerned that the focus has shifted from being an > extension of IMSC 1.0.1 > ... to being a subset of TTML2 and those things aren't > necessarily incompatible but they > ... change the risk profile, so I'd like the group to consider > the choice here. It may be that > ... we have to reference both TTML1 and TTML2, but changing > everything to TTML2 when > ... there's a risk that the processing would change. > > Nigel: I've always thought that TTML2 is a superset of TTML1, > and I've never seen anything > ... that made me doubt that. > > Pierre: There's a related issue w3c/ttml2#442 requesting that > the scope of TTML2 is > ... defined as a superset of TTML1. For example there are > changes to prose for style resolution. > > Glenn: Something to bear in mind is that a TTML2 document will > be processed differently > ... by a TTML1 processor and a TTML2 processor. But more > importantly if a TTML2 > ... processor is processing a TTML1 document then its incumbent > on the implementation > ... to behave modally as a TTML1 processor. It's not completely > clear what we're talking about. > > Mike: We need to make a fundamental decision that either IMSC > vNext is a superset of > ... IMSC 1.0.1 or a subset of TTML2. Based on what Glenn just > said I'm really concerned here > ... about replacing TTML1 references with TTML2 ones. > > Andreas: I think this is really important, that IMSC vNext is a > strict superset of 1.0.1. > ... The question for this superset in the next version of which > version of TTML should be > ... referenced for already present features is not easy to > answer. If we change any TTML1 > ... reference to TTML2 that could be a blocker for adoption of > IMSC vNext because all > ... implementers need to check everything that's referenced and > verify that their > ... implementation is still compliant. > > Pierre: I thought the goal was to make TTML2 a superset of > TTML1, but are you saying > ... that a TTML2 processor would process a document differently > from a TTML1 processor? > > Glenn: Not if it is processing it as a TTML1 processor. > > Pierre: What has changed? > > Glenn: Lots of things, I'd have to check. Looking at the > version number, treating origin and > ... position if both are present - if processing as a TTML2 > document it would use position > ... in preference to origin. > > Nigel: I think that's a different question - position would > never be present in a TTML1-only document. > > Mike: But other TTML2 properties may be added to a TTML1 > document, such as disparity, > ... as has been adopted by ATSC. If the presence of that TTML2 > attribute triggers different > ... processing of the whole document than in TTML1 that would > be a worry. > > Glenn: It may be that we need to think about this a bit more. > > Pierre: I'm happy to back out the TTML2 references and replace > by TTML1 in IMSC vNext, > ... or I'm equally happy to make TTML2 a superset of TTML1. > > Glenn: It is a superset in that it supports the features. The > question is which mode is it > ... operating in, either with the knowledge of some fixes > relative to TTML1, or if the author > ... declares that it's a TTML2 document, and puts a version="2" > parameter on it, then the > ... author has said that TTML2 rules should apply. > ... I don't see this as a binary answer. > > Mike: In the case of TTML1 vs TTML2 we can sort that out as we > go, but in the case of > ... IMSC vNext it's fundamental. If the intent is backwards > compatible then that's a different > ... thing to "it's compatible with some different behaviours". > > Glenn: I agree > > Mike: I'm aligned with Andreas that IMSC vNext should be a > superset of IMSC v1.0.1. > > Glenn: It may be that when there is an identified difference, I > wonder if we can make a default choice without studying each > case. > ... Absent of information, I would assume that a reference to > TTML1 would be a safer bet > ... than simply adopting references to TTML2 across the board. > > Nigel: How does rendering using CSS factor into this, given > that we're putting the mappings > ... from TTML style attributes to CSS informatively into TTML2? > > Pierre: If we want to continue referencing TTML1 for processing > behaviours but also add > ... TTML2 features like ruby, then we will have to create new > extension features for that syntax. We > ... can't reference the TTML2 features because that brings the > whole TTML2 processing model. > ... For disparity it's not an issue but for something like Ruby > then it might be an issue. > > Nigel: Adding something else into the mix here, we have an > intention to work on TTML1 Third Edition > ... which essentially backports the important fixes to TTML1 > Second Edition. Which version > ... of TTML1 do we want to reference in IMSC vNext? > > Pierre: Going back to Andreas's suggestion, if we explicitly > state in TTML2 that the > ... processor should process TTML1 documents as TTML1 then we'd > be good right? Why > ... can't we say that? > > Nigel: I have no reason not to be able to say that. > > Pierre: Can we say in TTML2 that a TTML2 processor should > process a TTML1 document > ... exactly as a TTML1 processor? > > Glenn: Yes, that's always been the goal. > ... There are no blanket statements to that effect. > > Pierre: Then we have the specific issue here that Mike has > raised - that ATSC allows > ... tts:disparity to be used in a TTML1 document without > specifying ttp:version="2". > ... Could one solution in the case of IMSC vNext be never to > use ttp:version="2" except when > ... using a whitelist of features that are known to affect the > processing model. Or prohibit > ... ttp:version altogether? > > Andreas: A question for my understtanding for ttp:version - if > we have a TTML1 document > ... and we add ttp:version="2" the rendered outcome of a TTML1 > document would be no > ... different from a TTML1 processor at the moment? That should > not have any effect on the > ... outcome. > > Pierre: The particular example that Glenn brought up is > position, if ttp:version="2". > > Glenn: More substantively if there's no profile present then > signalling ttp:version="2" > ... causes selection of a different default profile. If it is > missing then the default would be > ... as in TTML1, the old DFXP profiles. However if > ttp:version="2" is present then it would > ... substitute the TTML2 default profiles which bring in new > processor profile defaults. > > Pierre: If ttp:version is absent, and a TTML2 processor > encounters a ruby element what does > ... it do? > > Glenn: It depends on whether it is processing it as a TTML1 or > a TTML2 document, independently of ttp:version. > ... If it is processing as a TTML1 document then it might > ignore ruby even if it knows how > ... to process ruby. That's an implementation choice. We can't > from a spec perspective > ... mandate the implementation in terms of backward > compatibility in this regard. > > Pierre: If we remove ttp:version and let profile signalling > completely drive processing then > ... there would be no ambiguity. > > Mike: An IMSC1.0.1 document could add all the vNext features, > and the processor might > ... understand it, then the version becomes critical, because > you're explicitly telling the processor > ... to do something different. > > Pierre: In the case of IMSC vNext there would be a profile > identifier so version wouldn't be needed. > > Glenn: I disagree. We changed the profile mechanism. The > processor needs to know which > ... profile processing system is being used. > > Pierre: The mere presence of ttp:contentProfiles signals that > the new system is being used. > ... The processor can unambiguously identify which TTML version > it would be using. > > Glenn: You're suggesting removing ttp:version and adding an > algorithm for deriving the > ... TTML version being used. I don't see that as being any > different. > > Pierre: I'm addressing the case identified by Mike that > everyone might start putting ttp:version="2" in the IMSC > documents. > > Glenn: That's maybe something that IMSC vNext should say > something about but I see it > ... as a different issue from what is in TTML2. > > Pierre: TTML2 requires ttp:version="2" if any TTML2 feature is > used including ttp:contentProfile. > ... That's what the thread has said. > > Glenn: No you're overstating it. I said if an author requires > TTML2 processing they can > ... specify it. They can still not do so. If they fail to do so > then it would still provide some sort > ... processing dependent on the implementation. I guess the > question is what should TTML2 > ... say regarding documents without ttp:version that do use a > TTML2 feature. My response > ... would be as an implementer, since the author hasn't said it > is required, I would derive it > ... using other methods, for example seeing if contentProfiles > were present. I don't know > ... what you can say about authors blanket putting ttp:version > in the document. Maybe add > ... a big warning saying "If you put ttp:version="2" then that > may cause processing differences in TTMl2 processors compared > to TTML1". > > Pierre: What will ATSC signal as the profile in documents with > tts:disparity? > > Mike: There's no choice, just IMSC 1.0.1 with the extensions > and with no other signalling. > ... I don't remember if we suggested explicitly stating the > profile. > > Pierre: Yes, IMSC, absolutely. > > Mike: Ok, but there's no version, or other profile and there > probably never will be. To the > ... extent that IMSC 1 is deployed in the US, nobody believes > that the additions in IMSC vNext are needed. > ... If the additions land somewhere else, in a different > country, what is an ATSC decoder > ... going to do? I don't know, this isn't heading in a good > direction... > > Pierre: Imagine an IMSC 1 processor - it would ignore > tts:disparity. > > Mike: The ATSC processor would know what to do with it. It was > explicitly agreed by this > ... group that an IMSC processor ignore attributes it doesn't > understand. > > Pierre: Now the same document appears in a non-ATSC decoder, > but one that is IMSC vNext, > ... and it is labelled as IMSC v1 and there's no profile, and > it has tts:disparity, are we trying > ... to solve the case of what it does? > > Andreas: Isn't the question if we can make IMSC vNext use TTML2 > features in a TTML1 processor? > ... If a TTML2 feature is used then the processor must be a > TTML2 processor. > > Pierre: It's hard to specify that, is TTML2 processing required > whenever a TTML2 feature is encountered? > > Glenn: Here's something to consider: a complicated thing was > introduced in HTML5 - is it compatible with previous > specifications? > ... Probably not. Have implementers verified that it's > compatible with their own implementations? > ... Probably not. It was just defined. We have a similar issue. > We have to go ahead with > ... caution about changes that affect processing in older > processors. I don't know how we > ... check that we don't break compatibility. It's not out > intention to break it, and I don't have > ... a list where we have made that decision either. > > Mike: I understand the analogy, I'm not sure it's a good one. > > Nigel: It's hard to move from the abstract to the concrete > without any specific examples > ... where a TTML2 processor has a significantly worse > presentation than a TTML2 processor > ... for a TTML1 document. > > Pierre: I'm encouraged by Glenn's response that there's no > intention to differ. Glenn, do > ... you have any objection to making a blanket statement in > TTML2 that a TTML2 processor > ... processing a TTML1 document should yield identical results? > > Mike: Be careful of the language. > > Glenn: TBD the language, but I have no reason to object to > doing so. > ... The question is do we want to introduce extra language. I > think I added a compatibility section. > > Pierre: I would add it up front in the scope so the objective > is clear. > > Glenn: Putting that in the front matter should be okay. I'm > just going to find the section I think I added. > > Andreas: [I have to drop off] I support what Pierre suggested. > It's a good opportunity to > ... start the IMSC requirements and to keep the backward > compatibility, which means that > ... a TTML2 feature being used in an IMSC vNext processor would > not change any TTML1 > ... features used in IMSC. > > Glenn: I added §3.4 under conformance, and it has forward and > backward sections. It is > ... marked as non-normative but says things along the lines of > what we're talking about. > > Mike: The conformance is one angle - it's important that a > presentation processor also > ... does the same thing. > ... Currently all the language is about conformance of > documents as opposed to rendering. > ... Let's work on the language a bit - I'll take a run at it. > > Glenn: It's §3.4 in TTML2. > ... I recall we had a look at this in the past for TTML2 too. > > SUMMARY: Mike to study TTML2 §3.4 and propose any > modifications. > > SMPTE backgroundImage deprecation > > Nigel: We should defer discussing this. > > Pierre: Maybe a public document would help also. > > TTML2 Wide and Horizontal Review > > Thierry: I went through the archives and verified all the > comments sent in are there plus > ... I've added some sent as liaisons. They're all on GitHub. > Some issues don't need any > ... processing - if they say everything is fine. I still put > them on GitHub so they will be on > ... our disposition of comments. All the comments have a label, > open, pending, etc. When > ... the issue status changes we will add a new label. > > Nigel: Fantastic, thanks for that - a lot of work. > > Action-506? > > <trackbot> Action-506 -- Thierry Michel to Draft a wiki page > explaining our review and disposition steps and labels -- due > 2017-09-21 -- OPEN > > <trackbot> > [16]http://www.w3.org/AudioVideo/TT/tracker/actions/506 > > [16] http://www.w3.org/AudioVideo/TT/tracker/actions/506 > > close action-506 > > <trackbot> Closed action-506. > > Nigel: There were a number of issues that said thank you, they > would look at TTML2 but > ... not before 30th September. > > Thierry: If you agree I would take the action to write to them > to say we will process their > ... comments but they should send them ASAP after their > meetings. > > Pierre: I recommend to do nothing, and process them when they > come in, and put them > ... in a queue. > > Thierry: I've had comments come in 6 months late in the past > and the Director still wants > ... to take them into account. > ... I want to add a bit of pressure. > > Pierre: They know how this works, I would say nothing! > > Nigel: I'm happy to do nothing - they've told us they will do > something and we should assume that they will do so. > ... I just wanted to check if we want to explicitly extend the > deadline. > > Pierre: I would not. > > Thierry: I would not. > > Glenn: I agree, the deadline has passed. I would not put those > in as wide review comments anyway, they're not comments about > the spec. > > Nigel: The point at which we draw a close to the wide review > opportunity is when we > ... have agreed to request transition to CR. > > Thierry: Correct. > > Mike: Would it help to track comments as late and put them at > the bottom of the pile? > > Pierre: I like that, a priori put them at the bottom of the > pile unless we all see that it's a big > ... issue. > > Nigel: Okay this is all fine for me, thanks everyone, we don't > need to take any action at all here. > ... We simply need to come up with a disposition for every > substantive comment. > > Thierry: Some issues are marked as editorial - we should have a > type label for editorial vs substantive. > > Nigel: That works for me. > ... I think in the old tracker there was a flag for exactly > that. > > <scribe> ACTION: Thierry Check if there are > editorial/substantive labels for TTML2 issues and add if not. > [recorded in > [17]http://www.w3.org/2017/10/05-tt-minutes.html#action01] > > [17] http://www.w3.org/2017/10/05-tt-minutes.html#action01 > > <trackbot> Created ACTION-508 - Check if there are > editorial/substantive labels for ttml2 issues and add if not. > [on Thierry Michel - due 2017-10-12]. > > Nigel: Between now and next week please could everyone look at > the GitHub issues and > ... propose any dispositions, so that we can start to agree > them in next week's meeting, or > ... at any rate discuss them? > > Glenn: I've already addressed a couple of TTML2 issues, so if > we can get resolution on those > ... today then I would be happy to close something. > > IMSC vNext FPWD > > Pierre: I propose a 1 week review of the draft and the > requirements document, which go > ... hand in hand, and I keep synchronised. If there are no > major objections publish as a FPWD > ... and send a liaison informing them of the beginning of this > work and inviting them to provide comments. > > Nigel: What's the URL of the thing we're discussing? > ... I see that IMSCvNext is not on the master branch of the > imsc repo. > ... Can we put IMSC vNext in a new folder so we don't get a > clash of URIs? > > Pierre: I didn't do that because then I'd have to synchronise > IMSC 1.0.1 changes with > ... vNext. Also we haven't got a name for it yet. > > <pal> > [18]https://rawgit.com/w3c/imsc/6eafca943b2294d2d2d979960981429 > 9e4b361cf/imsc1/spec/ttml-ww-profiles.html > > [18] https://rawgit.com/w3c/imsc/6eafca943b2294d2d2d9799609814299e4b361cf/imsc1/spec/ttml-ww-profiles.html > > Nigel: Given that we're not proposing a pure subset of TTML2 I > would propose calling this > ... IMSC v1.1, especially since we seem to be targeting IMSC 1 > compatibility. > > Pierre: That's what I'm thinking too. > > Nigel: In that case I think we need an imsc1_1 folder. > > Pierre: I really would like to delay that as much as possible. > Once it's published on /TR > ... it doesn't really matter where it is in the repo. > > Nigel: It makes it really awkward to navigate though. When > would you move it to a different folder? > > Pierre: I think it will become obvious. > > Nigel: We're not really expecting any changes to 1.0.1 > > Pierre: Compare with software development - you'd maintain > different versions on different branches. > ... Here all the tests, examples etc are going to be > substantially the same. > > Nigel: The other thing you'd do is use release tags. > ... Okay, Pierre, you proceed as Editor. > > Pierre: Can you request a short name? > > <tmichel> > [19]https://lists.w3.org/Archives/Public/spec-prod/2017JulSep/0 > 005.html > > [19] https://lists.w3.org/Archives/Public/spec-prod/2017JulSep/0005.html > > Thierry: Yes I will. Just to let you know there's a new rule as > per the above link, and it > ... would be worth Editors looking at this. > > Nigel: This is a convention for Latest Version links, mainly. > ... Thanks for the reminder Thierry, I had seen that and not > taken any action. > > <pal> ttml-imsc1.1 > > PROPOSAL: Publish a FPWD of IMSC v1.1 with the short code > ttml-imsc1.1, based on the ED in the IMSCvNEXT branch > > Pierre: Would you like me to propose liaison text? > > Nigel: Yes please > > <scribe> ACTION: pal Propose liaison text for the IMSC 1.1 FPWD > [recorded in > [20]http://www.w3.org/2017/10/05-tt-minutes.html#action02] > > [20] http://www.w3.org/2017/10/05-tt-minutes.html#action02 > > <trackbot> Created ACTION-509 - Propose liaison text for the > imsc 1.1 fpwd [on Pierre-Anthony Lemieux - due 2017-10-12]. > > action-507? > > <trackbot> action-507 -- Nigel Megitt to Add imsc vnext repo to > agenda, board, github-bot etc -- due 2017-10-05 -- OPEN > > <trackbot> > [21]http://www.w3.org/AudioVideo/TT/tracker/actions/507 > > [21] http://www.w3.org/AudioVideo/TT/tracker/actions/507 > > Nigel: I link from the agenda to > [22]http://www.w3.org/AudioVideo/TT/board/ > ... Has anyone here ever followed that link and looked at it? > > [22] http://www.w3.org/AudioVideo/TT/board/ > > Pierre: I have not. > > Thierry: No. > > Nigel: Does anyone use it? > > Pierre: I didn't realise it existed > > Nigel: The reason I ask is that if nobody uses it then I will > drop it; conversely I could maintain it. > > Thierry: I think it's valuable. I did use it some times, I > recall, but I'd forgotten about it. > > Nigel: Okay I'll update the board and continue with it. > > TTML2 #454 Missing ruby attributes from list of styling attributes > > github: [23]https://github.com/w3c/ttml2/issues/454 > > [23] https://github.com/w3c/ttml2/issues/454 > > Glenn: This was an editorial change, I've already fixed it and > updated the ED. > ... I guess we can change the status of this with labels. It's > done. > > Nigel: I see, there's nothing significant to review here - > Thierry do you want to apply the > ... appropriate labels? > > Thierry: Yes, it's spec updated and WG approved. > > Nigel: I've assigned it to you Thierry. > > TTML2 #440 Condition attribute missing in Core catalog. > > github: [24]https://github.com/w3c/ttml2/issues/440 > > [24] https://github.com/w3c/ttml2/issues/440 > > Glenn: This is from Andreas and he's reviewed to say it looks > good. > > Nigel: Okay I'm assigning to Thierry to update the labels. > > Thierry: Once we have all three of: WG resolution + spec > updated + commenter agreement > ... we can close issues. > > Glenn: What if we cannot get agreement from the commenter, do > we have to leave issues > ... as open if we have disagreement? > > Thierry: We can close issues but it will red flag to the > Director that we will have to explain > ... to the Director. > > SUMMARY: WG approves, Thierry to update labels > > Other TTML2 issues > > Glenn: We haven't discussed XML, CSS comments etc. > > Pierre: I would like to close those issues off, so can we > schedule a time to do so? > > Nigel: Sure, if we cannot resolve it on the GitHub issue. > ... We have discussed over the years some issues about time, > mediaOffset, and begin and > ... end clipping, which I want to resolve soon too. > > Glenn: Check if there are existing issues. > > Nigel: Will do. > > Meeting close > > Nigel: Thanks everyone, we've done what we could on the agenda. > [adjourns meeting] > > Summary of Action Items > > [NEW] ACTION: pal Propose liaison text for the IMSC 1.1 FPWD > [recorded in > [25]http://www.w3.org/2017/10/05-tt-minutes.html#action02] > [NEW] ACTION: Thierry Check if there are editorial/substantive > labels for TTML2 issues and add if not. [recorded in > [26]http://www.w3.org/2017/10/05-tt-minutes.html#action01] > > [25] http://www.w3.org/2017/10/05-tt-minutes.html#action02 > [26] http://www.w3.org/2017/10/05-tt-minutes.html#action01 > > Summary of Resolutions > > [End of minutes] > __________________________________________________________ > > > Minutes formatted by David Booth's [27]scribe.perl version > 1.152 ([28]CVS log) > $Date: 2017/10/05 16:17:51 $ > > [27] http://dev.w3.org/cvsweb/~checkout~/2002/scribe/scribedoc.htm > [28] http://dev.w3.org/cvsweb/2002/scribe/ > > >
Received on Monday, 9 October 2017 23:45:42 UTC