14:59:44 RRSAgent has joined #tt 14:59:48 logging to https://www.w3.org/2024/06/20-tt-irc 14:59:48 RRSAgent, make logs Public 14:59:49 Meeting: Timed Text Working Group Teleconference 15:00:46 Agenda: https://github.com/w3c/ttwg/issues/284 15:01:00 Present: Matt, Pierre, Nigel, Andreas 15:01:06 scribe: nigel 15:01:14 Previous meeting: https://www.w3.org/2024/06/06-tt-minutes.html 15:01:21 MattS has joined #tt 15:01:29 Chair: Nigel 15:01:33 Regrets: Ewan 15:01:42 Regrets+ Gary 15:01:50 rrsagent, make minutes 15:01:51 I have made the request to generate https://www.w3.org/2024/06/20-tt-minutes.html nigel 15:02:09 Present+ Cyril 15:03:01 atai has joined #tt 15:03:18 Topic: This meeting 15:04:04 Nigel: Today we have a DAPT pull request, 15:04:14 .. a TTML2 ttm:role issue, 15:04:29 .. TPAC and one AOB so far: TTML in MP4 MPEG issue 15:04:35 present+ Atsushi 15:04:50 .. Is there any other "other business" to cover today? 15:05:01 no other business 15:05:52 Topic: DAPT 15:06:02 Nigel: There's one issue on the agenda 15:06:14 Subtopic: Add section about mapping from TTML to the DAPT data model w3c/dapt#216 15:06:22 github: https://github.com/w3c/dapt/pull/216 15:06:38 Nigel: Thank you Cyril for all the review comments. 15:06:54 .. I tried to resolve them but left this on the agenda so we could cover the questions that arose. 15:08:47 Nigel: Re the Script Event identification, thanks for raising the issue. 15:08:52 .. Can we tackle it as a separate pull request? 15:09:26 Cyril: I'm not sure, we may need to do it first because it could simplify the algorithm 15:09:34 .. for identifying Script Events and make this pull request simpler. 15:09:58 Nigel: I think my preference would be to finish this one before iterating over it again. 15:10:27 .. There's a lot more in this pull request than just that bit. 15:10:42 .. If we end up changing the algorithm significantly I don't really mind, but at least we would have 15:10:53 .. a logical development based on what we have now. 15:11:02 .. Is that ok? 15:11:13 Cyril: Let's see, I need to do a re-review following the recent changes. 15:14:52 .. Regarding DAPTv2 and extensibility, we say today that every DAPT document must write 15:15:08 .. the DAPT 1.0 content profile designator, which is a promise on all the future profiles we may generate, 15:15:17 .. and we're doing that for backwards compatibility in the future. 15:15:30 .. I'm not sure if we can hold that promise forever. 15:15:34 Nigel: Me neither 15:15:57 Cyril: My point was that "a profile compliant to this specification" without mentioning the profile version, 15:16:19 .. could be reworded so it doesn't need to change, a DAPT content profile designator 15:16:27 .. rather than forcing the v1.0 designator. 15:17:12 Nigel: That makes sense, please could you highlight where you mean and put a comment about it in the thread? 15:17:20 Cyril: I'll add that so we don't lose this thought. 15:19:26 Nigel: The next one is the additional validation steps, should I add a hypothetical example? 15:23:54 Pierre: Wasn't the original issue non-pruning of unsupported vocabulary? 15:24:42 Nigel: Right, this PR brings in the idea that stuff must be pruned everywhere outside metadata. 15:25:02 Pierre: Then there should be a corollary that metadata elements should not include metadata derived from 15:25:11 .. the document content, or temporal metadata. 15:25:24 .. We should cast a wide net, to strongly discourage people from getting into this trouble, which 15:25:29 .. is not solvable really. 15:25:56 .. My suggestion is, instead of recommending what a downstream processor should do, 15:26:09 .. if it encounters a document that contains vocabulary that belongs to a profile that is not signalled, 15:26:36 .. to recommend in the first place that metadata that would cause that situation should not be used. 15:26:48 Nigel: That's no problem, we can do that. 15:27:03 Cyril: I wonder if we shouldn't be more precise in terms of what types of processor we are talking about. 15:27:24 .. I.e. presentation processor behaviour, transformation processor behaviour, validation processor behaviour etc. 15:27:36 .. Here, if it's a presentation processor, saying SHOULD NOT implement is sufficient. 15:28:18 .. If it's a validation processor then you prune vocabulary that is not declared in the signalled profile, 15:28:26 .. so this paragraph is not applicable. 15:28:42 .. it's only applicable to transformation processors, right? Validation and presentation processors don't fix anything. 15:29:38 apols - I have to head to another meeting... 15:30:38 Nigel: Processors don't have to be exactly in one class, so we can't make opposing rules for a processor 15:30:46 .. that is both a transformation and a validation processor. 15:32:29 Cyril: If it's doing validation, then these rules apply? 15:32:38 .. If it said "taking steps to fix" the document I would be okay with that 15:32:51 .. If you meant that a validation processor might take extra steps to validate those features if it wants to, 15:32:58 .. maybe, yes, it's a permission as you said. 15:33:06 .. The sentence seems to be mixing the two parts. 15:33:29 Nigel: Okay. I've got a clearer handle on the problem here, and a couple of actions. 15:35:40 .. Next one is about processors SHOULD NOT implement support for features that the document 15:35:45 .. does not claim conformance to. 15:35:55 Cyril: We should not require implementers to model features. 15:36:11 Nigel: Should we be clear we mean non DAPT profiles? 15:36:33 Cyril: You can just know that your implementation supports each thing, without modelling features. 15:36:37 Nigel: Exactly. 15:37:08 .. The implementer can be aware of the features without writing software that explicitly models them. 15:37:46 Cyril: I'll read this again. The term feature could be interpreted loosely, it does not have to be something 15:37:51 .. defined in a profile definition. 15:37:54 Nigel: Right, yes. 15:38:27 Cyril: If it were treated as an "attribute" rather than a "feature" then I see. 15:38:38 .. I guess this is probably fine, let me review it again. 15:41:01 Nigel: next is nested divs. 15:43:28 Cyril: [suggests allowing a relaxed TTML representation that can have nested divs] 15:43:42 .. In the spec we don't say you cannot have Script Events inside other div elements 15:44:09 .. The xpath for Character, say, is really explicit, but it is not for Script Event. 15:44:23 .. I'm fine with having a section that says how to go from XML to the Data Model, 15:44:43 .. and the section you wrote is fine in spirit, but we don't give permission to writers to do it, or it is implicit. 15:45:19 Nigel: The easy way out is to define a generic grouping structure. 15:45:30 Pierre: Or you could forbid it, I would, if there are no semantics for it in the DAPT data model. 15:45:46 Cyril: But then it means in the future we cannot bring grouping in, because a v2 document would not be 15:45:53 .. a compliant v1 document. That's what we're trying to avoid. 15:46:05 Pierre: That's true. At some point data models have to have a scope. 15:46:18 .. Is there any conceivable reason for a script to be contained in another script? 15:46:27 Cyril: No, but other grouping could be possible. 15:46:43 Pierre: You could put grouping semantics in via other mechanisms, like a group attribute. 15:46:53 .. That's more flexible because one script can be in multiple groups. 15:47:07 .. Unless the semantic is super strong then you don't need such tight binding. 15:48:11 Pierre: You could say only terminal divs are Script Events 15:48:37 Cyril: That's the issue I opened this morning, that Script Events are identified more clearly. 15:48:50 Pierre: You're making v1 implementations more complex for a hypothetical future. 15:48:53 Cyril: You're right. 15:49:19 Pierre: Even in TTML2, a TTML2 doc is a valid TTML1 doc technically, but the outcome is never going to be good. 15:49:34 .. e.g. ruby - so too flexible is not always practically interesting. 15:50:02 Cyril: This was the design philosophy, that DAPT should be as simple as it can be. 15:50:34 .. Maybe what Pierre is saying is the way forward. 15:50:50 Nigel: Maybe - I do think there are semantics for divs in the future that would be interesting, like shifting timings. 15:51:02 Pierre: It could mean that a v1 processor would reject a v2 document 15:51:10 .. In many use cases that's actually a good thing 15:51:44 SUMMARY: Useful discussion, some ways forward, more thought and review needed 15:52:21 Topic: TPAC 2024 15:52:26 Nigel: TPAC registration is open 15:52:42 -> https://www.w3.org/2024/09/TPAC/Overview.html TPAC 2024 page 15:53:46 .. The schedule has us with some meetings on the Monday and others on the Friday. 15:54:13 .. Let me know if you think we should ask the organisers to shuffle the schedule to accommodate any needs. 15:55:27 Cyril: Do we need the Friday as a full meeting, or could we ask to move to the Tuesday? 15:55:31 Nigel: Maybe 15:55:35 Cyril: Just an option 15:55:51 Nigel: That's for me and Gary to check over and sort out 15:56:36 Cyril: A page where we put who is coming or not would be useful 15:56:40 Atsushi: I will be there 15:56:56 .. Please don't forget to register as early as possible. The price increases if you're late! 15:57:12 Topic: TTML in MP4 MPEG issue 15:57:43 -> https://github.com/MPEGGroup/FileFormat/issues/40 Use of edit lists and timed text tracks MPEGGroup/FileFormat#40 15:57:59 Cyril: The spec has some gaps about edit lists. 15:58:13 .. It could mean different things to use edit lists, leading to different results, unless we do something. 15:58:24 .. I think the text at the beginning tries to be clear enough, it's an old issue. 15:58:32 .. I'm trying to see if there's momentum to move clarification forward. 15:58:43 .. If you care about TTML in MP4 please express your opinion in the issue. 15:58:47 .. I know Nigel did in the past. 16:00:28 Nigel: I commented in some detail 16:00:40 .. Others agreed, so there's some feedback 16:00:52 Cyril: MPEG is working in July, so it is possible that we draft a change to this text. 16:02:07 Nigel: Thank you for reminding us about this 16:02:25 Topic: Meeting close 16:02:38 Nigel: We've gone over time, thank you very much everyone. [adjourns meeting] 16:02:41 rrsagent, make minutes 16:02:42 I have made the request to generate https://www.w3.org/2024/06/20-tt-minutes.html nigel 16:06:34 scribeOptions: -final -noEmbedDiagnostics 16:06:45 zakim, end meeting 16:06:45 As of this point the attendees have been Matt, Pierre, Nigel, Andreas, Cyril, Atsushi 16:06:47 RRSAgent, please draft minutes v2 16:06:48 I have made the request to generate https://www.w3.org/2024/06/20-tt-minutes.html Zakim 16:06:54 I am happy to have been of service, nigel; please remember to excuse RRSAgent. Goodbye 16:06:55 Zakim has left #tt 16:06:57 rrsagent, excuse us 16:06:57 I see no action items