16:00:38 RRSAgent has joined #tt 16:00:38 logging to https://www.w3.org/2020/01/16-tt-irc 16:00:40 RRSAgent, make logs Public 16:00:41 Meeting: Timed Text Working Group Teleconference 16:01:18 Present: Glenn, Pierre, Nigel 16:01:22 Chair: Nigel 16:01:24 scribe: nige 16:01:32 s/nige/nigel 16:01:36 glenn has joined #tt 16:01:37 rrsagent, make minutes 16:01:37 I have made the request to generate https://www.w3.org/2020/01/16-tt-minutes.html nigel 16:02:07 Previous meeting: https://www.w3.org/2020/01/09-tt-minutes.html 16:02:14 Agenda: https://github.com/w3c/ttwg/issues/89 16:02:27 Present+ Cyril, Atsushi 16:03:14 Present+ Andreas 16:03:20 Present+ Gary 16:03:22 Chair+ Gary 16:03:26 Topic: This meeting 16:04:25 Nigel: [iterates through agenda] 16:04:28 .. Any other business? 16:04:31 atai2 has joined #tt 16:04:45 Cyril: I tried to revive the thread on CSS WG about line shear so maybe we can talk about that. 16:04:49 Nigel: OK, let's cover in AOB 16:05:27 Nigel: If there's nothing else, let's get going. 16:05:42 Topic: IMSC 1.2 FPWD Next steps 16:05:48 Nigel: 2 issues to cover today 16:06:07 .. First one is #506. 16:06:15 Glenn: I'm afraid I'm going to have to beg off on this one again. 16:06:57 .. I will get around to looking at it. Please could you ping me on Monday so I won't forget it by next meeting? 16:08:22 Nigel: I'll try, but I'm a very bad PA! 16:08:50 Topic: font selection rules under-specified? imsc#516 16:08:58 github: https://github.com/w3c/imsc/issues/516 16:11:11 Nigel: 3 levels we could get to: 16:11:18 .. 1. Informative note - you can use font-face 16:11:27 .. 2. SHOULD use font-face 16:11:34 .. 3. MUST use font-face 16:11:41 .. I wanted MUST but concerns raised. 16:12:07 Glenn: If you make fontSelectionStrategy auto mean "use font-face" then it is no longer implementation dependent 16:12:20 .. so not backward compatible with existing implementations. 16:12:39 Pierre: So if I have a TTML2 compliant implementation that does not use font-face for auto 16:13:01 .. then that would have to be changed to conform to a new requirement specifying what auto means? 16:13:04 Glenn: Yes 16:13:24 Pierre: So it's a processor conformance issue not a document conformance one? 16:13:26 Glenn: Yes 16:13:44 Pierre: Another point Glenn made that I sympathise with is that before taking the plunge and doing a MUST at this 16:13:56 .. point in the process and with our limited experience with IMSC 1.2 and TTML2, it is not unreasonable to have a SHOULD 16:14:10 .. and if it turns out to be a success we can make it a MUST either in IMSC or through some scheme in TTML2, 16:14:27 .. but there's an argument to be made about the complexity and relative age of that feature then a recommendation 16:14:30 .. might be a good approach. 16:14:52 Glenn: I had previously suggested a SHOULD but in my last comment I was even not going that far and suggesting 16:14:59 .. that SHOULD might be going too far. 16:15:07 .. Because SHOULD add a normative aspect to it. 16:15:34 .. I would probably make it a hint or put it in a note and say that it is something that is being considered. 16:15:48 Pierre: Maybe one notch above a note could be a pointer: "here's a place where an algorithm is defined" 16:16:15 Glenn: That's possible. If we're going to point at a CSS3 font module algorithm then we need to due some serious due 16:16:31 .. diligence about semantic interaction with other normative language in TTML2 that may have to change or get 16:16:48 .. modified to interact with that 5.2 language. I pointed to one area regarding the line height algorithm where clearly 16:17:13 .. there's going to be some interactions. Just saying "use 5.2 as an algorithm" is risky at the moment. As a possible 16:17:28 .. implementation strategy then that's okay, as long as it doesn't invalidate the semantics of TTML2's line height semantics 16:17:44 .. and other semantics already implied by TTML2 as adopted by IMSC 1.2 then it's up to you as an implementer, 16:17:54 .. but putting it into language in IMSC 1.2 is going to be a little tricky. 16:18:42 Nigel: We have time at this stage, FPWD. 16:19:01 .. Secondly, if the line height algorithm is not orthogonal to the font selection algorithm then that's another separate issue. 16:19:17 Glenn: That's quite possible. It's one reason I didn't want to dive into this in TTML2 when it was originally raised, FYI. 16:20:51 Nigel: I made the point too that if someone provides a list of fonts where the font metrics differ substantially in terms 16:21:15 .. of line height calculation then that's a second order issue for us, it's a real edge case. 16:21:21 Glenn: It's a really complex area. 16:21:43 .. The algorithm finds F0 being a single font for the calculation of line height for the whole p. 16:21:58 .. The actual algorithm is fine grained - you have to walk down on a per character basis and this is where the 16:22:15 .. fontSelectionStrategy values come into play to determine whether you use character context, and what contextual 16:22:29 .. boundaries come into play to break the context into larger or smaller pieces, for example if you have grapheme 16:22:46 .. clusters or bidi boundaries or all kinds of other boundaries that might dictate that you do or do not consider 16:23:04 .. context for including larger or smaller pieces of text for choosing one font family vs another font family. 16:23:16 .. Those all feed into the algorithm that is used in §5.2 of the CSS Font module. 16:23:32 .. The algorithm that's used in lineHeight for choosing F0 is at a much higher level for choosing a default font family 16:23:49 .. for the line height used to drive the XSL-FO default font family for the line height algorithms that are used there. 16:24:02 .. There's a whole bunch of complexity and it is not just something that you can easily take on in one or two meetings. 16:24:12 .. Probably a week of reading time to work through the detail! 16:24:32 .. Just giving an overview of the work that would be involved in doing that. 16:24:44 .. Vladimir should probably attend that meeting! 16:26:11 Nigel: I don't quite buy that the lineHeight algorithm should stop us making progress. 16:26:33 .. If the lineHeight algorithm reproduces, either identically or differently to, the font selection strategy, then they 16:26:41 .. are not orthogonal but they possibly should be. 16:26:56 Glenn: It reproduces a simplified version of the algorithm for its own purposes. 16:27:51 Nigel: Already it is true that implementations may choose font families with a different algorithm than the lineHeight 16:28:07 .. algorithm and that is in spec, so if we change the font family selection algorithm that would not change. 16:28:25 Glenn: That is probably true. I can't comment on actual interoperability across implementations. 16:28:42 .. If we were to adopt CSS 3 font family selection and apply it to the font attribute at this time then it could be that 16:29:07 .. the line height algorithm could continue independently even though they might produce different font selection. 16:29:14 Nigel: I think that would be acceptable though not ideal. 16:29:30 Glenn: This opens up the elephant in the room that we have not done much interop testing. We have complained about 16:29:42 .. it with WebVTT but we have not done much testing of IMSC and TTML2 yet in my opinion. 16:30:02 Pierre: Just on that point, on IMSC 1.1 and IMSC 1.0 there is a lot of interop testing happening outside W3C. 16:30:14 .. Just in February there will be another plugfest where IMSC 1.1 will be front and centre. 16:30:22 Glenn: That's good, will you share those results with the group? 16:30:35 Pierre: I'll ask, I don't know why it hasn't happened before, it's a good idea. 16:30:45 Glenn: That'd be great. It's the kind of feedback we should be hearing. 16:32:37 Nigel: Going back to the topic, if lineHeight doesn't choose the same font, it still gives predictable results even if 16:32:41 .. they are not desirable ones. 16:32:58 Glenn: There's still the question of whether to do this in IMSC 1.2 or TTML2. It's complicated to know how to do that. 16:33:14 .. My opinion is it is not really tractable to bring it into TTML2 directly because it's a core semantic change. 16:33:29 .. It could be done via modules, and I suggested a way to do it via fontSelectionStrategy by introducing a new value, 16:33:39 .. which would require defining a new module. That would be the way forward. 16:35:24 Nigel: From what I've heard I don't think it would be a problem to say in IMSC 1.2 that we SHOULD use font-face. 16:35:26 Glenn: Not a MAY? 16:36:05 Nigel: There's very little difference between MAY and SHOULD, it's just how strong the hint is. 16:36:26 Glenn: A processor testing regime that's testing for SHOULD compliance may reject an implementation that doesn't 16:36:33 .. conform with it. 16:36:43 Nigel: That's what we want because it encourages more interoperability. 16:36:56 Glenn: Are there any processor SHOULD requirements in IMSC? I don't recall. 16:37:33 Pierre: Yes we have a couple of processor recommendations worded with a SHOULD. 16:37:47 .. I'm really happy with MAY, SHOULD or just "hey here's a place where there's an algorithm defined". 16:38:02 .. They're slightly different. MAY implies that we now permit something that was prohibited before. 16:38:17 .. SHOULD is definitely stronger. If we are really confident that the algorithm works then that's what we should do. 16:38:31 Glenn: "is permitted"? 16:38:36 Pierre: That's a MAY. 16:38:57 .. I haven't studied whether the algorithm is actually the right one. I'd like a plan from this meeting. 16:39:02 Nigel: Can I propose a pull request? 16:39:12 Glenn: I will not be happy with SHOULD but I can live with MAY or permitted. 16:40:56 Nigel: A testing regime that enforces SHOULD is downstream of us, and not our call. 16:41:15 .. My argument for SHOULD is that it helps encourage implementations to work the same way. 16:41:41 Glenn: Practically speaking MAY and SHOULD are the same for authors because authors need to check their implementations anyway. 16:41:56 Pierre: One argument for not doing SHOULD is that we haven't convinced ourselves that we're really doing the right thing. 16:42:02 Glenn: That's my rationale too. 16:42:11 Pierre: It's extremely complex - I think that's a true statement! 16:42:19 .. We don't have a body of documents or examples to guide us. 16:42:31 .. That's a strong argument for a MAY, and making clear that if someone were to implement 16:42:44 .. the CSS algorithm then that would not be non-compliant. We probably want to avoid that. 16:42:49 .. That's my input to the pull request. 16:43:16 Glenn: We don't even have the wording to consider. 16:43:23 Nigel: Ok I'll take the next step then. 16:43:31 SUMMARY: @nigelmegitt to draft a pull request 16:43:35 github-bot, end topic 16:43:57 Topic: IMSC 1.1 errata 16:44:01 Nigel: I think this has been fixed. 16:44:05 Pierre: Yes, all good. 16:44:10 Atsushi: I hope so! 16:44:16 Nigel: Thank you for sorting that out Atsushi. 16:44:35 Atsushi: Actually please let me say one point that I did a quick fix, so something may happen. 16:44:42 .. Please let me know if there is any issue with the updated page. 16:45:02 Topic: TTML2 2nd Edition Wide Review 16:45:57 q+ 16:46:22 ack at 16:46:45 Atsushi: During the weekly call of i18n WG we decided that Richard would raise issues by next week so 16:46:56 .. they may arrive by early next week. Of course input is welcome from TTWG. 16:48:20 Nigel: OK, thank you. I propose that we keep an eye out for those issues and make a call on them. 16:49:19 .. If it looks like they are substantive and cannot be dealt with during Proposed Rec then we may need to pause 16:49:30 .. our publication timeline while we address them, but we can't tell until we see them. 16:49:51 Glenn: Question - you said there was a review by Fuqiao, have you seen it? 16:50:04 Nigel: No, I just saw a message saying he'd done a review, but I don't know what the outcome was. 16:50:33 https://github.com/w3c/i18n-request/issues/86#issuecomment-568343266 16:50:34 Glenn: Can you share it with the group or forward it? 16:50:52 Atushi: I posted a link with some draft comments. 16:51:17 Nigel: Is this a full review of the spec or just the deltas? 16:51:22 Atsushi: Both 16:51:48 Nigel: Should we be looking at only comments with a △ at the beginning? 16:52:25 Glenn: This looks like it is not related to changes in 2nd Edition. 16:52:47 .. I did a quick review of all the 2nd Ed changes this morning and I posted a comment in the issue related to our meeting 16:53:19 .. agenda that there were two issues closed related to our agenda, 1076 and 1043, one about ignoring white space 16:53:33 .. inside a ruby container, and the other was the non-applicability of character properties in ruby container. 16:53:50 .. None of those have any i18n semantics and none of the other substantive issues that were addressed have any 16:54:07 .. i18n semantics as far as my review is concerned. So my review suggests there are no i18n semantics for any of the 16:54:24 .. substantive changes. My recommendation is that we politely decline to extend the review and allow the review to 16:54:28 .. continue into the CR period. 16:55:22 Nigel: I'd like to tweak that to say that if there are any comments not related to the delta between TTML2 2nd Ed and 16:55:41 .. 1st Ed then we welcome those in our repo but will likely deal with them in a future edition. 16:55:44 Glenn: I agree with that. 16:55:48 Pierre: What Nigel said. 16:55:57 Glenn: Unless there are any comments about things that are truly broken. 16:56:01 Pierre: Yes of course. 16:56:12 Nigel: OK I will respond to Addison and i18n explaining the situation. 16:56:22 Atsushi: Thank you for that. 16:56:32 Glenn: I have a follow-on. 16:56:54 .. I have sent a link to Atsushi and you Nigel to a tarball that is ready to upload to the dated URL /TR space for 16:57:06 .. publishing on 28th. Is there any reason to hold off on putting that in place at this point? 16:57:17 .. In the past Thierry always uploaded these dated URLs in prep for the publication. 16:57:25 .. Ahead of time, not at the last second. 16:57:39 .. If for some reason an update is needed because of some last minute change then we can always do that and 16:57:46 .. overwrite it with an edited tarball. 16:57:56 Nigel: I don't have a view on that, certainly no objection. 16:59:40 .. Can I suggest you take that offline Atsushi and let us know if there is anything else that needs to happen. 17:00:48 draft transition request on TTML2-2e CR https://github.com/w3c/transitions/issues/208 17:01:02 Topic: AOB CSS line shear 17:01:54 Nigel: We don't have much time to cover this now - Cyril perhaps you could send a summary of this to the 17:01:59 .. group so we can have a look? 17:02:40 atai2 has left #tt 17:03:14 Cyril: I tried contacting Tab Atkins, can you suggest anyone else from the Chrome team? 17:03:21 Glenn: I will point you to someone on the layout team. 17:03:23 Cyril: thank you 17:03:27 Topic: Meeting close. 17:03:38 Nigel: Thanks everyone, we're 2 minutes over, so let's adjourn. [adjourns meeting] 17:03:49 zakim, end meeting 17:03:49 As of this point the attendees have been Glenn, Pierre, Nigel, Cyril, Atsushi, Andreas, Gary 17:03:51 RRSAgent, please draft minutes v2 17:03:51 I have made the request to generate https://www.w3.org/2020/01/16-tt-minutes.html Zakim 17:03:54 I am happy to have been of service, nigel; please remember to excuse RRSAgent. Goodbye 17:03:58 Zakim has left #tt 17:14:16 s/github-bot, end topic//g 17:14:42 RRSAgent, please draft minutes v2 17:14:42 I have made the request to generate https://www.w3.org/2020/01/16-tt-minutes.html nigel 17:14:58 a/Atushi/Atsushi/g 17:15:02 RRSAgent, please draft minutes v2 17:15:02 I have made the request to generate https://www.w3.org/2020/01/16-tt-minutes.html nigel 17:15:32 s|a/Atushi/Atsushi/g|| 17:15:39 s/Atushi/Atsushi/g 17:15:41 RRSAgent, please draft minutes v2 17:15:41 I have made the request to generate https://www.w3.org/2020/01/16-tt-minutes.html nigel 17:16:08 scribeOptions: -final -noEmbedDiagnostics 17:16:10 RRSAgent, please draft minutes v2 17:16:10 I have made the request to generate https://www.w3.org/2020/01/16-tt-minutes.html nigel 17:17:01 github-bot, end topic