06:59:12 RRSAgent has joined #tt 06:59:12 logging to https://www.w3.org/2018/10/23-tt-irc 06:59:14 RRSAgent, make logs public 06:59:15 Zakim has joined #tt 06:59:16 Meeting: Timed Text Working Group Teleconference 06:59:16 Date: 23 October 2018 06:59:21 log: https://www.w3.org/2018/10/23-tt-irc 06:59:36 Present: Glenn, Nigel, Andreas 06:59:40 Chair: Nigel 06:59:42 scribe: nigel 06:59:48 Topic: Agenda for today 07:00:12 Nigel: Good morning everyone, let's do introductions. 07:00:21 atai has joined #tt 07:00:23 Nigel: Nigel Megitt, BBC, Chair 07:00:32 Andreas: Andreas Tai, IRT 07:00:44 Glenn: Glenn Adams, Skynav, been working on TTML since 2003! 07:00:51 Nigel: Thank you, and observers. 07:01:13 Masaya: Masaya Ikeo, NHK 07:01:36 Geun: Geun Hyung Kim, HTML5 Converged Technology Forum (Korea) 07:02:18 GeunHyung has joined #tt 07:02:46 Nigel: Today, we have Live subtitles and caption contribution, AC review feedback, 07:03:00 .. future requirements, and Audio profiles. 07:04:03 Nigel: Welcome, we have another observer: 07:04:22 Hiroshi: Hiroshi Fujisawa, NHK 07:04:32 MasayaIkeo has joined #tt 07:05:32 Toshihiko: Toshihiko Yamakami, Access Co., Ltd 07:06:21 Andreas: For the future requirements topic, after lunch, a colleague may want to join on 07:06:34 .. the requirements for 360º subtitles and possibly other TPAC attendees may want to 07:06:52 glenn has joined #tt 07:06:52 .. join so if we can figure out a specific slot that would be great. 07:07:11 Nigel: If there are timing preferences we can be flexible - probably any time after 11:30 we can do. 07:07:23 Andreas: Thanks, I'll get back to the group on that. 07:07:36 Topic: Live Subtitle and Caption contribution 07:07:44 Nigel: I uploaded a short presentation: 07:08:01 -> https://www.w3.org/wiki/images/f/f4/Live_subtitles_presentation_BBC_TPAC_2018.pdf Presentation on live subtitles and captions 07:08:12 Present+ Pierre 07:08:30 Pierre: Pierre Lemieux, Movielabs, Editor IMSC 07:09:36 Nigel: [presents slides] 07:10:32 fujisawa has joined #tt 07:18:24 Pierre: Question about the client device being unaware of live vs prepared source, and 07:18:38 .. the system being designed with that as a constraint. 07:18:42 Nigel: Yes, assume that is the case. 07:18:56 Glenn: The distribution packager might assign DTS or PTS? 07:19:14 Nigel: Yes, I should have added MPEG2 Transport Streams as a possible output, and we 07:19:28 .. should note that there is a DVB specification for insertion of TTML into MP2 TS. 07:23:11 ericc has joined #tt 07:39:43 Nigel: [slide on transport protocols] If there is timing information from the carriage 07:39:58 .. mechanism then that might need to be understood in relation to processing any 07:40:02 .. subtitle TTML document. 07:40:25 Glenn: Are you hoping an RTP packet will fit within a single UDP packet? 07:40:36 Nigel: In general that is likely to be true, but not necessarily. 07:41:14 Pierre: So you can't rely on the network providing you with ordered documents? 07:41:19 Nigel: Yes, that could be the case. 07:41:32 Pierre: So the protocol you use has to be able to handle non-sequential document transmission? 07:41:36 Nigel: Yes, potentially. 07:42:34 .. You do need to resolve the presentation in the end, and some deployments may 07:43:07 .. provide fixes for out of order delivery at the protocol level (WebSocket) or at the 07:43:45 .. application level and we need to deal with the whole range of possible operational conditions. 07:49:24 fujisawa has joined #tt 07:53:34 fujisawa has joined #tt 08:07:16 group: Discussion of options for defining the begin and end time of a TTML document. 08:25:55 Nigel: [proposal slide] 08:26:13 Glenn: I wouldn't object to using the ebu namespace as long we don't normatively 08:26:24 .. reference the EBU spec. I'm not willing to cross the rubicon when it comes to bringing 08:26:29 .. in non-W3C namespaces into TTML. 08:26:46 .. If it is published as a Rec track document and it refers to TTML and is a module that 08:26:50 fujisawa has joined #tt 08:26:58 .. blesses these features, using EBU namespace to define them, then that's okay with me. 08:27:09 .. If we have an assumption that we are going to pull that into TTML directly then I might 08:27:12 .. start having some discomfort. 08:27:24 Andreas: I think we are not there yet at this point in the discussion. First we have a problem 08:27:36 .. that we are trying to solve and we have a standard that is already out there. It is good 08:27:47 .. practice not to duplicate. What Nigel has proposed addresses a good part of this 08:28:00 .. scenario, and there has been a lot of discussion since 2012 on this with at least 3 years 08:28:12 .. regular active work on it, so I think it is worth looking at it. After reviewing this and 08:28:24 .. deciding that this is how we want to solve it then we can look at how to adopt it. 08:28:34 Glenn: Right, I just wanted to give fair warning about the questions I might have. 08:28:46 .. A question I have is why we need to do something in W3C? 08:29:01 .. Is it a profile of EBU-TT? 08:29:13 Andreas: Good question. It is limited to certain vocabulary and mainly has the constraints 08:29:24 .. from EBU-TT, which are not the same as for IMSC. It would be perfect to use the same 08:29:29 .. mechanism for all IMSC documents. 08:29:58 Nigel: That was my answer, it makes sense to bring these key semantics into the home 08:30:08 .. of TTML so that it can be applied to other profiles than EBU-TT. 08:30:28 Glenn: Is it an authoring guideline? 08:30:35 Nigel: Why would it be a guideline? 08:30:46 Glenn: It's not defining new technical features. 08:30:50 Nigel: It is indeed doing that. 08:31:03 Pierre: There might be technical features such as defining document times as mentioned. 08:31:16 .. A lot of the guidelines could be in the model, but I suspect there would be some 08:31:20 .. requirements and substantive features. 08:31:47 Nigel: [propose a break for 30 minutes] 08:31:49 rrsagent, make minutes 08:31:49 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 08:44:38 ericc has joined #tt 09:00:46 MasayaIkeo has joined #tt 09:08:11 atai has joined #tt 09:12:19 Topic: Live subtitle contribution - discussion 09:12:37 ericc has joined #tt 09:12:57 Pierre: Is the proposal for an EBU Member Submission? 09:13:09 Nigel: It could be but I think it is not needed - the IPR can be contributed by EBU as 09:13:19 .. a member based on any work that we do in this group. 09:13:32 Andreas: There is a question for a member submission if it will be superseded by a future 09:13:48 .. W3C specification. The market condition is that people are pushing for implementation 09:13:57 .. of EBU-TT Live so we should be clear about what we want to do in W3C. 09:14:27 Pierre: This sounds more like an EBU discussion, W3C cannot require implementation. 09:14:51 Andreas: It could affect adoption though since work on an alternative may change views. 09:15:06 Pierre: That's an EBU decision. Anything could happen when a member submission arrives here. 09:15:18 Andreas: We can review the document as it is and then review what is needed. I don't see 09:15:31 .. a need for a member submission at the moment. What advantage do you see in EBU submitting one? 09:15:44 .. The spec is out there, everyone can use it, IPR issues should not be a problem. 09:15:59 Pierre: I can't speak for EBU but I would think that a member submission clarifies 09:16:13 .. significantly the scope of the effort, being live subtitles within the member submission 09:16:18 .. scope rather than live subtitles in general. 09:16:35 .. IMSC ended up different from CFF-TT for good reason, but the scope of the features 09:16:48 .. for instance was set by the member submission. It would help. 09:17:01 Andreas: The different arguments that led other W3C members to make submission is more 09:17:14 .. internal, how to move on with some standardisation. In the past submissions are 09:17:31 .. submitted to W3C, then carefully reviewed, when W3C should take over certain 09:17:34 .. standardisation. 09:17:48 Pierre: For instance, CFF-TT - the Ultraviolet members and the larger community felt that 09:18:01 .. it would be beneficial if something like that specification were to be standardised by an 09:18:15 .. organisation like W3C. That was a decision by that community to do that. But it was not 09:18:29 .. happenstance. Here, I think it is up to EBU and its members and community to have an 09:18:41 .. opinion on whether or not standardisation by W3C helps or not. 09:18:51 .. It might not help if it changes the specification in a way that is not good for that 09:18:55 .. community. You tell me. 09:19:05 Andreas: We are not there yet. This group has not decided yet. 09:19:09 Pierre: Live is really important. 09:19:20 Andreas: Yes, this is something we need to discuss. What is in scope for this group? 09:19:29 Pierre: The industry is interested in live, period. 09:19:58 .. It is a really important use case. 09:21:36 Nigel: [repeats goal from earlier[ 09:21:42 s/r[/r] 09:21:57 Pierre: If the goal is to arrive at how to create a set of IMSC documents in a live environment... 09:22:10 Andreas: What Nigel said, and other EBU members, is there is support to make EBU-TT Live 09:22:21 .. a subset similar to how EBU-TT-D is a subset of IMSC Text Profile. 09:22:23 Zakim has left #tt 09:22:24 Pierre: That works. 09:22:39 Zakim has joined #tt 09:22:56 .. You don't need a member submission for that. Deciding on the scope early is a good idea. 09:22:58 Andreas: Yes 09:23:06 Pierre: Both make sense. Picking one is going to be really key. 09:23:44 Nigel: I think I hear consensus that some kind of TTWG technical report that addresses 09:23:58 .. the live contribution use case is worthwhile. 09:24:05 Glenn: Requirements would be useful to set the scope. 09:24:18 Pierre: Yes, a requirements document would be helpful. 09:24:35 Glenn: In general we should have requirements documents before new technical specifications. 09:24:41 .. I make a motion to require that. 09:25:01 Andreas: I propose a joint meeting with EBU group to discuss this. We have January in Munich 09:25:31 .. in mind. We wanted to bring this up and see what the availability of members. 09:25:42 Pierre: Feb 1 in Geneva would work for me. 09:25:46 Andreas: That is good. 09:26:29 Pierre: Specifically the morning of Feb 1! 09:26:43 Andreas: Propose 31st and 1st. 09:27:07 Pierre: I'm busy Friday 1st in the afternoon but the joint meeting could be just in the morning. 09:27:11 .. We don't need more than 3 hours. 09:27:30 Glenn: If we're having a face to face meeting it should be at least 2 days, if it is an official 09:27:34 .. WG face to face meeting. 09:27:47 Pierre: I think we are just proposing a joint TTWG - EBU meeting. 09:28:05 Glenn: That would make it a TTWG f2f, I can't justify a journey to Geneva for half a day. 09:28:39 Andreas: If we make a one and a half day meeting, on Thursday and Friday. 09:28:44 Glenn: I'm available on Saturday too. 09:28:56 Pierre: I'd rather not, my preference would be 30th and 31st and part of the 1st. 09:29:10 Andreas: It would be good anyway to have the EBU and TTWG members in a room together. 09:29:54 Pierre: We can do it during PTS, why not? 09:30:00 Andreas: We need to ask Frans and EBU. 09:30:30 .. I will ask Frans. 09:31:54 Nigel: Thanks, summarising the discussion: 09:32:11 .. * A technical report on live subtitle contribution is a good idea 09:32:18 .. * We need requirements for that 09:32:32 .. * We will investigate a joint meeting with EBU at end of Jan/beginning of Feb 09:33:04 .. Thank you. 09:33:13 Pierre: Thanks for bringing this up. 09:33:22 .. At some point we will have a technical discussion about the details, based on the 09:33:32 .. requirements, which will be crafted hopefully prior to that meeting, and that would be 09:33:40 .. a good time to have a technical discussion. 09:33:51 glenn has joined #tt 09:34:27 Glenn: Does the current Charter cover this work? 09:35:20 Nigel: The requirements document would be a Note so that would certainly be covered. 09:36:26 .. We don't have a specific deliverable for a Recommendation listed at present, so that 09:36:36 .. may be something that we should consider for a Charter revision. 09:36:56 .. By the way, if we proceed with David Singer's proposal from yesterday, that could be a 09:37:10 .. good moment to revise the Charter in any case, since the WebVTT Rec deliverable would 09:37:14 .. have to be pulled from the Scope. 09:38:01 .. For example we could target a Charter revision in May 2019 for another 2 years, pulling 09:38:09 .. the end date to 2021. 09:38:19 Glenn: 2023 will be the 20th anniversary of this WG. 09:39:47 Andreas: Noting that there are observers here who might be interested in this topic, if we 09:40:00 .. proceed with this work we should make it possible for new members to join our meetings. 09:41:37 Nigel: As Chair, I would like to know if there are any potential members especially in 09:41:52 .. different time zones and to be flexible about how we meet to allow them to participate. 09:42:15 Andreas: I also meant that it should be possible for non-members of TTWG to participate 09:42:20 .. in the discussion. 09:43:07 Nigel: For a non-Rec track requirements document with no IPR, that is fine of course. 09:44:07 .. To clear IPR rules when we get to a Rec track document obviously contributors do need 09:44:11 .. to be WG members, effectively. 09:44:29 Glenn: If we publish a Rec track document that is based in large part on another spec 09:44:39 .. outside of W3C then that may be precedent-setting. 09:44:43 Pierre: Like IMSC? 09:44:51 Nigel: It's not precedent setting. 09:45:01 Pierre: It's the same, it's based on TTML. 09:45:06 Nigel: I agree. 09:45:21 Pierre: From what I have read it's a how-to-interpret TTML document crafted in a particular way. 09:45:25 Glenn: That's reasonable. 09:46:30 Topic: AC Review feedback 09:48:50 Nigel: Reviews AC feedback. We don't have any comments to respond to. 09:51:28 .. We have a reasonable number of responses now, some more would be good. 09:52:13 Topic: TTML1 3rd Edition Rec CfC 09:52:29 Nigel: I realised that in my CfC for publishing the TTML1 3rd Ed Recommendation, I did not 09:52:41 .. include any consideration of superseding 2nd Edition. I don't think we need to do that 09:52:58 .. for TTML2 or IMSC 1.1, because the previous Recs still stand, i.e. TTML1 3rd Ed and IMSC 1.0.1. 09:53:36 Nigel: Can I make it a condition of the CfC that we supersede TTML1 2nd Ed when we 09:53:40 .. publish TTML1 3rd Ed. 09:53:45 Glenn: It would be inconsistent not to. 09:54:03 Pierre: Yes, supersede not obsolete. 09:54:14 .. In the fullness of time we should probably make an Edited Recommendation of 09:54:23 .. IMSC 1.0.1 to point to TTML1 3rd Edition too. 09:54:38 Andreas: Yes, superseding is okay. 09:54:47 Nigel: Thank you, that's a decision. 09:55:15 RESOLUTION: As part of the request to publish TTML1 3rd Ed as a Recommendation we will supersede TTML1 2nd Ed. 10:01:13 rrsagent, make minutes 10:01:13 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 10:02:46 Nigel: We'll break for lunch now, back at 1300. 10:14:07 mdjp has joined #tt 10:30:12 fujisawa has joined #tt 10:42:12 fujisawa has joined #tt 11:04:10 MasayaIkeo has joined #tt 11:07:22 atai has joined #tt 11:07:49 nigel has joined #tt 11:10:54 Topic: Future Requirements 11:11:06 Nigel: Since the break, we have a new observer and a new attendee: 11:11:40 Vladimir: Vladimir Levantovsky, Monotype, AC Rep, Chair of Web Fonts WG (awaiting re-charter) 11:11:53 .. I have a very keen interest in anything relating to text matters, including composition, 11:12:01 .. rendering, fonts and anything else you can imagine related to that. 11:12:43 fujisawa has joined #tt 11:12:57 Yam_ACCESS has joined #tt 11:13:07 mdjp: Matt Paradis, BBC, Chair of the Web Audio WG, and I run an accessibility and interactive 11:13:15 .. work stream for BBC R&D, which is where my interest in this group lies. 11:13:22 Nigel: Thank you, welcome. 11:13:46 glenn has joined #tt 11:13:56 s/Nigel: Thank you, welcome./ 11:14:11 Peter: I'm Peter tho Pesch, from IRT. I'm working on a project to do with accessibility of 11:14:20 .. 360 and AR environments, particularly subtitles. 11:15:23 Nigel: Thank you, welcome. 11:16:05 .. Can I first get a very quick list of the new requirements areas that we want to cover in 11:16:06 Peter__IRT_ has joined #tt 11:16:08 .. this conversation? 11:16:19 .. I already have 360º/AR/VR requirements. 11:16:39 Vlad has joined #tt 11:16:44 .. This morning we covered live subtitle use cases so we don't need to duplicate that work. 11:16:45 present+ 11:17:00 Present+ Vladimir, Peter 11:17:19 Nigel: I need to present some styling attributes for consideration, actually a bigger question 11:17:32 .. about bringing in arbitrary CSS and how we might go about doing that. 11:17:50 Andreas: I recently came across a requirement for a TTML documents container element. 11:18:12 Topic: New requirements: 360º/AR/VR 11:18:56 Andreas: Just to start on this, yesterday we had at the Media and Entertainment IG a 11:19:10 .. brief session where I showed some of the results of the work Peter has been doing. 11:19:19 .. We did not get into the detail, I just showed the videos and we agreed there is a use 11:19:30 .. case that needs to be solved, and there is not complete agreement, or it is not clear yet 11:19:44 .. where it should be solved. The M&E IG action was to organise a telco where we get the 11:19:57 .. necessary people from different groups together, discuss the problem scenario and then 11:20:02 .. work out where the work will be done. 11:20:16 .. Yesterday, because I walked through the different examples, I would like to repeat this 11:20:28 .. with Peter's comments because he has the necessary input. 11:20:37 ericc has joined #tt 11:20:39 .. Because Vladimir is working on a similar topic and yesterday brought up some additional 11:20:50 .. issues we may want to make a list of all the things that could be in scope of the TTWG. 11:21:21 Nigel: Just to note, our Charter includes in the Scope: "Investigate caption format requirements for 360 Degree, AR and VR video content." 11:21:51 Vladimir: And "caption" doesn't necessarily mean subtitles, it could be any text label that 11:21:57 .. is part of the content? 11:22:06 Glenn: We don't distinguish between subtitle and caption any more! 11:22:14 Vladimir: Would text label be considered in scope? 11:22:17 Glenn: Why not? 11:22:28 Andreas: The group name is Timed Text, which is very generic and doesn't say what it is 11:22:39 .. used for. For general matters also there is the CSS group. 11:22:53 Vladimir: I understand we will not cover all the presentation cases. 11:23:10 .. For example when you're in a 360º environment the text will be defined by timed text, 11:23:17 .. but the composition might be defined by CSS. 11:23:27 Nigel: Consider this in scope. 11:24:23 Andreas: [shows examples] 11:24:39 Peter: I will start here at this slide. Yesterday you showed already a little bit of the scope. 11:24:51 .. I often use this image because for me it was the easiest way to picture the coordinate system 11:24:55 .. we are using. 11:25:07 .. [world map, equirectangular projection] 11:25:24 .. You also know how this would map onto a sphere. This is a common way to represent 11:25:40 .. 360º videos, using this map and wrapping it round a sphere, putting the viewer at the 11:25:52 .. centre looking out (the other way from the way you see a globe normally). 11:26:00 fujisawa has joined #tt 11:26:12 .. Within the project I am working on, we are looking into ways of adding accessibility 11:26:24 .. services to VR, focusing on 360º videos right now. 11:26:35 .. There are some challenges, maybe we start with the videos to show you some of the 11:26:40 .. thoughts we had on this. 11:26:59 .. [always visible] This is the simplest mode, where the subtitles are always shown in the 11:27:21 .. viewport where the viewer is looking. 11:27:35 .. This is a basic implementation, you can see the subtitle text always sticks in one position. 11:27:50 .. In this example the text is aligned to the viewport not to the video. 11:28:20 .. [example with arrow pointing at the speaker] 11:28:35 .. Here if the speaker is off screen an arrow points to the left or right to show where the 11:28:45 .. speaker is located. It disappears when the speaker is in the field of view. 11:28:53 .. It's a small help for people to find where the action is. 11:29:05 .. The basic presentation mode is the same. 11:29:20 .. [fixed positioned] This is a completely different approach. 11:29:33 .. The subtitle is now fixed to the video not the viewport, like a burned in subtitle. The way 11:29:48 .. it is shown here, I don't know where this is used in practice, but there is an example 11:30:05 .. where the subtitle text is burned into the video at three different positions and fixed there. 11:30:11 .. [Formats] 11:30:19 .. A quick overview of how we implemented this. 11:30:31 .. IMSC, DASH, h.264 video. 11:30:44 .. Custom extensions to IMSC for providing the information we needed. 11:31:14 .. In this example, imac:equirectangularLong and imac:equirectangularlat are specified on the p element. 11:31:27 .. They specify a direction in the coordinate system, not really a position. You could specify 11:31:41 .. a vector and where the vector hits the sphere, that is where the subtitle is located. 11:31:47 .. This is used for the different implementations. 11:31:55 .. This is the current status. 11:32:07 .. Future thoughts: subtitles with two lines in each subtitle, belonging to different speakers 11:32:22 .. at different positions, so different angles for each speaker. We could add the attributes 11:32:31 .. at the span level but we did not do that yet. 11:32:46 .. Also what information the author can add to indicate the suitable rendering style. 11:33:10 Andreas: That's better than what I said yesterday! And it doesn't contradict it. 11:33:20 .. Yesterday there was the generic question where should this gap be addressed. 11:33:33 .. It was clear that TTWG comes into this. I think it's worthwhile first discussing if this kind 11:33:44 .. of use case falls in scope, and if these two attributes would be something that could 11:33:54 .. be added to TTML and IMSC, and what additional features are needed. 11:34:00 q+ to ask about distance 11:34:20 +q 11:34:37 q+ to ask about other presentation models 11:34:41 ack glenn 11:34:58 Glenn: Those are very long property names, and they embed a particular projection semantic. 11:35:10 .. If they were to be put into TTML I would probably prefer shorter names as well as 11:35:22 .. extracting the projection method to a separate parameter for the document level. 11:35:38 q+ to ask about doing the projection based on a rectangular region 11:36:07 Glenn: As far as potential requirements, I think this is good and we should consider doing something in a standard. 11:36:22 .. We would have to define in the spec the transformation from the spherical coordinate 11:36:50 .. space to the projection coordinate space, for different projections, e.g. a projection method parameter. 11:37:24 ack n 11:37:24 nigel, you wanted to ask about distance and to ask about other presentation models and to ask about doing the projection based on a rectangular region 11:37:51 Nigel: Why not use a 2d coordinate like for the video image and then project the text in 11:37:59 .. the same way as the video, rather than including the coordinates? 11:38:16 Peter: We thought about that. We have an additional mapping step. One way would be to 11:38:28 .. base the IMSC file on the 2D texture and then use the mapping mechanism that is 11:38:39 .. defined by the standard for mapping the video, also for the subtitle file, or to define 11:38:50 .. information directly in the IMSC in the target coordinate system. 11:39:00 .. We used this approach here because it is a lot easier to implement. This is the 11:39:11 .. rendering coordinate system and it is easy to map the video texture on a sphere in the 11:39:28 .. framework we are using. Then it is a lot easier to define the coordinates directly. 11:39:38 Glenn: Right now the x and y coordinate space in TTML is cartesian based and we have a 11:39:49 .. great deal of semantics, for example the extent of a region, is defined in x and y 11:40:05 .. coordinate space. You could use a reverse transformation as long as you have the 11:40:18 .. central meridian and standard parallels for doing a reverse projection to the 11:40:33 .. equirectangular form. I think we should be hesitant to express coordinates in a 11:40:44 .. coordinate space that is not based on our assumed cartesian space. I would rather do 11:40:58 .. a reverse transformation, specify x and y and map to spherical coordinate space. 11:41:11 Vladimir: A question. Everything so far seems to be related to flat 2D projections. How would 11:41:23 .. that apply to a stereoscopic environment. 11:41:37 Nigel: That was one of my questions - how do you specify depth? 11:41:49 Vladimir: You can break the user perception by getting it wront. 11:41:54 s/wront/wrong 11:42:21 Nigel: We have disparity already but I don't know how disparity fits with the 3d coordinate system. 11:42:36 Peter: We also looked at MPEG OMAF (omnidirectional media application format) and the 11:42:47 .. draft describes how to add subtitles to the 3d space, and it supports WebVTT and IMSC 11:42:59 .. subtitles, and the IMSC subtitles are added in a way where the MPEG scope provides a 11:43:11 .. rendering plane for the IMSC to be rendered onto. The information in the IMSC document 11:43:24 .. is included in the OMAF format. There's an additional metadata track that contains those 11:43:36 .. information and that handles the information in the way MPEG does it. There is a box, 11:43:53 .. for regions, and for points in their coordinate system. You basically get a rectangular 11:43:58 .. plane for rendering your subtitles onto. 11:44:11 .. It also includes depth information for stereoscopic content. 11:44:42 Nigel: If there's depth information in the video then there must be depth in the subtitles, 11:44:47 .. how do those two get aligned? 11:45:02 Peter: I didn't fully look into this, but the standard suggests a default depth and radius 11:45:12 .. for the video sphere, and according to this you can either add depth information relating 11:45:25 .. to radius or directly add disparity information. The disparity information is not connected 11:45:37 .. to the video because it is connected to the presentation of the stereoscopic image, and 11:45:52 .. you would need to provide a left eye and right eye video stream. 11:46:20 q? 11:46:37 Andreas: I want to point to Vladimir and ask: yesterday you brought up some additional 11:46:46 .. things. Apart from positioning, what other things may be useful or needed? 11:47:03 MasayaIkeo has joined #tt 11:47:04 Vladimir: Yesterday I mentioned, speculatively, without a specific application in mind, 11:47:36 .. text objects need some kind of perspective transform to be applied. 11:48:14 .. How much detail we go into depends on how the responsibilities of text transform are 11:48:19 .. split between different parts. 11:48:29 Andreas: I wondered if CSS WG are working on the same thing, or another WG. 11:48:38 Present+ Philippe 11:48:53 Andreas: I think positioning of arbitrary HTML or whatever in this space could be in the long 11:49:09 .. run in the requirements. I don't want to contradict here what is being done in other groups. 11:49:20 Vladimir: I haven't heard anything about CSS considering 3D layout issues. 11:50:06 Philippe: The Immersive Web WG was created last month. 11:50:12 Andreas: I spoke with Chris Wilson yesterday. 11:50:18 Philiipe: He's one of the Chairs. 11:50:32 Andreas: I asked if we could present this use case tomorrow, he thinks it's not the right 11:50:50 .. moment, and prefers that it gets discussed in the WebXR CG, which has a repository 11:51:12 .. for requirements. If we open a requirement then we should open it there. 11:51:24 Philippe: We should ask the APA WG which is a coordination group for accessibility too, 11:51:37 .. you should ask Janina. She might well say it came up on their radar. I don't think they 11:51:41 .. have done any work on it. 11:51:59 Andreas: In this project we are also discussing user interfaces and this is definitely an 11:52:11 .. issue for the APA WG, UIs for navigation and control of access services. 11:52:22 Philippe: It's not just UI! 11:52:31 Andreas: OK. 11:52:42 Philippe: We don't have an accessibility group for the 3d space right now but that is where 11:52:46 .. the discussion should begin. 11:53:14 Vladimir: The Virtual Reality Industry Forum is another one outside W3C. We are still in the 11:53:29 .. exploration stage. We know what needs to happen to do what needs to be done in the 11:53:47 .. web, for example what to do with web fonts. 11:53:59 .. [i.e. web fonts might need some work] 11:54:09 Andreas: That group could point to something in W3C? 11:54:20 Vladimir: Yes, it would be a huge help to point to something from W3C. 11:54:52 Peter: There's one thought I wanted to add. When we look at the scope of MPEG OMAF, 11:55:04 .. keep in mind it is a distribution format, and it specifies how to bring the content to the 11:55:14 .. consumer but when you look at the complete chain the content will probably not be 11:55:30 .. described in OMAF. The subtitle workflow - it makes sense all the subtitle information is 11:55:48 .. kept in one place. You can look at it in two ways - either the positional description being 11:56:02 .. like a styling attribute or a kind of metadata to transport the information to the MPEG 11:56:14 .. format to distribute it to the user. Maybe there are two different use cases. One to 11:56:26 .. describe subtitles in a 3D space, something like an extended IMSC, or you could say 11:56:37 .. we need additional metadata, just tunnel this information to the point where the complete 11:56:43 .. format is mapped to a 3D space. 11:57:12 Nigel: Question: Do you need to describe the speaker position, the text position, or both? 11:57:25 Peter: That's a very good question. At the moment we are just pointing at the centre of the 11:57:37 .. speaker with no height information. We don't differentiate the speaker position or the 11:57:52 .. text position. They might be different. 11:58:32 Nigel: A follow-on question: what user information do have about preferences? Which of 11:58:44 q+ 11:58:46 .. these do people want to use, one in particular or different people prefer different ones? 11:59:01 Peter: It's too early to say, research is ongoing. There are different results from different 11:59:16 .. tests pointing in different directions. For example a university in Munich found that half 11:59:32 .. of the test users preferred fixed position, and half didn't like it. It has the advantage 11:59:45 .. that it is more comfortable to view and induces less sickness but you can miss the 12:00:01 .. subtitle if you are not looking the right way. We are still looking to find the best way. 12:00:03 ack a 12:00:19 Andreas: How does VR-IF Forum relate to MPEG OMAF? 12:00:37 Vladimir: I think they have a liaison or they are just the same members. I doubt there is a 12:00:45 .. direct official relationship between the two. 12:01:03 .. VR-IF doesn't specify anything but produces usage guidelines. It's a different level, not 12:01:06 .. technical specifications. 12:01:20 Andreas: The other question is regarding font technology. Recently I have seen a lot of 12:01:35 .. advancement of the use of variable fonts on the web, with one font file with a large number 12:01:51 .. of font faces you could use. From the discussion I've heard this 3D space presents a 12:02:04 .. different kind of graphical challenge, and I see good application of variable fonts in this 12:02:08 .. space which I think should be explored. 12:02:13 Vladimir: I absolutely agree. 12:02:24 .. The reality is when you rely on a particular font feature to be available it would be 12:02:38 .. too optimistic to rely on the font that happens to be resident on the user's device. 12:02:52 .. When you rely on a specific font feature you're best/only bet is to serve the font to the 12:02:57 .. user so you know the font is present. 12:03:12 .. Same with variable fonts, which are in the early stages of deployment. If you want to use 12:03:17 .. them then you need to provide the font. 12:03:36 .. In VR-IF nothing is taken for granted, and if a particular font is needed, for feature or 12:03:55 .. language support, then that font has to be provided. On the web the font can be downloaded, 12:04:02 .. in ISOBMFF there is a way to provide a font. 12:04:17 Glenn: TTML2 supports font embedding now either directly in the TTML document or by 12:04:29 .. URL reference to the environment somewhere which in the context of ISOBMFF could be 12:04:34 .. part of the font carousel that's available. 12:04:39 Andreas: Is this in IMSC 1.1? 12:05:40 Nigel: I don't think so. 12:06:09 .. [confirms this by looking at the spec] 12:06:21 Andreas: TTML2 has a wide feature, IMSC is a subset that doesn't support this. At the 12:06:32 .. bottom line there should at least be a mechanism for the content provider to provide 12:06:33 .. the font. 12:06:48 Vladimir: Absolutely. If you expect that variable fonts are useful in this environment then 12:06:49 cpn has joined #tt 12:06:53 .. you have to provide them. 12:07:06 Andreas: As a proposal for the next steps, would it be a strategy to first try to fix the 12:07:15 .. requirements and describe the use cases we are trying to solve? 12:07:36 .. If this is ready then we can schedule the Web Media & Entertainment call on the IG and 12:07:39 .. discuss it. 12:07:59 Nigel: Sounds good. Are there other members than IRT interested in this? 12:08:07 Vladimir: I am interested, I am learning more than I can contribute. 12:10:38 Observer: Can TTML associate a piece of timed text with a point in space where the sound originated from? 12:10:49 Nigel: I think there is no standard way to do that now, no. 12:11:03 Vladimir: You're suggesting two independent spatial references, one for a specific location 12:11:19 .. and the other for a location of the source so if we wanted to implement the arrows 12:11:28 .. solution we would know the location of the source? 12:11:35 Observer: yes, I'm just curious. 12:11:43 Nigel: I think that is for the requirements document to describe. 12:12:27 Nigel: Matt, do we have data for object based media pointing to where sound should be positioned in space? 12:12:44 Matt: We do have prototype metadata for azimuth, elevation and distance, but there's a long 12:13:00 .. step between that prototype form and something that could be broadcast. 12:13:06 Nigel: Does it inform the data modelling? 12:13:21 Matt: It does, elsewhere we look at graph data for object based productions, and this is 12:13:41 .. at a higher layer than something like the Audio Definition Model. 12:13:58 .. It gives a reference for speaker or events or "sounding objects". 12:14:19 Nigel: I would suggest we should use the same coordinate system for things we can see 12:14:45 .. and things we can hear. It could be an accessibility issue, to allow transformation between 12:14:52 .. visual and auditory information. 12:15:14 Matt: It's a fundamental to get the coordinate system right. For example in Web Audio WG 12:15:31 .. we had to decide whether azimuth goes clockwise or anti-clockwise. Standardising on 12:15:36 .. a common API is important. 12:15:51 Andreas: For gathering requirements, typically we would start to describe what we want 12:16:04 .. to solve, and then all these questions will come up. We also learned from this discussion 12:16:18 .. that a lot of things come to mind based on what has already been specified, which will 12:16:30 .. come up when the requirements are clear and we are moving to a solution. 12:16:41 .. Peter you said you are willing to put some work into the requirements? 12:16:46 Peter: Yes definitely. 12:17:02 Andreas: Vladimir also said you are interested. I can be involved but I'm not an expert in this. 12:17:06 .. I can be a link and help out. 12:17:21 .. That would be my proposed action that you two and anyone else who is interested tries 12:17:33 .. to work out these use cases, and directly post it on the GitHub repository. 12:17:37 Nigel: What GitHub repo? 12:17:55 Andreas: The XR CG has a repo for requirements or proposals, that was Chris Wilson's 12:18:06 .. proposal and it's a good start to get it out there for everyone to access. 12:18:18 Peter: OK, for my understanding what we provide first is the use cases and what we want 12:18:34 .. to do, and the question is does it involve links to existing standards? 12:18:41 .. What standards are there to help solve these issues? 12:18:50 .. What is within the scope of the TTML WG? 12:19:05 .. Or the other WGs. 12:19:15 Vladimir: At this point we should probably have a critical eye on the existing standards. 12:19:27 .. If the standard exists it doesn't mean it was complete, correct or designed with the same 12:19:41 .. use cases in mind. The existing standards may need to be amended to be useful. 12:19:54 .. There may be something missing, which is useful information for the folks who 12:20:06 .. developed those standards. For example just because OMAF exists, doesn't mean it is 12:20:19 .. capable of supporting all possible use cases. If we find one that is not supported they 12:20:23 .. would welcome the contribution. 12:20:25 Peter: +1 12:20:37 Andreas: What you say makes a lot of sense Vladimir. I would propose to systematically 12:20:49 .. separate this so first we have a green field of what the use case is to solve, and the 12:21:00 .. requirements, and open up the issue on GitHub, then immediately afterwards reply to 12:21:13 .. it and say "these standards address this already" and then the discussion starts. 12:21:27 Peter: Yes 12:22:18 rrsagent, make minutes 12:22:18 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 12:23:52 Vladimir: I have to leave now, thank you. 12:24:00 Peter: I will leave too, thank you. 12:24:07 Philippe: [went some time ago] 12:24:12 Nigel: Thank you all. 12:24:58 Topic: TTML Documents Container 12:25:12 Andreas: Recently a European broadcaster asked me if TTML can have multiple tracks, 12:25:20 .. for example different languages per file. 12:25:31 .. I said no that's not how it is defined, you have one document per track. 12:25:47 .. For authoring and archiving they thought about one file system with all the representatinos 12:25:55 .. for the same content in one file. I said no not now. 12:26:10 .. Then I realised you can put the root element of each document in a parent container, 12:26:23 .. and get this with a separate "TTMLContainer" element whose children are tt elements. 12:26:25 +present 12:26:33 s/tinos/tions 12:26:51 present+ 12:26:53 Andreas: I wondered if this is a more generic use case where you want to specify something. 12:27:22 Nigel: One option available in TTML2 is to use the condition mechanism to extract just 12:27:38 .. the content for, say, a specific language, and put all the different content in a single TTML document. 12:27:43 .. That's an alternative to what you suggested. 12:28:01 .. Another is to use a different manifest format, like IMF etc to handle this kind of case. 12:28:17 Glenn: I would have answered "yes of course" and it's the responsibility of the application 12:28:30 .. that's using TTML to define how to use it. It's something external to the TTML file. 12:28:46 .. I would refocus the question on making that an application specific usage scenario. 12:29:00 .. Like if you want a PNG, JPEG and SVG version of a single image, there's no requirement 12:29:11 .. for each file to know about each other but the outside usage may have a manifest of 12:29:20 .. potential realisations of that resource. 12:29:37 .. This is like the semantics of URNs and URIs. URIs are abstract, and URNs more so, but they 12:29:51 .. map to one or more URL that realises the resource, and each URL might have a different 12:29:58 .. aspect like language and so forth. 12:30:24 Andreas: I know that we delegate this. What Nigel said is to pick something out of the file 12:30:39 .. but you want to store it without picking something. You don't want to say which one is 12:30:54 .. preferred. You could specify the condition for a default to be selected. 12:30:55 Nigel: True 12:31:09 Andreas: The other storage scenarios are too big. It depends on the overall system 12:31:23 .. environment if they use IMF or something else. I don't think it makes sense just to store 12:31:33 .. subtitles in IMF without the video. 12:32:18 Nigel: It begs the question why localise subtitles only and not other resources like audio, 12:32:30 .. and if you are localising audio, then it starts to make more sense to use something like IMF. 12:32:42 Andreas: You may have the problem that you want the different subtitle versions in one 12:32:53 .. file. The condition attribute is an interesting thought to check out. It is not in IMSC? 12:32:55 Pierre: No. 12:33:09 Andreas: The easiest one is just to have multiple TTML documents in one file. Then you 12:33:22 .. can easily access the complete document tree and switch easily between different documents. 12:33:26 ericc has joined #tt 12:33:39 .. Then from one big file you can generate easily a separate document just for one version 12:33:41 .. or language. 12:33:50 Glenn: I don't like it at all. 12:33:56 Nigel: Don't like what? 12:34:16 Glenn: Multiple TTML documents as children of a parent element. It raises all sorts of 12:34:25 .. questions about semantics, like do they all start at the same begin time. 12:34:42 .. It is more reasonable that applications of TTML should define their own way to manage 12:34:47 .. groups of TTML documents. 12:35:41 Nigel: That sounded contradictory - do you mean it's okay for an application but not for this group to do? 12:35:50 Glenn: Yes, for example you could just put them in a zip file. 12:35:56 Nigel: Yes and give each a language-specific filename. 12:36:12 Glenn: Right [cites an existing example of this kind of technique] 12:36:28 .. It seems to closely arranged to specific application requirements, for example what is 12:36:43 .. the criteria for semantically grouping? Right now we define three different root level 12:37:03 .. element types, actually four, that can appear in a TTML document: tt, ttp:profile, isd:sequence and isd:isd. 12:37:17 .. The isd:sequence is a bit like what you're suggesting except you're suggesting a group 12:37:19 .. not a sequene. 12:37:22 s/ene/ence 12:37:42 Andreas: The use case could be that you have one file and a player like VLC offers the choice 12:37:57 .. of languages, and the same file would work in other players too. Two broadcasters 12:38:13 .. mentioned this to me recently, and others before. The scenario exists, and operational 12:38:26 .. people are looking for something like that. They can come up with their own solution, 12:38:35 .. the question is if a common solution makes sense. 12:39:03 Glenn: In HTML there's something called a "web archive" that a lot of tools can work with, 12:39:15 .. which saves all the page's files together in some form. 12:39:32 .. I've never seen any proposal within W3C to define a standard container for a collection 12:39:43 .. of HTML files, or PNG files or whatever basic content format file is being defined. 12:39:59 Andreas: The video element can have multiple text track child elements. 12:41:02 Nigel: I would push back against this because I think that the use case of localisation 12:41:22 .. goes beyond just subtitles, and should include all media types as first class citizens, 12:41:39 .. audio, video and anything else. It's detrimental to be too specific. 12:42:01 Nigel: Thanks, it seems like we don't have consensus to develop a requirements document 12:42:07 .. for grouping TTML documents at this stage. 12:42:18 Topic: Additional styling 12:42:31 Nigel: I wanted to raise this because we have an interesting use case in the BBC that 12:42:45 .. TTML cannot currently handle, even though it seems like it should be able to. 12:43:56 fujisawa has joined #tt 12:49:50 Nigel: [demonstrates some internal pages showing TTML presentation of narrative 12:50:03 .. text captions in video styled with CSS, animations, borders, border gradients etc.] 12:50:29 .. At the moment the CSS properties we would need are specific borders, clip-path and 12:50:35 .. background linear gradients. 12:50:45 .. I'm much more worried about future CSS properties that would be needed though. 12:50:47 fujisawa has joined #tt 12:50:59 Glenn: There are a couple of problems. One is testing - if we have a generic pass-through 12:51:14 .. mechanism, like a "css" property, whose value is a CSS expression, what do you put in 12:51:36 .. your profile? Right now we don't have a notion of parameterised set of values. 12:52:05 Andreas: In general I like the idea to use CSS features before they enter TTML properly. 12:52:16 .. I don't know how exactly, but in general I would support figuring out how this could work. 12:52:20 Glenn: It is worth investigating. 12:52:34 Pierre: Since the alignment has been with CSS it is worth a longer discussion. 12:52:46 .. Just in names there's friction for some folks, even though the gap is reducing. I also 12:52:58 .. like the way it is clear you don't have to import all of CSS, which is a relief to others. 12:53:12 .. For a computer, mapping a TTML name to a CSS name is a no-op. Alignment between 12:53:20 .. TTML and CSS has served us well so we should continue doing it. 12:53:35 Glenn: It would make it easier to expose CSS properties without the expense of a TTML 12:53:44 .. style attribute. There may be a sacrifice of interoperability. 12:53:54 Andreas: This group would just define the mechanism and then it is the responsibility 12:54:01 .. of the application if it supports it or not. 12:54:09 Glenn: Then there's the profile mechanism issue. 12:54:18 Andreas: Just say nothing about it. 12:54:26 Andreas: [leaves] 12:54:30 Pierre: [leaves] 12:54:39 Nigel: Thank you both. 12:54:59 .. OK for this requirement, I think it is worth spending some time describing the 12:55:14 .. requirement more fully, which I will try to do. Obvious solutions to this kind of thing 12:55:30 .. include specifying CSS properties directly on content elements or style elements, 12:55:43 .. and allowing a class attribute to define CSS classes that apply to a content element. 12:56:01 .. I realise both of these could create clashes between TTML styling and CSS styling and 12:56:22 .. we would need some mechanism for resolving those clashes. Especially class styling 12:56:39 .. is very different to the applicative styling we have in TTML, since it goes the other way 12:56:55 .. in terms of traversal. 12:57:19 Glenn: Class is a shorthand for id, and we already have id. 12:57:23 Nigel: It's not a shorthand for id 12:57:37 Glenn: You can have a CSS stylesheet associated with a TTML document and have #id styles 12:57:52 .. that are associating elements in TTML with CSS. In that sense adding class is just a 12:57:58 .. shorthand for aggregating multiple ids into one group. 12:58:01 Nigel: That's true. 12:58:38 Glenn: At application level you could put a CSS stylesheet on one side. 12:58:48 atai has joined #tt 12:58:50 .. There's a precedent here in WebVTT of applying a stylesheet on the outside, though it 12:59:02 .. it not defined clearly. Then it becomes a player dependent function whether it ingests 12:59:10 .. and uses the stylesheet during the formatting process. 12:59:26 .. Especially if you are doing a process where you're converting TTML to HTML/CSS. 12:59:38 .. I would be reluctant to buy into an approach that requires mapping to HTML and CSS. 12:59:52 .. Provided that we can have native implementations or things that don't map to HTML/CSS 13:00:10 .. and still use whatever we develop here that would be my mental model for acceptability. 13:00:40 Nigel: Just wondering about how big a problem space I'm opening up. If we map TTML 13:00:56 .. to SVG do we have to define how any classes or styles are tunnelled through? 13:01:08 Glenn: It could be done, the implementation would need to do some book-keeping as it 13:01:26 .. goes through the area mapping process, to get to the SVG elements that can be styled. 13:01:37 .. One TTML element can generate multiple areas and you can have multiple TTML elements 13:01:40 .. generating one area. 13:02:19 Nigel: In terms of spec work should we feel obliged to define the tunnelling into SVG? 13:02:24 Glenn: I don't think so. 13:02:39 .. We just need to be careful not to impose a restriction to a particular mapping format. 13:02:52 .. It should be possible to make a native implementation that doesn't use CSS or SVG. 13:03:04 .. In such a situation the native player would have to interpret the CSS and do what CSS 13:03:18 .. does in that circumstance. A lot of CSS semantics are based on the box model and there 13:03:41 .. may be some minor impedance mismatches between our area model and the CSS box 13:03:42 .. model. 13:03:55 Nigel: I take your word for that, but our model came from XSL-FO, which was at least once 13:04:07 .. aligned with CSS> 13:04:09 s/>/. 13:04:21 Glenn: For example CSS doesn't allow width or height to be specified on non-replaced 13:04:41 .. inline elements whereas we do allow that for ipd and bpd on a span, even if it does not 13:05:16 .. have display "inline-block". I just wanted to mention that we have taken various 13:05:30 .. decisions semantic-wise where if we just expose CSS into the mix we may have to deal 13:05:36 .. with incompatibilities that might arise. 13:05:49 .. One answer to the implementer is "do whatever makes sense" which is generally how 13:05:57 .. implementers operate anyway, but then you get interop issues. 13:06:09 Nigel: That's the point, to make an extensible model that allows a greater variety of CSS 13:06:20 .. styles to be applied in applications that can support them. 13:06:36 .. For example we could put all the "CSS tunnelling" semantics behind a feature designator. 13:07:22 Glenn: Yes. The general approach for CSS is that implementations ignore what they do not 13:07:30 .. recognise. There are no guarantees. 13:07:46 Nigel: Some implementations support @support queries, but older ones might not. 13:08:08 Nigel: I think we have consensus to work this up in terms of requirements and head towards 13:08:15 .. a solution in some future version of TTML. 13:08:49 rrsagent, make minutes 13:08:49 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 13:09:52 Topic: Audio Profiles 13:10:06 s/Topic: Audio Profiles/ 13:10:27 Topic: Audio Profiles 13:10:42 Nigel: I presented something here to the joint meeting with the Media and Entertainment IG 13:10:58 .. yesterday, and there's an Audio Description CG meeting on Thursday. 13:11:13 .. For this group's benefit, the idea is to create a profile of TTML2 which supports the 13:11:19 .. features needed for audio description. 13:11:53 -> https://www.w3.org/2011/webtv/wiki/images/3/30/AD_CG_presentation_TPAC_2018.pdf Presentation to joint meeting 13:14:55 Nigel: [shows TTML2 feature list] 13:15:52 .. I've just been told that the BBC implementation is live on github.io, but not quite working yet 13:16:08 -> https://bbc.github.io/Adhere/ BBC Adhere implementation 13:16:23 .. It has some build issues to fix. 13:16:37 .. My intent is that when the CG is settled on the profile we add it to the TTWG Charter 13:16:41 .. as a Rec track document. 13:17:13 Glenn: During the drive up to the implementation report you mentioned some challenges 13:17:27 .. and we made changes to some of the feature definitions - we removed embedded-audio 13:17:41 .. from the audio-description feature. Was that due to an implementation constraint? 13:18:00 Nigel: We made different changes. The embedded audio was one where I wasn't sure if 13:18:19 .. we would hit time limits. The other was text to speech in conjunction with web audio, 13:18:32 .. which is an API limitation that web speech output is not available as an input to web audio. 13:18:41 Glenn: Can that be rectified? 13:18:51 Matt: I had a response about this a couple of weeks ago. Due to licensing of some of the 13:19:06 .. recognisers and synthesisers in the Web Speech API they are not licensed for recording 13:19:19 .. so there was little enthusiasm for making an API call that would capture speech output 13:19:31 .. from the API. Of course there are other ways to do it, but making it a feature would 13:19:48 .. open it up to licensing issues. 13:20:01 Nigel: The Web Speech API never got towards Rec, it's a Note I think. 13:21:10 Glenn: Generally IPR isn't an issue for W3C specs. 13:21:19 Matt: It has multiple implementations but is still a CG report. 13:21:34 .. The "terms of service" for many voices allow use in real time but prohibit recording the 13:21:38 ericc has joined #tt 13:21:39 .. audio and saving it for later playback. 13:25:31 Nigel: If we can encourage that to get to resolution then we could use it for AD. 13:25:45 .. The other issue to note is that for embedded audio, there's a bit of a challenge 13:26:02 .. implementing clipBegin and clipEnd. For normal audio resources you can use media 13:26:33 .. fragments on URLs to make a time range request, but in our testing it didn't seem to 13:26:52 .. honour the end time always, just the begin time. But more seriously for embedded audio, 13:27:21 .. if you implement it as a data: url then those URL media fragments seem to be completely ignored. 13:27:46 Matt: Range requests have to be supported by the server I think. Most do, but it's not a given. 13:27:51 .. The data URL may not be supported at all. 13:28:09 .. The response has to have the accept-ranges header set. 13:28:26 range requests https://developer.mozilla.org/en-US/docs/Web/HTTP/Range_requests 13:29:05 Nigel: I think this is a different thing. It's byte ranges. 13:29:28 -> https://www.w3.org/TR/media-frags/ Media Fragments URI 13:29:35 Nigel: That's what I meant. 13:31:05 .. It allows for a url#t=10,20 for example to give everything between 10 and 20s. In testing 13:31:11 .. that doesn't seem to work with data urls. 13:31:28 .. That's something that may need an explicit mention in a future edition of TTML2, for example. 13:32:32 .. While we're on future editions of TTML2, and audio, I hope to be able to define the 13:32:42 .. audio processing model more normatively than it is now. 13:33:06 Nigel: The Web Audio spec is in CR at the moment, isn't it? 13:33:25 Matt: Yes. Timeline to be discussed in the meeting on Thursday. No issues have been 13:33:35 .. raised, we're not aware of any problems. On a similar note I should say we're meeting 13:33:48 .. on Thursday and Friday, which conflicts with the AD CG but the main topic will be 13:33:59 .. use cases, requirements and features that have been omitted from v1 so if there's anything 13:34:13 .. around this work that would require Web Audio work to facilitate it now would be a good 13:34:19 .. time to provide them. 13:34:31 Nigel: Thanks for that, if any arise I will let you know! 13:35:51 Glenn: Back on the issue of speech, I had pointed out how in TTML we defined a special 13:36:03 .. resource URL for output of the speech processor, and how that was intended to be 13:36:19 .. potentially used as an input to the audio element, so you could say an audio element 13:36:35 .. is the speech resource instead of a pre-defined clip, and that would be useful for mix 13:36:41 .. and gain operations. 13:36:43 ericc has joined #tt 13:36:55 Nigel: It's unnecessary - we didn't need to use that in our implementation. 13:37:08 Glenn: The connection between the speech processor's output and the audio node 13:37:17 .. hierarchy does not exist. 13:37:22 Nigel: We take it as an implied one. 13:37:33 Glenn: That's an implementation choice that I didn't intend in the spec. 13:38:08 Nigel: That seems to be unnecessary pain - if you bother to put tta:speak in as anything other than none 13:38:44 .. then you obviously want to generate audio. 13:38:52 Glenn: You need it to be able to pan the speech output, for example. 13:38:57 Nigel: That's true, I didn't consider that. 13:40:29 .. You could posit an implied anonymous audio element if the span's tta:speak is not "none" and there is no explicit audio element child. 13:40:40 Glenn: That's a bit like putting origin and extent on a content element! 13:40:52 Nigel: I sort of see what you mean [scrunches eyes] 13:41:07 Glenn: In the definitions section I define a speech data resource. 13:43:19 Nigel: It doesn't seem clear what happens if tta:speak is not "none" and there is no 13:43:21 .. audio element child. 13:43:46 .. It is possible that we can tidy this up in a future edition. 13:44:00 Glenn: It could be improved - we could tie it to that binding mechanism more explicitly. 13:44:06 Nigel: +1 13:44:38 .. However I would like to see a syntactic shortcut that avoids the need to have an audio 13:45:58 .. element with a long string in it just for "mix this audio" when tta:speak is set, because 13:46:01 .. that's obvious. 13:48:59 Glenn: I notice that it is not possible to add audio as a child of body, in TTML2. Why not? I don't recall my logic there, if there was any. 13:49:12 Nigel: I think it's clear that there's a bucket of audio-related potential improvements that 13:49:29 .. are most likely to come out of work in the AD CG, which we should consider for a future 13:49:34 .. edition of TTML2. 14:01:59 Topic: Meeting close 14:02:46 Nigel: Thank you everyone, we've reached the end of our agenda for today. 14:03:02 .. We should take a moment to celebrate the success we've had in all the work we've done 14:03:12 .. on TTML and IMSC over the past few years! 14:03:35 .. Next week we have no weekly call, the week after I will send an agenda as usual. 14:03:37 .. [meeting adjourned] 14:03:42 rrsagent, make minutes 14:03:42 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 14:06:06 s/Observer:/Masaya:/g 14:07:55 s/Masaya Ikeo, NHK/Masaya Ikeo, NHK - Yam_ACCESS 14:24:28 rrsagent, make minutes 14:24:28 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 14:53:05 Zakim has left #tt 15:07:10 s/It seems to closely arranged to specific application requirements/It seems too closely aligned to specific application requirements 15:11:58 atai has joined #tt 15:13:30 rrsagent, make minutes 15:13:30 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 15:13:54 scribeOptions: -final -noEmbedDiagnostics 15:13:57 rrsagent, make minutes 15:13:57 I have made the request to generate https://www.w3.org/2018/10/23-tt-minutes.html nigel 17:19:20 github-bot has joined #tt