IRC log of tt on 2016-07-14

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logging to http://www.w3.org/2016/07/14-tt-irc

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Zakim, this will be TTML

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Meeting: Timed Text Working Group Teleconference

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Date: 14 July 2016

14:01:09 [nigel]

Present: Glenn, Harold, Nigel

14:01:12 [nigel]

chair: Nigel

14:01:15 [nigel]

scribe: nigel

14:02:18 [nigel]

regrets: Mike, Andreas, Frans, Thierry

14:03:54 [nigel]

Present+ Pierre

14:04:06 [nigel]

Topic: This meeting

14:04:49 [nigel]

nigel: I think we're mainly covering TTML stuff today. Any other business to cover?

14:04:56 [nigel]

group: no other business

14:05:18 [nigel]

Topic: TTML1 & TTML2 issues, actions, PRs, editorial actions etc

14:05:29 [nigel]

action-472?

14:05:30 [trackbot]

action-472 -- Nigel Megitt to Make sure there is a ttml2 issue for considering adjustment of inline region semantics -- due 2016-06-16 -- PENDINGREVIEW

14:05:30 [trackbot]

http://www.w3.org/AudioVideo/TT/tracker/actions/472

14:06:01 [nigel]

nigel: I did this, by adding https://github.com/w3c/ttml2/issues/168

14:06:14 [nigel]

close action-472

14:06:14 [trackbot]

Closed action-472.

14:07:42 [nigel]

action-443?

14:07:42 [trackbot]

action-443 -- Glenn Adams to Prepare a document showing mapping arib ruby extension features to ttml2 for use as a liaison document to arib. -- due 2015-11-05 -- OPEN

14:07:42 [trackbot]

http://www.w3.org/AudioVideo/TT/tracker/actions/443

14:08:01 [nigel]

glenn: Can we reword this somehow - I think it's low priority.

14:08:18 [nigel]

nigel: Are all the ARIB ruby extension features mapped to something in TTML2?

14:08:40 [nigel]

glenn: I know on the ARIB set they had support for a marquee functionality which I have

14:08:50 [nigel]

... not had a chance to investigate its semantics. That would be the only one.

14:09:02 [nigel]

... My hope is that we could map that to set or animate without any additional features.

14:09:10 [nigel]

nigel: I think that's a dependency then.

14:09:30 [nigel]

glenn: That's the only feature in the ARIB extensions that I have not accounted for explicitly.

14:09:56 [nigel]

... I have also not checked if the ARIB spec has added any new features. Probably a year and a half since I reviewed in Japanese.

14:10:08 [nigel]

nigel: I think they did an English translation too.

14:10:11 [nigel]

glenn: I did not use that.

14:10:32 [nigel]

nigel: In that case the dependency is on https://github.com/w3c/ttml2/issues/119

14:11:04 [nigel]

action-443: [Meeting 2016-07-14] There is a dependency on https://github.com/w3c/ttml2/issues/119 before commencing this.

14:11:05 [trackbot]

Notes added to action-443 Prepare a document showing mapping arib ruby extension features to ttml2 for use as a liaison document to arib..

14:11:56 [nigel]

nigel: I've changed the due date on this action to 26th August.

14:12:59 [nigel]

nigel: Let's move to the recent issues on github

14:13:17 [nigel]

glenn: There's an open PR: https://github.com/w3c/ttml2/pull/167

14:14:24 [nigel]

nigel: I made one comment on this re the use of the term absolute profile designator.

14:14:31 [nigel]

glenn: That's a good point - I'll try to fix this.

14:18:45 [nigel]

glenn: Does the Repository Manager run any other checks than the IPR one?

14:19:00 [nigel]

nigel: I don't believe so - it might be useful to use a Continuous Integration tool to check

14:19:17 [nigel]

... that each commit results in a successful build of the HTML. Would that be of interest?

14:19:40 [nigel]

glenn: I'd consider it, however I have to go through the generate ED process each time I edit anyway

14:19:46 [nigel]

... so it's not really needed right now.

14:20:20 [nigel]

nigel: Thanks for that PR. I encourage everyone else to have a look and review it.

14:20:33 [nigel]

glenn: By the way, with the PR I intend only to modify the XML source and not the HTML

14:20:44 [nigel]

... version, so that means that if anyone wants to review then they need to run the tool

14:20:58 [nigel]

... to generate the HTML themselves. The reason I don't want to do it in the branch is

14:21:12 [nigel]

... that then I would have to manually merge the XML only. I don't want to regenerate the HTML

14:21:23 [nigel]

... each time because it makes a lot of minor modifications in the file that are not visible

14:23:05 [nigel]

... such as ID generations and timestamps. If we have multiple commits it would likely

14:23:12 [nigel]

... make automatic merging complicated.

14:23:28 [nigel]

nigel: This suggests an elegant solution that we may not have time or inclination to pursue right now

14:23:36 [nigel]

... would be to generate the HTML only in the gh-pages branch.

14:24:05 [nigel]

nigel: For this kind of change I think most folk could review just the XML change. I was

14:24:17 [nigel]

... able to check out the branch, run ant to make the HTML, and review that locally.

14:25:37 [nigel]

glenn: https://github.com/w3c/ttml2/issues/164

14:25:59 [nigel]

glenn: In TTML1 (not SE) we did not use Root Temporal Extent, but External Time Interval

14:26:12 [nigel]

... and it was defined by the external processing context. I'm reviewing notes to understand

14:26:23 [nigel]

... why we changed it. That review will have an impact on what we recommend.

14:26:40 [nigel]

... There are some problems with circular definitions in the current text, in how the body

14:26:52 [nigel]

... element references the root temporal interval, and the root temporal interval references

14:27:06 [nigel]

... the body definition. Maybe the suggestion to redo some of the terminology will be appropriate.

14:27:16 [nigel]

nigel: Yes, it certainly is complex!

14:27:32 [nigel]

glenn: Maybe the reason for differences in interpretation is because we have different

14:27:47 [nigel]

... understandings of what is meant by the term. For example in my mental model the

14:28:02 [nigel]

... idea of a media offset seemed to make sense, and in Nigel's it made less sense.

14:28:13 [nigel]

nigel: Indeed, it is extremely problemati!

14:28:18 [nigel]

c/i!/ic!

14:28:23 [nigel]

glenn: We need to resolve that pretty soon.

14:28:49 [nigel]

pal: Nigel, can you summarise what you mean by media offset and what the problems are?

14:30:48 [nigel]

nigel: It's a value that is used to add or subtract from media time expressions in the

14:31:10 [nigel]

... documents to arrive at some other timeline. My problem with it is that it creates an

14:32:23 [nigel]

... ambiguity with other ways of solving this problem that exist, such as ISOBMFF.

14:33:21 [nigel]

glenn: It's similar to the referenceBegin that's in N.2 https://www.w3.org/TR/ttml1/#time-expression-semantics-media

14:35:04 [nigel]

pal: I don't understand why we need this. If you want to offset why not just modify all the times in the document?

14:35:36 [nigel]

nigel: By the way, you could just modify the effective value of referenceBegin just by

14:35:41 [nigel]

... adding a begin attribute to the body element.

14:35:56 [nigel]

glenn: You can also put times on style and region elements, which are not descendants

14:36:03 [nigel]

... of body, so that wouldn't be complete.

14:36:44 [nigel]

nigel: I'd like to mention the Safe Crop Area proposal. https://lists.w3.org/Archives/Public/public-tt/2016Jun/0003.html

14:42:19 [nigel]

nigel: [describes the problem statement and proposed solution from the PDF document]

14:42:50 [nigel]

glenn: I wonder if we could achieve this using a convention on the region, such as an

14:43:06 [nigel]

... attribute that designates a region as specifying a safe crop area. It would be a little

14:44:07 [nigel]

... simpler because there are already a lot of tools and parsers that already process regions.

14:44:25 [nigel]

nigel: That could be made to work: this is not about where to position relative to the

14:44:38 [nigel]

... root container region though, but about which parts of the root container region must

14:44:51 [nigel]

... be shown. Also you would have to go a long way down parsing the document to find

14:45:11 [nigel]

... this information if present, which would not be ideal.

14:45:19 [nigel]

glenn: I see, yes, you're probably right about that.

14:45:35 [nigel]

glenn: In terms of which namespace to put this in, my rule of thumb is that if a piece

14:45:45 [nigel]

... of information is used formally by the processor in some way then it should be in the

14:45:52 [nigel]

... parameter namespace rather than in metadata.

14:45:57 [nigel]

nigel: I agree.

14:46:24 [nigel]

nigel: This proposal defines some processor behaviour so I would put it into the parameter namespace.

14:46:46 [nigel]

glenn: We already have one parameter, pixel aspect ratio, which has never really been used,

14:46:58 [nigel]

... and one might ask if there are any semantics for what a processor should do with that.

14:47:25 [nigel]

... Up until now people have wondered if it is metadata.

14:47:38 [nigel]

nigel: I think it is a parameter since extent and pixel aspect ratio tell you the shape of the

14:47:47 [nigel]

... root container region, i.e. the display aspect ratio.

14:48:21 [nigel]

glenn: That's true, but now we have display aspect ratio there's over-constraint, so we

14:48:30 [nigel]

... need to define what gives if they don't agree.

14:48:42 [nigel]

nigel: Agreed - I thought we had some text on order of precedence.

14:49:08 [nigel]

glenn: We may do. The text needs to be changed to say Display Aspect Ratio in place of Storage Aspect Ratio.

14:49:31 [nigel]

nigel: There's an issue I believe. https://github.com/w3c/ttml2/issues/30

14:50:07 [nigel]

nigel: Any other comments on SCA?

14:50:48 [nigel]

glenn: We should also factor in Mike's comments with the SMPTE documents.

14:50:59 [nigel]

nigel: Thanks for the reminder. My reading of those is that the documents Mike referenced

14:51:12 [nigel]

... explain the background for how this problem situation can occur but are orthogonal

14:51:31 [nigel]

... to the SCA proposal - the SCA proposal does not duplicate the active format descriptor

14:51:49 [nigel]

... semantics but provides for dealing with some of the scenarios it can result in.

14:53:39 [nigel]

nigel: Returning to https://github.com/w3c/ttml2/issues/166 (duplicate designators)

14:53:47 [nigel]

... is there any semantic ambiguity introduced by having duplicates?

14:54:05 [nigel]

glenn: Interesting. If you have any(X Y X), and on the first attempt to resolve X you get

14:54:20 [nigel]

... an access error, and proceed to Y and get "not available" too then you would proceed

14:54:33 [nigel]

... to "X" again which now may be available. Because there's a sequential access operation

14:54:47 [nigel]

... there you might end up with different semantics. From a cleanliness perspective, we

14:55:01 [nigel]

... also don't allow attributes on XML elements with duplicated information even though

14:55:17 [nigel]

... you could argue that they're semantically equivalent. I prefer not to allow duplicates

14:55:33 [nigel]

... unless I can think of some kind of rational interpretation of it. That was my conclusion.

14:55:57 [nigel]

... Further, we've already implemented that semantic in TTV (not yet checked in).

14:57:34 [nigel]

nigel: Well you may want to respond to my comment asking this on the github issue.

14:57:37 [nigel]

glenn: Ok

14:58:42 [nigel]

nigel: Thanks all, we're out of issues to discuss for today, so I'll adjourn. [adourns meeting]

14:58:45 [nigel]

rrsagent, generate minutes

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I have made the request to generate http://www.w3.org/2016/07/14-tt-minutes.html nigel

15:01:44 [nigel]

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15:02:31 [nigel]

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15:02:49 [nigel]

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15:05:16 [nigel]

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I have made the request to generate http://www.w3.org/2016/07/14-tt-minutes.html nigel

15:11:32 [nigel]

s|/run ant/run ant (see https://github.com/w3c/ttml2/blob/gh-pages/spec/README.md)||

15:11:58 [nigel]

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15:12:00 [nigel]

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I have made the request to generate http://www.w3.org/2016/07/14-tt-minutes.html nigel

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15:12:29 [nigel]

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I have made the request to generate http://www.w3.org/2016/07/14-tt-minutes.html nigel

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