TTWG Meeting Minutes Feb 14, 2013

See: http://www.w3.org/2013/02/14-tt-minutes.html,text
http://www.w3.org/2013/02/14-tt-minutes.html

   [1]W3C

      [1] http://www.w3.org/

                               - DRAFT -

                Timed Text Working Group Teleconference

14 Feb 2013

   See also: [2]IRC log

      [2] http://www.w3.org/2013/02/14-tt-irc

Attendees

   Present
          +1.408.216.aaaa, +44.118.900.aabb, +1.408.335.aacc,
          +1.858.847.aadd, pal, +1.417.671.aaee, glenn, Sean,
          mmartin3, mike, Anthony, +1.408.515.aaff, David_Ronca,
          Plh, mijordan

   Regrets
          None

   Chair
          <scribe> Sean Hayes

   Scribe
          Monica Martin

Contents

     * [3]Topics
         1. [4]Aspect Ratio
     * [5]Summary of Action Items
     __________________________________________________________

   <trackbot> Date: 14 February 2013

   <scribe> scribenick: mmartin3

   <scribe> Agenda:

   [6]http://lists.w3.org/Archives/Public/public-tt/2013Feb/0037.h
   tml

      [6] http://lists.w3.org/Archives/Public/public-tt/2013Feb/0037.html

Aspect Ratio

   Netflix presentation:

   [7]http://lists.w3.org/Archives/Public/public-tt/2013Feb/0036.h
   tml

      [7] http://lists.w3.org/Archives/Public/public-tt/2013Feb/0036.html

   anthony: Positioning and aspect ratio are becoming a problem
   because of the content of what we receive from providers.
   ... Slide 3
   ... Slide 4 authoring intent
   ... Slide 5
   ... Captions can be delivered and displayed on a different
   aspect ratio.
   ... Slide 7 what is rendered isn't what the author intended
   ... Rendering interpretations
   ... Slide 10 Disregard the 320x240px note
   ... We favor #4.
   ... Slide 10.
   ... Aligns to Proposal #1 in Slide 11.

   sean: Would need to intend that there is centering in the
   display area as well.

   anthony: Neither proposal clarifies this.

   glenn: We don't have a model on how to express authoring intent
   for registering the root container extent with a related media
   object for display or video.
   ... If we choose to handle, we have to look to this general
   problem.
   ... Singer asked if transforming video resolution, why couldn't
   you do captions?
   ... Origins match root container extent in examples. This is
   different than we defined regions. Regions are designed
   differently.
   ... Percentages to position regions according to a 4x3 area no
   matter what the video resolution was. What happens in that
   case?

   anthony: If we knew aspect ratio, we could position regions on
   4x3 aspect ratio. Issue is we don't know of the aspect ratio of
   the video at authoring.

   glenn: Could have 4x3 and 16x9.

   david: Captioning tooling have limitations. They typically
   don't use master video when generating captions.

   c/genereating/generating

   scribe: Use a proxy and the proxy may not be known and the
   video for delivery.

   sean: Are they making decisions with what they want to align
   with video pixels or a general area.

   david: Most of what we see is intended for 4x3.
   ... Interpret intent.
   ... CEA-608 data 4x3
   ... SMPTE
   ... Conformance is widely varied. Give guidance to content
   houses.

   mike: CEA-608 didn't solve this problem because it was 4x3
   only. This is a hole in the end to end processing.
   ... External data with aspect ratio relayed separately.
   ... DECE whatever you have done, stretch to width and height of
   video. This is a deterministic option. CEA-708 SMPTE new
   release sets aspect ratio as metadata. Don't know how to
   generalize style element to handle.

   sean: Pixels is based on XSL which is the wrong measure and
   need something else for consistency. Issues are related.
   ... No video object in TTML
   ... SDP-US does and maps to Proposal #1.
   ... TTML could be positioned to HTML5; many videos could be
   present. There are different interpretations given the assets
   involved.
   ... Add notes. Complete fix isn't found in this proposal.

   anthony: We align to video.

   sean: Unless you understand the application and the pipeline,
   you can't express in TTML.
   ... Constraints could be applied in your implementation or in a
   profile.

   david: Our client may not be doing presentation. We may deliver
   to a game console which renders the captions.
   ... We have to be able to tell a client here is an asset and
   know how to display.
   ... Working with device partners how to resolve how to render.
   Prefer a standard guide.
   ... We can specify what is intended. Otherwise, we also need to
   give client guidance on what to do. Different entities in the
   pipeline.

   mike: Make it better even if not entirely.
   ... Use metadata.
   ... Skeptical to satisfy for all cases in TTML.

   sean: Solved in SDP-US profile already.

   mike: Clearly unambiguous in DECE.
   ... Use SMPTE metadata that is defined?

   anthony: Working on our own captions. Caption studios are
   creating content. Small % are CEA-608, -708.

   david: Seeing a lot of CEA-608 and old EBU.
   ... A mess of caption world. Not designed for scale. Government
   requirements are a stress on ecosystem.
   ... Large effort to author and manage.

   glenn: If SMPTE asked for metadata, satisfy?

   sean: Can use metadata today.
   ... Has no semantic interpretation. There is no guarantee it
   will be displayed in that way.

   pal: Define metadata and author intent. Figure out how profiles
   use metadata is separate.

   glenn: Won't define semantics for how a tool uses metadata.

   sean: General solution is to have a mechanism to reference
   where the existence of the region is. Top Left isn't the same
   in 4x3 and 16x9.
   ... We don't have tools to accommodate. That would be part of
   TTML 1.1.
   ... Immediately, if we take Proposal #1, we can't guarantee
   players do the same thing.

   anthony: Need long term soluton.
   ... Netflix specific metadata tag.

   sean: Use SMPTE metadata tag.
   ... Doesn't have rendering model.
   ... Fold into Issue #179.
   ... Resolve in TTML 1.1.

   Technical report:
   [8]http://lists.w3.org/Archives/Public/public-tt/2013Jan/0006.h
   tml

      [8] http://lists.w3.org/Archives/Public/public-tt/2013Jan/0006.html

   mike: Doesn't include aspect ratio for CEA-708.

   sean: Mike provide relevant data.

   [9]http://www.w3.org/AudioVideo/TT/tracker/issues/179

      [9] http://www.w3.org/AudioVideo/TT/tracker/issues/179

   Issue Anthony How to specify aspect ratio to understand
   positioning that may apply for display or video.

   Create Issue Anthony How to specify aspect ratio to understand
   positioning that may apply for display or video

   pal: SMPTE when will we walk through SMPTE request? How do we
   handle from a process perspective?

   sean: Put in semantic buckets to handle in TTML 1.1.

   mike: Encourage vendors to look at a profile to implement
   captions. Look at SDP-US.

   david: Ingest is challenging. We use a constrainted TTML set to
   deploy.

   mike: Evaluate SDP-US.

   david: Have own profile.

   pal: No complete TTML implementation everywhere.
   ... In practice is to follow a documented subset.
   ... Look at SDP-US and body of generated documents to see gaps.
   ... Extended profile or SDP-US or other.

   sean: Use for your use case.

   david: Work with PLH on ensuring Netflix are fully part of
   TTWG.
   ... Netflix has own profile for required and optional features.
   We're not using pubic SDP-US.

   pal: Stated requirements are that the generated documents had
   to be able to play on clients not under Netflix control. No
   implementation will do all of TTML. Follow constrained profiles
   only. By not following one of those, there will be clients that
   can't play Netflix documents.
   ... Desire to use more standard one if we can get display issue
   resolved.

   anthony: Our profile is exactly a subset of that profile.

   sean: Where are you in conflict?
   ... Your content should render as well.
   ... Defined rendering.

   trackbot, end meeting

   <plh> Chair: Sean Hayes

   <plh> Scribe: Monica Martin

Summary of Action Items

   [End of minutes]
     __________________________________________________________


Monica J Martin
Senior Program Manager
Microsoft Open Technologies, Inc.
A subsidiary of Microsoft Corporation