ISSUE-332: #cellResolution support

#cellResolution support

#cellResolution support

State:
CLOSED
Product:
TTML IMSC 1.0
Raised by:
Frans de Jong
Opened on:
2014-08-07
Description:
------------------
Request
------------------
Chapter 4.8 (Common Constraints -> Features)

The part:

"#cellResolution SHALL NOT be used."

should be deleted.

------------------
Reasoning
------------------
IMSC currently does not allow the use of the feature #cellResolution
https://dvcs.w3.org/hg/ttml/raw-file/tip/ttml-ww-profiles/ttml-ww-profiles.html#features

It is not sufficient that an IMSC processor processes the EBU-TT-D document but ignores cellResolution values. Indirectly the cellResolution defines the fontSize. IMSC calculates the fontSize in percentages with an implicit cellResolution (with the TTML initial value, "32 15"). EBU-TT-D documents (example here: http://tech.ebu.ch/docs/ebu-tt/ebu-tt-d-imsc-compliance-example.xml ) will renderin a different font-size and therefore intended line breaks cannot be guaranteed. In this use case this is not acceptable for the broadcaster.

--------------------------
General use case
-------------------------
A german broadcaster uses an EBU-TT-D document (https://tech.ebu.ch/docs/ebu-tt/ebu-tt-d-imsc-compliance-example.xml) for HbbTV subtitles and for their catch up tv - portal for PC. Both the HbbTV application (or in the future the HbbTV 2.0 compliant device) and the player of the EBU-TT-D portal support EBU-TT-D. Now the broadcaster licences the same AV content together with the subtitles to a commercial on-demand Internet streaming media provider. The provider distributes its content to a client which is conformant to IMSC 1.0 (IMSC 1.0 Text - http://www.w3.org/ns/ttml/profile/imsc1/text). Conformance to EBU-TT-D of this player is not documented.

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Requirement
-------------------
The broadcaster demands from the provider that the subtitles will be displayed as specified in the EBU-TT-D file. The provider will distribute the EBU-TT-D file as it is provided and will not convert the EBU-TT-D file.
Related Actions Items:
No related actions
Related emails:
  1. {agenda} TTWG Meeting 25/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-24)
  2. Re: ISSUE-332 (-): #cellResolution support [TTML IMSC 1.0] (from pal@sandflow.com on 2014-09-23)
  3. Re: {minutes} TTWG Meeting 11/9/2014 (from silviapfeiffer1@gmail.com on 2014-09-13)
  4. Re: IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from nigel.megitt@bbc.co.uk on 2014-09-12)
  5. Re: {minutes} TTWG Meeting 11/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-12)
  6. Re: {minutes} TTWG Meeting 11/9/2014 (from silviapfeiffer1@gmail.com on 2014-09-12)
  7. Re: {minutes} TTWG Meeting 11/9/2014 (from silviapfeiffer1@gmail.com on 2014-09-12)
  8. Re: {minutes} TTWG Meeting 11/9/2014 (from ckennedy@apple.com on 2014-09-11)
  9. Re: IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from John.Birch@screensystems.tv on 2014-09-11)
  10. Re: IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from pal@sandflow.com on 2014-09-11)
  11. Re: IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from nigel.megitt@bbc.co.uk on 2014-09-11)
  12. Re: IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from pal@sandflow.com on 2014-09-11)
  13. {minutes} TTWG Meeting 11/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-11)
  14. Re: IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from John.Birch@screensystems.tv on 2014-09-11)
  15. IMSC 1 re: ISSUE-332, ISSUE-342 and ISSUE-339 (from pal@sandflow.com on 2014-09-10)
  16. Re: {agenda} TTWG Meeting 11/9/2014 (from glenn@skynav.com on 2014-09-10)
  17. {agenda} TTWG Meeting 11/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-10)
  18. {agenda} TTWG Meeting 4/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-03)
  19. {agenda} TTWG Meeting 21/8/2014 (from nigel.megitt@bbc.co.uk on 2014-08-20)
  20. Re: New Change Proposal 28 on IMSC 1: Profile refactoring (from nigel.megitt@bbc.co.uk on 2014-08-14)
  21. Re: New Change Proposal 28 on IMSC 1: Profile refactoring (from pal@sandflow.com on 2014-08-14)
  22. {agenda} TTWG Meeting 14/8/2014 (from nigel.megitt@bbc.co.uk on 2014-08-13)
  23. New Change Proposal 28 on IMSC 1: Profile refactoring (from nigel.megitt@bbc.co.uk on 2014-08-08)
  24. Re: {minutes} TTWG Meeting 7/8/2014 (from glenn@skynav.com on 2014-08-07)
  25. {minutes} TTWG Meeting 7/8/2014 (from nigel.megitt@bbc.co.uk on 2014-08-07)
  26. ISSUE-332 (-): #cellResolution support [TTML IMSC 1.0] (from sysbot+tracker@w3.org on 2014-08-07)

Related notes:

See also Change Proposal 28 [1] which helps enable this change to be implemented by removing the strong requirement to meet the HRM constraints: the proposal in this issue does not consider any impact on complexity.

[1] https://www.w3.org/wiki/TTML/changeProposal028

Nigel Megitt, 8 Aug 2014, 13:28:36

Addressed at [2] per [1]

[1] https://dvcs.w3.org/hg/ttml/rev/7084721154b6
[2] http://lists.w3.org/Archives/Public/public-tt/2014Sep/0031.html

Pierre-Anthony Lemieux, 24 Sep 2014, 22:43:20

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David Singer <singer@apple.com>, Nigel Megitt <nigel.megitt@bbc.co.uk>, Chairs, Thierry Michel <tmichel@w3.org>, Philippe Le H├ęgaret <plh@w3.org>, Atsushi Shimono <atsushi@w3.org>, Staff Contacts
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