Edit ISSUE-225: tts:fontSize as percentage of container dimensions

Nickname:

Title:

State:

Product:

Raised By:

Description:

Add notes (no markup allowed, URIs get automatically hyperlinked):

Related emails:

  1. Re: [ttml2] Action-369 Action-382 - draft dispositions flattened thread incorporating changes (from nigel.megitt@bbc.co.uk on 2015-03-19) (from nigel.megitt@bbc.co.uk on 2015-03-19)
  2. Re: [ttml2] Action-369 - collate smpte issues and draft dispositions (from nigel.megitt@bbc.co.uk on 2015-03-18) (from nigel.megitt@bbc.co.uk on 2015-03-18)
  3. Re: [ttml2] Action-369 - collate smpte issues and draft dispositions (from glenn@skynav.com on 2015-03-05) (from glenn@skynav.com on 2015-03-05)
  4. Re: [ttml2] Action-369 - collate smpte issues and draft dispositions (from nigel.megitt@bbc.co.uk on 2015-03-05) (from nigel.megitt@bbc.co.uk on 2015-03-05)
  5. Re: [ttml2] Action-369 - collate smpte issues and draft dispositions (from glenn@skynav.com on 2015-03-04) (from glenn@skynav.com on 2015-03-04)
  6. Re: [ttml2] Action-369 - collate smpte issues and draft dispositions (from nigel.megitt@bbc.co.uk on 2015-03-04) (from nigel.megitt@bbc.co.uk on 2015-03-04)
  7. Re: [ttml2] Action-369 - collate smpte issues and draft dispositions (from nigel.megitt@bbc.co.uk on 2015-02-25) (from nigel.megitt@bbc.co.uk on 2015-02-25)
  8. [ttml2] Action-369 - collate smpte issues and draft dispositions (from nigel.megitt@bbc.co.uk on 2015-02-06) (from nigel.megitt@bbc.co.uk on 2015-02-06)
  9. {minutes} TTWG Meeting 2015-01-15 (from nigel.megitt@bbc.co.uk on 2015-01-15) (from nigel.megitt@bbc.co.uk on 2015-01-15)
  10. {agenda} TTWG Meeting 2015-01-15 (from nigel.megitt@bbc.co.uk on 2015-01-14) (from nigel.megitt@bbc.co.uk on 2015-01-14)
  11. CORRECTION to {minutes} TTWG Meeting 28/10/2014 (from nigel.megitt@bbc.co.uk on 2014-11-21) (from nigel.megitt@bbc.co.uk on 2014-11-21)
  12. RE: {minutes} TTWG Meeting 27/10/2014 (from nigel.megitt@bbc.co.uk on 2014-10-29) (from nigel.megitt@bbc.co.uk on 2014-10-29)
  13. {minutes} TTML Meeting of 24/10/13 (from glenn@skynav.com on 2013-10-24) (from glenn@skynav.com on 2013-10-24)
  14. RE: TTML Agenda for 24/10/13 (from mdolan@newtbt.com on 2013-10-23) (from mdolan@newtbt.com on 2013-10-23)
  15. TTML Agenda for 24/10/13 (from nigel.megitt@bbc.co.uk on 2013-10-23) (from nigel.megitt@bbc.co.uk on 2013-10-23)
  16. Re: TTML Minutes for 25/09/13 (from tmichel@w3.org on 2013-09-27) (from tmichel@w3.org on 2013-09-27)
  17. RE: TTML Minutes for 25/09/13 (from silviapfeiffer1@gmail.com on 2013-09-27) (from silviapfeiffer1@gmail.com on 2013-09-27)
  18. RE: TTML Minutes for 25/09/13 (from nigel.megitt@bbc.co.uk on 2013-09-26) (from nigel.megitt@bbc.co.uk on 2013-09-26)
  19. TTML Agenda for 25/09/13 (from Sean.Hayes@microsoft.com on 2013-09-25) (from Sean.Hayes@microsoft.com on 2013-09-25)
  20. TTML Agenda for 19/09/13 (from Sean.Hayes@microsoft.com on 2013-09-19) (from Sean.Hayes@microsoft.com on 2013-09-19)
  21. No Meeting today 12-09-13 (from Sean.Hayes@microsoft.com on 2013-09-12) (from Sean.Hayes@microsoft.com on 2013-09-12)
  22. RE: Action-201 and Issue-225 (from John.Birch@screensystems.tv on 2013-09-09) (from John.Birch@screensystems.tv on 2013-09-09)
  23. Re: Action-201 and Issue-225 (from glenn@skynav.com on 2013-09-09) (from glenn@skynav.com on 2013-09-09)
  24. Re: Action-201 and Issue-225 (from nigel.megitt@bbc.co.uk on 2013-09-09) (from nigel.megitt@bbc.co.uk on 2013-09-09)
  25. RE: Action-201 and Issue-225 (from John.Birch@screensystems.tv on 2013-09-09) (from John.Birch@screensystems.tv on 2013-09-09)
  26. RE: Action-201 and Issue-225 (from mdolan@newtbt.com on 2013-09-06) (from mdolan@newtbt.com on 2013-09-06)
  27. Action-201 and Issue-225 (from nigel.megitt@bbc.co.uk on 2013-09-06) (from nigel.megitt@bbc.co.uk on 2013-09-06)
  28. Minutes for 05/09/13 (from nigel.megitt@bbc.co.uk on 2013-09-05) (from nigel.megitt@bbc.co.uk on 2013-09-05)
  29. Agenda for 05/09/13 (from glenn@skynav.com on 2013-09-04) (from glenn@skynav.com on 2013-09-04)
  30. RE: TTML Agenda for 29/08/13 (from mdolan@newtbt.com on 2013-08-28) (from mdolan@newtbt.com on 2013-08-28)
  31. TTML Agenda for 29/08/13 (from glenn@skynav.com on 2013-08-28) (from glenn@skynav.com on 2013-08-28)
  32. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-17) (from glenn@skynav.com on 2013-07-17)
  33. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from John.Birch@screensystems.tv on 2013-07-17) (from John.Birch@screensystems.tv on 2013-07-17)
  34. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from tai@irt.de on 2013-07-17) (from tai@irt.de on 2013-07-17)
  35. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from nigel.megitt@bbc.co.uk on 2013-07-17) (from nigel.megitt@bbc.co.uk on 2013-07-17)
  36. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from nigel.megitt@bbc.co.uk on 2013-07-16) (from nigel.megitt@bbc.co.uk on 2013-07-16)
  37. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from nigel.megitt@bbc.co.uk on 2013-07-16) (from nigel.megitt@bbc.co.uk on 2013-07-16)
  38. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from nigel.megitt@bbc.co.uk on 2013-07-16) (from nigel.megitt@bbc.co.uk on 2013-07-16)
  39. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from tai@irt.de on 2013-07-16) (from tai@irt.de on 2013-07-16)
  40. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-16) (from glenn@skynav.com on 2013-07-16)
  41. RE: Interdependency between fontSize, lineHeight and cellResolution in TTML (from John.Birch@screensystems.tv on 2013-07-16) (from John.Birch@screensystems.tv on 2013-07-16)
  42. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-16) (from glenn@skynav.com on 2013-07-16)
  43. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-16) (from glenn@skynav.com on 2013-07-16)
  44. RE: Interdependency between fontSize, lineHeight and cellResolution in TTML (from John.Birch@screensystems.tv on 2013-07-16) (from John.Birch@screensystems.tv on 2013-07-16)
  45. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-16) (from glenn@skynav.com on 2013-07-16)
  46. RE: Interdependency between fontSize, lineHeight and cellResolution in TTML (from John.Birch@screensystems.tv on 2013-07-16) (from John.Birch@screensystems.tv on 2013-07-16)
  47. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-16) (from glenn@skynav.com on 2013-07-16)
  48. Re: Interdependency between fontSize, lineHeight and cellResolution in TTML (from glenn@skynav.com on 2013-07-16) (from glenn@skynav.com on 2013-07-16)
  49. Interdependency between fontSize, lineHeight and cellResolution in TTML (from tai@irt.de on 2013-07-16) (from tai@irt.de on 2013-07-16)
  50. ISSUE-225 (Relative tts:fontSize): tts:fontSize as percentage of container dimensions [TTML.next] (from sysbot+tracker@w3.org on 2013-05-30) (from sysbot+tracker@w3.org on 2013-05-30)

Related notes:

It may be possible to do this by introducing the new vh/vw units from CSS3 Values and Units [1].

[1] http://www.w3.org/TR/css3-values/#viewport-relative-lengths

Glenn Adams, 30 May 2013, 19:43:51

It looks like TTML 1.0 already allows fontSize to be specified relative to the root container by using a combination of (a) percentage metric, (b) default fontSize of 1c and (c) cellResolution value.

In order to not invalidate existing TTML 1.0 documents, it makes sense to introduce new vh/vw metric in TTML.next instead of redefining percentage semantics.

Pierre-Anthony Lemieux, 11 Jul 2013, 20:19:31

Add vw, vh, vmin, vmax units. https://dvcs.w3.org/hg/ttml/rev/36456238998f

Glenn Adams, 28 Aug 2013, 19:41:53

[glenn]: add comment under tts:fontSize indicating that vw/vh could also be expressed using cell (c) units

5 Sep 2013, 15:45:24

As per action-201 [1], I've looked to see if pixel aspect ratio would or should affect the meaning of vmin and vmax.

[1] https://www.w3.org/AudioVideo/TT/tracker/actions/201

It is possible to construct an example where taking pixel aspect ratio in to account to calculate actual dimensions would give a different result from omitting it. However the root definition of vmin and vmax, in [2], is unclear or at best non-specific about the intended behaviour. It appears to depend on how the viewport size itself was defined, i.e. if in physical units then vmin and vmax should relate to those physical sizes but if in pixels then vmin and vmax should relate to the pixel dimensions.

[2] http://www.w3.org/TR/css3-values/#viewport-relative-lengths

In TTML we only define a logical coordinate plane but we do allow ttp:pixelAspectRatio to be defined. I think there is very likely a use case for referring to the minimum or maximum size after pixelAspectRatio conversion to relate these terms to 'real' sizes. Certainly this should be considered and made explicit in the definition of the attributes.

For reference, here's one contrived example in which vmin and vmax have different values depending on whether the extent is multiplied by the pixelAspectRatio before the min/max decision or after it. Take an extent of 400w x 300h and a pixel aspect ratio of "1 1.5". Before conversion vmin=300/100 and vmax=400/100. Taking pixelAspectRatio into account, the min/max choice is between 400x1=400 and 300x1.5=450, and the decision is made the other way, so, after returning to our extent coordinate system, vmin=400/100 whereas vmax=300/100.

The question comes down to whether vmin and vmax apply numerically to our extent or is intended to compare actual sizes.

Nigel Megitt, 6 Sep 2013, 09:44:24

Additionally, we should make clear if the size implied by vmin and vmax is a physical size or a coordinate unit size. You might think that my contrived example is absurd because there is no qualification to indicate whether vmin/vmax is a horizontal or a vertical value, but implementing processors could of course internally keep track of that. There is no requirement to expose the actual numbers used; my conversion back to the extent coordinate system is merely there to indicate that the choice of algorithm can result in a different choice of value.

Nigel Megitt, 6 Sep 2013, 15:39:12

Can we provide a use case for vmin/vmax, since it seems to introduce many questions?

Pierre-Anthony Lemieux, 26 Sep 2013, 14:54:44

EBU liaison has requested "the ability to specify heights and widths relative to the size of the overall display area (“viewport” in some terminologies) independent of the number of device pixels present on the display." i.e. not just for specifying fontSize but other dimensions too.

EBU has not requested vmin and vmax, which still do not have a stated use case.

Nigel Megitt, 23 Oct 2013, 14:11:25

Nigel: Owned by PAL and Andreas
Nigel: P1

Philippe Le Hégaret, 24 Oct 2013, 15:39:41

[nigel]: (f2f meeting) We agreed to remove vmin and vmax.

29 Oct 2014, 00:57:59

Removed vmin and vmax in https://dvcs.w3.org/hg/ttml/rev/d92f703d67c6

Glenn Adams, 8 Jan 2015, 07:12:02


David Singer <singer@apple.com>, Nigel Megitt <nigel.megitt@bbc.co.uk>, Chairs, Thierry Michel <tmichel@w3.org>, Philippe Le Hégaret <plh@w3.org>, Staff Contacts
Tracker: documentation, (configuration for this group), originally developed by Dean Jackson, is developed and maintained by the Systems Team <w3t-sys@w3.org>.
$Id: index.php,v 1.325 2014-09-10 21:42:02 ted Exp $