ISSUE-319: HRM should be a processor compliance test and allow different levels of complexity for different use cases

HRM should be a processor compliance test

HRM should be a processor compliance test and allow different levels of complexity for different use cases

State:
OPEN
Product:
TTML IMSC 2.0
Raised by:
Nigel Megitt
Opened on:
2014-05-23
Description:
The Hypothetical Render Model is defined as a content profile constraint, which appears to set a maximum complexity on all documents. It would be better to make it a minimal processor profile constraint, i.e. so that it can be used to construct maximally complex test documents that compliant processors must be able to process successfully, while permitting processors to process even more complex documents.

This would open up the possibility for future increases in complexity by allowing the threshold values for sub-profiles of IMSC to be changed to 'greater complexity', in the knowledge that pre-existing IMSC compliant documents will be continue to be processable.

Very closely related to this, the HRM (§7) [1] in various places sets threshold parameter values using the wording "Unless specified otherwise, the following table shall specify..." but there is no mechanism for specifying otherwise; §4.7 simply states that all sequences "of intermediate synchronic documents SHALL be reproducible..." without providing any reference to an external location where the parameters in the HRM can be set to other values.

One possible solution to this is to introduce a 'complexity level' table and list the current parameter values as, for example 'complexity level 1' and change the wording in §4.7 to state that for use cases that need to specify complexity they must either specify an equivalent table with alternative parameter values or use the default 'level 1' values. It should be permitted for processors not to be subject to the HRM values at all, and there should be scope in future versions of IMSC to add more levels, if there is a strong argument for doing so.

[1] http://www.w3.org/TR/ttml-imsc1/#hypothetical-render-model
Related Actions Items:
No related actions
Related emails:
  1. {agenda} TTWG Meeting 2014-12-04 (from nigel.megitt@bbc.co.uk on 2014-12-03)
  2. {agenda} TTWG Meeting 25/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-24)
  3. Re: {agenda} TTWG Meeting 11/9/2014 (from glenn@skynav.com on 2014-09-10)
  4. {agenda} TTWG Meeting 11/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-10)
  5. {agenda} TTWG Meeting 4/9/2014 (from nigel.megitt@bbc.co.uk on 2014-09-03)
  6. {agenda} TTWG Meeting 21/8/2014 (from nigel.megitt@bbc.co.uk on 2014-08-20)
  7. Re: New Change Proposal 28 on IMSC 1: Profile refactoring (from nigel.megitt@bbc.co.uk on 2014-08-14)
  8. Re: New Change Proposal 28 on IMSC 1: Profile refactoring (from pal@sandflow.com on 2014-08-14)
  9. {agenda} TTWG Meeting 14/8/2014 (from nigel.megitt@bbc.co.uk on 2014-08-13)
  10. New Change Proposal 28 on IMSC 1: Profile refactoring (from nigel.megitt@bbc.co.uk on 2014-08-08)
  11. Re: {agenda} TTWG Meeting 7/8/2014 (from pal@sandflow.com on 2014-08-06)
  12. {agenda} TTWG Meeting 7/8/2014 (from nigel.megitt@bbc.co.uk on 2014-08-06)
  13. {agenda} TTWG Meeting 31/7/2014 (from nigel.megitt@bbc.co.uk on 2014-07-30)
  14. {minutes} TTWG Meeting 19/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-19)
  15. RE: {agenda} TTWG Meeting 19/6/2014 (from mdolan@newtbt.com on 2014-06-18)
  16. {agenda} TTWG Meeting 19/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-18)
  17. IMSC feature designators (from nigel.megitt@bbc.co.uk on 2014-06-13)
  18. RE: {agenda} TTWG Meeting 12/6/2014 (from mdolan@newtbt.com on 2014-06-12)
  19. Re: {agenda} TTWG Meeting 12/6/2014 (from pal@sandflow.com on 2014-06-11)
  20. Re: {agenda} TTWG Meeting 12/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-11)
  21. Re: {agenda} TTWG Meeting 12/6/2014 (from pal@sandflow.com on 2014-06-11)
  22. Re: {agenda} TTWG Meeting 12/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-11)
  23. {agenda} TTWG Meeting 12/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-11)
  24. RE: {agenda} TTWG Meeting 5/6/2014 (from mdolan@newtbt.com on 2014-06-04)
  25. {agenda} TTWG Meeting 5/6/2014 (from nigel.megitt@bbc.co.uk on 2014-06-04)
  26. {agenda} TTWG Meeting 29/5/2014 (from nigel.megitt@bbc.co.uk on 2014-05-28)
  27. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from pal@sandflow.com on 2014-05-27)
  28. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-27)
  29. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from pal@sandflow.com on 2014-05-27)
  30. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-27)
  31. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from pal@sandflow.com on 2014-05-27)
  32. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-27)
  33. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from pal@sandflow.com on 2014-05-23)
  34. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from nigel.megitt@bbc.co.uk on 2014-05-23)
  35. Re: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from pal@sandflow.com on 2014-05-23)
  36. RE: ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from mdolan@newtbt.com on 2014-05-23)
  37. ISSUE-319 (HRM should be a processor compliance test): HRM should be a processor compliance test and allow different levels of complexity for different use cases [TTML IMSC 1.0] (from sysbot+tracker@w3.org on 2014-05-23)

Related notes:

TTML1 offers a mechanism for defining processor features that are required by compliant processors, so I propose we use it. See also Issue-307.

I'd advocate fine-grained feature designators aggregated with a coarse-grained feature that simply makes reference to the relevant set of fine-grained features.

For example:
#concurrent-regions-4 for processors that can support up to 4 concurrent regions (I know that's not part of the HRM, please don't write in).
#hrm-ipd-max-1s for processors that can process documents authored for rendering with an HRM whose IPD >= 1s.
#hrm-bdraw-max-12-per-s
#hrm-ICpy-max-6
#hrm-Idec-max-1-per-s
#hrm-ndibs-max-a (don't really want to put decimal fractions in designator names, so used a code letter - maybe there's a better way!)
#hrm-GCpy-max-12
#hrm-Ren-non-CJK-a for 1.2
#hrm-Ren-CJK-a for 0.6
#hrm-NBGS-max-1
#hrm-reference-fonts-monospaceSerif
#hrm-reference-fonts-proportionalSansSerif

then grouping:
#hrm-reference-fonts if both #hrm-reference-fonts-monospaceSerif and #hrm-reference-fonts-proportionalSansSerif
#hrm-performance-level-a-text if all of the #hrm-* features listed above for glyph drawing
#hrm-performance-level-a-graphics if all of the #hrm-* features listed above for graphics copying
#hrm-performance-level-a-text-and-graphics if both #hrm-performance-level-a-text and #hrm-performance-level-a-graphics.


Nigel Megitt, 13 Jun 2014, 16:37:56

See also Change Proposal 28 [1].

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

Nigel Megitt, 8 Aug 2014, 13:27:16

CP28 was withdrawn 2014-09-05.

TTML1 doesn't support both content and processor profiles. Since this is a request for a processor profile definition, and is therefore dependent on TTML2, deferring this issue to IMSC 2.

Nigel Megitt, 28 Nov 2014, 15:57:40

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