Aspect ratios when SAR specified, but DAR and PAR not specified.

[skynavga]

In order to be consistent with IMSC1 7.7.1, we need to update H.1.2 to read as follows (or equivalent):

a. if a related media object exists and has a defined DAR, then the resolved value of SAR is the display aspect ratio of the related media object and the value of PAR is then resolved according to H.1.3 Two Aspect Ratios below;
b. otherwise, the resolved value of DAR is determined by the document processing context and the value of PAR is then resolved according to H.1.3 Two Aspect Ratios below.

[css-meeting-bot]

The Working Group just discussed Aspect ratios when SAR specified, but DAR and PAR not specified. ttml2#539.

The full IRC log of that discussion

<nigel> Topic: Aspect ratios when SAR specified, but DAR and PAR not specified. ttml2#539
<nigel> github: https://github.com//issues/539
<nigel> Cyril: Yesterday we reviewed with Pierre and Glenn the discrepancies between
<nigel> .. ittp:aspectRatio and ttp:displayAspectRatio and there were two cases where the text
<nigel> .. was not aligned, which is this issue.
<nigel> Glenn: There's now a PR open on this.