[ttml2] Pull Request: Initial pass at rationalizing aspect ratio and pixel dimensions

palemieux has just submitted a new pull request for https://github.com/w3c/ttml2:

== Initial pass at rationalizing aspect ratio and pixel dimensions ==
This is an initial pass at rationalizing computation of aspect ratio and pixel dimensions.

Some highlights:

- IMHO the ultimate goal is to determine (a) the intended display aspect ratio of the root container, i.e. what the viewer sees, and (b) the meaning of `px` within the document coordinate system

- the mapping of the root container to the `presentation viewport` is left to profiles and/or applications, but can use the computed PAR, SAR, and DAR.

- the document coordinate system is specified as an abstract Cartesian coordinate system, i.e. independently of the notion of pixels.

I expect additional editorial will be needed, at the very least, but wanted to get the review started.

See https://github.com/w3c/ttml2/pull/321

Received on Wednesday, 17 May 2017 22:24:00 UTC