[imsc] Mixed units in tts:origin and tts:extent value

spoeschel has just created a new issue for https://github.com/w3c/imsc:

== Mixed units in tts:origin and tts:extent value ==
I wonder whether the mixing of different units (e.g. `px` and `%`) within the same attribute value is allowed for `tts:origin` and `tts:extent` in IMSC1, e.g. usage of the value `10% 200px`.

My understanding is that according to the table in §7.4, it is is allowed for `tts:origin`, as for the `#origin` feature the "Additional provisions" column states:

"The tts:origin attribute SHALL use px units or "percentage" representation, and SHALL NOT use em units."

For `tts:extent` in contrast it is not allowed according to my understanding, as that table column for the `#extent-region` feature states:

"The tts:extent attribute SHALL be present on all region elements, where it SHALL use either px units or "percentage" syntax."

Is this interpretation correct? As my expectation was that is it premitted either for both attributes or for neither of them.

Please view or discuss this issue at https://github.com/w3c/imsc/issues/249 using your GitHub account

Received on Tuesday, 1 August 2017 06:56:51 UTC