[imsc] Pull Request: Loosen and clarify tts:extent constraints

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

== Loosen and clarify tts:extent constraints ==
Close #475 

Propose to obsolete #480

See https://github.com/w3c/imsc/pull/482

Received on Monday, 15 July 2019 15:25:48 UTC