[ttml1] Pull Request: Clarify definition of epoch and epoch-related offsets

palemieux has just submitted a new pull request for https://github.com/w3c/ttml1:

== Clarify definition of epoch and epoch-related offsets ==
Close #266

See https://github.com/w3c/ttml1/pull/302

Received on Wednesday, 20 December 2017 04:43:41 UTC