It is proposed that a TextTrackCue.endTime value of Infinity be used to represent an unbounded time, i.e. an unspecified future time. This is a simple extension of the existing HTML standard where media.duration = Infinity represents the duration of an unbounded stream, which is consistent with the definition of unbounded time. Further details at: https://github.com/whatwg/html/pull/5953
<rdar://problem/71042767>
Update: The following Pull Requests are now ready and should be merged soon. TextTrackCue.endTime: https://github.com/whatwg/html/pull/5953 VTTCue constructor: https://github.com/w3c/webvtt/pull/493 Web Platform Tests: https://github.com/web-platform-tests/wpt/pull/28394 Please let me know if you have any questions.
Update: https://github.com/whatwg/html/pull/5953 and https://github.com/web-platform-tests/wpt/pull/28394 have been merged. TextTrackCue.endTime now allows unbounded cues in the WHATWG HTML spec: https://html.spec.whatwg.org/multipage/media.html#text-track-cue-end-time
Update: https://github.com/w3c/webvtt/pull/493 has been merged which enables the tests in https://github.com/web-platform-tests/wpt/pull/28394 and concludes the supporting changes required for https://github.com/whatwg/html/pull/5953.
Failing following test here: https://wpt.fyi/results/webvtt/api/VTTCue/constructor.html?label=master&label=experimental&aligned=&q=webvtt%2F