Regression in ogv.js video playback on Safari Technology Preview (Safari 12), noticed in version 59 but might have come in a bit earlier.
A video with no audio plays fine:
A video with audio does not play, and stays at time 0:00 (or wherever you seek to) without progressing frames or playing any audio:
They do work in Safari Technology Preview playing on ogv.js's demo page:
which indicates it's likely a problem with the delayed initialization after the MwEmbedPlayer play button. Will take a look at how things have changed and try to resolve.