platform/video.videojs/dist/video.es.js
function checkProgress() {
        if (_this3.el_.currentTime > 0) {
          // Trigger durationchange for genuinely live video
          if (_this3.el_.duration === Infinity) {
            _this3.trigger('durationchange');
          }
          _this3.off('timeupdate', checkProgress);
        }
      }
function checkProgress() {
        if (_this3.el_.currentTime > 0) {
          // Trigger durationchange for genuinely live video
          if (_this3.el_.duration === Infinity) {
            _this3.trigger('durationchange');
          }
          _this3.off('timeupdate', checkProgress);
        }
      }
Wait for the first `timeupdate` with currentTime > 0 - there may be several with 0