platform/video.videojs/dist/video.es.js
function checkVolumeSupport(self, player) {
  // hide volume controls when they're not supported by the current tech
  if (player.tech_ && !player.tech_.featuresVolumeControl) {
    self.addClass('vjs-hidden');
  }

  self.on(player, 'loadstart', function () {
    if (!player.tech_.featuresVolumeControl) {
      self.addClass('vjs-hidden');
    } else {
      self.removeClass('vjs-hidden');
    }
  });
}
function checkVolumeSupport(self, player) {
  // hide volume controls when they're not supported by the current tech
  if (player.tech_ && !player.tech_.featuresVolumeControl) {
    self.addClass('vjs-hidden');
  }

  self.on(player, 'loadstart', function () {
    if (!player.tech_.featuresVolumeControl) {
      self.addClass('vjs-hidden');
    } else {
      self.removeClass('vjs-hidden');
    }
  });
}
Check if volume control is supported and if it isn't hide the
`Component` that was passed  using the `vjs-hidden` class.

@param {Component} self
The component that should be hidden if volume is unsupported

@param {Player} player
A reference to the player

@private