private function get_players() {
        // Save time by only building the list once.
        if (!$this->players) {
            $sortorder = \core\plugininfo\media::get_enabled_plugins();

            $this->players = [];
            foreach ($sortorder as $name) {
                $classname = "media_" . $name . "_plugin";
                if (class_exists($classname)) {
                    $this->players[] = new $classname();
                }
            }
        }
        return $this->players;
    }