public function getAudioChannels()
    {
        if ($this->audioChannels === null) {
            $match = [];
            preg_match(self::$REGEX_AUDIO_CHANNELS, $this->output, $match);
            if (array_key_exists(1, $match)) {
                switch (trim($match[1])) {
                    case 'mono':
                        $this->audioChannels = 1;
                        break;
                    case 'stereo':
                        $this->audioChannels = 2;
                        break;
                    case '5.1':
                        $this->audioChannels = 6;
                        break;
                    case '5:1':
                        $this->audioChannels = 6;
                        break;
                    default:
                        $this->audioChannels = (int)$match[1];
                }
            } else {
                $this->audioChannels = 0;
            }
        }

        return $this->audioChannels;
    }