protected function buildAudioSubdef(SimpleXMLElement $sd)
    {
        $audio = new Audio($this->translator);
        if ($sd->acodec) {
            $audio->setOptionValue(Audio::OPTION_ACODEC, (string) $sd->acodec);
        }
        if ($sd->audiobitrate) {
            $audio->setOptionValue(Audio::OPTION_AUDIOBITRATE, (int) $sd->audiobitrate);
        }
        if ($sd->audiosamplerate) {
            $audio->setOptionValue(Audio::OPTION_AUDIOSAMPLERATE, (int) $sd->audiosamplerate);
        }
        if ($sd->audiochannel) {
            $audio->setOptionValue(Audio::OPTION_AUDIOCHANNEL, (string) $sd->audiochannel);
        }

        return $audio;
    }