Extract the MFCCs from the given audio file.

        :rtype: :class:`~aeneas.audiofilemfcc.AudioFileMFCC`

def _extract_mfcc(self, file_path=None, file_format=None, audio_file=None):
        """
        Extract the MFCCs from the given audio file.

        :rtype: :class:`~aeneas.audiofilemfcc.AudioFileMFCC`
        """
        audio_file_mfcc = AudioFileMFCC(
            file_path=file_path,
            file_format=file_format,
            audio_file=audio_file,
            rconf=self.rconf,
            logger=self.logger
        )
        if self.rconf.mmn:
            self.log(u"Running VAD inside _extract_mfcc...")
            audio_file_mfcc.run_vad(
                log_energy_threshold=self.rconf[RuntimeConfiguration.MFCC_MASK_LOG_ENERGY_THRESHOLD],
                min_nonspeech_length=self.rconf[RuntimeConfiguration.MFCC_MASK_MIN_NONSPEECH_LENGTH],
                extend_before=self.rconf[RuntimeConfiguration.MFCC_MASK_EXTEND_SPEECH_INTERVAL_BEFORE],
                extend_after=self.rconf[RuntimeConfiguration.MFCC_MASK_EXTEND_SPEECH_INTERVAL_AFTER]
            )
            self.log(u"Running VAD inside _extract_mfcc... done")
        return audio_file_mfcc