extractAudio() {
    return new Promise((resolve, reject) => {
      const opts =
        this.endTime === DEFAULT_TIME ? [] : ['-ss', this.startTime, '-to', this.endTime];
      this.materials.apath = this.getAOutput();

      this.acommand
        .addInput(this.getPath())
        .noVideo()
        .audioCodec('libmp3lame')
        .outputOptions(opts)
        .output(this.materials.apath);

      this.acommand
        .on('end', () => {
          FFLogger.info({ pos: 'FFVideo', msg: 'Audio preProcessing completed!' });
          resolve();
        })
        .on('error', err => {
          FFLogger.error({ pos: 'FFVideo', msg: 'Audio preProcessing error', error: err });
          reject(err);
        });

      this.acommand.run();
    });
  }
Extract the audio file from the movie
@private