      struct _mp3_header_internal //http://www.mp3-tech.org/programmer/frame_header.html
  {
      unsigned char frame_sync_a : 11;
      unsigned char id : 2;
      unsigned char layer : 2;
      unsigned char protection_bit : 1;
      unsigned char bitrate_index : 4;
      unsigned char frequency : 2;
      unsigned char padding_bit : 1;
      unsigned char private_bit : 1;
      unsigned char mode : 2;
      unsigned char mode_ext : 2;
      unsigned char copyright : 1;
      unsigned char original : 1;
      unsigned char emphasis : 2;
  };
