public static function MPEGaudioModeExtensionArray() {
    static $MPEGaudioModeExtension;
    if (empty($MPEGaudioModeExtension)) {
      $MPEGaudioModeExtension = array (
        1 => array('4-31', '8-31', '12-31', '16-31'),
        2 => array('4-31', '8-31', '12-31', '16-31'),
        3 => array('', 'IS', 'MS', 'IS+MS')
      );
    }
    return $MPEGaudioModeExtension;
  }