public static function serviceTypeLookup($bsmod, $acmod) {
    static $serviceTypeLookup = array();
    if (empty($serviceTypeLookup)) {
      for ($i = 0; $i <= 7; $i++) {
        $serviceTypeLookup[0][$i] = 'main audio service: complete main (CM)';
        $serviceTypeLookup[1][$i] = 'main audio service: music and effects (ME)';
        $serviceTypeLookup[2][$i] = 'associated service: visually impaired (VI)';
        $serviceTypeLookup[3][$i] = 'associated service: hearing impaired (HI)';
        $serviceTypeLookup[4][$i] = 'associated service: dialogue (D)';
        $serviceTypeLookup[5][$i] = 'associated service: commentary (C)';
        $serviceTypeLookup[6][$i] = 'associated service: emergency (E)';
      }

      $serviceTypeLookup[7][1]      = 'associated service: voice over (VO)';
      for ($i = 2; $i <= 7; $i++) {
        $serviceTypeLookup[7][$i] = 'main audio service: karaoke';
      }
    }
    return (isset($serviceTypeLookup[$bsmod][$acmod]) ? $serviceTypeLookup[$bsmod][$acmod] : false);
  }