public static function channelsEnabledLookup($acmod, $lfeon) {
    $lookup = array(
      'ch1'=>($acmod == 0),
      'ch2'=>($acmod == 0),
      'left'=>($acmod > 1),
      'right'=>($acmod > 1),
      'center'=>(bool) ($acmod & 0x01),
      'surround_mono'=>false,
      'surround_left'=>false,
      'surround_right'=>false,
      'lfe'=>$lfeon);
    switch ($acmod) {
      case 4:
      case 5:
        $lookup['surround_mono']  = true;
        break;
      case 6:
      case 7:
        $lookup['surround_left']  = true;
        $lookup['surround_right'] = true;
        break;
    }
    return $lookup;
  }