/**
  * generateVideoFilters
  * @param $vid
  * @return array of filters 
  */
 protected static function generateVideoFilters($vid)
 {
     /*
      * FFMpeg 2.7 automatically rotates the output 
      * into 'non-rotated' orientation. No need to do it explicitly 
      */
     $rotation = null;
     if (isset($vid->_rotation)) {
         $rotation = $vid->_rotation;
         $vid->_rotation = null;
     }
     $filters = parent::generateVideoFilters($vid);
     $vid->_rotation = $rotation;
     return $filters;
 }