public function build()
 {
     $writer = new Media_SWF_Parser();
     $writer->putUI16LE($this->_fields['CharacterId']);
     $writer->putUI16LE($this->_fields['Depth']);
     $writer->putMatrix($this->_fields['Matrix']);
     if (isset($this->_fields['ColorTransform'])) {
         $writer->putColorTransform($this->_fields['ColorTransform']);
     }
     return $writer->output();
 }