can you help... in Pagination I modified View and Controller function

As you say in Post #2 above 

public function page() {
    $this->load->library('pagination');
    $config['base_url'] = base_url('admin/ads/page');
    $config['total_rows'] = $this->db->count_all('videos');

having 1 2 3 4 5 next>
pages 

changing Page will run again page() ... ? if yes this isset() check should faster the function if run only for first time ?
if having

$config['total_rows'] = $this->db->count_all('video')

each time this will run again and again slowing the function... ? so required the >>  // ???

isset($config['total_rows']) ? '' : ($config['total_rows'] = $this->db->where('public',1)->count_all('videos')) ;