uploaded file exceeds the maximum allowed size

[eluser]Zeeshan Rasool[/eluser]
Hi, plz help me in this case,
An error is there!
Error:The uploaded file exceeds the maximum allowed size in your PHP configuration file

My code is:

$config['upload_path'] = './resources/admin_videos';
$config['allowed_types'] = 'mp3';
$config['max_size'] = '500000';
$config['overwrite'] = false;

$this->upload->initialize($config);
$this->load->library('upload', $config);
if(!$this->upload->do_upload($video))
{
$error = array('error' => $this->upload->display_errors());
return $error;
}
else
{
$data = array('upload_data' => $this->upload->data());
$video_path =$data['upload_data']['file_name'];

}
////////// also included 'mp3' => array('audio/mpeg', 'audio/mpg') but no result
Any guy who know the solu.
....................JamZee