I want download window appear instead of showing my mp4 file
You can do this using htaccess, Open your .htaccess file and add the following...

&lt;FilesMatch "\.(mp4)$"&gt;
  ForceType application/octet-stream
  Header set Content-Disposition attachment
&lt;/FilesMatch&gt;


This should force the browser to do a left click download, rather than play the content. You can do it for multiple files types as well. After the mp4 just add |mp3, so it would look like &lt;FilesMatch “.(?i:(mp4|mp3|pdf))$”&gt;