www.foo.com/player.html
www.foo.com/videos/video.mp4

www.foo.com/videos/.htaccess

#Contents of .htaccess

RewriteEngine on
RewriteCond %{HTTP_REFERER} !^http://foo.com/.*$ [NC]
RewriteCond %{HTTP_REFERER} !^http://www.foo.com/.*$ [NC]
RewriteRule .(mp4|mp3|avi)$ – [F]