How to limit stream speed

I have implemented a limit_rate speed for my mp4 stream, and this working fine,

(my mp4 config)

location ~ \.mp4$ {
secure_link $arg_s,$arg_e;
secure_link_md5 sifra$uri$arg_e;
if ($secure_link = "") {
return 403;
}
if ($secure_link = "0") {
return 403;
}

limit_rate_after 5m;
limit_rate 400k;
#gzip off;
mp4;
}

But on many sites i can found something like this ..
http://site.com/high.flv?s=1393534948&e=1393549348&ri=5000&rs=70&r=site.com&h=d39bc2dd269583dc1f828111e5ed4786&ev=1

arg. rs is limit_rate as i can see.. because when i try download i can see max 70KB/s download speed at my download menager ... but when i try change for example rs=75 or any other value i have error 403 ...

Also different videos have different rs value as i can see...

I want make something like this on my site, but i need more info about example above...? How to control limit rate via url ?