Our ISPs are all disaster here no help from their side.
Anyway I have problem with IPTV and when I have massive HTTP download or something else.
So I am searching some kind solution for a very long time for IPTV priority.
Just found this old thread from 2004
http://forum.mikrotik.com/t/qos-shaping-traffic-with-priorities-and-variable-adsl-bandw/192/1