First of all I want to tell you the network topology --- ISP link terminates on the 2821 router, router is connected to the asa 5510, asa in connected to the IDS-4215, IDS is connected to the cisco 3750 core switch, core switch is connected to the 2960 access layer switch & finally end user is connected to the 2960 switch.
I have done classification & marking on the core switch & apply service-policy on the router WAN interface.
Switch QoS config ---
switch#access-list 11 permit 192.168.10.0 255.255.255.0
access-list 12 permit 192.168.20.0 255.255.255.0
match access-list 11
match access-list 12
And mark the video class as dscp 41 & traffic class as dscp 25.
match dscp value 41 and set the bandwidth percent is 75% apply on the router's wan interface.
After applying these commands on the router -- there are delays of 300-400 ms more than normal delay of 200ms.
If video devices are available then bandwidth should be distributed , but if it is unavailable, then the whole bandwidth should be allocated to traffic class user.