IPTV through fortigate

Hi, I just got IPTV at home and trying to get it to work with my fortigate instead of the router that the broadband company sent. But I don't really know how to configure the fortigate to get it working. I've tried to enable multicast routing and created multicast policy but it won't work. If I sniff the traffic on the external interface I can see that the provider is sending multicast as tagged traffic on vlan 46. I guess Internet traffic is sent on the native vlan. You guys got any ideas how to get this working?