IPTV broken with FW 39, 40b1 for RT-AC66?

[test011]

First, IPTV + VLAN works.
If you set a port option and IGMP proxy, IPTV works. (with "Choose IPTV STB Port" and "Enable multicast routing (IGMP Proxy)")

What does not work is IGMP + no VLAN setting with IGMP Snooping. (The title should be "IGMP Snooping broken?")

IGMP proxy enables multi-casting packets to flow and flood whole switch ports, then whole network is saturated. We don't want that, thus IGMP Snoofing. IGMP Snooping is the solution, when STB needs to be on the same subnet with the local network. Right now it seems that does not work.

With recent firmware, whether IGMP Snoofing is enabled or disabled, all the ports are flooded with multi-casing packets.

My ISP requires STB to be behind router. The STB only works with a private IP. Can't use "Choose IPTV STB Port" since STB demand a public IP.

I thought AsusWRT supported IGMP Snooping. Not sure now.
It seems almost everybody is using IPTV with VLAN. Does anybody can confirm "Enable efficient multicast forwarding (IGMP Snooping)" is actually working?

 

[test011]

I dare to say RT-AC66U/R's IGMP snoofing is broken at some point and nobody is noticing it as long as IGMP flooding and VLAN combination does the similar thing.