In fact what my setup do is instead of having the my router connected to the sagemcom connected to the ont, my sagemcom is connected to my router connected to the ONT.
ONT(port1) connected to (WAN) MyRouter (port1) connected to (WAN) sagemcom (port1) connected to my PVR.
Instead of doing complicated things in my router for IPTV, the sagemcom is doing everything but after my own router.
I have only one tv, but because the sagemcom is still functionnal you can use the same tv setup.
In my router i run Tomato but any router supporting vlan 34-36 you're okay. So in my router i have:
-Original mac address of my router
- WAN and port1 tagged with VLAN34 VLAN35 VLAN36
- VLAN35 connected to bridge "Wan" with normal PPPoE setup