RTSP multicast traffic & IGMP Proxy

I have a Synology Surveillance Station that is configured with Live View Multicast. I have activated Multicast on one of the cameras attached to the Surveillance Station (Live View->Advanced->Activate multicast).

I am able to view the Multicast RTSP stream from a VLC Media Player but only as long as it is connected o the same VLAN as the Synology (CCTV VLAN).

I would like to access the Multicast stream on another VLAN (IoT), so I have set up a rule on my pfSense filerwall to allow IoT to access CCTV over port 554 (TCP and UDP). However, it does not work.

I suspect that it has something to do with the Multicast traffic not being passed between the two VLANS and that the solution might be to configure IGMP Proxy on pfSense?

Do anyone have an example that shows how to configure IGMP Proxy for this application?