How can I pick up a multicast from a remote network via pptp?

Question

Computer networks

Network:
1) Home router R1 ordinary (dir 3xx-6xx) to provider 1.2.3.4 - external address via dhcp, 192.168.0.1/24 - internal network
2) Additional router R2 to raise pptp, connects to an external server 5.6.7.8 and gets VPN address 10.0.0.2
The second network is exactly the same.
Suppose one network has some multicast TV channels, the second network also has some other channels. The task is to collect all the TV on one machine into some kind of VLC-like playlist.
While trying different things. Now connected WAN R2 to LAN R1 , thus. R2connected to a pptp server and received an Internet from it (and we don't need it). Earned forwarding from external address to http R2 via VPN tunnel
Added route 0.0.0.0 0.0.0.0 192.168.0.1 to R2 so that R2 gets Internet from R1 - Internet stopped working, but 2ip now shows local address when you log in with R2 .
Anyone understand what's going on here?

Answer 1

Passed everything with the help of igmp-proxy. But it's even easier to use updxy. It is unicast and over http, but there is no need to waste time =)