There are some Cisco platforms that can translate multicast source/destination groups. As an example the Nexus 3500 has a feature called multicast service reflection that can work this way. There are some other platforms running XE that also support this feature, as well as some older boxes (7200/6500, for example).
In any case, service reflection works as follows: the configured router will join the source multicast group - call it (S1,G1) and then originate the same traffic into a new group with a source on a virtual subnet: (S2,G2) that clients can then join via normal means.
There are definitely some potential design caveats here in terms of loops and such, so exercise caution. I've honestly primarily seen this used in large enterprise multicast environments where streams were coming from third parties and either the source had to be fixed to keep RPF from going haywire or there was a need to disambiguate groups in very dense environments (or, occasionally, both).
I understand that it may simply be for purpose of example, but it's also worth noting that the lowest subnets in the multicast/class-D space have special meaning. 184.108.40.206/24 is explicitly defined in RFC 5571 and there are static definitions maintained by the IANA. It's legitimate to route this traffic but is likely bad form for typical end-user applications.