Multicast: ip multicast ttl-threshold x

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Some references in Blogs here

basically, the TTL of packet received should be higher than the TTL threshold configured

So if the config is as follows
PE3(config)#int f0/0.13
PE3(config-subif)#ip mul
PE3(config-subif)#ip multicast tt
PE3(config-subif)#ip multicast ttl-threshold 9
PE3(config-subif)#

Then any incoming multicast packet with TTL=10 or greater will be forwarded.
Any incoming multicast packet with TTL=9 or lesser will be discarded.