How to set multicast input url with unicast source? (Source-specific multicast)

[Canta]

Question

I need to set up a multicast URL with specific unicast source as a mediamtx path source.
Please note the difference in context for the "source" term. The second instance of that term points to mediamtx terminology, while the first one refers to source-specific multicast, or SSM.

For example, I need to be able to do something like this:

paths:
  mystream:
    source: "udp://[email protected]:12345"

or this:

paths:
  mystream:
    source: "udp://[email protected]:12345"

or this:

paths:
  mystream:
    source: "udp://239.0.0.1:12345?source=1.2.3.4"

I haven't found a proper syntax to set this up, and I'm doubting if this is even possible.
Is there any way to use SSM with multicast UDP URLs as sources?

[aler9]

moved in #4178