Parallel forking with early media

I’d like to implement the following scenario:

  • I have 3 SIP endpoints, say A, B anc C
  • Asterisk, say X
  • B and C belong to the same group (implemented in Asterisk with queue method and ringall strategy).
  • A, B and C use the same media and media attributes

A calls the group and both B and C have to ring in parallel. I have already achieved this with the configuration mentioned above.

Now, I’d like to have the same behavior but also to make B and C opening early media channels each (I need just a recv only channel) towards the caller A, in order to receive media from A, before picking up the call.
My idea is that B and C should respond to the invite with 180 or 183 with SDP and X should forward one “equivalent” message (183 with SDP) to A. Then X should be able to receive media from A and forwards it to both B and C.

Is this possible with Asterisk? Could someone address me to the solution or proper configuration?

With configuration mentioned above (queue and ringall strategy), I see the 180 with SDP from B and C to X but not from X to A and early media doesn’t work. Maybe something missing in my configuration…

Thanks in advance.