matrix-spec/data/event-schemas/examples/m.call.negotiate.yaml

{
  "$ref": "core/room_event.json",
  "type": "m.call.negotiate",
  "content": {
    "version" : "1",
    "party_id": "67890",
    "call_id": "12345",
    "description": {
      "type" : "offer",
      "sdp" : "v=0\r\no=- 6584580628695956864 2 IN IP4 127.0.0.1[...]"
    }
  }
}