matrix-spec/event-schemas/examples/m.call.candidates

{
  "$ref": "core/room_event.json",
  "type": "m.call.candidates",
  "content": {
    "version" : 0,
    "call_id": "12345",
    "candidates": [
      {
        "sdpMid": "audio",
        "sdpMLineIndex": 0,
        "candidate": "candidate:863018703 1 udp 2122260223 10.9.64.156 43670 typ host generation 0"
      }
    ]
  }
}