anchor.diff:        "c=IN IP4 0.0.0.0\r\n",
         "t=0 0\r\n",
         "m=audio ", Port/binary, " RTP/AVP 112 113\r\n",
  -      "a=rtpmap:112 L16/48000/2\r\n",
  -      "a=rtpmap:113 DAT12/32000/4\r\n",
  -      "a=fmtp:113 contents:DV L/R/C/WO\r\n">>.
  -
  +      "a=rtpmap:112 speex/32000/1\r\n",
  +      "a=fmtp:112 vbr=on">>.
  
positive.code: %% @doc Serve requests to user `hang'
  %% @end
  is_applicable(#sip_request{uri = #sip_uri{user = <<"hang">>}}) -> true;
  is_applicable(#sip_request{}) -> false.
  
  -spec init({}) -> {ok, #state{}}.
  init({}) ->
  
negative.code:     % Request will be cancelled automatically after 5 seconds
      Request4 = sip_message:append_header(expires, 5, Request3),
  
      % put session in INVITE
      Request5 = sip_message:append_header('content-type', <<"application/sdp">>, Request4),
      Request6 = Request5#sip_request{body = sdp()},
  
      % Call
      io:format("HANG: Calling to ~s~n", [to(Request6)]),
      {ok, _RequestId} = sip_ua:send_request(Request6),
  
      {reply, ok, State};
  
  