rtp: Add lua script to split a trace by SSRC/streams

This can be used to replay RTP streams with more or less the
same timing as the original one.

openbsc/contrib/rtp/timestamp_rtp.lua

@@ -0,0 +1,28 @@
+print("Ni hao")
+
+
+do
+	local tap = Listener.new("ip", "rtp")
+	local rtp_ssrc = Field.new("rtp.ssrc")
+	local frame_time = Field.new("frame.time_relative")
+	local rtp = Field.new("rtp")
+
+	function tap.packet(pinfo, tvb, ip)
+		local ip_src, ip_dst = tostring(ip.ip_src), tostring(ip.ip_dst)
+		local rtp_data = rtp()
+		local filename = "rtp_ssrc" .. rtp_ssrc() "_src_" .. ip_src .. "_to_" .. ip_dst .. ".state"
+		local f = io.open(filename, "a")
+
+		f:write(tostring(frame_time()) .. " ")
+		f:write(tostring(rtp_data.value))
+		f:write("\n")
+		f:close()
+	end
+
+	function tap.draw()
+		print("DRAW")
+	end
+	function tap.reset()
+		print("RESET")
+	end
+end