Wireshark-dev: [Wireshark-dev] Question regarding the information provided by Wireshark in the
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From: "Andreina Toro" <andreina.toro@xxxxxxxxx>
Date: Wed, 18 Oct 2006 10:38:52 -0400

Hi everyone, I have a question regarding the calculation of interarrival jitter and the information provided by Wireshark in the "RTP Stream Analysis Wndow" for each call.

I can see that Wireshark gives me in the 4th Row of the RTP Stream Analysis Wndow the Jitter for each packet of each call.
 
In the other hand I´ve read that:
 
"If Si is the RTP timestamp from packet i, and Ri is the time of arrival in RTP timestamp units for packet i, then for two packets i and j, D may be expressed as 
                                           D(i,j)=(Rj-Ri)-(Sj-Si)=(Rj-Sj)-(Ri-Si)
The interarrival jitter is calculated continuously as each data packet i is received from source SSRC_n, using this difference D for that packet and the previous packet i-1 in order of arrival (not necessarily in sequence), according to the formula                                 J=J+(|D(i-1,i)|-J)/16
Whenever a reception report is issued, the current value of J is sampled."
 
What I don´t have clear is what this Jitter in the 4th Row represents in the interarrival jitter calculation?
 
Can I calculate the jitter J, defined to be the mean deviation, with that data? I mean, can I use the values of the jitters of each packet given in that RTP Stream Analysis in every call and calculate the difference D??
                        D_m = \frac{1}{n} \sum_{i=1}^n \left| x_i - \overline{x} \right|

Thanks, and sorry for any inconvinience

Best Regards,

Andreina