Wireshark · Ethereal-dev: [Ethereal-dev] Jitter validity

[Szymon Fedor <Szymon.Fedor@xxxxxxxxxxxx>]

Hello,

I would like to analyse the RTP protocol with Ethereal, especially I am
concerned about the Jitter calculation. Below is the example of a RTP statistic
displayed with Ehereal.

Packet Sequence Delay      Jitter
106    39378    0          0
107    39379    0.002983   0.001689
108    39380    0.006785   0.003034
109    39381    0.003869   0.004478
110    39382    0.004391   0.005798


As I read on the mailing list, the Jitter is calculated with the following
formula:
J = J + ( | D(i-1, i) | - J) / 16
where J is jitter and D is delay between two frames

If I apply this formula to the sequence above I don't get wright result
(for example: 0.001689+(0.006785-0.001689)/16=0.0020075<>0.003034)

Do you know where is the problem? Do you really use the above formula to
calculate the Jitter or I just apply it in a wrong way?

Thank's for the answers

regards
Simon


-- 
INSA Lyon
Département Télécommunications, Services et Usages
Courriel: szymon.fedor@xxxxxxxxxxxx