Wireshark-users: Re: [Wireshark-users] Calculate Jitter
From: Lars Ruoff <[email protected]>
Date: Thu, 22 Feb 2007 10:28:15 +0100
Wireshark *does* use that formula.
Can you give an example where you think it doesn't work?
Note that you need to know the RTP clock sampling time (depends on codec)) to do the transformation from RTP timestamps to real time.
br,
Lars Ruoff

Goran Štrok wrote:
I do not understand how jitter is exactly calculated. I have tried with theese formula, but do not get the same results like Wireshark gets. Can anyone little explain me about this. 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 SHOULD be 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(i) = J(i-1) + (|D(i-1,i)| - J(i-1))/16
Thanks.


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