["Lars Ruoff" <Lars.Ruoff@xxxxxxxxxx>]

RTP delay and jitter are calculated as described in RFC 1889
(http://www.ietf.org/rfc/rfc1889.txt),
that is:

<quote>
   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
</quote>

regards,
Lars Ruoff


----- Original Message ----- 
From: "Volker Steinmann" <steinmann@xxxxxx>
To: <ethereal-users@xxxxxxxxxxxx>
Sent: Thursday, November 04, 2004 5:39 PM
Subject: [Ethereal-users] RTP Stream Analysis


> Hello,
>
> does anyone know how jitter and delay is calculated in the Statistics -
> RTP Stream Analysis menu?
> We measured IP jitter using hardware measurement device and got
> different results. While the device measured 150ms IP jitter, Ethereal
> measured 500ms RTP jitter which does even not match with the arrival
> time. As any RTP packet is mapped into an IP packet the jitter should be
> similar.
>
> Thanks for your help.
>
> Volker
>
>
>
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