Hello Lars,
thanks for your fast reply.
I know this formula, however I do not comprehend the real values.
Do you know which value does the RTP analysis use for (i renamed it) J'
in the formula:
J=J'+(|D(i-1,i)|-J')/16
Furthermore Ethereal calculates two different results for the jitter
using version 0.9.13 and the current version. It seems that the results
of the old version are more realistic.
Volker
----- Original Message -----
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
>