Seems as if Net-observer uses another algorithm for calculation of jitter.
Ethereal uses that of RFC 3550 (RTP/RTCP):
<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 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
</quote>
br,
Lars
----- Original Message -----
From: <mark_lawrence@xxxxxxxxxxxxx>
To: <ethereal-users@xxxxxxxxxxxx>
Sent: Monday, February 06, 2006 12:14 AM
Subject: [Ethereal-users] Jitter and Delay problems
Hi,
I?ve recently taken a trace from two machines running Microsoft Netmeeting,
and was checking for Jitter and Delay. The sniffer trace worked perfectly,
but the figures are some what shocking, jitter has a mean of 10ms and the
Delta varies between 30 -60ms. However this is all fine, but when I run
the same trace using Network observer or clear sight the values of jitter
are 8 times greater at 80ms and well above desired levels. If the capture
from Ethereal is exported to Network observer the values are that of 80 ms
jitter. Anyone seen this before and can explain why this is the case?
Really
confusing, need to get the same values from both?
Thanks
Mark
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