Hi Volker,
J' starts as zero for the first iteration.
At the end of each iteration, J' is replaced with the current value of J.
Can you post a capture file or a .csv-output of values where you believe
there is a calculation error?
regards,
Lars
----- Original Message -----
From: "Volker Steinmann" <steinmann@xxxxxx>
To: <ethereal-users@xxxxxxxxxxxx>
Sent: Tuesday, November 09, 2004 11:41 AM
Subject: Re: [Ethereal-users] RTP Stream Analysis
> 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
> >
>
>
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