Re: quesiton about PerfSocket_UDP.cpp
As per the source we are using the algorithm defined in RFC 1889 for the
Real Time Protocol to calculate jitter, defined in section 6.3.1 and
coded in A.8 (which looks very familiar to the iperf code). That formula
is:
J = J + ( | D(i-1,i) | - J ) / 16
The deltatransit is the "D(i-1,i)" part. It is measured in seconds and is
a double type.
Therefore this is not really a difference from average (since we don't
compute an average), but a difference from the last packet. I hope that
helps, but I am not sure it was exactly what you were looking for.
Kevin
On Wed, 31 Mar 2004, John J. Sheftic wrote:
> I am trying to determine some jitter variations in my wireless network
> and was trying to record the differences in transit time across the
> network. Since Jitter is an unsigned value it is difficult to tell
> exactly if packets are consistently arriving
> late or both early and late compared to the average. In the
> PerfSocket_UDP.cpp class I noticed a deltaTransit variable and that
> looks promising. What exactly is deltaTransit calculating and what unit
> is it reported in. I need to be able to see if
> packets are arriving early and then late causing Jitter to rise or
> whether it is a consistent late arrival. Thanks for your help.
>