Hi, All.
In Ethereal V0.99, /Statistics/RTP/Show All Streams,
The case that the said value is abnormaly large is found.
For Example, VoIP 20ms G.711;
RTP Time Stamp = 2^32-1(FFFFFFFF) at Seq1
and
RTP Time Stamp = 159 at Seq2
RTP Time Stamp = 319 at Seq3
foliows +160 by Seq.
In this case, Jitter Value is shown as about 10^6 msec in
/Statistics/RTP/Show All Streams.
It seems that Ethereal calculate the Jitter Value as follows;
Delta between Seq1 and Seq2 : 159-(2^32-1) = |-(2^32-160)|
However, TimeStamp means + Signed Time Unit, therefore, the calculation may
be better
as follows;
Delta between Seq1 and Seq2 :
159-(2^32-1) = -(2^32-160)
= +2^32 -(2^32-160)
= 160
=
In other words,
In case of
Timestamp(Seq=N+1) - Timestamp(N) <0
It is necessary to Normalize Delta by adding 2^32.
Bset Redards
