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Levels
MOS vs. Time
Delay vs. Time
C H A P T E R
6 :
T E L E P H O N Y
T E S T I N G
For a more detailed analysis of delay variations refer to the Delay vs. Time
Diagram and the Delay Histogram.
Information on the measured signal levels is also given in the Final results
window. In the tables on the right side of the diagram the signal levels in dB
well as the loudness in Sone are found.
Figure 6.25
shows the MOS vs. Time diagram. This diagram indicates the
perceived voice quality as measured by PESQ on a frame by frame basis. Use
this diagram to analyze sequences that have spurious audible distortions. Search
the peak in the MOS vs. Time diagram and then analyse the signals around this
time stamp using the other provided diagrams.
Figure 6.25:
MOS vs. Time diagram.
represents the Delay vs. Time diagram. It shows the time on the x-
Figure 6.26
axis and the delay in ms on the y-axis. Especially with packet networks,
significant variations of the delay during a call can be observed. This diagram is
generally very useful for the analysis of jitter buffer adaptation algorithms, which
are the main source for varying delays on IP networks. Additional information is
shown on the right side of the diagram. This information includes the time and
date of the measurement, as well as general information on the input data. The
delay shown is the average delay in milliseconds as well as in samples. This
average delay can also be plotted as a graph into the diagram. It is important to
note that the average delay shown as a yellow line in
number. It is the average delay over the entire measurement period. Since the
delay in real systems usually varies in discrete steps only, this average delay
probably never really occurs.
B A N D
Figure 6.24:
PESQ Delay Jitter display.
146
V O I C E
Q U A L I T Y
is a pure virtual
Figure 6.26
as
ov
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