OPTICOM OPERA - V 3.5 User Manual page 139

C H A P T E R 6 : T E L E P H O N Y
T E S T I N G
P.861 is not taken into account. To know the result at the stop point, Refer to
the "Final Result" diagram.
ITU P.861 provisionally recommends
MOS calculation. A value of 0.4 is sometimes found in listening only
experiments. Concerning a conversational quality prediction, a silence weight
of 0.0 is recommended.
Note:
An interpretation of MOS values using different playback level
settings is dangerous. If the playback level is decreased, the noise
disturbance will decrease, thus leading to an increase in MOS.
There is no experimental data available to verify this level
dependency of the MOS value.
This diagram type (see Figure 6.18) shows the PSQM MOS over all frames in
the history buffer. This figure is not an averaged value and no weighting factor is
used for this result value. When scrolling through the buffer, a pink cursor
indicates the current position within the diagram.
Figure 6.18: The MOS vs. Time diagram type
This window (Figure 6.19) shows the most important results at the end of the
measurement. The end is defined by the stop point according to P.861, which
means that trailing silence before the end of the input files/streams is excluded.
The content of this diagram remains constant even when scrolling back through
the history buffer. To scroll back in the buffer to find the moment of the stop
point, just remember the "Rel. Time" field of this diagram and scroll back
through the buffer until the "Rel. Time" field of any of the other diagrams
matches this value.
B A N D V O I C E Q U A L I T Y
a silence weight of 0.2 to be used for the
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MOS vs. Time
Final Results