OPTICOM OPERA Broadcast, User Manual

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C H A P T E R 6 : T E L E P H O N Y B A N D V O I C E Q U A L I T Y
T E S T I N G
135
Keyword Add. Parameters Comment
HothNoise Use background masking
noise
HothNoiseLevel Level of Hoth
noise in dBSPL
Level of background
masking noise
ListeningLevel Level of a 1kHz
0dBov sine tone
in dBSPL
Listening level acc.
to P.861
UpperFreq Frequency in Hz specify upper
frequency limit for
measuring
Flat Listening condition:
Flat frequency
response
IRS Listening condition:
IRS
telephone) filtering
Headphones Listening condition:
Headphones
HeadphonesDiff Listening condition:
Headphones (diffuse
field)
Speakers Listening condition:
Loudspeakers
Table 6.5:
PSQM specific command line parameters.
6.5.6 Common Mistakes
When all of your measurement results show a MOS of 5.0, while at the same
time clearly audible distortions exist, please check the following:
•
Are the correct files used?
•
Are the listening level and the upper frequency limit set up properly (check
under Algorithm Properties)?
•
If "Delay Tracking" is enabled, it will discard all frames, for which it could
not detect a reliable delay. In extreme cases this may result in almost all
invalid frames and the default score of 5.0.
If you always measure a MOS of 1.0, the most frequent reason is – despite the
trivial solution of mixed up files – that either the Delay Compensation algorithm
is not set to "Auto", or that the delay can not be compensated by the system due
to its length or variation. Check the delay status. If it is very low (<40) then
examine the time signals and verify that the waveforms of the reference and the
test signal do indeed match. Assuming the delay is simply too long, you can try
setting a static delay offset. Supposing it varies too much, the scope of P.861 is
exceeded in any case and measurements should be performed with PESQ.
There are clearly
Audible Distortions,
but PSQM scores
around 5.0
I always measure a
MOS near 1.0