Advanced Version - OPTICOM OPERA - V 3.5 User Manual

C H A P T E R 5 :
temporal resolution is in the same range as the timing of any backward masking
effects, which therefore can not be modelled. Nevertheless, experiments have
shown that backward masking is very coarsely modelled by side effects of the
FFT.
Using the feature extractor, eleven MOVs are extracted from the comparison of
the Ear model output. Table 5.1 shows a list of those MOVs and their
interpretation. For further information about the MOVs please refer to the
papers of the ITU-R recommendation BS.1387 in the appendix.
Note:
The lowered index "B" indicates an MOV of the ear model of the
Basic version. A lowered "A" (see Table 5.2) indicates an
MOV of the ear model of the Advanced version, respectively.
Model Output Variable (MOV)
WinModDiff1
B
AvgModDiff1
B
AvgModDiff2
B
RmsNoiseLoud
BandwidthRef
B
BandwidthTest
RelDistFrames
B
Total NMR
B
MFPD
B
ADB
B
EHS
B
Table 5.1: MOVs used by the PEAQ "Basic" version, and their interpretation

5.4.4 Advanced Version

The "Advanced" version uses some MOVs derived by implementing the ear
model of the "Basic" version but in addition to that, the "Advanced" version
introduces a second ear model with improved temporal resolution, as illustrated
in Figure 5.4.
Compared to the "Basic" version, the "Advanced" version model performs the
time to frequency warping using a filter bank, consequently grouping the signal
into 40 auditory bands with a temporal resolution of approximately 0.66 ms.
This allows for a very accurate modelling of backward masking effects. After the
calculation of backward and simultaneous masking, the signal is sub-sampled
by a factor of 1:6 in order to improve the computational efficiency. Following
the addition of the internal noise to the sub-sampled signal and finally
modelling the forward masking effects, the output of this model is again the
excitation.
W I D E B A N D A U D I O
Changes in modulation
Loudness of the distortion
B
Linear distortions
B
Frequency of audible distortions
Noise-to-mask ratio
Detection probability
Harmonic structure of the error
Q U A L I T Y T E S T I N G
Interpretation
(related to roughness)
(frequency response etc.)
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