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those frames are compared to each other that also correspond to each other. It takes into account that variable
temporal frame delays as well as shifts of the frame's content may have occurred due to the coding procedure.
The second block calculates the perceptual difference of the aligned signals. The perceptual difference is a
weighted difference between a reference and an impaired signal with the emphasis on those artefacts, which are
perceived by a human viewer. The module considers the differences in the luminance and chrominance domain
and calculates quality indicators from them. Furthermore the activity of the motion in the reference signal provides
another indicator representing the temporal information. This indicator is important as it takes into account that in
frame series with low activity the perception of details is much higher than in frame series with quick motion.
The third block in figure 1 classifies the previously calculated indicators and detects certain types of distortions.
Finally, in the fourth block all the appropriate indicators according to the detected distortions are aggregated,
forming the final result - the mean opinion score (MOS). The representation of the objective quality by a MOS is
already known from speech quality models like PESQ and 3SQM. The MOS value describes the video quality on a
range from 1 for very bad quality, to 5 for excellent quality. Beside the final quality score additional internal
indicators are provided at the output of the algorithm for further cause analysis.
6.2 Supported File Formats
PEVQ is continously being improved. Missing features can be added quickly to this product. For further information
please contact OPTICOM via email
Supported frame format resolutions:
CIF (352x288 pixels)
QCIF (176x144 pixels)
VGA (640x480 pixels)
Supported video file format:
Microsoft AVI with RGB24 data
Supported frame rates:
Basically all frame rates (30, 25, 15, 12.5, 8, 5, 2.5fps) are supported but it is recommended that reference
files have a frame rate of 25fps. NOTE: Reference and impaired video file pair must have the same frame
rate. If they have different frame rates up sampling of the file with lower frame rate is required – down
sampling would possibly mean loss of information.
The current version of PEVQ is optimized for CIF sized video streams. VGA and QCIF formats should however work
nevertheless, but with reduced prediction accuracy.
6.3 Features and Limitations of PEVQ
Currently there are no known limitations of PEVQ. But due to the early stage of the development, it is assumed
that the prediction accuracy will continuously be improved.
info@opticom.de
or have a look at our web site www.opticom.de.
A D V A N C E D
E V A L U A T I O N
O F
P E R C E P T U A L
V I D E O
Q U A L I T Y
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