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4 SUBJECTIVE TESTING
The motivation for the development of objective models like PESQ, 3SQM and PEVQ is that they deliver quickly
repeatable results with only a simple test setup for a much lower price than subjective tests. Subjective tests
require a number of test persons, which have to listen to an audio file or watch a video sequence, while they have
to score them. Often a separate room needs to be installed were the tests can take place; appointments have to
be made with the test persons, and then it often takes even days until the first test results become available. In
some applications subjective tests are even prohibitive.
However, subjective tests are a crucial task before objective measurement algorithms can be developed at all.
This is because objective measurement algorithms model subjective tests. Only with a big fund of subjective
measurement data objective algorithms can be made robust enough to accurately predict the human quality
scoring.
At OPTICOM we conducted such subjective measurements of video quality in cooperation with the Institute for
Mobile Communications at the University of Erlangen-Nuernberg. The picture below shows the test room, the
scoring device and the display where the video sequences were played back. Of course all the used equipment
and the test procedure were selected and prepared to match the required standards of the ITU-T and the VQEG.
Figure 4-1 Viewing test room at the University of Erlangen where
OPTICOM conducted subjective tests. The test subject watches a
scene on an adjusted TFT screen from a well defined distance. By
pressing one of the keys, the test subject will be able to score the
scene on the 5 point opinion scale.
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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