In this work, we studied how video compression and lightness scaling interact to affect the overall video quality and the
color quality attributes. We examined three subjective attributes: perceived color preference, perceived color
naturalness, and overall annoyance as digital videos were subjected to compression and lightness scaling.
Psychophysical experiments were carried out in which naïve subjects made numerical judgments of the three subjective
attributes. We found that preference and naturalness scores are concave down functions of mean lightness with an
associated maximum, while annoyance scores are concave up with an associated minimum. As compression increases,
both preference and naturalness scores decrease and vary less with mean lightness. Maximum preference, naturalness,
and annoyance scores generally occur at similar mean lightness values. Preference, naturalness, and annoyance scores
for individual videos, are approximated relatively well by Gaussian functions of mean lightness. Preference and
naturalness scores decreases while annoyance scores increase as an S-shaped function of the logarithm of the total
squared error. A three-parameter model is shown to provide a good description of how each attribute depends on
lightness and compression for individual videos. Model parameters vary with video content.
KEYWORDS: Video, Video compression, Video processing, Affine motion model, Data modeling, Distortion, Digital video discs, Statistical analysis, Psychology, Electronic imaging
In this work, we studied how video compression and color scaling interact to affect the overall video quality and the
color quality attributes. We examined the three subjective attributes: perceived color preference, perceived color
naturalness, and overall annoyance, as digital videos were subjected to compression and chroma scaling. Our objectives
were: (1) to determine how the color chroma scaling of compressed digital videos affected the mean color preference
and naturalness and overall annoyance ratings across subjects and (2) to determine how preference, naturalness, and
annoyance were related. Psychophysical experiments were carried out in which naïve subjects made numerical
judgments of these three attributes. Preference and naturalness scores increased to a maximum and decreased as the
mean chroma of the videos increased. As compression increased, both preference and naturalness scores decreased and
they varied less with mean chroma. Naturalness scores tended to reach a maximum at lower mean chroma than
preference scores. Annoyance scores decreased to a minimum and then increased as mean chroma increased. The mean
chroma at which annoyance was minimum was less than the mean chroma at which naturalness and preference were
maximum. Preference, naturalness, and annoyance scores for individual videos, were approximated relatively well by
Gaussian functions of mean chroma. Preference and naturalness scores decreased linearly as a function of the logarithm
of the total squared error, while annoyance scores increased as an S-shaped function of the logarithm of the total squared
error. A three-parameter model is shown to provide a good description of how each attribute depends on chroma and
compression for individual videos. Model parameters vary with video content.
KEYWORDS: Video, Molybdenum, Video processing, Algorithm development, Data modeling, CRTs, Psychology, Digital video discs, Video compression, Distortion
In this study, we examined the subjective attributes of color preference and perceived naturalness of digital videos when the chroma of the color content was varied. More specifically, the objectives were: (1) to determine how the scaling of color chroma affected the mean color preference rating and the mean naturalness rating across subjects and (2) to determine how preference and naturalness were related. To this end, psychophysical experiments were carried out in which naive subjects provided us with their subjective assessments of these two attributes. Data from the experiments indicated that for both preference and naturalness, the mean opinion scores (MOS) increased to a maximum and decreased as the mean chroma (MC) of the videos was varied. NaturalnessMOS (NMOS) tended to reach a maximum at lower MC than preferenceMOS (PMOS). The maximums for both PMOS and NMOS occurred at relatively close MC levels for most of the videos. The individual functions relating MOS to chroma were modeled by simple Gaussian functions relatively well. However, the mean, amplitude and standard deviation varied with video. It was possible to reduce the total number of parameters from 36 to 15 parameters by making use of relationships between the model parameters. In this model the chroma corresponding to maximum preference is about 1.1 times the chroma corresponding to maximum naturalness.
In this work we describe a study on a limited number of artifacts in MPEG-2 compressed video with the primary aim to analyze how annoying these compression artifacts are. More specifically, the objectives were: (1) to determine how the subjective annoyances of individual artifacts contribute to the overall annoyance, (2) to obtain the subjective ranks of the artifacts, and (3) to determine what relationships exist between annoyance values and annoyance ranks. To this end, a psychophysical experiment was carried out in which observers provided us with their subjective assessment of video sequences. The results showed that at low compression bit-rates, the blocking artifacts were the most annoying, whereas at higher compression bit-rates the ringing artifacts were the most annoying. The blocking artifact had the highest mean annoyance rank across all videos and compression bit-rates. Mean annoyance values were ordered differently from mean annoyance ranks due to very high annoyance values associated with some artifacts. Overall annoyance was related to the total squared error by a Logistic function. Individual artifact annoyance was related to overall annoyance by a weighted Minkowski metric.
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