To understand the viewing strategies employed in a quality estimation task, we compared two visual tasks—quality estimation and difference estimation. The estimation was done for a pair of natural images having small global changes in quality. Two groups of observers estimated the same set of images, but with different instructions. One group estimated the difference in quality and the other the difference between image pairs. The results demonstrated the use of different visual strategies in the tasks. The quality estimation was found to include more visual planning during the first fixation than the difference estimation, but afterward needed only a few long fixations on the semantically important areas of the image. The difference estimation used many short fixations. Salient image areas were mainly attended to when these areas were also semantically important. The results support the hypothesis that these tasks’ general characteristics (evaluation time, number of fixations, area fixated on) show differences in processing, but also suggest that examining only single fixations when comparing tasks is too narrow a view. When planning a subjective experiment, one must remember that a small change in the instructions might lead to a noticeable change in viewing strategy.
The most common tasks in subjective image estimation are change detection (a detection task) and image quality
estimation (a preference task). We examined how the task influences the gaze behavior when comparing detection and
preference tasks. The eye movements of 16 naïve observers were recorded with 8 observers in both tasks. The setting
was a flicker paradigm, where the observers see a non-manipulated image, a manipulated version of the image and again
the non-manipulated image and estimate the difference they perceived in them. The material was photographic material
with different image distortions and contents. To examine the spatial distribution of fixations, we defined the regions of
interest using a memory task and calculated information entropy to estimate how concentrated the fixations were on the
image plane. The quality task was faster and needed fewer fixations and the first eight fixations were more concentrated
on certain image areas than the change detection task. The bottom-up influences of the image also caused more variation
to the gaze behavior in the quality estimation task than in the change detection task The results show that the quality
estimation is faster and the regions of interest are emphasized more on certain images compared with the change
detection task that is a scan task where the whole image is always thoroughly examined. In conclusion, in subjective
image estimation studies it is important to think about the task.
In this study, two experiments were conducted to evaluate the psycho-physiological effects by practical use of monocular
head-mounted display (HMD) in a real-world environment, based on the assumption of consumer-level applications as
viewing video content and receiving navigation information while walking. In the experiment 1, the workload was
examined for different types of presenting stimuli using an HMD (monocular or binocular, see-through or non-see-through).
The experiment 2 focused on the relationship between the real-world environment and the visual information
presented using a monocular HMD. The workload was compared between a case where participants walked while
viewing video content without relation to the real-world environment, and a case where participants walked while
viewing visual information to augment the real-world environment as navigations.
We measured the eye movements of participants who watched a 6-minute movie in stereoscopic and non-stereoscopic
form. We analyzed four shots of the movie. The results indicate that in a 2D movie viewers tended to look at the actors,
as most of the eye movements were clustered there. The significance of the actors started at the beginning of a shot, as
the eyes of the viewer focused almost immediately to them. In S3D movie the eye movement patterns were more widely
distributed to other targets. For example, complex stereoscopic structures and objects nearer than the actor captured the
interest and eye movements of the participants. Also, the tendency to first look at the actors was diminished in the S3D
shots. The results suggests that in a S3D movie there are more eye movements which are directed to wider array of objects
than in a 2D movie.
In this paper, the authors conducted an experiment to evaluate the UX in an actual outdoor environment, assuming the
casual use of monocular HMD to view video content while short walking. In conducting the experiment, eight subjects
were asked to view news videos on a monocular HMD while walking through a large shopping mall. Two types of
monocular HMDs and a hand-held media player were used, and the
psycho-physiological responses of the subjects were
measured before, during, and after the experiment. The VSQ, SSQ and NASA-TLX were used to assess the subjective
workloads and symptoms. The objective indexes were heart rate and stride and a video recording of the environment in
front of the subject's face. The results revealed differences between the two types of monocular HMDs as well as
between the monocular HMDs and other conditions. Differences between the types of monocular HMDs may have been
due to screen vibration during walking, and it was considered as a major factor in the UX in terms of the workload.
Future experiments to be conducted in other locations will have higher cognitive loads in order to study the performance
and the situation awareness to actual and media environments.
We present a Videospace framework for classification of selected videos with chosen user-groups, device-types or
device-classes. Photospace has proven to be effective in classifying large amounts of still images via simple technical
parameters. We use the measures of subject-camera distance, scene lighting and object motion to classify single videos
and finally represent all videos of the chosen group in a
3-dimensional space. An expert-rated sample of video was
collected to obtain an estimation of the parameters for a chosen group of videos. Sub-groups of videos were found using
Videospace measures. The presented framework can be used to obtain information about technical requirements of
general device use and typical shooting conditions of the end users. Future measurement efficiency and precision could
be improved by using computer-based algorithms or device based measurement techniques to obtain better samples
Videospace parameters. Videospace information could be used for finding the most meaningful benchmarking contexts
or getting information about shooting in general with chosen devices or devices groups. Using information about typical
parameters for a chosen video group, algorithm and device development can be focused on typical shooting situations, if
processing power and device-size are otherwise reduced.
Subjective image quality data for 9 image processing pipes and 8 image contents (taken with mobile phone
camera, 72 natural scene test images altogether) from 14 test subjects were collected. A triplet comparison setup
and a hybrid qualitative/quantitative methodology were applied. MOS data and spontaneous, subjective
image quality attributes to each test image were recorded. The use of positive and negative image quality
attributes by the experimental subjects suggested a significant difference between the subjective spaces of low
and high image quality. The robustness of the attribute data was shown by correlating DMOS data of the test
images against their corresponding, average subjective attribute vector length data. The findings demonstrate
the information value of spontaneous, subjective image quality attributes in evaluating image quality at variable
quality levels. We discuss the implications of these findings for the development of sensitive performance
measures and methods in profiling image processing systems and their components, especially at high image
quality levels.
KEYWORDS: 3D displays, 3D image processing, Mobile devices, Image quality, Visualization, 3D vision, Glasses, Large screens, Small screens, 3D visualizations
High-quality stereoscopic image content must be viewable in a variety of visual environments, from 3-D theaters to 3-D
mobile devices. Stereoscopic effects, however, are affected by screen size, viewing distance, and other parameters. In
this study, the authors focus on the stereoscopic image quality experience of viewing 3-D content on a mobile device in
order to compare it with that of viewing 3-D content on a large screen. The stereoscopic image quality experience was
evaluated using Interpretation Based Quality (IBQ) methodology, which combines existing approaches to image quality
evaluation, such as the paired comparison and interview, and assesses the viewer experience using both quantitative and
qualitative data. Five stereoscopic images were used in the experiment. The results of the experiment suggest that the
discomfort felt while viewing stereoscopic images on a 3-D mobile device arise from not only visual fatigue but also the
effects of the smaller screen size. The study also revealed the types of stereoscopic images that are suitable for viewing
on 3-D mobile devices.
Subjective quality rating does not reflect the properties of the image directly, but it is the outcome of a quality decision
making process, which includes quantification of subjective quality experience. Such a rich subjective content is often
ignored. We conducted two experiments (with 28 and 20 observers), in order to study the effect of paper grade on image
quality experience of the ink-jet prints. Image quality experience was studied using a grouping task and a quality rating
task. Both tasks included an interview, but in the latter task we examined the relations of different subjective attributes in
this experience. We found out that the observers use an attribute hierarchy, where the high-level attributes are more
experiential, general and abstract, while low-level attributes are more detailed and concrete. This may reflect the
hierarchy of the human visual system. We also noticed that while the observers show variable subjective criteria for IQ,
the reliability of average subjective estimates is high: when two different observer groups estimated the same images in
the two experiments, correlations between the mean ratings were between .986 and .994, depending on the image
content.
KEYWORDS: 3D image processing, 3D displays, Visualization, Safety, Prototyping, Image analysis, 3D imaging standards, Software development, Standards development, Algorithm development
Digital 3D cinema has recently become popular and a number of high-quality 3D films have been produced. However, in
contrast with advances in 3D display technology, it has been pointed out that there is a lack of suitable 3D content and
content creators. Since 3D display methods and viewing environments vary widely, there is expectation that high-quality
content will be multi-purposed. On the other hand, there is increasing interest in the bio-medical effects of image content
of various types and there are moves toward international standardization, so 3D content production needs to take into
consideration safety and conformity with international guidelines. The aim of the authors' research is to contribute to the
production and application of 3D content that is safe and comfortable to watch by developing a scalable 3D conversion technology. In this paper, the authors focus on the process of changing the screen size, examining a conversion algorithm and its effectiveness. The authors evaluated the visual load imposed during the viewing of various 3D content converted by the prototype algorithm as compared with ideal conditions and with content expanded without conversion. Sheffe's paired comparison method was used for evaluation. To examine the effects of screen size reduction on viewers, changes in user impression and experience were elucidated using the IBQ methodology. The results of the evaluation are presented along with a discussion of the effectiveness and potential of the developed scalable 3D conversion algorithm
and future research tasks.
The subjective quality of an image is a non-linear product of several, simultaneously contributing subjective factors such
as the experienced naturalness, colorfulness, lightness, and clarity. We have studied subjective image quality by using a
hybrid qualitative/quantitative method in order to disclose relevant attributes to experienced image quality. We describe
our approach in mapping the image quality attribute space in three cases: still studio image, video clips of a talking head
and moving objects, and in the use of image processing pipes for 15 still image contents. Naive observers participated in
three image quality research contexts in which they were asked to freely and spontaneously describe the quality of the
presented test images. Standard viewing conditions were used. The data shows which attributes are most relevant for
each test context, and how they differentiate between the selected image contents and processing systems. The role of
non-HVS based image quality analysis is discussed.
Stereoscopic technologies have developed significantly in recent years. These advances require also more understanding
of the experiental dimensions of stereoscopic contents. In this article we describe experiments in which we explore the
experiences that viewers have when they view stereoscopic contents. We used eight different contents that were shown
to the participants in a paired comparison experiment where the task of the participants was to compare the same content
in stereoscopic and non-stereoscopic form. The participants indicated their preference but were also interviewed about
the arguments they used when making the decision. By conducting a qualitative analysis of the interview texts we
categorized the significant experiental factors related to viewing stereoscopic material. Our results indicate that reality-likeness
as well as artificiality were often used as arguments in comparing the stereoscopic materials. Also, there were
more emotional terms in the descriptions of the stereoscopic films, which might indicate that the stereoscopic projection
technique enhances the emotions conveyed by the film material. Finally, the participants indicated that the three-dimensional
material required longer presentation time, as there were more interesting details to see.
This study presents a methodology of forming contextually valid scales for subjective video quality measurement. Any
single value of quality e.g. Mean Opinion Score (MOS) can have multiple underlying causes. Hence this kind of a
quality measure is not enough for example, in describing the performance of a video capturing device. By applying
Interpretation Based Quality (IBQ) method as a qualitative/quantitative approach we have collected attributes familiar to the end user and that are extracted directly from the material offered by the observers' comments. Based on these
findings we formed contextually valid assessment scales from the typically used quality attributes. A large set of data
was collected from 138 observers to generate the video quality vocabulary. Video material was shot by three types of
video cameras: Digital video cameras (4), digital still cameras (9) and mobile phone cameras (9). From the quality
vocabulary, we formed 8 unipolar 11-point scales to get better insight of video quality. Viewing conditions were adjusted
to meet the ITU-T Rec. P.910 requirements. It is suggested that the applied qualitative/quantitative approach is especially
efficient for finding image quality differences in video material where the quality variations are multidimensional in
nature and especially when image quality is rather high.
Due to the rise in performance of digital printing, image-based applications are gaining popularity. This creates needs for
specifying the quality potential of printers and materials in more detail than before. Both production and end-use
standpoints are relevant. This paper gives an overview of an
on-going study which has the goal of determining a
framework model for the visual quality potential of paper in color image printing. The approach is top-down and it is
founded on the concept of a layered network model. The model and its subjective, objective and instrumental
measurement layers are discussed. Some preliminary findings are presented. These are based on data from samples
obtained by printing natural image contents and simple test fields on a wide range of paper grades by ink-jet in a color
managed process. Color profiles were paper specific. Visual mean opinion score data by human observers could be
accounted for by two or three dimensions. In the first place these are related to brightness and color brightness. Image
content has a marked effect on the dimensions. This underlines the challenges in designing the test images.
The psychological complexity of multivariate image quality evaluation makes it difficult to develop general image quality metrics. Quality evaluation includes several mental processes and ignoring these processes and the use of a few test images can lead to biased results. By using a qualitative/quantitative (Interpretation Based Quality, IBQ) methodology, we examined the process of pair-wise comparison in a setting, where the quality of the images printed by laser printer on different paper grades was evaluated. Test image consisted of a picture of a table covered with several objects. Three other images were also used, photographs of a woman, cityscape and countryside. In addition to the pair-wise comparisons, observers (N=10) were interviewed about the subjective quality attributes they used in making their quality decisions. An examination of the individual pair-wise comparisons revealed serious inconsistencies in observers' evaluations on the test image content, but not on other contexts. The qualitative analysis showed that this inconsistency was due to the observers' focus of attention. The lack of easily recognizable context in the test image may have contributed to this inconsistency. To obtain reliable knowledge of the effect of image context or attention on subjective image quality, a qualitative methodology is needed.
Subjective evaluation is used to identify impairment factors of multimedia quality. The final quality is often formulated
via quantitative experiments, but this approach has its constraints, as subject's quality interpretations, experiences and
quality evaluation criteria are disregarded. To identify these quality evaluation factors, this study examined qualitatively
the criteria participants used to evaluate audiovisual video quality. A semi-structured interview was conducted with 60
participants after a subjective audiovisual quality evaluation experiment. The assessment compared several, relatively
low audio-video bitrate ratios with five different television contents on mobile device. In the analysis, methodological
triangulation (grounded theory, Bayesian networks and correspondence analysis) was applied to approach the qualitative
quality. The results showed that the most important evaluation criteria were the factors of visual quality, contents,
factors of audio quality, usefulness - followability and audiovisual interaction. Several relations between the quality
factors and the similarities between the contents were identified. As a research methodological recommendation, the
focus on content and usage related factors need to be further examined to improve the quality evaluation experiments.
We present an effective method for comparing subjective audiovisual quality and the features related to the quality
changes of different video cameras. Both quantitative estimation of overall quality and qualitative description of critical
quality features are achieved by the method. The aim was to combine two image quality evaluation methods, the
quantitative Absolute Category Rating (ACR) method with hidden reference removal and the qualitative Interpretation-
Based Quality (IBQ) method in order to see how they complement each other in audiovisual quality estimation tasks. 26
observers estimated the audiovisual quality of six different cameras, mainly mobile phone video cameras. In order to
achieve an efficient subjective estimation of audiovisual quality, only two contents with different quality requirements
were recorded with each camera. The results show that the subjectively important quality features were more related to
the overall estimations of cameras' visual video quality than to the features related to sound. The data demonstrated two
significant quality dimensions related to visual quality: darkness and sharpness. We conclude that the qualitative
methodology can complement quantitative quality estimations also with audiovisual material. The IBQ approach is
valuable especially, when the induced quality changes are multidimensional.
There are innumerable concepts, terms and definitions for user experience. Few of them have a solid empirical foundation.
In trying to understand user experience in interactive technologies such as computer games and virtual environments,
reliable and valid concepts are needed for measuring relevant user reactions and experiences. Here we present
our approach to create both theoretically and methodologically sound methods for quantification of the rich user experience
in different digital environments. Our approach is based on the idea that the experience received from a content
presented with a specific technology is always a result of a complex psychological interpretation process, which components
should be understood. The main aim of our approach is to grasp the complex and multivariate nature of the experience
and make it measurable. We will present our two basic measurement frameworks, which have been developed
and tested in large data set (n=2182). The 15 measurement scales extracted from these models are applied to digital
gaming with a head-mounted display and a table-top display. The results show how it is possible to map between experience,
technology variables and the background of the user (e.g., gender). This approach can help to optimize, for
example, the contents for specific viewing devices or viewing situations.
The visual quality of images is outward in image presentation, compression and analysis. Depending on the use, the quality of images may give more information or more experiences to the viewer. However, the relations between mathematical and human methods for grouping the images are not obvious. For example, different humans think differently and so, they make the grouping differently. However, there may be some connections between image mathematical features and human selections. Here we try to find such relations that could give more possibilities for developing the actual quality of images for different purposes. In this study, we present some methods and preliminary results that are based on psychological tests to humans, MPEG-7 based features of the images and face detection methods. We also show some notes and questions belonging to this problem and plans for the future research.
Stereoscopic display produces enhanced game playing experience for the user. However, this experience might be affected by eye strain symptoms produced by the convergence-accommodation conflict in the visual system. In this study we measured the level of sickness symptoms in mobile stereoscopic game playing situation. Our results showed that playing a mobile game with an autostereoscopic display did not cause eye strain that differed from eye strain caused by ordinary mobile device usage. The results suggest that with sufficiently small disparities a mobile stereoscopic display can be used to achieve a comfortable user experience. We also found links between experienced sickness symptoms and background variables. Firstly, our results indicated that females reported higher symptom levels than males. Secondly, we showed that the participants with higher susceptibility to motion sickness reported higher sickness
levels in the experiment. Thirdly, we showed that participants with less computes skills or with less enthusiastic attitude towards new technology had significantly more sickness symptoms than the other participants.
Image evaluation schemes must fulfill both objective and subjective requirements. Objective image quality evaluation models are often preferred over subjective quality evaluation, because of their fastness and cost-effectiveness. However, the correlation between subjective and objective estimations is often poor. One of the key reasons for this is that it is not known what image features subjects use when they evaluate image quality. We have studied subjective image quality evaluation in the case of image sharpness. We used an Interpretation-based Quality (IBQ) approach, which combines both qualitative and quantitative approaches to probe the observer's quality experience. Here we examine how naive subjects experienced and classified natural images, whose sharpness was changing. Together the psychometric and qualitative information obtained allows the correlation of quantitative evaluation data with its underlying subjective attribute sets. This offers guidelines to product designers and developers who are responsible for image quality. Combining these methods makes the end-user experience approachable and offers new ways to improve objective image quality evaluation schemes.
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