Hani Alers

Studying the effect of optimizing image quality in salient regions at the expense of background content

Abstract. Manufacturers of commercial display devices continuously try to improve the perceived image quality of their products. By applying postprocessing techniques on the incoming signal, they aim to enhance the quality level perceived by the viewer. These postprocessing techniques are usually applied globally over the whole image but may cause side effects, the visibility and annoyance of which differ with local content characteristics. To better understand and utilize this, a three-phase experiment was conducted where observers were asked to score images that had different levels of quality in their regions of interest and in the background areas. The results show that the region of interest has a greater effect on the overall quality of the image than the background. This effect increases with the increasing quality difference between the two regions. Based on the subjective data we propose a model to predict the overall quality of images with different quality levels in different regions. This model, which is constructed on empirical bases, can help craft weighted objective metrics that can better approximate subjective quality scores.

Distributed collaborative situation-map making for disaster response

A situation map that shows the overview of a disaster situation serves as a valuable tool for disaster response teams. It helps them to orientate their location and to make disaster response decisions. It is, however, a complicated task to rapidly generate a complete and comprehensive situation map of a disaster area, particularly due to the centralized organization of disaster management and the limited emergency services. In this study, we propose to let the affected population be utilised as an additional resource that can actively help to make such a situation map. The aim of this study was to investigate the possibility of constructing a shared situation map using a collaborative distributed mechanism. By examining earlier research, a detailed list of potential problems is identified in the collaborative map-making process. These problems were then addressed in an experiment which evaluated a number of proposed solutions. The results showed that more collaboration channels led to a situation map of better quality, and that including confidence information for objects and events in the map helped the discussion process during the map-making.

Comparing Subjective Image Quality Measurement Methods for the Creation of Public Databases

The Single Stimulus (SS) method is often chosen to collect subjective data testing no-reference objective metrics, as it is straightforward to implement and well standardized. At the same time, it exhibits some drawbacks; spread between different assessors is relatively large, and the measured ratings depend on the quality range spanned by the test samples, hence the results from different experiments cannot easily be merged . The Quality Ruler (QR) method has been proposed to overcome these inconveniences. This paper compares the performance of the SS and QR method for pictures impaired by Gaussian blur. The research goal is, on one hand, to analyze the advantages and disadvantages of both methods for quality assessment and, on the other, to make quality data of blur impaired images publicly available. The obtained results show that the confidence intervals of the QR scores are narrower than those of the SS scores. This indicates that the QR method enhances consistency across assessors. Moreover, QR scores exhibit a higher linear correlation with the distortion applied. In summary, for the purpose of building datasets of subjective quality, the QR approach seems promising from the viewpoint of both consistency and repeatability.

Studying the effect of optimizing the image quality in saliency regions at the expense of background content

Manufacturers of commercial display devices continuously try to improve the perceived image quality of their products. By applying some post processing techniques on the incoming image signal, they aim to enhance the quality level perceived by the viewer. Applying such techniques may cause side effects on different portions of the processed image. In order to apply these techniques effectively to improve the overall quality, it is vital to understand how important quality is for different parts of the image. To study this effect, a three-phase experiment was conducted where observers were asked to score images which had different levels of quality in their saliency regions than in the background areas. The results show that the saliency area has a greater effect on the overall quality of the image than the background. This effect increases with the increasing quality difference between the two regions. It is, therefore, important to take this effect into consideration when trying to enhance the appearance of specific image regions.

Examining the effect of task on viewing behavior in videos using saliency maps

Research has shown that when viewing still images, people will look at these images in a different manner if instructed to evaluate their quality. They will tend to focus less on the main features of the image and, instead, scan the entire image area looking for clues for its level of quality. It is questionable, however, whether this finding can be extended to videos considering their dynamic nature. One can argue that when watching a video the viewer will always focus on the dynamically changing features of the video regardless of the given task. To test whether this is true, an experiment was conducted where half of the participants viewed videos with the task of quality evaluation while the other half were simply told to watch the videos as if they were watching a movie on TV or a video downloaded from the internet. The videos contained content which was degraded with compression artifacts over a wide range of quality. An eye tracking device was used to record the viewing behavior in both conditions. By comparing the behavior during each task, it was possible to observe a systematic difference in the viewing behavior which seemed to correlate to the quality of the videos.

A SmartTV Platform for Wellbeing, Care and Social Support for Elderly at Home

This paper presents Care@Home, a smartTV platform integrating assistive living services for elderly in their homes. The SmartTV is acting as a user-centered ‘hub’ providing communication that connects the elderly to their formal care network, family, friends, communities, and provides services including household help, healthcare, exercise programmes and entertainment. The paper highlights Care@Home as a low-cost, personalized and open platform that is flexible and easy-to-use. We describe the human-centered design and first results from user studies.

Quantifying the importance of preserving video quality in visually important regions at the expense of background content

Advances in digital technology have allowed us to embed significant processing power in everyday video consumption devices. At the same time, we have placed high demands on the video content itself by continuing to increase spatial resolution while trying to limit the allocated file size and bandwidth as much as possible. The result is typically a trade-off between perceptual quality and fulfillment of technological limitations. To bring this trade-off to its optimum, it is necessary to understand better how people perceive video quality. In this work, we particularly focus on understanding how the spatial location of compression artifacts impacts visual quality perception, and specifically in relation with visual attention. In particular we investigate how changing the quality of the region of interest of a video affects its overall perceived quality, and we quantify the importance of the visual quality of the region of interest to the overall quality judgment. A three stage experiment was conducted where viewers were shown videos with different quality levels in different parts of the scene. By asking them to score the overall quality we found that the quality of the region of interest has 10 times more impact than the quality of the rest of the scene. These results are in line with similar effects observed in still images, yet in videos the relevance of the visual quality of the region of interest is twice as high than in images. The latter finding is directly relevant for the design of more accurate objective quality metrics for videos, that are based on the estimation of local distortion visibility. When watching videos, attention is drawn mainly to the region of interest.Quality of the region of interest can dictate overall perceived quality in videos.Region of interest effects overall perceived quality similarly in images and videos.

Effects of task and image properties on visual-attention deployment in image-quality assessment

Abstract. It is important to understand how humans view images and how their behavior is affected by changes in the properties of the viewed images and the task they are given, particularly the task of scoring the image quality (IQ). This is a complex behavior that holds great importance for the field of image-quality research. This work builds upon 4 years of research work spanning three databases studying image-viewing behavior. Using eye-tracking equipment, it was possible to collect information on human viewing behavior of different kinds of stimuli and under different experimental settings. This work performs a cross-analysis on the results from all these databases using state-of-the-art similarity measures. The results strongly show that asking the viewers to score the IQ significantly changes their viewing behavior. Also muting the color saturation seems to affect the saliency of the images. However, a change in IQ was not consistently found to modify visual attention deployment, neither under free looking nor during scoring. These results are helpful in gaining a better understanding of image viewing behavior under different conditions. They also have important implications on work that collects subjective image-quality scores from human observers.

Efficient neural-network–based no-reference approach to an overall quality metric for JPEG and JPEG2000 compressed images

Reliably assessing overall quality of JPEG/JPEG2000 coded images without having the original image as a reference is still challenging, mainly due to our limited understanding of how humans combine the various perceived artifacts to an overall quality judgment. A known approach to avoid the explicit simulation of human assessment of overall quality is the use of a neural network. Neural network approaches usually start by selecting active features from a set of generic image characteristics, a process that is, to some extent, rather ad hoc and computationally extensive. This paper shows that the complexity of the feature selection procedure can be considerably reduced by using dedicated features that describe a given artifact. The adaptive neural network is then used to learn the highly nonlinear relationship between the features describing an artifact and the overall quality rating. Experimental results show that the simplified feature selection procedure, in combination with the neural network, indeed are able to accurately predict perceived image quality of JPEG/JPEG2000 coded images.

Towards Community-Based Co-creation

Current AAL solutions are often rejected by senior end-users, who do not perceive their benefits or themselves as the target group. This is due to the prevailing technology-driven design process that does not account for human needs. To shift the focus from the technology to the human, involvement of stakeholders in the design process is crucial. In this paper we outline some issues with involvement and continuous engagement of seniors and propose the concept of community-based co-creation as a way forward. Key is the facilitation of long-term collaboration of a community comprised of stakeholders including among others seniors, caregivers and researchers. Their neighborhoods serve as a natural context for designing and implementing their own solutions. We raise several points for consideration and first steps to be discussed.