Jenni Radun

Measuring Stereoscopic Image Quality Experience with Interpretation Based Quality Methodology

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.

Content and quality: Interpretation-based estimation of image quality

Test image contents affect subjective image-quality evaluations. Psychometric methods might show that contents have an influence on image quality, but they do not tell what this influence is like, i.e., how the contents influence image quality. To obtain a holistic description of subjective image quality, we have used an interpretation-based quality (IBQ) estimation approach, which combines qualitative and quantitative methodology. The method enables simultaneous examination of psychometric results and the subjective meanings related to the perceived image-quality changes. In this way, the relationship between subjective feature detection, subjective preferences, and interpretations are revealed. We report a study that shows that different impressions are conveyed in five test image contents after similar sharpness variations. Thirty naïve observers classified and freely described the images after which magnitude estimation was used to verify that they distinguished the changes in the images. The data suggest that in the case of high image quality, the test image selection is crucial. If subjective evaluation is limited only to technical defects in test images, important subjective information of image-quality experience is lost. The approach described here can be used to examine image quality and it will help image scientists to evaluate their test images.

Convicted of fatigued driving: who, why and how?

Fatigue is a major cause of road traffic accidents. However, due to the blurred concept of fatigue and the lack of reliable testing devices (cf. the breath analyzer for alcohol levels), it is extremely difficult to incorporate fatigue in operationalized terms into either traffic or criminal law. Even though the Finnish Road Traffic Act explicitly forbids driving while tired, it is done only on a general level among other factors (sickness, etc.) that impair a drivers fitness to drive (Article 63). The present study was done to investigate the circumstances of fatigue driving offenses. From the Finnish Vehicle Administration driver record database we extracted all drivers (N=768) punished under Article 63 from 2004-2005. Of these drivers, 90.4% committed a fatigue-related traffic offense. Accidents, predominantly single vehicle, were the most common (92.5%) consequence of fatigued driving. Although fatigue-related accidents are thought to be serious, our data shows that most of the accidents (81.6%) did not involve personal injuries. Almost every twentieth driver was punished because his vehicle was drifting on the road. The presence of alcohol or drugs was noted in 13% of the cases. Only 3.1% of the punished drivers officially denied being tired or falling asleep. Young men (< or =35 yrs) represented 50% of all punished drivers. Time of day and seasonal effects were clear in this data. This study shows that even without a reliable fatigue detector and unambiguous criteria for recognizing the contribution of fatigue to accident causation, Finnish police and the courts punish a significant number of drivers every year on the basis of fatigue.

Evaluating the multivariate visual quality performance of image-processing components

The estimation of image quality is a demanding task, especially when estimating different high-quality imaging products or their components. The challenge is the multivariate nature of image quality as well as the need to use naïve observers as test subjects, since they are the actual end-users of the products. Here, we use a subjective approach suitable for estimating the quality performance of different imaging device components with naïve observers—the interpretation-based quality (IBQ) approach. From two studies with 61 naïve observers, 17 natural image contents, and 13 different camera image signal processor pipelines, we determined the subjectively crucial image quality attributes and dimensions and the description of each pipelines perceived image quality performance. We found that the subjectively most important image quality dimensions were color shift/naturalness, darkness, and sharpness. The first dimension, which was related to naturalness and colors, distinguished the good-quality pipelines from the middle- and low-quality groups, and the dimensions of darkness and sharpness described why the quality failed in the low-quality pipelines. The study suggests that the high-level concept naturalness is a requirement for high-quality images, whereas quality can fail for other reasons in low-quality images, and this failure can be described by low-level concepts, such as darkness and sharpness.

What do users really perceive - : probing the subjective image quality

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 observers 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.

Seasonal variation of falling asleep while driving: An examination of fatal road accidents

Road accidents related to sleep show a clear time‐of‐day pattern. Following the previous finding that such accidents in Finland happen more often (absolutely and relatively) during the summer months, especially during the afternoon, the main aim of this study was to reveal the factors behind such seasonality. The data included the computerized database of the Finnish fatal road accident investigation system restricted to nonprofessional, nonintoxicated car drivers (N=1464) and sample of the original folders (N=101). The results of the analysis on the sample of the original folders showed that investigation teams adequately documented and explained their decisions concerning falling‐asleep accidents and that the observed seasonality is a real phenomenon, not a result of bias of the teams. With the exception of 26–35‐year‐olds, men of all of the other age groups had a notable absolute and relative increase of sleep‐related accidents in the summer. Young male drivers (≤25 yrs), followed by the oldest group (≥66 yrs) had the highest increase in the absolute number of sleep‐related accidents between the summer and winter months, while the relative change was the highest for ages 56–65. Women showed similar trends. A detailed analysis of 44 cases of summer afternoon falling‐asleep accidents revealed that many drivers were engaged in unusual activities the day or night before the accident. The findings are discussed in relation to different driving and lifestyle habits between seasons, including sleep quality.

Subjective experience of image quality: attributes, definitions, and decision making of subjective image quality

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.

Categorization of Natural Dynamic Audiovisual Scenes

This work analyzed the perceptual attributes of natural dynamic audiovisual scenes. We presented thirty participants with 19 natural scenes in a similarity categorization task, followed by a semi-structured interview. The scenes were reproduced with an immersive audiovisual display. Natural scene perception has been studied mainly with unimodal settings, which have identified motion as one of the most salient attributes related to visual scenes, and sound intensity along with pitch trajectories related to auditory scenes. However, controlled laboratory experiments with natural multimodal stimuli are still scarce. Our results show that humans pay attention to similar perceptual attributes in natural scenes, and a two-dimensional perceptual map of the stimulus scenes and perceptual attributes was obtained in this work. The exploratory results show the amount of movement, perceived noisiness, and eventfulness of the scene to be the most important perceptual attributes in naturalistically reproduced real-world urban environments. We found the scene gist properties openness and expansion to remain as important factors in scenes with no salient auditory or visual events. We propose that the study of scene perception should move forward to understand better the processes behind multimodal scene processing in real-world environments. We publish our stimulus scenes as spherical video recordings and sound field recordings in a publicly available database.

Using eye-tracking and correlates of brain activity to predict quality scores

Subjective quality tests give important information about the users perception on the quality of an audio or video signal. These tests are helpful but usually lack information about the users cognitive state. This might be crucial when consuming a service, as lower quality services may lead to a less frequent use. Therefore, physiological measures have become more popular in the domain of quality assessment as they give more detailed insights about e.g. fatigue and attention of a person. In the current study we used spatially degraded videos and obtained 1) standard subjective quality judgments, 2) eye movement parameters and 3) brain activity using electroencephalography (EEG). The results indicate more focused attention on the degraded area once participants found that area, as pupil diameter increases and the proportion of alpha activity decreases. On the basis of the data a model is proposed which predicts the quality scores from the obtained physiological measures.

Alcohol Ignition Interlocks in All New Vehicles: A Broader Perspective

Objective: To discuss the implications of widespread implementation of alcohol ignition interlocks. Method: We base our discussion on data from Finland including crash statistics and surveys collected from criminal justice professionals and general driving population. Results: Alcohol ignition interlocks are an effective preventive measure against drunk driving when installed in the vehicles of convicted drunk drivers. However, once they are removed from the vehicles, drivers typically return to their habit of drinking and driving. Furthermore, for a number of reasons, the proportion of convicted drunk drivers that install an interlock in their vehicles is quite small. Therefore, many stakeholders believe that the solution to the drunk driving problem will come when interlocks become standard equipment in all new vehicles. However, drunk driving is a complex sociopsychological problem, and technology can rarely offer a solution to such complex problems. Consequently, many aspects of such interventions might be difficult to identify and include in cost–benefit analysis. Conclusion: We express caution about requiring an interlock as standard equipment in all new vehicles.