Дисертації з теми "Objective and subjective quality assessment"
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1
Sendjasni, Abderrezzaq. "Objective and subjective quality assessment of 360-degree images." Electronic Thesis or Diss., Poitiers, 2023. http://www.theses.fr/2023POIT2251.
Анотація:
Les images à 360 degrés, aussi appelées images omnidirectionnelles, sont au cœur des contenus immersifs. Avec l’augmentation de leur utilisation notamment grâce à l’expérience interactive et immersive qu’ils offrent, il est primordial de garantir une bonne qualité d’expérience (QoE). Cette dernière est considérablement impactée par la qualité du contenu lui-même. En l’occurrence, les images à 360 degrés, comme tout type de signal visuel, passent par une séquence de processus comprenant l’encodage, la transmission, le décodage et le rendu. Chacun de ces processus est susceptible d’introduire des distorsions dans le contenu. Pour améliorer la qualité d’expérience, toutes ces dégradations potentielles doivent être soigneusement prises en compte et réduites à un niveau imperceptible. Pour atteindre cet objectif, l’évaluation de la qualité de l’image est l’une des stratégies devant être utilisée. Cette thèse aborde l’évaluation de la qualité des images à 360 degrés des points de vue objectif et subjectif. Ainsi, en s’intéressant à l’effet des visiocasques sur la qualité perçue des images 360 degrés, une étude psycho-visuelle est conçue et réalisée en utilisant quatre dispositifs différents. À cette fin, une base de données a été créé et un panel d’observateurs a été impliqué. L’impact des visiocasques sur la qualité a été identifié et mis en évidence comme un facteur important à prendre en compte lors de la réalisation d’expériences subjectives pour des images à 360 degrés. D’un point de vue objectif, nous avons d’abord procédé à une étude comparative extensive de plusieurs modèles de réseaux de neurones convolutifs (CNN) sous diverses configurations. Ensuite, nous avons amélioré la chaîne de traitement de l’évaluation de la qualité basée sur les CNN à différentes échelles, de l’échantillonnage et de la représentation des entrées à l’agrégation des scores de qualité. En se basant sur les résultats de ces études, et de l’analyse comparative, deux modèles de qualité basés sur les CNN sont proposés pour prédire avec précision la qualité des images à 360 degrés. Les observations et les conclusions obtenues à partir des différentes contributions de cette thèse apporteront un éclairage sur l’évaluation de la qualité des images à 360 degrés360-degree images, a.k.a. omnidirectional images, are in the center of immersive media. With the increase in demands of the latter, mainly thanks to the offered interactive and immersive experience, it is paramount to provide good quality of experience (QoE). This QoE is significantly impacted by the quality of the content. Like any type of visual signal, 360-degree images go through a sequence of processes including encoding, transmission, decoding, and rendering. Each of these processes has the potential to introduce distortions to the content. To improve the QoE, image quality assessment (IQA) is one of the strategies to be followed. This thesis addresses the quality evaluation of 360-degree images from the objective and subjective perspectives. By focusing on the influence of Head Mounted Displays (HMDs) on the perceived quality of 360-degree images, a psycho-visual study is designed and carried out using four different devices. For this purpose, a 360-degree image datasets is created and a panel of observers is involved. The impact of HMDs on the quality ratings is identified and highlighted as an important factor to consider when con- ducting subjective experiments for 360-degree images. From the objective perspective, we first comprehensively benchmarked several convolutional neural network (CNN) models under various configurations. Then, the processing chain of CNN-based 360-IQA is improved at different scales, from input sampling and representation to aggregating quality scores. Based on the observations of the above studies as well as the benchmark, two 360-IQA models based on CNNs are proposed to accurately predict the quality of 360-degree images. The obtained observations and conclusions from the various contributions shall bring insights for assessing the quality of 360-degree images
360-graders bilder, også kjent som rundstrålende bilder, er i sentrum av oppslukende medier. Med økningen i forventninger til sistnevnte, hovedsakelig takket være den aktiverte interaktive og oppslukende opplevelse, er det avgjørende å gi god kvaliteten på opplevelsen (QoE).Denne QoE er betydelig påvirket av kvaliteten på innholdet. Som alle typer visuelle signaler går 360-graders bilder gjennom en sekvens av prosesser, inkludert koding, overføring, dekoding og gjengivelse. Hver av disse prosessene har potensial til å introdusere forvrengninger til innholdet.For å forbedre QoE er vurdering av bildekvalitet (IQA) en av strategiene å følge. Denne oppgaven tar for seg kvalitetsevaluering av 360-graders bilder fra objektive og subjektive perspektiver. Ved å fokusere på påvirkningen av Head Mounted Displays (HMD-er) på den oppfattede kvaliteten til 360-graders bilder, er en psyko-visuell studie designet og utført ved hjelp av fire forskjellige enheter. For dette formålet opprettes et 360-graders bildedatasett og et panel av observatører er involvert. Virkningen av HMD-er på valitetsvurderingene identifiseres og fremheves som en viktig faktor når du utfører subjektive eksperimenter for 360-graders bilder.Fra det objektive perspektivet benchmarket vi først flere konvolusjonelle nevrale nettverk (CNN) under forskjellige konfigurasjoner. Deretter forbedres prosesseringskjeden til CNN-baserte 360-IQA i forskjellige skalaer, fra input-sampling og representasjon til aggregering av kvalitetspoeng. Basert på observasjonene av de ovenfornevnte studiene så vel som benchmark, foreslås to 360-IQA-modeller basert på CNN-er for å nøyaktig forutsi kvaliteten på 360-graders bilder.De innhentede observasjonene og konklusjonene fra de ulike bidragene skal gi innsikt for å vurdere kvaliteten på 360-graders bilder
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Dalasari, Venkata Gopi Krishna, and Sri Krishna Jayanty. "Low Light Video Enhancement along with Objective and Subjective Quality Assessment." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13500.
Анотація:
Enhancing low light videos has been quite a challenge over the years. A video taken in low light always has the issues of low dynamic range and high noise. This master thesis presents contribution within the field of low light video enhancement. Three models are proposed with different tone mapping algorithms for extremely low light low quality video enhancement. For temporal noise removal, a motion compensated kalman structure is presented. Dynamic range of the low light video is stretched using three different methods. In Model 1, dynamic range is increased by adjustment of RGB histograms using gamma correction with a modified version of adaptive clipping thresholds. In Model 2, a shape preserving dynamic range stretch of the RGB histogram is applied using SMQT. In Model 3, contrast enhancement is done using CLAHE. In the final stage, the residual noise is removed using an efficient NLM. The performance of the models are compared on various Objective VQA metrics like NIQE, GCF and SSIM. To evaluate the actual performance of the models subjective tests are conducted, due to the large number of applications that target humans as the end user of the video.The performance of the three models are compared for a total of ten real time input videos taken in extremely low light environment. A total of 25 human observers subjectively evaluated the performance of the three models based on the parameters: contrast, visibility, visually pleasing, amount of noise and overall quality. A detailed statistical evaluation of the relative performance of the three models is also provided.
3
Guo, Jinjiang. "Contributions to objective and subjective visual quality assessment of 3d models." Thesis, Lyon, 2016. http://www.theses.fr/2016LYSEI099.
Анотація:
Dans le domaine de l’informatique graphique, les données tridimensionnelles, généralement représentées par des maillages triangulaires, sont employées dans une grande variété d’applications (par exemple, le lissage, la compression, le remaillage, la simplification, le rendu, etc.). Cependant, ces procédés introduisent inévitablement des artefacts qui altèrent la qualité visuelle des données 3D rendues. Ainsi, afin de guider perceptuellement les algorithmes de traitement, il y a un besoin croissant d'évaluations subjectives et objectives de la qualité visuelle à la fois performantes et adaptées, pour évaluer et prédire les artefacts visuels. Dans cette thèse, nous présentons d'abord une étude exhaustive sur les différentes sources d'artefacts associés aux données numériques graphiques, ainsi que l’évaluation objective et subjective de la qualité visuelle des artefacts. Ensuite, nous introduisons une nouvelle étude sur la qualité subjective conçue sur la base de l’évaluations de la visibilité locale des artefacts géométriques, dans laquelle il a été demandé à des observateurs de marquer les zones de maillages 3D qui contiennent des distorsions visibles. Les cartes de distorsion visuelle collectées sont utilisées pour illustrer plusieurs fonctionnalités perceptuelles du système visuel humain (HVS), et servent de vérité-terrain pour évaluer les performances des attributs et des mesures géométriques bien connus pour prédire la visibilité locale des distorsions. Notre deuxième étude vise à évaluer la qualité visuelle de modèles 3D texturés, subjectivement et objectivement. Pour atteindre ces objectifs, nous avons introduit 136 modèles traités avec à la fois des distorsions géométriques et de texture, mené une expérience subjective de comparaison par paires, et invité 101 sujets pour évaluer les qualités visuelles des modèles à travers deux protocoles de rendu. Motivés par les opinions subjectives collectées, nous proposons deux mesures de qualité visuelle objective pour les maillages texturés, en se fondant sur les combinaisons optimales des mesures de qualité issues de la géométrie et de la texture. Ces mesures de perception proposées surpassent leurs homologues en termes de corrélation avec le jugement humainIn computer graphics realm, three-dimensional graphical data, generally represented by triangular meshes, have become commonplace, and are deployed in a variety of application processes (e.g., smoothing, compression, remeshing, simplification, rendering, etc.). However, these processes inevitably introduce artifacts, altering the visual quality of the rendered 3D data. Thus, in order to perceptually drive the processing algorithms, there is an increasing need for efficient and effective subjective and objective visual quality assessments to evaluate and predict the visual artifacts. In this thesis, we first present a comprehensive survey on different sources of artifacts in digital graphics, and current objective and subjective visual quality assessments of the artifacts. Then, we introduce a newly designed subjective quality study based on evaluations of the local visibility of geometric artifacts, in which observers were asked to mark areas of 3D meshes that contain noticeable distortions. The collected perceived distortion maps are used to illustrate several perceptual functionalities of the human visual system (HVS), and serve as ground-truth to evaluate the performances of well-known geometric attributes and metrics for predicting the local visibility of distortions. Our second study aims to evaluate the visual quality of texture mapped 3D model subjectively and objectively. To achieve these goals, we introduced 136 processed models with both geometric and texture distortions, conducted a paired-comparison subjective experiment, and invited 101 subjects to evaluate the visual qualities of the models under two rendering protocols. Driven by the collected subjective opinions, we propose two objective visual quality metrics for textured meshes, relying on the optimal combinations of geometry and texture quality measures. These proposed perceptual metrics outperform their counterparts in term of the correlation with the human judgment
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Shahid, Muhammad. "Methods for Objective and Subjective Video Quality Assessment and for Speech Enhancement." Doctoral thesis, Blekinge Tekniska Högskola [bth.se], Faculty of Engineering - Department of Applied Signal Processing, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00603.
Анотація:
The overwhelming trend of the usage of multimedia services has raised the consumers' awareness about quality. Both service providers and consumers are interested in the delivered level of perceptual quality. The perceptual quality of an original video signal can get degraded due to compression and due to its transmission over a lossy network. Video quality assessment (VQA) has to be performed in order to gauge the level of video quality. Generally, it can be performed by following subjective methods, where a panel of humans judges the quality of video, or by using objective methods, where a computational model yields an estimate of the quality. Objective methods and specifically No-Reference (NR) or Reduced-Reference (RR) methods are preferable because they are practical for implementation in real-time scenarios. This doctoral thesis begins with a review of existing approaches proposed in the area of NR image and video quality assessment. In the review, recently proposed methods of visual quality assessment are classified into three categories. This is followed by the chapters related to the description of studies on the development of NR and RR methods as well as on conducting subjective experiments of VQA. In the case of NR methods, the required features are extracted from the coded bitstream of a video, and in the case of RR methods additional pixel-based information is used. Specifically, NR methods are developed with the help of suitable techniques of regression using artificial neural networks and least-squares support vector machines. Subsequently, in a later study, linear regression techniques are used to elaborate the interpretability of NR and RR models with respect to the selection of perceptually significant features. The presented studies on subjective experiments are performed using laboratory based and crowdsourcing platforms. In the laboratory based experiments, the focus has been on using standardized methods in order to generate datasets that can be used to validate objective methods of VQA. The subjective experiments performed through crowdsourcing relate to the investigation of non-standard methods in order to determine perceptual preference of various adaptation scenarios in the context of adaptive streaming of high-definition videos. Lastly, the use of adaptive gain equalizer in the modulation frequency domain for speech enhancement has been examined. To this end, two methods of demodulating speech signals namely spectral center of gravity carrier estimation and convex optimization have been studied.
5
Khaustova, Darya. "Objective assessment of stereoscopic video quality of 3DTV." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S021/document.
Анотація:
Le niveau d'exigence minimum pour tout système 3D (images stéréoscopiques) est de garantir le confort visuel des utilisateurs. Le confort visuel est un des trois axes perceptuels de la qualité d'expérience (QoE) 3D qui peut être directement lié aux paramètres techniques du système 3D. Par conséquent, le but de cette thèse est de caractériser objectivement l'impact de ces paramètres sur la perception humaine afin de contrôler la qualité stéréoscopique. La première partie de la thèse examine l'intérêt de prendre en compte l'attention visuelle des spectateurs dans la conception d'une mesure objective de qualité 3D. Premièrement, l'attention visuelle en 2D et 3D sont comparées en utilisant des stimuli simples. Les conclusions de cette première expérience sont validées en utilisant des scènes complexes avec des disparités croisées et décroisées. De plus, nous explorons l'impact de l'inconfort visuel causé par des disparités excessives sur l'attention visuelle. La seconde partie de la thèse est dédiée à la conception d'un modèle objectif de QoE pour des vidéos 3D, basé sur les seuils perceptuels humains et le niveau d'acceptabilité. De plus nous explorons la possibilité d'utiliser la modèle proposé comme une nouvelle échelle subjective. Pour la validation de ce modèle, des expériences subjectives sont conduites présentant aux sujets des images stéréoscopiques fixes et animées avec différents niveaux d'asymétrie. La performance est évaluée en comparant des prédictions objectives avec des notes subjectives pour différents niveaux d'asymétrie qui pourraient provoquer un inconfort visuelThe minimum requirement for any 3D (stereoscopic images) system is to guarantee visual comfort of viewers. Visual comfort is one of the three primary perceptual attributes of 3D QoE, which can be linked directly with technical parameters of a 3D system. Therefore, the goal of this thesis is to characterize objectively the impact of these parameters on human perception for stereoscopic quality monitoring. The first part of the thesis investigates whether visual attention of the viewers should be considered when designing an objective 3D quality metrics. First, the visual attention in 2D and 3D is compared using simple test patterns. The conclusions of this first experiment are validated using complex stimuli with crossed and uncrossed disparities. In addition, we explore the impact of visual discomfort caused by excessive disparities on visual attention. The second part of the thesis is dedicated to the design of an objective model of 3D video QoE, which is based on human perceptual thresholds and acceptability level. Additionally we explore the possibility to use the proposed model as a new subjective scale. For the validation of proposed model, subjective experiments with fully controlled still and moving stereoscopic images with different types of view asymmetries are conducted. The performance is evaluated by comparing objective predictions with subjective scores for various levels of view discrepancies which might provoke visual discomfort
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Ansari, Yousuf Hameed, and Sohaib Ahmed Siddiqui. "Quality Assessment for HEVC Encoded Videos: Study of Transmission and Encoding Errors." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-13656.
Анотація:
There is a demand for video quality measurements in modern video applications specifically in wireless and mobile communication. In real time video streaming it is experienced that the quality of video becomes low due to different factors such as encoder and transmission errors. HEVC/H.265 is considered as one of the promising codecs for compression of ultra-high definition videos. In this research, full reference based video quality assessment is performed. The raw format reference videos have been taken from Texas database to make test videos data set. The videos are encoded using HM9 reference software in HEVC format. Encoding errors has been set during the encoding process by adjusting the QP values. To introduce packet loss in the video, the real-time environment has been created. Videos are sent from one system to another system over UDP protocol in NETCAT software. Packet loss is induced with different packet loss ratios into the video using NETEM software. After the compilation of video data set, to assess the video quality two kind of analysis has been performed on them. Subjective analysis has been carried on different human subjects. Objective analysis has been achieved by applying five quality matrices PSNR, SSIM, UIQI, VFI and VSNR. The comparison is conducted on the objective measurement scores with the subjective and in the end results deduce from classical correlation methods.
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Servetkienė, Vaida. "Gyvenimo kokybės daugiadimensis vertinimas, identifikuojant kritines sritis." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2013. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2013~D_20131115_113802-40756.
Анотація:
Disertacijoje nagrinėjama aktuali gyvenimo kokybės vertinimo problema. Mokslinėje literatūroje vis dar nėra vienodo gyvenimo kokybės suvokimo ir mokslinio apibrėžimo. Kiekvienas asmuo šiai sąvokai gali suteikti savo prasminį atspalvį, tačiau moksle gyvenimo kokybė turi būti konkrečiais rodikliais išreiškiama ir matuojama sąvoka, susijusi su visuomenės gerove konkrečioje šalyje. Šio darbo tyrimo objektas yra gyvenimo kokybės vertinimas. Disertacijos tikslas – išanalizavus mokslinius tarpdisciplininius požiūrius į gyvenimo kokybės vertinimą, parengti daugiadimensį gyvenimo kokybės vertinimo modelį ir nustatyti kritines jos sritis Lietuvoje. Darbe atlikta gyvenimo kokybės apibrėžties, koncepcijų ir praktikoje taikomų gyvenimo kokybės vertinimo metodų lyginamoji analizė, konceptualizuota gyvenimo kokybės sąvoka, ją traktuojant kaip ekonomikos mokslo tyrimo objektą, atspindintį valstybės vykdomos ekonominės politikos efektyvumą, nustatytos pagrindinės gyvenimo kokybės sritys, pateikta gyvenimo kokybės koncepcija ir pasiūlyti jos vertinimo metodologiniai principai, sudarytas daugiadimensis gyvenimo kokybės vertinimo modelis, jį taikant, įvertinta Lietuvos gyventojų gyvenimo kokybė ES šalių kontekste ir nustatytos kritinės jos sritys.The dissertation examines the topical issue of assessment of the quality of life. Scientific literature still does not offer a uniform perception and scientific definition of the quality of life. Every person can provide this concept with his own interpretation, but in science the quality of life must be a concept expressed by means of specific indicators and measured in relation to the welfare of the population in a specific country. The object of research in this dissertation is the assessment of the quality of life. The aim of the dissertation is, upon analysing interdisciplinary scientific approaches to assessment of the quality of life, to develop a multidimensional model of assessment of the quality of life and to identify the critical areas of the quality of life in Lithuania. The author of the dissertation has carried out a comparative analysis of the definition and conceptions of the quality of life and the quality of life assessment methods employed in practice, conceptualised the concept of the quality of life treating it as an object of economic research which reflects the efficiency of the economic policy of the state, identified the key areas of the quality of life, provided a conception of the quality of life and proposed methodological principles for its assessment, developed a multidimensional quality of life assessment model and, by applying the model, evaluated the quality of life of the Lithuanian population in the context of the EU Member States and... [to full text]
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Zerman, Emin. "Evaluation et analyse de la qualité vidéo à haute gamme dynamique." Electronic Thesis or Diss., Paris, ENST, 2018. http://www.theses.fr/2018ENST0003.
Анотація:
Au cours de la dernière décennie, la technologie de l’image et de la vidéo à haute gamme dynamique (High dynamic range - HDR) a attiré beaucoup d’attention, en particulier dans la communauté multimédia. Les progrés technologiques récents ont facilité l’acquisition, la compression et la reproduction du contenu HDR, ce qui a mené à la commercialisation des écrans HDR et à la popularisation du contenu HDR. Dans ce contexte, la mesure de la qualité du contenu HDR joue un rôle fondamental dans l’amélioration de la chaîne de distribution du contenu ainsi que des opérations qui la composent, telles que la compression et l’affichage. Cependant, l’évaluation de la qualité visuelle HDR présente de nouveaux défis par rapport au contenu à gamme dynamique standard (Standard dynamic range -SDR). Le premier défi concerne les nouvelles conditions introduites par la reproduction du contenu HDR, par ex. l’augmentation de la luminosité et du contraste. Même si une reproduction exacte de la luminance d’une scène n’est pas nécessaire pour la plupart des cas pratiques, une estimation précise de la luminance émise est cependant nécessaire pour les mesures d’évaluation objectives de la qualité HDR. Afin de comprendre les effets du rendu d’affichage sur la perception de la qualité, un algorithme permettant de reproduire très précisement une image HDR a été développé et une expérience subjective a été menée pour analyser l’impact de différents rendus sur l’évaluation subjective et objective de la qualité HDR. En outre, afin de comprendre l’impact de la couleur avec la luminosité accrue des écrans HDR, les effets des différents espaces de couleurs sur les performances de compression vidéo HDR ont également été analysés dans une autre étude subjective. Un autre défi consiste à estimer objectivement la qualité du contenu HDR, en utilisant des ordinateurs et des algorithmes. Afin de relever ce défi, la thèse procède à l’évaluation des performances des métriques de qualité d’image HDR avec référence (Full reference-FR). Les images HDR ont une plus grande plage de luminosité et des valeurs de contraste plus élevées. Etant donné que la plupart des métriques de qualité d’image sont développées pour les images SDR, elles doivent être adaptées afin d’estimer la qualité des images HDR. Différentes méthodes d’adaptation ont été utilisées pour les mesures SDR, et elles ont été comparées avec les métriques de qualité d’image existantes développées exclusivement pour les images HDR. De plus, nous proposons une nouvelle méthode d’évaluation des métriques objectives basée sur une nouvelle approche de classification. Enfin, nous comparons les scores de qualité subjectifs acquis en utilisant différentes méthodologies de test subjectives. L’évaluation subjective de la qualité est considérée comme le moyen le plus efficace et le plus fiable d’obtenir des scores de qualité «vérité-terrain» pour les stimuli sélectionnés, et les scores moyens d’opinion (Mean opinion scores-MOS) obtenus sont les valeurs auxquelles les métriques objectives sont entraînées pour correspondre. En fait, de fortes divergences peuvent facilement être rencontrés lorsque différentes bases de données de qualité multimédia sont considérées. Afin de comprendre la relation entre les valeurs de qualité acquises à l’aide de différentes méthodologies, la relation entre les valeurs MOS et les résultats des comparaisons par paires rééchellonés (Pairwise comparisons - PC) a été comparée. A cette fin, une série d’expériences ont été menées entre les méthodologies double stimulus impairment scale (DSIS) et des comparaisons par paires. Nous proposons d’inclure des comparaisons inter-contenu dans les expériences PC afin d’améliorer les performances de rééchelonnement et de réduire la variance inter-contenu ainsi que les intervalles de confiance. Les scores de PC rééchellonés peuvent également être utilisés pour des scénarios subjectifs d’évaluation de la qualité multimédia autres que le HDRIn the last decade, high dynamic range (HDR) image and video technology gained a lot of attention, especially within the multimedia community. Recent technological advancements made the acquisition, compression, and reproduction of HDR content easier, and that led to the commercialization of HDR displays and popularization of HDR content. In this context, measuring the quality of HDR content plays a fundamental role in improving the content distribution chain as well as individual parts of it, such as compression and display. However, HDR visual quality assessment presents new challenges with respect to the standard dynamic range (SDR) case. The first challenge is the new conditions introduced by the reproduction of HDR content, e.g. the increase in brightness and contrast. Even though accurate reproduction is not necessary for most of the practical cases, accurate estimation of the emitted luminance is necessary for the objective HDR quality assessment metrics. In order to understand the effects of display rendering on the quality perception, an accurate HDR frame reproduction algorithm was developed, and a subjective experiment was conducted to analyze the impact of different display renderings on subjective and objective HDR quality evaluation. Additionally, in order to understand the impact of color with the increased brightness of the HDR displays, the effects of different color spaces on the HDR video compression performance were also analyzed in another subjective study. Another challenge is to estimate the quality of HDR content objectively, using computers and algorithms. In order to address this challenge, the thesis proceeds with the performance evaluation of full-reference (FR) HDR image quality metrics. HDR images have a larger brightness range and higher contrast values. Since most of the image quality metrics are developed for SDR images, they need to be adapted in order to estimate the quality of HDR images. Different adaptation methods were used for SDR metrics, and they were compared with the existing image quality metrics developed exclusively for HDR images. Moreover, we propose a new method for the evaluation of metric discriminability based ona novel classification approach. Motivated by the need to fuse several different quality databases, in the third part of the thesis, we compare subjective quality scores acquired by using different subjective test methodologies. Subjective quality assessment is regarded as the most effective and reliable way of obtaining “ground-truth” quality scores for the selected stimuli, and the obtained mean opinion scores (MOS) are the values to which generally objective metrics are trained to match. In fact, strong discrepancies can easily be notified across databases when different multimedia quality databases are considered. In order to understand the relationship between the quality values acquired using different methodologies, the relationship between MOS values and pairwise comparisons (PC) scaling results were compared. For this purpose, a series of experiments were conducted using double stimulus impairment scale (DSIS) and pairwise comparisons subjective methodologies. We propose to include cross-content comparisons in the PC experiments in order to improve scaling performance and reduce cross-content variance as well as confidence intervals. The scaled PC scores can also be used for subjective multimedia quality assessment scenarios other than HDR
9
Sanches, Silvio Ricardo Rodrigues. "Avaliação objetiva de qualidade de segmentação." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-26062014-111553/.
Анотація:
A avaliação de qualidade de segmentação de vídeos tem se mostrado um problema pouco investigado no meio científico. Apesar disso, estudos recentes na área resultaram em algumas métricas que têm como finalidade avaliar objetivamente a qualidade da segmentação produzida pelos algoritmos. Tais métricas consideram as diferentes formas em que os erros ocorrem (fatores perceptuais) e seus parâmetros são ajustados de acordo com a aplicação em que se pretende utilizar os vídeos segmentados. Neste trabalho apresentam-se: i) uma avaliação da métrica que representa o estado-da-arte, demonstrando que seu desempenho varia de acordo com o algoritmo; ii) um método subjetivo para avaliação de qualidade de segmentação; e iii) uma nova métrica perceptual objetiva, derivada do método subjetivo aqui proposto, capaz de encontrar o melhor ajuste dos parâmetros de dois algoritmos de segmentação encontrados na literatura, quando os vídeos por eles segmentados são utilizados na composição de cenas em ambientes de Teleconferência Imersiva.Assessment of video segmentation quality is a problem seldom investigated by the scientific community. Nevertheless, recent studies presented some objective metrics to evaluate algorithms. Such metrics consider different ways in which segmentation errors occur (perceptual factors) and its parameters are adjusted according to the application for which the segmented frames are intended. In this work: i) we demonstrate empirically that the performance of existing metrics changes according to the segmentation algorithm; ii) we developed a subjective method to evaluate segmentation quality; and iii) we contribute with a new objective metric derived on the basis of experiments from subjective method in order to adjust the parameters of two bilayer segmentation algorithms found in the literature when these algorithms are used for compose scenes in Immersive Teleconference environments.
10
Ševčík, Martin. "Modelování vlastností modelu HVS v Matlabu." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2008. http://www.nusl.cz/ntk/nusl-217656.
Анотація:
In theoretical part Diploma thesis deals with the model of human vision HVS (Human Visual System), which can be used for image quality assessment in TV technique area. It has been described calculations of selected JND (Just Noticeable Difference) metrics, used in evaluation of HVS. In practical part of the thesis it has been suggested and realized simulation model in Matlab, which may be used for evaluation of three JND metrics from color and grayscale images and evaluation in spatial a frequency domain. Results of JND models have been compared to another objective image quality evaluation metrics (MSE, NMSE, SNR and PSNR). For interpretation of dependencies it has been used images with different defined content.
11
Xiao, Yao. "User perceived video quality modelling on mobile devices for Vp9 and H265 encoders." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/81842/1/Yao_Xiao_Thesis.pdf.
Анотація:
This study constructs performance prediction models to estimate the end-user perceived video quality on mobile devices for the latest video encoding techniques –VP9 and H.265. Both subjective and objective video quality assessments were carried out for collecting data and selecting the most desirable predictors. Using statistical regression, two models were generated to achieve 94.5% and 91.5% of prediction accuracies respectively, depending on whether the predictor derived from the objective assessment is involved. These proposed models can be directly used by media industries for video quality estimation, and will ultimately help them to ensure a positive end-user quality of experience on future mobile devices after the adaptation of the latest video encoding technologies.
12
Nouri, Nedia. "Évaluation de la qualité et transmission en temps-réel de vidéos médicales compressées : application à la télé-chirurgie robotisée." Thesis, Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL049N/document.
Анотація:
L'évolution des techniques chirurgicales, par l'utilisation de robots, permet des interventions mini-invasives avec une très grande précision et ouvre des perspectives d'interventions chirurgicales à distance, comme l'a démontré la célèbre expérimentation « Opération Lindbergh » en 2001. La contrepartie de cette évolution réside dans des volumes de données considérables qui nécessitent des ressources importantes pour leur transmission. La compression avec pertes de ces données devient donc inévitable. Celle-ci constitue un défi majeur dans le contexte médical, celui de l'impact des pertes sur la qualité des données et leur exploitation. Mes travaux de thèse concernent l'étude de techniques permettant l'évaluation de la qualité des vidéos dans un contexte de robotique chirurgicale. Deux approches méthodologiques sont possibles : l'une à caractère subjectif et l'autre à caractère objectif. Nous montrons qu'il existe un seuil de tolérance à la compression avec pertes de type MPEG2 et H.264 pour les vidéos chirurgicales. Les résultats obtenus suite aux essais subjectifs de la qualité ont permis également de mettre en exergue une corrélation entre les mesures subjectives effectuées et une mesure objective utilisant l'information structurelle de l'image. Ceci permet de prédire la qualité telle qu'elle est perçue par les observateurs humains. Enfin, la détermination d'un seuil de tolérance à la compression avec pertes a permis la mise en place d'une plateforme de transmission en temps réel sur un réseau IP de vidéos chirurgicales compressées avec le standard H.264 entre le CHU de Nancy et l'école de chirurgieThe digital revolution in medical environment speeds up development of remote Robotic-Assisted Surgery and consequently the transmission of medical numerical data such as pictures or videos becomes possible. However, medical video transmission requires significant bandwidth and high compression ratios, only accessible with lossy compression. Therefore research effort has been focussed on video compression algorithms such as MPEG2 and H.264. In this work, we are interested in the question of compression thresholds and associated bitrates are coherent with the acceptance level of the quality in the field of medical video. To evaluate compressed medical video quality, we performed a subjective assessment test with a panel of human observers using a DSCQS (Double-Stimuli Continuous Quality Scale) protocol derived from the ITU-R BT-500-11 recommendations. Promising results estimate that 3 Mbits/s could be sufficient (compression ratio aroundthreshold compression level around 90:1 compared to the original 270 Mbits/s) as far as perceived quality is concerned. Otherwise, determining a tolerance to lossy compression has allowed implementation of a platform for real-time transmission over an IP network for surgical videos compressed with the H.264 standard from the University Hospital of Nancy and the school of surgery
13
Bršel, Boris. "Porovnání objektivních a subjektivních metrik kvality videa pro Ultra HDTV videosekvence." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2016. http://www.nusl.cz/ntk/nusl-241052.
Анотація:
Master's thesis deals with the assessment of quality of Ultra HDTV video sequences applying objective metrics. Thesis theoretically describes coding of selected codecs H.265/HEVC and VP9, objective video quality metrics and also subjective methods for assessment of the video sequences quality. Next chapter deals with the implementation of the H.265/HEVC and the VP9 codecs at selected video sequences in the raw format from which arises the test sequences database. Quality of these videos is measured afterwards by objective metrics and selected subjective method. These results are compared for the purpose of finding the most consistent correlations among objective metrics and subjective assessment.
14
Nouri, Nedia. "Évaluation de la qualité et transmission en temps-réel de vidéos médicales compressées : application à la télé-chirurgie robotisée." Electronic Thesis or Diss., Vandoeuvre-les-Nancy, INPL, 2011. http://www.theses.fr/2011INPL049N.
Анотація:
L'évolution des techniques chirurgicales, par l'utilisation de robots, permet des interventions mini-invasives avec une très grande précision et ouvre des perspectives d'interventions chirurgicales à distance, comme l'a démontré la célèbre expérimentation « Opération Lindbergh » en 2001. La contrepartie de cette évolution réside dans des volumes de données considérables qui nécessitent des ressources importantes pour leur transmission. La compression avec pertes de ces données devient donc inévitable. Celle-ci constitue un défi majeur dans le contexte médical, celui de l'impact des pertes sur la qualité des données et leur exploitation. Mes travaux de thèse concernent l'étude de techniques permettant l'évaluation de la qualité des vidéos dans un contexte de robotique chirurgicale. Deux approches méthodologiques sont possibles : l'une à caractère subjectif et l'autre à caractère objectif. Nous montrons qu'il existe un seuil de tolérance à la compression avec pertes de type MPEG2 et H.264 pour les vidéos chirurgicales. Les résultats obtenus suite aux essais subjectifs de la qualité ont permis également de mettre en exergue une corrélation entre les mesures subjectives effectuées et une mesure objective utilisant l'information structurelle de l'image. Ceci permet de prédire la qualité telle qu'elle est perçue par les observateurs humains. Enfin, la détermination d'un seuil de tolérance à la compression avec pertes a permis la mise en place d'une plateforme de transmission en temps réel sur un réseau IP de vidéos chirurgicales compressées avec le standard H.264 entre le CHU de Nancy et l'école de chirurgieThe digital revolution in medical environment speeds up development of remote Robotic-Assisted Surgery and consequently the transmission of medical numerical data such as pictures or videos becomes possible. However, medical video transmission requires significant bandwidth and high compression ratios, only accessible with lossy compression. Therefore research effort has been focussed on video compression algorithms such as MPEG2 and H.264. In this work, we are interested in the question of compression thresholds and associated bitrates are coherent with the acceptance level of the quality in the field of medical video. To evaluate compressed medical video quality, we performed a subjective assessment test with a panel of human observers using a DSCQS (Double-Stimuli Continuous Quality Scale) protocol derived from the ITU-R BT-500-11 recommendations. Promising results estimate that 3 Mbits/s could be sufficient (compression ratio aroundthreshold compression level around 90:1 compared to the original 270 Mbits/s) as far as perceived quality is concerned. Otherwise, determining a tolerance to lossy compression has allowed implementation of a platform for real-time transmission over an IP network for surgical videos compressed with the H.264 standard from the University Hospital of Nancy and the school of surgery
15
Begazo, Dante Coaquira. "Método de avaliação de qualidade de vídeo por otimização condicionada." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/3/3142/tde-09032018-152946/.
Анотація:
Esta Tese propõe duas métricas objetivas para avaliar a percepção de qualidade de vídeos sujeitos a degradações de transmissão em uma rede de pacotes. A primeira métrica usa apenas o vídeo degradado, enquanto que a segunda usa os vídeos de referência e degradado. Esta última é uma métrica de referência completa (FR - Full Reference) chamada de QCM (Quadratic Combinational Metric) e a primeira é uma métrica sem referência (NR - No Reference) chamada de VQOM (Viewing Quality Objective Metric). Em particular, o procedimento de projeto é aplicado à degradação de variação de atraso de pacotes (PDV - Packet Delay Variation). A métrica NR é descrita por uma spline cúbica composta por dois polinômios cúbicos que se encontram suavemente num ponto chamado de nó. Para o projeto de ambas métricas, colhem-se opiniões de observadores a respeito das sequências de vídeo degradadas que compõem o conjunto. A função objetiva inclui o erro quadrático total entre as opiniões e suas estimativas paramétricas, ainda consideradas como expressões algébricas. Acrescentam-se à função objetiva três condições de igualdades de derivadas tomadas no nó, cuja posição é especificada dentro de uma grade fina de pontos entre o valor mínimo e o valor máximo do fator de degradação. Essas condições são afetadas por multiplicadores de Lagrange e adicionadas à função objetiva, obtendo-se o lagrangiano, que é minimizado pela determinação dos coeficientes subótimos dos polinômios em função de cada valor do nó na grade. Finalmente escolhe-se o valor do nó que produz o erro quadrático mínimo, determinando assim os valores finais para dos coeficientes do polinômio. Por outro lado, a métrica FR é uma combinação não-linear de duas métricas populares, a PSNR (Peak Signal-to-Noise Ratio) e a SSIM (Structural Similarity Index). Um polinômio completo de segundo grau de duas variáveis é usado para realizar a combinação, porque é sensível a ambas métricas constituintes, evitando o sobreajuste em decorrência do baixo grau. Na fase de treinamento, o conjunto de valores dos coeficientes do polinômio é determinado através da minimização do erro quadrático médio para as opiniões sobre a base de dados de treino. Ambas métricas, a VQOM e a QCM, são treinadas e validadas usando uma base de dados, e testadas com outra independente. Os resultados de teste são comparados com métricas NR e FR recentes através de coeficientes de correlação, obtendo-se resultados favoráveis para as métricas propostas.This dissertation proposes two objective metrics for estimating human perception of quality for video subject to transmission degradation over packet networks. The first metric just uses traffic data while the second one uses both the degraded and the reference video sequences. That is, the latter is a full reference (FR) metric called Quadratic Combinational Metric (QCM) and the former one is a no reference (NR) metric called Viewing Quality Objective Metric (VQOM). In particular, the design procedure is applied to packet delay variation (PDV) impairments, whose compensation or control is very important to maintain quality. The NR metric is described by a cubic spline composed of two cubic polynomials that meet smoothly at a point called a knot. As the first step in the design of either metric, the spectators score a training set of degraded video sequences. The objective function for designing the NR metric includes the total square error between the scores and their parametric estimates, still regarded as algebraic expressions. In addition, the objective function is augmented by the addition of three equality constraints for the derivatives at the knot, whose position is specified within a fine grid of points between the minimum value and the maximum value of the degradation factor. These constraints are affected by Lagrange multipliers and added to the objective function to obtain the Lagrangian, which is minimized by the suboptimal polynomial coefficients determined as a function of each knot in the grid. Finally, the knot value is selected that yields the minimum square error. By means of the selected knot value, the final values of the polynomial coefficients are determined. On the other hand, the FR metric is a nonlinear combination of two popular metrics, namely, the Peak Signal-to-Noise Ratio (PSNR) and the Structural Similarity Index (SSIM). A complete second-degree two-variable polynomial is used for the combination since it is sensitive to both constituent metrics while avoiding overfitting. In the training phase, the set of values for the coefficients of this polynomial is determined by minimizing the mean square error to the opinions over the training database. Both metrics, the VQOM and the QCM, are trained and validated using one database and tested with a different one. The test results are compared with recent NR and FR metrics by means of correlation coefficients, obtaining favorable results for the proposed metrics.
16
Chaabouni, Amine. "Compression vidéo basée sur HEVC pour la télémédecine sur des réseaux hauts débits, bas débits et vers des terminaux mobiles : application à la cancérologie." Electronic Thesis or Diss., Université de Lorraine, 2017. http://www.theses.fr/2017LORR0326.
Анотація:
Ce travail de thèse répond à la problématique du transfert de la vidéo à haute résolution sur les réseaux bas débit. Dans le contexte du projet européen E3, des scénarios de téléconsultation, télésurveillance et télé-enseignement, sont définis et mis en place via des outils et des services de télémédecine. Par ailleurs, deux solutions concrètes sont proposées. Une première partie est consacrée à l’évaluation des performances de la nouvelle norme d’encodage vidéo HEVC dans le contexte médical. Les métriques objectives et les notes subjectives valident les améliorations effectuées sur cette norme par rapport au standard AVC-H.264, montrant qu’on peut gagner jusqu’à 54% en débit de compression pour une même qualité acceptable par les experts. Malgré la complexité de son architecture, une configuration adaptée au contexte bas débit (< 3 Mbits/s), a été définie et recommandée en utilisant l’encodeur temps réel x265. Une deuxième solution consiste à l’utilisation d’une méthode originale de dissimulation de données, basée sur une approche zonale, afin d’insérer des données médicales dans les séquences endoscopiques. Par rapport à l’état de l’art, cette méthode est plus performante en capacité d’insertion, imperceptibilité et complexité. Cette technique nous offre la possibilité d’insérer, en temps réel, jusqu’à 3 Mbits de données dans une vidéo médicale FHD de 10s, sans ajouter de débit ou de temps de traitement supplémentaire à l’encodeur « x265 ». La solution est améliorée par la saillance visuelle, en dissimulant dans les zones saillantes plutôt que dans toute l’imageThis thesis deals with HD video transmission over low-bandwidth networks. In the context of the European project E3, scenarios such as remote consultation, telemonitoring and remote lecture, have been defined and implemented thanks to telemedicine tools and services. A first part was devoted to assess the performance of the new video encoding standard HEVC in the medical context. Objective metrics and subjective scores validated the improvements offered by this standard compared to the AVC-H.264 standard, showing that we could save up to 54% in terms of compression bitrate for a same quality, acceptable by experts. Despite the complexity of its architecture, a configuration adapted to the low bit rate context (<3 Mbps/s) was defined and recommended by using the x265 real-time encoder. A second solution has been proposed: an original method of data hiding, based on a zonal approach, to hide medical data into the endoscopic sequences. Compared to the state of the art, this method offers more efficient performance in payload, imperceptibility and complexity. This technique allows us to hide, in real time, up to 3 Mbits of data in a 10s FHD medical video, without requiring more bandwidth or an additional processing time to the encoder “x265”. The solution has been still improved by visual saliency techniques, by hiding in salient areas rather than throughout the entire image
17
Bednarz, Robin. "Analýza kvality obrazu v digitálních televizních systémech." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217810.
Анотація:
Diploma thesis deals with the analysis of quality in digital television systems and contains theoretical description of subjective and objective assessment of quality picture methods. The thesis contains short-term and long-term analysis of quality picture of terrestrial television DVB-T. Measurements and experimentations were carried out with the help of Rohde&Schwarz DVQ analyzer of picture quality and software MPEG-2 Quality Monitor and MPEG-2 Elementary stream analyzer.
18
Statham, Andrew. "Subjective and objective assessment of tennis racket performance play." Thesis, Loughborough University, 2007. https://dspace.lboro.ac.uk/2134/4080.
Анотація:
Assessment of wielded implement performance is important to a variety of human endeavours and often critical to success in a sports context, particularly so in the game of tennis. Tennis racket design and manufacture is a multimillion business involving 10 major international companies. Tennis participation is currently estimated at around 60 million individuals worldwide. Thus the importance of optimum racket performance to maximise competitive advantage and minimise the risks of injury is clear. This thesis presents work to enable advances in tennis racket performance with respect to player feel perception, measurement of physical phenomena and the correlation of these aspects within real play contexts. To investigate feel perception a methodology was adapted from the existing literature. Interview testing was conducted to elicit a comprehensive range of tennis specific vocabulary. The end goal was to create a perception relationship map or 'feel map'. The inductive analysis was used to link all the related clustered themes identified from the vocabulary to sub and base themes describing the relationship. Further analysis introduced higher level general dimensions that unified common base themes. The resulting feel maps were created from both English and German sample groups, with a view to subsequent comparison. To complete the map and broaden its application a wide scale questionnaire was distributed to a tennis playing population. The responses provided data indicating percentile use of selected vocabulary within the tennis community and the relative importance players associate with assorted perception groups. Visual representations of the data were introduced to the map for quick and easy use and an associated lexicon compiled to provide a reference for more detailed information. The feel maps and lexicon provide users with a versatile tool in the form of a 'perception relationship model'. The map itself can act as an overall research guide for future work in the field. The addition of percentile use and relative importance data mean the map can be used to create more informed and subtle player test questionnaires or as a design aid, with interdependency links indicating which additional factors should be considered or exploited for their influence on the characteristic areas in question. Interestingly the general dimensions of highest relative importance were sound and grip respectively. This may be due to the basic level of interaction between player and racket which ultimately has to be perceived either through the grip or from the sound. A perception test questionnaire was also created with the use of the feel map and later used to study the correlation between objective and subjective measures. To best attain objective measures from the racket an innovative instrumentation system was created. Two alternative systems were designed and tested, the first based on wired instrumentation and data capture the second based on wireless technologies as these became available. Both systems were required to take measures of grip pressure and acceleration with 6 degrees of freedom. The first system utilised uniaxial accelerometers mounted on an aluminium bracket, and a triaxial accelerometer inserted inside the butt of the racket arranged to allow measurement and calculation of acceleration from the required 6 degrees of freedom. The system could be adapted to include either TekScan multi-cell full grip coverage force measurement, or 2 single point higher sample rate single cell grip force sensors. All data was fed via 15 m of cable to data acquisition systems. This restricted the participants' freedom of movement and encumbered the racket and thus the systems application, making it unsuitable for extensive perception or fatigue testing. The second system utilised a compact data logger with an integrated on board tri-axial accelerometer small enough to be mounted within the racket handle. A revised mount overcame the need for the aluminium throat bracket, moving the uniaxial accelerometers into a bulbous addition to the butt of the racket. The system was capable of capturing 8 channels simultaneously which allowed for the 6 accelerometers and two single cell grip force sensors to be located under the grip. The system was more difficult to adapt and maintain than the wired system, but improved freedom and reduced added weight to the racket made the system far more suitable for the planned perception and fatigue testing. Fatigue testing conducted with the wireless device investigated the effect of full body fatigue on players' performance by monitoring the resultant effects in the racket. The protocol was based on the multistage fitness test, designed to progressively increase in difficulty until volitional fatigue. Heart rate data indicated that the protocol was successful in fatiguing the participants to a point at or near their VO2max. Unfortunately, with the wireless system in its early stages of development, the device failed mid way through testing. The limited data set that was collected indicated that technique was affected by fatigue. Further research is required to confirm this finding and to make comparisons between racket types during the fatiguing process. The wireless device was adapted to make it more durable and reliable before the planned perception testing was conducted. A protocol was developed to investigate the affect of changing racket moment of inertia on player perception and physical measures. The test questionnaire developed from the feel map was used to evaluate player perception ratings of various elements of racket feel, and the wireless instrumentation system was used as part of methodology designed to compile a set of comparable physical data. A detailed analysis of the results revealed that there was some evidence of correlation between the perceptions of power, balance, flexibility and control and the moment of inertia of the racket. In a design optimisation context, however, more definitive correlations would be more useful. These would be expected to be found with future testing utilising a wider range of racket properties. The research proves to a large extent the original hypothesis that through the use of non invasive instrumentation and improved player perception elicitation techniques it is possible to substantially and usefully improve the objective and subjective assessment of tennis racket performance in play to enable investigation of better design characteristics and fatigue related injury phenomena.
19
Freeman, Jonathan. "Subjective and objective approaches to the assessment of presence." Thesis, University of Essex, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.298879.
20
Malekmohamadi, Hossein. "Objective models for subjective quality estimate of stereoscopic video." Thesis, University of Surrey, 2013. http://eprints.lincoln.ac.uk/12756/.
21
Skildheim, Kim Daniel. "Subjective and Objective Crosstalk Assessment Methodologies for Auto-stereoscopic Displays." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elektronikk og telekommunikasjon, 2012. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-18913.
Анотація:
Stereoscopic perception is achievable when the observer sees a scene from a slightly different angle. Auto-stereoscopic displays utilize several separate views to achieve this without using any special glasses. Crosstalk is an undesired effect of separating views. It is one of the most annoying artefacts occurring in an auto-stereoscopic display. This experiment has two parts. The first part proposes a subjective assessment methodology for characterizing crosstalk in an auto-stereoscopic display, without restriction of subjects’ viewing behaviour. The intention was to create an inexpensive method. The measurement was performed by using a Kinect prime sensor as a head tracking system combined with subjective score evaluation to get a data plot of the perceived crosstalk. The crosstalk varies in line with image content, disparity and viewing position. The result is a data plot that approaches a periodically pattern, which is consistent with the characteristics of an auto-stereoscopic display. The result is not perfect since there are many sources of errors occurring. These errors can be improved with better head tracking, an improved movement system, post processing of data, more data and removal of outliers.The second part proposes methods for extracting subjective values based on interpolated plots and creating objective crosstalk influenced pictures which correlate with the subjective data. The best extraction method was to combine an adapted sine regression curve with a linear interpolation. This interpolation followed the subjective values in a parallel slice plot at 3.592 m from the screen. The interpolation was adapted to fit a derived model as best as possible to achieve a good correlation. Objective crosstalk pictures were created, where the amount of crosstalk was determined by the neighbouring view that influenced the current view the most. The correlation was based on the relationship between the SSIM value from the created crosstalk picture and the extracted subjective value. The total correlation of the pictures together were 0,8249, where the picture with the highest correlation had 0,9561. This method is quite good for pictures that have a maximum disparity grade below 38 pixels. The overall result is good and it is also a measure of quality for the subjective test. This result can be improved by increasing the complexity of how the objective crosstalk pictures are created by adding more views into account or try another method to create crosstalk. Improved extraction of subjective values will also be beneficial in terms of improving the correlation even more.
22
Sadeghi, Reza. "Predicting Subjective Sleep Quality Using Objective Measurements in Older Adults." Wright State University / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=wright1588627876830938.
23
Su, He Zhicheng Xuxin. "Links between Subjective Assessments and Objective Metrics for Steering." Thesis, KTH, Fordonsdynamik, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-101925.
Анотація:
The characteristics of vehicle steering perception are decisive factors concerning vehicle safety and overall pleasure behind the wheel. It is a challenge for vehicle manufacturers to achieve these features and qualities, because usually vehicle tuning almost only relies on subjective evaluation of test drivers, which is costly and time consuming. In order to optimize suspension design and develop a tool that can be used to evaluate steering with objective metrics instead of subjective assessment, links between them must be confirmed. In this master thesis, both objective and subjective testing data of over 20 vehicles across four different segments are introduced in linear and nonlinear analysis. Linear regression analysis is applied to investigate simply positive or negative correlation between a pair of subjective-objective parameters. However, even if certain linear correlations are obtained, it is still hard to define the optimal value for objective metrics. Considering that the general shape of a correlation function can reveal which objective range give higher subjective rating, it is possible to define these preferred ranges with Neural Network (NN). The best data available is adopted from three drivers who tested 15 sedans, and some interesting results are found. The initial results demonstrate that NN is a powerful tool to uncover and graphically illustrate the links between objective metrics and subjective assessments, i.e., the specific range leading to better steering feel. Given a larger sample size, more reliable and optimal links can be defined by following the same method. These confirmed links would enable vehicle dynamics engineers to more effectively develop new vehicles with nearly perfect steering feel.
24
Luotonen, David, and Markus Hasselström. "Subjective and objective performance assessment : Performance pay at Trelleborg Forsheda AB." Thesis, Jönköping University, JIBS, Business Administration, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:hj:diva-9660.
Анотація:
The purpose of this thesis is to understand the opinions and potential effects of objective and subjective assessments of performance as a basis for performance pay for blue-collar workers.
The study takes a qualitative approach to find out how and why four companies - Trelleborg Forsheda, Finnveden Powertrain, Isaberg Rapid and Parker Hannifin- work with salaries, incentive system and performance assessment the way they do.
The concept of individual salary is central in this thesis, and individual salary is based on four criteria; capabilities, performance, work demand and formal competence. These can be divided in subjective or objective criteria. Individual salaries also contribute to salary divergence, which in many studies have indicated higher performance. Important to remember is that it has to exist a purpose to salary divergence and how salary is diverged in the company is related to the goals and strategy of the company. If the company chooses to have performance based salaries- which is salary divergence- another question arise; what is good performance?
In organizations that have performance salaries, a group or an individual (often the middle manager) have to decide if a certain group of personnel performs good or bad. This can mainly be done in two different ways; objective performance assessment or subjective performance assessment. Objective performance assessment is based on numerical calculation of measures, which will form the basis for rewarding employees using a salary system that reward performance. Subjective performance measurements are based on judgment. Instead of relying on numerical calculations, one evaluates if the results reflect good or bad performance.
For both methods it is essential that the personnel feels that the salaries are fair, and that the salary system is clear and easy to understand. Something else that is important to understand is that employer and employee have different views in what is a fair salary.
Objective assessments are based on numerical calculations of measures, and one important property such measures have is that they don’t leave any room for excuses. Research indicate that performance pay has important motivation enhancing effects, but the profitability doesn’t always benefit from it. When monitoring costs are high, or product quality or long term thinking is required, hourly wages may be preferable. Tasks which are measured, will naturally be prioritized by the organization. This means that the choice of measures is very important. The amount of measures mustn’t be too high, and they have to be carefully considered. Subjective assessments are the opposite to objective ones. The advantages with subjective performance assessments are, among other things, that additional information which have surfaced during the period of measurements can be taken into consideration, errors in the measurement process can be corrected and unlucky circumstances can be dealt with. However, problems exist in unfair assessments, which are based on prejudice.
Findings in this report shows that profitable companies have large differences in their salary systems. This is also supported by other research. The company Isaberg Rapid AB only uses objective criteria, focused on simplicity and group rewards. Finnveden Powertrain on the other hand, has a system focused on individuals and subjective assessments. Some conclusions could be drawn; one of the most important being that connections between the type of activities and the salary system is positive, and that salary systems have to be updated and revised continuously.
25
Santos, Magalhães André. "Subjective and objective assessment of physically active people with knee injury." Thesis, University of Kent, 2016. https://kar.kent.ac.uk/60066/.
Анотація:
Knee injuries are highly prevalent in physically active individuals and are frequently associated with sport participation. Independently of the nature of the injury, subjective and objective clinical measures are used to assess, monitor and evaluate treatment outcomes in this population. To be clinically meaningful, these outcome measures should be relevant to the condition, the anatomical area, the individual or population, and importantly, possess adequate psychometric properties. Despite a high prevalence of knee injuries, there are several aspects of the subjective and objective knee evaluation in physically active individuals that remain unclear or have not been considered in previous research. The main aim of the present thesis was to fill some of the gaps identified in the literature regarding both subjective and objective knee measures in physically active individuals. Therefore, this thesis was divided into two distinct parts. The first part looked at the patient-reported outcome (PRO) measures of the knee and physical activity, and consisted of two studies. The first study was a systematic review conducted to explore the PRO measures that are commonly used in the evaluation of physical activity and return to sport following autologous chondrocyte implantation (ACI). Aiming as well, to provide a critical analysis of these instruments from a rehabilitative perspective. This review revealed not only the heterogeneity in the selection, but also in the timing and reporting of patient-reported activity scoring instruments following ACI, which makes a systematic comparison difficult and introduces bias into the interpretation of these outcomes. Another important finding of this review, was that the instruments currently used to evaluate postoperative outcomes in an articular cartilage repair population do not always fulfil the rehabilitative needs of physically active individuals. The second study was conducted in recreational marathon runners and aimed to provide normative values for a widely used knee specific PRO measure in athletes with knee injury, the Knee Injury Osteoarthritis Outcome Score (KOOS). Alongside the normative KOOS subscales values stratified by age group and history of knee injury that were presented, this study also showed that recent history of knee running-related injury (RRI) has a negative impact on the KOOS scores. In runners with no history of knee RRI, the results observed suggested a lack of interaction between KOOS subscale values and age. Furthermore, the KOOS values seen were substantially higher compared to previously published normative population-based KOOS values. The second part of the present thesis comprised three experimental studies concerning single-leg cycling (SLC) exercise testing, in particular assessing the potential use of the self-paced test (SPT) concept as an objective measure following knee surgery. The first study analysed the reliability of a 5x2 min stages SPT anchored to the rate of perceived exertion (RPE) for SLC exercise testing. This study showed that this test protocol elicits reliable cardiorespiratory and metabolic responses. The second study examined the validity of the SPT protocol used in the previous study, through a concurrent comparison against a conventional fixed power incremental SLC exercise test. This investigation showed that the 5x2 min SPT provides a valid objective means for assessing peak aerobic capacity in SLC exercise testing. Moreover, it may be associated with increased activity enjoyment comparatively to conventional testing. The third and last experimental study investigated the effect of a 10 kg counterweight device (CW10) on cardiorespiratory, metabolic and perceptual responses to SLC exercise testing. The results of this study demonstrated that the CW10 despite eliciting an improvement in the activity enjoyment, did not affect peak cardiorespiratory and metabolic responses to SLC exercise testing. When matched for test duration the SPT elicited higher peak power output and peak oxygen consumption than conventional incremental testing, regardless of the CW10 usage or not. In conclusion, the original work of the present thesis increases the body of knowledge of two distinct, but complementary fields in the subjective and objective knee assessment of physically active individuals. The outcomes provided both on PRO measures and SLC exercise testing, may have impact on the clinical practice of clinicians, sport rehabilitation professionals and researchers.
26
Anani, John Kodjo. "A subjective and objective assessment of sound insulation in newly converted dwellings." Thesis, Open University, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.316964.
27
Fernandes, Andreia Sofia Pires. "" Objective and Subjective Assessment of Qigong Related Effects in Breast Cancer Patients "." Master's thesis, Instituto de Ciências Biomédicas Abel Salazar, 2011. http://hdl.handle.net/10216/57089.
28
Fernandes, Andreia Sofia Pires. "" Objective and Subjective Assessment of Qigong Related Effects in Breast Cancer Patients "." Dissertação, Instituto de Ciências Biomédicas Abel Salazar, 2011. http://hdl.handle.net/10216/57089.
29
Huber, Rainer. "Objective assessment of audio quality using an auditory processing model." [S.l. : s.n.], 2003. http://deposit.ddb.de/cgi-bin/dokserv?idn=971182167.
30
Guo, Ziyuan. "Objective Audio Quality Assessment Based on Spectro-Temporal Modulation Analysis." Thesis, KTH, Ljud- och bildbehandling, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-91847.
Анотація:
Objective audio quality assessment is an interdisciplinary research area that incorporates audiology and machine learning. Although much work has been made on the machine learning aspect, the audiology aspect also deserves investigation. This thesis proposes a non-intrusive audio quality assessment algorithm, which is based on an auditory model that simulates human auditory system. The auditory model is based on spectro-temporal modulation analysis of spectrogram, which has been proven to be effective in predicting the neural activities of human auditory cortex. The performance of an implementation of the algorithm shows the effectiveness of the spectro-temporal modulation analysis in audio quality assessment.
31
Harnett, Philip. "Objective methods for the assessment of passenger car steering quality." Thesis, Cranfield University, 2002. http://dspace.lib.cranfield.ac.uk/handle/1826/8571.
Анотація:
Steering feel and quality are terms commonly used in the automotive industry when
describing passenger car steering systems. However, a procedure for the quantification
of these terms does not exist, let alone a concise definition of what they constitute.
This thesis puts forward a hypothesis by which steering quality and feel are described
by the input/output relationships of the steering system and how they are perceived
by the driver. Good control properties are postulated for these relationships and an
experiment is conducted, where they are altered in a manner proposed to affect quality.
A methodology for the objective assessment of the control properties is developed,
employing vehicle dynamic testing and representation by a mathematical model. This
is put into practice to evaluate the outcome of the experiment.
It was found that the methodology was successful in detecting and quantifying the
alteration in the vehicle control properties. A subjective evaluation was performed to
assess the experiment in terms of the quality and feel perceived by the driver. The
subjective judgement delivered a result, where the deviation in quality agreed with
the objective quantities hypothesised to describe quality.
The thesis provides a significant step in the understanding of what is termed steering
feel and quality. The methodology, successful in quantifying the experimental results
with respect to quality, constitutes a scientific advancement in the current procedures
for the assessment of steering quality.
32
Torkhani, Fakhri. "Analyse subjective et évaluation objective de la qualité perceptuelle des maillages 3D." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENT051/document.
Анотація:
Les maillages 3D polygonaux sont largement utilisés dans diverses applications telles que le divertissement numérique, la conception assistée par ordinateur et l'imagerie médicale. Un maillage peut être soumis à différents types d'opérations comme la compression, le tatouage ou la simplification qui introduisent des distorsions géométriques (modifications) à la version originale. Il est important de quantifier ces modification introduites au maillage d'origine et d'évaluer la qualité perceptuelle des maillages dégradés. Dans ce cadre, on s'intéresse dans cette thèse à l'évaluation de la qualité perceptuelle des maillages 3D statiques et dynamiques. On présente des études expérimentales pour l'évaluation subjective de la qualité des maillages 3D dynamiques.On présente également de nouvelles métriques objectives, de type avec-référence complète ou de type avec référence-réduite, qui sont efficaces pour l'estimation de la qualité perçue des maillages statiques et dynamiques3D mesh animations have been increasingly used in various applications, e.g., in digital entertainment, computer-aided design and medical imaging. It is possible that a mesh model undergoes some lossy operations, e.g., compression, watermarking or simplification, which can impair the original mesh surface and introduce geometric distortions. An important task is to quantify such distortions and assess the perceptual quality of impaired meshes. In this manuscript, we focus on the perceptual quality assessment of 3D static and dynamic meshes. We present psychometric experiments that we conducted to measure the subjective perceptual quality of dynamic meshes. We also present new full-reference and reduced-reference objective metrics capable of faithfully evaluating the perceptual quality of 3D static and dynamic meshes
33
Budhrani, Pinky H. "Race/Ethnicity, Subjective and Objective Sleep Quality, Physical and Psychological Symptoms in Breast Cancer Survivors." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4645.
Анотація:
Breast cancer is a major health problem and comprises the largest population of cancer survivors in the United States, estimated at 2.9 million women, accounting for 22% of all cancer survivors (National Cancer Institute, 2013). The advances in breast cancer screening, diagnosis and treatment has increased the importance of survivorship needs. A major concern among breast cancer survivors (BCS) is sleep disturbances. This study used an innovative approach to examine ethnic and racial disparities in sleep disturbances present in BCS. In addition, this study also explored sleep disturbances across different races/ethnicities. This study was a secondary data analysis of baseline data from the supplement study of the MBSR Symptom Cluster Trial for Breast Cancer Survivors/ 1R01CA131080, conducted by Dr. Lengacher. Sleep was measured using the Pittsburgh Sleep Quality Index, sleep diary (subjective), and sleep actigraphy (objective). The sample consists of 79 women who had been diagnosed with breast cancer (Stage 0, I, II, III), completed lumpectomy and/or mastectomy, and were within 2 weeks to 2 years post radiation and/or chemotherapy treatment. The aims for this study were to: 1) explore racial/ethnic differences in objectively measured sleep patterns among BCS; 2) estimate and compare the correlation between objective and subjective sleep quality by racial/ethnic groups among BCS; 3) examine which sleep actigraphy measure appears to have the strongest relationship with physical and psychological symptoms; and 4) explore whether these relationships (i.e. between objective sleep and self-reported symptoms) appear to be modified by race/ethnicity.
The first aim was conducted using analysis of variance (ANOVA) and analysis of covariance (ANCOVA). Results indicated that white, non Hispanic BCS had improved objective sleep quality compared to minority BCS. The second aim was conducted using Pearson's correlation with significant correlations found between subjective and objective sleep onset latency (r= .310, p= .016), and total sleep time (TST) (r= .328, p= .011) for the white, non-Hispanic group. The third aim was conducted using Pearson's correlation with significant correlations between sleep onset latency and depression (r= .247, p= .029); sleep efficiency and depression (r= -.233, p= .040); sleep efficiency and fatigue (r= -.207, p= .045); and WASO and pain (r= .277, p= .014). There were no significant correlations between the anxiety score and actigraphy parameters.
Using the significant correlations from the results of the third aim, multiple regression analysis was conducted with age as a covariate to test the fourth aim. The main effect of depression on sleep efficiency was significant (p= .044) with less depression associated with higher sleep efficiency. The interaction term, depression by race/ethnicity, had a non-significant effect on sleep efficiency (p= .299). The main effect of pain on WASO was significant (p= .008), and increased pain was associated with longer WASO. The interaction term, race/ethnicity by pain, had a non-significant effect on WASO (p= .148). The main effect of depression predicting sleep onset latency was significant (p= .027), and the interaction term, depression by race/ethnicity, had a trend towards a significant effect (p= .092) on predicting sleep onset latency. The interaction between depression and race/ethnicity predicting sleep onset latency was further decomposed using multiple regression. The average sleep onset latency was longer in the minority group with high depression levels (42 minutes) compared to the white, non-Hispanics with high depression levels (29 minutes). Race modified the effect of depression on sleep onset latency in this sample of BCS.
These finding suggest that the experience of objective sleep disturbances is different among races/ethnicities. Additional research is needed to further explore racial/ethnic differences in subjective and objective sleep disturbances and its impact on physical and psychological symptoms among BCS. As the number of BCS continue to rise, it is becoming increasingly important to recognize sleep disturbances and their potential physical and psychological effects early in BCS, specifically in different races and ethnicities. It is anticipated that these findings may contribute to improved symptom management for women of different races and ethnicities.
34
Swenson, Andrea Valeria Roets. "Making Romantic Relationships Tick: Objective and Subjective Time Use and Relationship Quality Among Business Owners." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/70908.
Анотація:
This study assesses the contextual aspect of working in a family business on intimate relationships. Guided by principles of ecological theory, this study explores the unique situation of individuals who work with an intimate partner in a business they own and how this situation manifests itself in their close relationship. Individuals in a family business are confronted with a potentially unique family-work experience, especially for spouses/partners who work together in a business. It is hypothesized that objective and subjective work time influence couple relationship quality.
Six specific hypotheses centered on the connection between family and work microsystems as well as the influence of macrosystem beliefs regarding family, work, and gender were assessed by regression analysis. Ninety-nine individuals completed a demographic and daily diary online. The sample was 52.53% men, 78.79% White, and educated (63.63% held at least Bachelor degrees). The majority of the sample was legally married (91.92%), with an average relationship length of 16.20 years (SD = 12.74 years).
Regression analyses revealed limited support for the hypotheses. For people in family businesses, working more hours was associated with greater withdrawal from their intimate partner. Perceiving work time as sad was linked to more withdrawal from partner and more anger with partner, but not linked with feelings of closeness to partner. People who felt time at work as appreciated reported feeling closer to their intimate partner. The more respondents believed it was meaningful to distinguish between work and family, the less closeness to their partner they reported. Finally, age was significant for relationship quality, with younger individuals reporting more withdrawal and anger with partner and less closeness to their partner than did older individuals.
This study contributes to research exploring the connection between family and work among individuals who work together in family businesses. While objective work time was associated with the measure of withdrawal from a partner, objective work time did not significantly contribute to the report of anger with a partner or closeness to a partner. Overall, how individuals felt during work time had an effect on their spousal/partner relationship, with feeling sad at work associated with more relationship withdrawal and anger, and feeling appreciated at work associated with more closeness. Limited support for the model suggests there may be unique processes of work and family operating within family businesses. Although work and family microsystems were connected in this study of family business owners, the links between work and family were different from previous research on dual- and single-earner families. Future research should untangle the processes through which work and family and time are connected, with attention to larger cultural influences, particularly how individuals within family businesses do work and family and how families ascribe to and enact gender within family businesses. In addition, further research should assess the degree to which microsystems can be differentiated in populations characterized by an extreme mesosystem connection between work and family.Ph. D.
35
Sahu, Amit K. "Objective assessment of image quality (OAIQ) in fluorescence-enhanced optical imaging." [College Station, Tex. : Texas A&M University, 2006. http://hdl.handle.net/1969.1/ETD-TAMU-1068.
36
Nocito, Carlos Daniel. "A Network Conditions Estimator for Voice Over IP Objective Quality Assessment." Scholarly Repository, 2011. http://scholarlyrepository.miami.edu/oa_theses/292.
Анотація:
Objective quality evaluation is a key element for the success of the emerging Voice over IP (VoIP) technologies. Although there are extensive economic incentives for the convergence of voice, data, and video networks, packet networks such as the Internet have inherent incompatibilities with the transport of real time services. Under this paradigm, network planners and administrators are interested in ongoing mechanisms to measure and ensure the quality of these real time services. Objective quality assessment algorithms can be broadly divided into a) intrusive (methods that require a reference signal), and b) non intrusive (methods that do not require a known reference signal). The latter group, typically requires knowledge of the network conditions (level of delay, jitter, packet loss, etc.), and that has been a very active area of research in the past decade. The state of the art methods for objective non-intrusive quality assessment provide high correlations with the subjective tests. Although good correlations have been achieved already for objective non-intrusive quality assessment, the current large voice transport networks are in a hybrid state, where the necessary network parameters cannot easily be observed from the packet traffic between nodes. This thesis proposes a new process, the Network Conditions Estimator (NCE), which can serve as bridge element to real-world hybrid networks. Two classifications systems, an artificial neural network and a C4.5 decision tree, were developed using speech from a database collected from experiments under controlled network conditions. The database was composed of a group of four female speakers and three male speakers, who conducted unscripted conversations without knowledge about the details of the experiment. Using mel frequency cepstral coefficients (MFCCs) as the feature-set, an accuracy of about 70% was achieved in detecting the presence of jitter or packet loss on the channel. This resulting classifier can be incorporated as an input to the E-Model, in order to properly estimate the QoS of a network in real time. Additionally, rather than just providing an estimation of subjective quality of service provided, the NCE provides an insight into the cause for low performance.
37
Foley, Jennifer A. "Retrospective and prospective memory in healthy and cognitively impaired older adults : using subjective and objective assessment." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/2205.
Анотація:
BACKGROUND: Retrospective and prospective memory deteriorate with age and deteriorate further with the onset of dementia. As previous research has tended to use idiosyncratic and heterogeneous methodologies, it is not known if the deterioration in retrospective or prospective memory is equal or how such deterioration is related to insight into mnemonic performance. DESIGN: The present study used a mixed, cross-sectional design. It examined retrospective and prospective memory in healthy and cognitively impaired older adults using objective and subjective assessment. METHODOLOGY: Twenty healthy and twenty cognitively impaired older adults were assessed. The objective measures were standardised and had high ecological validity, to maximise the assessments’ generalisability to everyday mnemonic functioning. The subjective measure was a standardised assessment of subjective appraisal of retrospective and prospective memory. This subjective assessment was used to gain self-ratings from the healthy and cognitively impaired older adults and, in addition, to gain proxy-ratings from the cognitively impaired older adults’ partners/carers. Participants were also assessed using a measure of general cognitive functioning. RESULTS: Healthy older adults performed significantly better than cognitively impaired older adults on both the retrospective and prospective memory test, although performance in both groups was higher on the prospective memory test than on the retrospective memory test. Neither proxy-ratings, nor overall severity of impairment, were associated with subjective assessment of prospective or retrospective memory. In the healthy older adults, self-rating of memory was not associated with objective memory performance. In the cognitively impaired older adults, however, higher self-ratings of memory were associated with poorer performance on the prospective memory test. DISCUSSION: The results suggested that both healthy and cognitively impaired older adults perform better on prospective memory tasks than retrospective memory tasks, but both types of memory deteriorate with the onset of dementia. Subjective memory appraisal is not related to objective memory performance in healthy older adults, but is negatively associated with prospective memory performance in cognitively impaired older adults. Findings were discussed in relation to previous research, along with a review of the strengths and limitations of the study. Clinical implications and directions for future research are also suggested.
38
Chintala, Bala Venkata Sai Sundeep. "Objective Perceptual Quality Assessment of JPEG2000 Image Coding Format Over Wireless Channel." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-17785.
Анотація:
A dominant source of Internet traffic, today, is constituted of compressed images. In modern multimedia communications, image compression plays an important role. Some of the image compression standards set by the Joint Photographic Expert Group (JPEG) include JPEG and JPEG2000. The expert group came up with the JPEG image compression standard so that still pictures could be compressed to be sent over an e-mail, be displayed on a webpage, and make high-resolution digital photography possible. This standard was originally based on a mathematical method, used to convert a sequence of data to the frequency domain, called the Discrete Cosine Transform (DCT). In the year 2000, however, a new standard was proposed by the expert group which came to be known as JPEG2000. The difference between the two is that the latter is capable of providing better compression efficiency. There is also a downside to this new format introduced. The computation required for achieving the same sort of compression efficiency as one would get with the original JPEG format is higher. JPEG is a lossy compression standard which can throw away some less important information without causing any noticeable perception differences. Whereas, in lossless compression, the primary purpose is to reduce the number of bits required to represent the original image samples without any loss of information. The areas of application of the JPEG image compression standard include the Internet, digital cameras, printing, and scanning peripherals. In this thesis work, a simulator kind of functionality setup is needed for conducting the objective quality assessment. An image is given as an input to our wireless communication system and its data size is varied (e.g. 5%, 10%, 15%, etc) and a Signal-to-Noise Ratio (SNR) value is given as input, for JPEG2000 compression. Then, this compressed image is passed through a JPEG encoder and then transmitted over a Rayleigh fading channel. The corresponding image obtained after having applied these constraints on the original image is then decoded at the receiver and inverse discrete wavelet transform (IDWT) is applied to inverse the JPEG 2000 compression. Quantization is done for the coefficients which are scalar-quantized to reduce the number of bits to represent them, without the loss of quality of the image. Then the final image is displayed on the screen. The original input image is co-passed with the images of varying data size for an SNR value at the receiver after decoding. In particular, objective perceptual quality assessment through Structural Similarity (SSIM) index using MATLAB is provided.
39
Reilly, Andrew James. "Uniform framework for the objective assessment and optimisation of radiotherapy image quality." Thesis, University of Edinburgh, 2011. http://hdl.handle.net/1842/5589.
Анотація:
Image guidance has rapidly become central to current radiotherapy practice. A uniform framework is developed for evaluating image quality across all imaging modalities by modelling the ‘universal phantom’: breaking any phantom down into its constituent fundamental test objects and applying appropriate analysis techniques to these through the construction of an automated analysis tree. This is implemented practically through the new software package ‘IQWorks’ and is applicable to both radiotherapy and diagnostic imaging. For electronic portal imaging (EPI), excellent agreement was observed with two commercial solutions: the QC-3V phantom and PIPS Pro software (Standard Imaging) and EPID QC phantom and epidSoft software (PTW). However, PIPS Pro’s noise correction strategy appears unnecessary for all but the highest frequency modulation transfer function (MTF) point and its contrast to noise ratio (CNR) calculation is not as described. Serious flaws identified in epid- Soft included erroneous file handling leading to incorrect MTF and signal to noise ratio (SNR) results, and a sensitivity to phantom alignment resulting in overestimation of MTF points by up to 150% for alignment errors of only ±1 pixel. The ‘QEPI1’ is introduced as a new EPI performance phantom. Being a simple lead square with a central square hole it is inexpensive and straightforward to manufacture yet enables calculation of a wide range of performance metrics at multiple locations across the field of view. Measured MTF curves agree with those of traditional bar pattern phantoms to within the limits of experimental uncertainty. An intercomparison of the Varian aS1000 and aS500-II detectors demonstrated an improvement in MTF for the aS1000 of 50–100% over the clinically relevant range 0.4–1 cycles/mm, yet with a corresponding reduction in CNR by a factor of p 2. Both detectors therefore offer advantages for different clinical applications. Characterisation of cone-beam CT (CBCT) facilities on two Varian On-Board Imaging (OBI) units revealed that only two out of six clinical modes had been calibrated by default, leading to errors of the order of 400 HU for some modes and materials – well outside the ±40 HU tolerance. Following calibration, all curves agreed sufficiently for dose calculation accuracy within 2%. CNR and MTF experiments demonstrated that a boost in MTF f50 of 20–30% is achievable by using a 5122 rather than a 3842 matrix, but with a reduction in CNR of the order of 30%. The MTF f50 of the single-pulse half-resolution radiographic mode of the Varian PaxScan 4030CB detector was measured in the plane of the detector as 1.0±0.1 cycles/mm using both a traditional tungsten edge and the new QEPI1 phantom. For digitally reconstructed radiographs (DRRs), a reduction in CT slice thickness resulted in an expected improvement in MTF in the patient scanning direction but a deterioration in the orthogonal direction, with the optimum slice thickness being 1–2 mm. Two general purposes display devices were calibrated against the DICOM Greyscale Standard Display Function (GSDF) to within the ±20% limit for Class 2 review devices. By providing an approach to image quality evaluation that is uniform across all radiotherapy imaging modalities this work enables consistent end-to-end optimisation of this fundamental part of the radiotherapy process, thereby supporting enhanced use of image-guidance at all relevant stages of radiotherapy and better supporting the clinical decisions based on it.
40
Wulf, Steffen [Verfasser]. "Human Perception in Objective Video Quality Assessment and Video Coding / Steffen Wulf." München : Verlag Dr. Hut, 2017. http://d-nb.info/113953839X/34.
41
Juhlin, Magnus. "Assessment of crosswind performance of buses." Doctoral thesis, Stockholm : Skolan för teknikvetenskap, Kungliga Tekniska högskolan, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-10382.
42
Silk, Eric Edward. "Relationship between Subjective and Objective Measures of Attention in a Clinical Population of Children and Adolescents." Thesis, NSUWorks, 2012. https://nsuworks.nova.edu/cps_stuetd/66.
Анотація:
Attention problems can pose a serious challenge to the academic progress of children and adolescents. Currently, there are several different assessment methods utilized in the clinical diagnosis of Attention-Deficit/Hyperactivity Disorder (ADHD). Subjective and objective assessment measures purport to be measuring similar constructs of inattention, hyperactivity, and impulsivity. The present study examines the degree of correlation between the constructs of attention problems, hyperactivity/impulsivity, and signal detection between the Conners' Continuous Performance Test II Version 5 (CPT II) and a parent-report measure of attention problems, hyperactivity/impulsivity, aggression, emotional problems, and learning problems in a general clinical population of children and adolescents. This study also measures the correlation between these measures and the Woodcock Johnson III Tests of Cognitive Abilities (WJ-III COG) Auditory Attention subtest.
No significant correlations were found among the CPT II errors of omission score or commissions score and attention problems or hyperactivity/impulsivity. No significant correlations were found among attention problems or hyperactivity/impulsivity and CPT II Reaction Time (RT), variability, or attentiveness. No significant correlations were found among the CPT II errors of omission or commissions scores and emotional problems, aggression, or learning problems. No significant correlations were found among the CPT II errors of omission score, commissions score, or RT and the WJ-III COG Auditory Attention subtest. A significant negative correlation was found between the CPT II variability score and the WJ-III COG Auditory Attention subtest. A significant positive correlation was found between the CPT II attentiveness score and the WJ-III COG Auditory Attention subtest. No significant correlations were found among any of the parent measures of attention problems Auditory Attention subtest.
In a canonical correlation analysis there were high loadings on attention problems and hyperactivity/impulsivity on the parent-measure set and on commission errors and RT on the CPT II set. A modest loading on the multiple imputation set was also found on aggression problems and the parent-measure set. These findings support the overall conclusion that the CPT II does not generally relate to the parent-report measures. These findings indicate that there is little meaningful relationship between these two measures, which clinically are both used to assess attention problems.
43
McFarland, Mark A. "A subjective video quality test methodology for the assessment of recorded surveillance video." Connect to online resource, 2007. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1447690.
44
Manka, David L. "Voice over Internet Protocol testbed design for non-intrusive, objective voice quality assessment." Thesis, Monterey, Calif. : Naval Postgraduate School, 2007. http://bosun.nps.edu/uhtbin/hyperion-image.exe/07Sep%5FManka.pdf.
Анотація:
Thesis (M.S. in Electrical Engineering)--Naval Postgraduate School, September 2007.Thesis Advisor(s): Tummala, Murali ; McEachen, John C. "September 2007." Description based on title screen as viewed on October 23, 2007. Includes bibliographical references (p.91-94). Also available in print.
45
Grönborg, Felix, and Otto Ortega. "Evaluation of Methods for Image Analysis with the Purpose of Imitating Subjective Quality Assessment." Thesis, Linköpings universitet, Medie- och Informationsteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-174849.
Анотація:
Detta examensarbete gjordes i samarbete med Husfoto AB där syftet var att undersöka potentialen i att använda maskininlärniningsalgoritmer för att utföra automatiska klassificeringar mellan godkända och icke-godkända bilder enligt en subjektivt framställd kvalitetsstandard. Både metoder som använder maskininlärning, samt mer traditionella bildanalysmetoder användes, testades och jämfördes inom kvalitetsmåtten precision, känslighet, träffsäkerhet och balanserad träffsäkerhet. Maskininlärningsmetoder som användes var en linjär och en icke-linjär variant av Support Vector Machine (SVM), samt XGboost. De manuella metoderna var en variant av White Patch, samt två egna metoder framtagna för projektet. Bildfelen som undersöktes var vitbalans och färgen på himmel för exteriörbilder, och datan samlades in och annoterades parallellt med arbetet. Trots att mängden data var begränsad så erhölls bättre resultat än förväntat, vilket ger en indikation på att maskininlärning kan användas för klassificeringar med subjektiva bedömningar som referensmått med gott resultat. Resultaten visar att kvalitetsmåtten för flera metoder presterar relativt likvärdigt i många fall med vissa avvikande skillnader. Genom att använda den subjektiva bedömningen av Husfoto för att skapa ett objektivt mått med metoderna som används så visar resultatet att metoderna för vissa fel kommer upp i över 80% träffsäkerhet.Examensarbetet är utfört vid Institutionen för teknik och naturvetenskap (ITN) vid Tekniska högskolan, Linköpings universitet
46
Kaya, Safak. "Quality Of Life In Turkey: A Comparative Analysis With The European Union Member States." Master's thesis, METU, 2006. http://etd.lib.metu.edu.tr/upload/3/12607932/index.pdf.
Анотація:
This study aims to describe the quality of life of Turkey in comparison with the European Union Member States including the other candidate countries Bulgaria and Romania. The main question in the study is to determine where Turkey stands in terms of quality of life domains in the membership process to the European Union.
For this aim, &ldquoThe European Quality of Life Survey&rdquo
that has been launched in 2003 including 28 countries in Europe has been used. The survey consists of eight life domains including different objective and subjective indicators to measure the quality of life in these countries. The findings revealed that although Turkey displays similar patterns with the other candidate countries, it lags behind the European Union Member States in most of these eight quality of life domains.
47
Suresh, Nitin. "Mean Time Between Visible Artifacts in Visual Communications." Diss., Georgia Institute of Technology, 2007. http://hdl.handle.net/1853/16238.
Анотація:
As digital communication of television content becomes more pervasive, and as networks supporting such communication become increasingly diverse, the long-standing problem of assessing video quality by objective measurements becomes particularly important. Content owners as well as content distributors stand to benefit from rapid objective measurements that correlate well with subjective assessments, and further, do not depend on the availability of the original reference video.
This thesis investigates different techniques of subjective and objective video evaluation. Our research recommends a functional quality metric called Mean Time Between Failures (MTBF) where failure refers to video artifacts deemed to be perceptually noticeable, and investigates objective measurements that correlate well with subjective evaluations of MTBF.
Work has been done for determining the usefulness of some existing objective metric by noting their correlation with MTBF. The research also includes experimentation with network-induced artifacts, and a study on statistical methods for correlating candidate objective measurements with the subjective metric. The statistical significance and spread properties for the correlations are studied, and a comparison of subjective MTBF with the existing subjective measure of MOS is performed. These results suggest that MTBF has a direct and predictable relationship with MOS, and that they have similar variations across different viewers.
The research is particularly concerned with the development of new no-reference objective metrics that are easy to compute in real time, as well as correlate better than current metrics with the intuitively appealing MTBF measure. The approach to obtaining greater subjective relevance has included the study of better spatial-temporal models for noise-masking and test data pooling in video perception.
A new objective metric, 'Automatic Video Quality' metric (AVQ) is described and shown to be implemented in real time with a high degree of correlation with actual subjective scores, with the correlation values approaching the correlations of metrics that use full or partial reference. This is metric does not need any reference to the original video, and when used to display MPEG2 streams, calculates and indicates the video quality in terms of MTBF. Certain diagnostics like the amount of compression and network artifacts are also shown.
48
Bensaied, Ghaly Rania. "Subjective quality assessment : a study on the grading scales : illustrations for stereoscopic and 2D video content." Thesis, Evry, Institut national des télécommunications, 2018. http://www.theses.fr/2018TELE0013/document.
Анотація:
Les recommandations (normes) élaborées par l'UIT (l'Union Internationale de Télécommunications) précisent avec rigueur les conditions dans lesquelles les tests subjectifs de qualité visuelle doivent avoir lieu: la salle de test, les conditions de visualisation, le protocole d'évaluation, les méthodes de post-traitement des scores accordées par les évaluateurs, etc... Pourtant, les études de l'état de l'art mettent en évidence que des nombreuses inadvertances perdurent au niveau théorique et expérimental: (1) la modélisation statistique précise des scores attribués par les observateurs humains à un certain type de contenu reste encore inconnue, (2) la différence théorique et applicative entre les évaluations sur des échelles discrètes et continues ne fait pas encore l'objet d'une étude dédiée et (3) l'impact sémantique (psycho-cognitif) des étiquettes associées à l'échelle d'évaluation est toujours invoqué mais jamais évalué. Notre thèse offre un cadre méthodologique et expérimental permettant de: 1. Modéliser avec précision statistique la distribution des scores attribués par les observateurs et évaluer l'impact pratique d'une telle modélisation, 2. Établir la relation théorique entre les scores attribués par les observateurs sur une échelle continue et une échelle discrète, 3. Établir le cadre statistique permettant de quantifier l'impact sémantique induit par les étiquettes sémantiques associées à l'échelle d'évaluation, 4. Spécifier et réaliser un cadre expérimental de référence, à vocation d'utilisation ultérieure par les instances de l'UITQuality evaluation is an ever-fascinating field, covering at least a century of research works emerging from psychology, psychophysics, sociology, marketing, medicine… While for visual quality evaluation the IUT recommendations pave the way towards well-configured, consensual evaluation conditions granting reproducibility and comparability of the experimental results, an in-depth analysis of the state-of-the-art studies shows at least three open challenges related to the: (1) the continuous vs. discrete evaluation scales, (2) the statistical distribution of the scores assigned by the observers and (3) the usage of semantic labels on the grading scales. Thus, the present thesis turns these challenges into three research objectives: 1. bridging at the theoretical level the continuous and the discrete scale evaluation procedures and investigating whether the number of the classes on the discrete scales is a criterion meaningful in the results interpretations or just a parameter; studying the theoretical influence of the statistical model of evolution results and of the size of the panel (number of observers) in the accuracy of the results are also targeted; 2. quantifying the bias induced in subjective video quality experiments by the semantic labels (e.g. Excellent, Good, Fair, Poor and Bad) generally associated to the discrete grading scales; 3. designing and deploying an experimental test-bed able to support their precision and statistical relevance. With respect to these objectives, the main contributions are at theoretical, methodological and experimental levels
49
Bensaied, Ghaly Rania. "Subjective quality assessment : a study on the grading scales : illustrations for stereoscopic and 2D video content." Electronic Thesis or Diss., Evry, Institut national des télécommunications, 2018. http://www.theses.fr/2018TELE0013.
Анотація:
Les recommandations (normes) élaborées par l'UIT (l'Union Internationale de Télécommunications) précisent avec rigueur les conditions dans lesquelles les tests subjectifs de qualité visuelle doivent avoir lieu: la salle de test, les conditions de visualisation, le protocole d'évaluation, les méthodes de post-traitement des scores accordées par les évaluateurs, etc... Pourtant, les études de l'état de l'art mettent en évidence que des nombreuses inadvertances perdurent au niveau théorique et expérimental: (1) la modélisation statistique précise des scores attribués par les observateurs humains à un certain type de contenu reste encore inconnue, (2) la différence théorique et applicative entre les évaluations sur des échelles discrètes et continues ne fait pas encore l'objet d'une étude dédiée et (3) l'impact sémantique (psycho-cognitif) des étiquettes associées à l'échelle d'évaluation est toujours invoqué mais jamais évalué. Notre thèse offre un cadre méthodologique et expérimental permettant de: 1. Modéliser avec précision statistique la distribution des scores attribués par les observateurs et évaluer l'impact pratique d'une telle modélisation, 2. Établir la relation théorique entre les scores attribués par les observateurs sur une échelle continue et une échelle discrète, 3. Établir le cadre statistique permettant de quantifier l'impact sémantique induit par les étiquettes sémantiques associées à l'échelle d'évaluation, 4. Spécifier et réaliser un cadre expérimental de référence, à vocation d'utilisation ultérieure par les instances de l'UITQuality evaluation is an ever-fascinating field, covering at least a century of research works emerging from psychology, psychophysics, sociology, marketing, medicine… While for visual quality evaluation the IUT recommendations pave the way towards well-configured, consensual evaluation conditions granting reproducibility and comparability of the experimental results, an in-depth analysis of the state-of-the-art studies shows at least three open challenges related to the: (1) the continuous vs. discrete evaluation scales, (2) the statistical distribution of the scores assigned by the observers and (3) the usage of semantic labels on the grading scales. Thus, the present thesis turns these challenges into three research objectives: 1. bridging at the theoretical level the continuous and the discrete scale evaluation procedures and investigating whether the number of the classes on the discrete scales is a criterion meaningful in the results interpretations or just a parameter; studying the theoretical influence of the statistical model of evolution results and of the size of the panel (number of observers) in the accuracy of the results are also targeted; 2. quantifying the bias induced in subjective video quality experiments by the semantic labels (e.g. Excellent, Good, Fair, Poor and Bad) generally associated to the discrete grading scales; 3. designing and deploying an experimental test-bed able to support their precision and statistical relevance. With respect to these objectives, the main contributions are at theoretical, methodological and experimental levels
50
Palit, Robin. "Computational Tools and Methods for Objective Assessment of Image Quality in X-Ray CT and SPECT." Diss., The University of Arizona, 2012. http://hdl.handle.net/10150/268492.
Анотація:
Computational tools of use in the objective assessment of image quality for tomography systems were developed for computer processing units (CPU) and graphics processing units (GPU) in the image quality lab at the University of Arizona. Fast analytic x-ray projection code called IQCT was created to compute the mean projection image for cone beam multi-slice helical computed tomography (CT) scanners. IQCT was optimized to take advantage of the massively parallel architecture of GPUs. CPU code for computing single photon emission computed tomography (SPECT) projection images was written calling upon previous research in the image quality lab. IQCT and the SPECT modeling code were used to simulate data for multimodality SPECT/CT observer studies. The purpose of these observer studies was to assess the benefit in image quality of using attenuation information from a CT measurement in myocardial SPECT imaging. The observer chosen for these studies was the scanning linear observer. The tasks for the observer were localization of a signal and estimation of the signal radius. For the localization study, area under the localization receiver operating characteristic curve (A(LROC)) was computed as A(LROC)^Meas = 0.89332 ± 0.00474 and A(LROC)^No = 0.89408 ± 0.00475, where "Meas" implies the use of attenuation information from the CT measurement, and "No" indicates the absence of attenuation information. For the estimation study, area under the estimation receiver operating characteristic curve (A(EROC)) was quantified as A(EROC)^Meas = 0.55926 ± 0.00731 and A(EROC)^No = 0.56167 ± 0.00731. Based on these results, it was concluded that the use of CT information did not improve the scanning linear observer's ability to perform the stated myocardial SPECT tasks. The risk to the patient of the CT measurement was quantified in terms of excess effective dose as 2.37 mSv for males and 3.38 mSv for females.Another image quality tool generated within this body of work was a singular value decomposition (SVD) algorithm to reduce the dimension of the eigenvalue problem for tomography systems with rotational symmetry. Agreement in the results of this reduced dimension SVD algorithm and those of a standard SVD algorithm are shown for a toy problem. The use of SVD toward image quality metrics such as the measurement and null space are also presented.