An IP based set-top box (STB) is essentially a lightweight computer used to receive video over the Internet and convert it to analog or digital signals understood by the television. During this transformation from a digital image to an analog video signal many different types of distortions can occur. Some of these distortions will affect the image quality in a negative way. If these distortions could be measured they might be corrected and give the system a better image quality. This thesis is a continuation of two previous theses where a custom hardware for sampling analog component video signals was created. A software used to communicatewith the sampling hardware and perform several different measurementson the samples collected has been created in this thesis. The analog video signal quality measurement system has been compared to a similar commercial product and it was found that all except two measurement methods gave very good results. The remaining two measurement methods gave acceptable result. However the differences might be due to differences in implementation. The most important thing for the measurement system is to have consistency. If a system has consistency then any changes leading to worse videoquality can be found.

This master’s theses consists of theoretical introduction which includes basic search of referenced literature about digital television systems and picture quality classification. The results of signal character measurement of selected TV channels from satellites ASTRA 1E (DVB-S) and ASTRA 1L (DVB-S2) are provided. The energy budget calculation of downlink and results of 24-hour TS error rate measurement is included as well. The video quality by DVQL metric for each particular program of CS link stream was measured during full 24 hours.

<p>У овој дисертацији разматране су објективне мере процене квалитета<br />слике и видеа са потпуним и делимичним референцирањем на изворни<br />сигнал. За потребе евалуације квалитета развијене су поуздане,<br />рачунски ефикасне мере, засноване на очувању информација о<br />градијенту. Мере су тестиране на великом броју тест слика и видео<br />секвенци, различитих типова и степена деградације. Поред јавно<br />доступних база слика и видео секвенци, за потребе истраживања<br />формиране су и нове базе видео секвенци са преко 300 релевантних<br />тест узорака. Поређењем доступних субјективних и објективних скорова<br />квалитета показано је да је објективна евалуација квалитета веома<br />сложен проблем, али га је могуће решити и доћи до високих<br />перформанси коришћењем предложених мера процене квалитета слике<br />и видеа.</p> / <p>U ovoj disertaciji razmatrane su objektivne mere procene kvaliteta<br />slike i videa sa potpunim i delimičnim referenciranjem na izvorni<br />signal. Za potrebe evaluacije kvaliteta razvijene su pouzdane,<br />računski efikasne mere, zasnovane na očuvanju informacija o<br />gradijentu. Mere su testirane na velikom broju test slika i video<br />sekvenci, različitih tipova i stepena degradacije. Pored javno<br />dostupnih baza slika i video sekvenci, za potrebe istraživanja<br />formirane su i nove baze video sekvenci sa preko 300 relevantnih<br />test uzoraka. Poređenjem dostupnih subjektivnih i objektivnih skorova<br />kvaliteta pokazano je da je objektivna evaluacija kvaliteta veoma<br />složen problem, ali ga je moguće rešiti i doći do visokih<br />performansi korišćenjem predloženih mera procene kvaliteta slike<br />i videa.</p> / <p>This thesis presents an investigation into objective image and video quality<br />assessment with full and reduced reference on original (source) signal. For<br />quality evaluation purposes, reliable, computational efficient, gradient-based<br />measures are developed. Proposed measures are tested on different image<br />and video datasets, with various types of distorsions and degradation levels.<br />Along with publicly available image and video quality datasets, new video<br />quality datasets are maded, with more than 300 relevant test samples.<br />Through comparison between available subjective and objective quality<br />scores it has been shown that objective quality evaluation is highly complex<br />problem, but it is possible to resolve it and acchieve high performance using<br />proposed quality measures.</p>

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 visuel. / The 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.

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.