Dissertations / Theses: 'Video Quality Assessment'

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Banitalebi, Dehkordi Amin. "3D video quality assessment." Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/54581.

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A key factor in designing 3D systems is to understand how different visual cues and distortions affect the perceptual quality of 3D video. The ultimate way to assess video quality is through subjective tests. However, subjective evaluation is time consuming, expensive, and in most cases not even possible. An alternative solution is objective quality metrics, which attempt to model the Human Visual System (HVS) in order to assess the perceptual quality. The potential of 3D technology to significantly improve the immersiveness of video content has been hampered by the difficulty of objectively assessing Quality of Experience (QoE). A no-reference (NR) objective 3D quality metric, which could help determine capturing parameters and improve playback perceptual quality, would be welcomed by camera and display manufactures. Network providers would embrace a full-reference (FR) 3D quality metric, as they could use it to ensure efficient QoE-based resource management during compression and Quality of Service (QoS) during transmission. In this thesis, we investigate the objective quality assessment of stereoscopic 3D video. First, we propose a full-reference Human-Visual-system based 3D (HV3D) video quality metric, which efficiently takes into account the fusion of the two views as well as depth map quality. Subjective experiments verified the performance of the proposed method. Next, we investigate the No-Reference quality assessment of stereoscopic video. To this end, we investigate the importance of various visual saliency attributes in 3D video. Based on the results gathered from our study, we design a learning based visual saliency prediction model for 3D video. Eye-tracking experiments helped verify the performance of the proposed 3D Visual Attention Model (VAM). A benchmark dataset containing 61 captured stereo videos, their eye fixation data, and performance evaluations of 50 state-of-the-art VAMs is created and made publicly available online. Finally, we incorporate the saliency maps generated by our 3D VAM in the design of the state-of-the- art no-reference (NR) and also full-reference (FR) 3D quality metrics.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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Prytz, Anders. "Video Quality Assessment in Broadcasting." Thesis, Norwegian University of Science and Technology, Department of Electronics and Telecommunications, 2010. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-10870.

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In broadcasting, the assessment of video quality is mostly done by a group of highly experienced people. This is a time consuming task and demands lot of resources. In this thesis the goal is to investigate the possibility to assess perceived video quality with the use of objective quality assessment methods. The work is done in collaboration with Telenor Satellite Broadcasting AS, to improve their quality verification process from a broadcasting perspective. The material used is from the SVT Fairytale tape and a tape from the Norwegian cup final in football 2009. All material is in the native resolution of 1080i and is encoded in the H.264/AVC format. All chosen compression settings are more or less used in daily broadcasting. A subjective video quality assessment been carried out to create a comparison basis of perceived quality. The subjective assessment sessions carried out by following ITU recommendations. Telenor SBc provided a video quality analysing system, the Video Clarity Clearview system that contains the objective PSNR, DMOS and JND. DMOS and JND are two pseudo-subjective assessment methods that use objective methods mapped to subjective results. The methods hopefully predict the perceived quality and eases quality assessment in broadcasting. The correlation between the subjective and objective results is tested with linear, exponential and polynomial fitting functions. The correlation for the different methods did not achieve a result that proved use of objective methods to assess perceived quality, independent of content. The best correlation result is 0.75 for the objective DMOS method. The analysis shows that there are possible dependencies in the relationship between subjective and objective results. By measuring spatial and temporal information possible dependent correlation results are investigated. The results for dependent relationships between subjective and objective results are good. There are some indications that the two pseudo-subjective methods, JND and DMOS, can be used to assess perceived video quality. This applies when the mapping functions are dependent on spatial and temporal information of the reference sequences. The correlation achieved for dependent fitting functions, that has a suitable progression, are in the range 0.9 -- 0.98. In the subjective tests, the subjects used were non-experts in quality evaluation. Some of the results indicate that subjects might have a problem with assessing sequences with high spatial information. This thesis creates a basis for further research on the use of objective methods to assess the perceived quality.

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Dhakal, Prabesh, Prabhat Tiwari, and Pawan Chan. "Perceptual Video Quality Assessment Tool." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-2576.

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Subjective video quality is a subjective characteristic of video quality. It is concerned with how a video is perceived by the viewer and designates his or her opinion on the particular video sequence. Subjective video quality tests are quite expensive in terms of time (preparation and running) and human resources. The main objectives of this testing is how the human observes the video quality since they are the ultimate end user. There are many ways of testing the quality of the videos. We have used ITU-T Recommendation P.910.
In our research work, we have designed the tool that can be used to conduct a mass-scale level survey or subjective tests. ACR is the only method used to carry out the subjective video assessment. The test is very useful in the context of a video streaming quality. The survey can be used in various countries and sectors with low internet speeds to determine the kind of video or the compression technique, bit rate, or format that gives the best quality.
0700627491, 0760935352

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Jung, Agata. "Comparison of Video Quality Assessment Methods." Thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-15062.

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Context: The newest standard in video coding High Efficiency Video Coding (HEVC) should have an appropriate coder to fully use its potential. There are a lot of video quality assessment methods. These methods are necessary to establish the quality of the video. Objectives: This thesis is a comparison of video quality assessment methods. Objective is to find out which objective method is the most similar to the subjective method. Videos used in tests are encoded in the H.265/HEVC standard. Methods: For testing MSE, PSNR, SSIM methods there is special software created in MATLAB. For VQM method downloaded software was used for testing. Results and conclusions: For videos watched on mobile device: PSNR is the most similar to subjective metric. However for videos watched on television screen: VQM is the most similar to subjective metric. Keywords: Video Quality Assessment, Video Quality Prediction, Video Compression, Video Quality Metrics

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Yang, Kai-Chieh. "Perceptual quality assessment for compressed video." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3284171.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed Mar. 14, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 149-156).

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Sarikan, Selim Sefa. "Visual Quality Assessment For Stereoscopic Video Sequences." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613689/index.pdf.

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The aim of this study is to understand the effect of different depth levels on the overall 3D quality and develop an objective video quality metric for stereoscopic video sequences. Proposed method is designed to be used in video coding stages to improve overall 3D video quality. This study includes both objective and subjective evaluation. Test sequences with different coding schemes are used. Computer simulation results show that overall quality has a strong correlation with the quality of the background, where disparity is smaller relative to the foreground. This correlation indicates that background layer is more prone to coding errors. The results also showed that content type is an important factor in determining the visual quality.

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Jenadeleh, Mohsen [Verfasser]. "Blind Image and Video Quality Assessment / Mohsen Jenadeleh." Konstanz : Bibliothek der Universität Konstanz, 2018. http://d-nb.info/117308777X/34.

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Qadri, Muhammad Tahir. "Blockiness and blurriness measurement for video quality assessment." Thesis, University of Essex, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.574461.

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Rapid growth of wired and wireless multi-media data challenges the researchers to develop an efficient objective assessment meter to estimate their quality. This research is focused to design objective quality assessment meters for images and video sequences. In this work, we proposed blockiness and blurriness distortion meters using full, reduced and no reference approaches. Both blockiness and blurriness distortions are calculated using frequency domain analysis. Since blockiness is an abrupt luminance change at DCT block boundaries which is also periodic therefore it generates harmonics in frequency domain, we used the strength of harmonics to estimate blockiness distortion. The more severe the blockiness is, the stronger will be the strength of harmonics in frequency domain. While blurriness removes the sharpness of the image by removing the high frequency components therefore we studied the loss of high frequency coefficients to measure blurriness artefact. We also aimed to design a multi-artefact distortion meter which can estimate the distortion without prior knowledge of distortion type. We developed the combined distortion meter for full, reduced and no reference approaches to estimate both blockiness and blurriness artefacts. We also studied the impact of spatial masking in image quality estimation. Due to the non linear behaviour of human visual system which perceives different amount of distortions at different spatial frequencies, we applied the masking process which weights the visibility of distortion according to the local spatial activity of the image. We investigated the importance of spatial masking in FR, RR and NR modes. Finally for video sequences, the quality metric of each frame is calculated and then we explored the methods to integrate these scores into a single value. Then the temporal masking is applied to mask the motion by using motion vectors and their standard deviations. The results are compared with the subjective scores provided by LIVE image and video database.

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Galkandage, Chathura. "Perception inspired stereoscopic image and video quality assessment." Thesis, University of Surrey, 2018. http://epubs.surrey.ac.uk/845426/.

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Recent developments in 3D media technology have brought to life numerous applications of interactive entertainment such as 3D cinema, 3DTV and gaming. Due to the data intensive nature of 3D visual content, Quality of Experience (QoE) has become a major driving factor to optimise the end-to-end content delivery process. However, to ensure the QoE, there is a need to develop more robust and accurate objective metrics for stereoscopic image and video quality assessment. Existing stereoscopic QoE metrics tend to lack in accuracy and robustness compared to its 2D counterparts as they are either extensions of 2D metrics or are based on simple perceptual models. However, measuring stereoscopic QoE requires more perceptually inspired metrics. This research introduces full-reference stereoscopic image and video quality metrics based on a Human Visual System (HVS) model incorporating important physiological findings on binocular vision. Firstly, a novel HVS model extending existing models in the literature is proposed to include the phenomena of binocular suppression and recurrent excitation towards stereoscopic image quality assessment. Secondly the research is extended to the temporal domain using temporal pooling of the HVS model outputs for individual frames and using a spatio-temporal model in the HVS model towards two distinct temporally inspired stereoscopic video quality metrics. Finally, motion sensitivity is introduced to the HVS model towards a perception inspired stereoscopic video quality metric. The proposed QoE metrics are trained, verified and tested using four publicly available stereoscopic image databases and two stereoscopic video datasets. They indicate an increase of average correlation index from 0.66 (baseline method) to 0.86 for the stereoscopic images and a maximum increase of average correlation index from 0.57 (baseline method) to 0.93 for stereoscopic videos. These results demonstrate the benefits of using a perceptually inspired approach in this research.

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Khaustova, Darya. "Objective assessment of stereoscopic video quality of 3DTV." Thesis, Rennes 1, 2015. http://www.theses.fr/2015REN1S021/document.

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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

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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.

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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.

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Zhu, Kongfeng [Verfasser]. "No-reference Video Quality Assessment and Applications / Kongfeng Zhu." Konstanz : Bibliothek der Universität Konstanz, 2014. http://d-nb.info/1058326015/34.

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Mu, Mu. "Parametric assessment of video quality in content distribution networks." Thesis, Lancaster University, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.587509.

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IP-based packet-switched networks have become one of the main content distribution platforms for emerging multimedia services such as IPTV, thanks to the rapidly growing bandwidth and exclusive internetworking and interactivity features of IP-based networks. Meanwhile, high quality video content services are becoming particularly popular within content delivery networks (CDN). During content distribution, packets of encoded video streams can be delayed, corrupted or dropped due to network impairments in packet-switched networks. This leads to perceptual quality degradations of the delivered content at receiver. Although network impairments are rare in commercial managed networks, any distortion caused by impairments can be highly detrimental to end users' experience. Consequently the ability to meet customer expectations on video quality has become a critical service differentiator. Quality of Experience (QoE) that was merely recognised as a value-added service of traditional content distribution services is now one of the fundamental requirements and challenges of providing high quality video services. In order to maintain a high level of user experience throughout the life-cycle of a video service, a service quality measurement and management service must be established. In this thesis a parametric assessment model is designed and implemented to provide accurate in-service quality assessment services with respect to human users' perception of visual distortions. The model monitors video quality specifically in response to discrete network impairment events. Multiple impact factors and quantification metrics have been defined for the realisation of assessment functions. Exploiting specifically designed discrete analysis methodology and packet inspection mechanisms, the designed assessment model aims at supporting a quality monitoring service in large scale commercial video content networks. A testbed system, the LA2 system, is also developed to provide an assortment of tools for the design and evaluation of parametric assessment models. Using the LA2 system, comprehensive test plans and subjective experiments are specified and conducted to establish relevant impact factors and to quantitatively model users' opinion of visual distortions as a set of assessment functions. Specifically, the statistical binary logistic model and cumulative logit model are employed to model the distribution of perceivability of content loss distortion in dichotomous and polytomous scales. The designed model provides high performance estimations to subjective user opinions according to selected statistical fitness tests. A validation test also verifies the generality of the designed model

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Kong, Lingchao. "Modeling of Video Quality for Automatic Video Analysis and Its Applications in Wireless Camera Networks." University of Cincinnati / OhioLINK, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1563295836742645.

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Gao, Zhigang. "Image/video compression and quality assessment based on wavelet transform." Columbus, Ohio : Ohio State University, 2007. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1187195053.

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Huynh-Thu, Quan. "Perceptual quality assessment of communications-grade video with temporal artefacts." Thesis, University of Essex, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.502128.

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Druda, Luca. "Quality of experience in skype video calls." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2012. http://amslaurea.unibo.it/4005/.

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Skype is one of the well-known applications that has guided the evolution of real-time video streaming and has become one of the most used software in everyday life. It provides VoIP audio/video calls as well as messaging chat and file transfer. Many versions are available covering all the principal operating systems like Windows, Macintosh and Linux but also mobile systems. Voice quality decreed Skype success since its birth in 2003 and peer-to-peer architecture has allowed worldwide diffusion. After video call introduction in 2006 Skype became a complete solution to communicate between two or more people. As a primarily video conferencing application, Skype assumes certain characteristics of the delivered video to optimize its perceived quality. However in the last years, and with the recent release of SkypeKit1, many new Skype video-enabled devices came out especially in the mobile world. This forced a change to the traditional recording, streaming and receiving settings allowing for a wide range of network and content dynamics. Video calls are not anymore based on static ‘chatting’ but mobile devices have opened new possibilities and can be used in several scenarios. For instance, lecture streaming or one-to-one mobile video conferences exhibit more dynamics as both caller and callee might be on move. Most of these cases are different from “head&shoulder” only content. Therefore, Skype needs to optimize its video streaming engine to cover more video types. Heterogeneous connections require different behaviors and solutions and Skype must face with this variety to maintain a certain quality independently from connection used. Part of the present work will be focused on analyzing Skype behavior depending on video content. Since Skype protocol is proprietary most of the studies so far have tried to characterize its traffic and to reverse engineer its protocol. However, questions related to the behavior of Skype, especially on quality as perceived by users, remain unanswered. We will study Skype video codecs capabilities and video quality assessment. Another motivation of our work is the design of a mechanism that estimates the perceived cost of network conditions on Skype video delivery. To this extent we will try to assess in an objective way the impact of network impairments on the perceived quality of a Skype video call. Traditional video streaming schemes lack the necessary flexibility and adaptivity that Skype tries to achieve at the edge of a network. Our contribution will lye on a testbed and consequent objective video quality analysis that we will carry out on input videos. We will stream raw video files with Skype via an impaired channel and then we will record it at the receiver side to analyze with objective quality of experience metrics.

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Khan, Asiya. "Video quality prediction for video over wireless access networks (UMTS and WLAN)." Thesis, University of Plymouth, 2011. http://hdl.handle.net/10026.1/893.

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Transmission of video content over wireless access networks (in particular, Wireless Local Area Networks (WLAN) and Third Generation Universal Mobile Telecommunication System (3G UMTS)) is growing exponentially and gaining popularity, and is predicted to expose new revenue streams for mobile network operators. However, the success of these video applications over wireless access networks very much depend on meeting the user’s Quality of Service (QoS) requirements. Thus, it is highly desirable to be able to predict and, if appropriate, to control video quality to meet user’s QoS requirements. Video quality is affected by distortions caused by the encoder and the wireless access network. The impact of these distortions is content dependent, but this feature has not been widely used in existing video quality prediction models. The main aim of the project is the development of novel and efficient models for video quality prediction in a non-intrusive way for low bitrate and resolution videos and to demonstrate their application in QoS-driven adaptation schemes for mobile video streaming applications. This led to five main contributions of the thesis as follows:(1) A thorough understanding of the relationships between video quality, wireless access network (UMTS and WLAN) parameters (e.g. packet/block loss, mean burst length and link bandwidth), encoder parameters (e.g. sender bitrate, frame rate) and content type is provided. An understanding of the relationships and interactions between them and their impact on video quality is important as it provides a basis for the development of non-intrusive video quality prediction models.(2) A new content classification method was proposed based on statistical tools as content type was found to be the most important parameter. (3) Efficient regression-based and artificial neural network-based learning models were developed for video quality prediction over WLAN and UMTS access networks. The models are light weight (can be implemented in real time monitoring), provide a measure for user perceived quality, without time consuming subjective tests. The models have potential applications in several other areas, including QoS control and optimization in network planning and content provisioning for network/service providers.(4) The applications of the proposed regression-based models were investigated in (i) optimization of content provisioning and network resource utilization and (ii) A new fuzzy sender bitrate adaptation scheme was presented at the sender side over WLAN and UMTS access networks. (5) Finally, Internet-based subjective tests that captured distortions caused by the encoder and the wireless access network for different types of contents were designed. The database of subjective results has been made available to research community as there is a lack of subjective video quality assessment databases.

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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.

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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.

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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.

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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'UIT
Quality 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

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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.

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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.

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Rossholm, Andreas. "On Enhancement and Quality Assessment of Audio and Video in Communication Systems." Doctoral thesis, Blekinge Tekniska Högskola, Institutionen för tillämpad signalbehandling, 2014. http://urn.kb.se/resolve?urn=urn:nbn:se:bth-00604.

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The use of audio and video communication has increased exponentially over the last decade and has gone from speech over GSM to HD resolution video conference between continents on mobile devices. As the use becomes more widespread the interest in delivering high quality media increases even on devices with limited resources. This includes both development and enhancement of the communication chain but also the topic of objective measurements of the perceived quality. The focus of this thesis work has been to perform enhancement within speech encoding and video decoding, to measure influence factors of audio and video performance, and to build methods to predict the perceived video quality. The audio enhancement part of this thesis addresses the well known problem in the GSM system with an interfering signal generated by the switching nature of TDMA cellular telephony. Two different solutions are given to suppress such interference internally in the mobile handset. The first method involves the use of subtractive noise cancellation employing correlators, the second uses a structure of IIR notch filters. Both solutions use control algorithms based on the state of the communication between the mobile handset and the base station. The video enhancement part presents two post-filters. These two filters are designed to improve visual quality of highly compressed video streams from standard, block-based video codecs by combating both blocking and ringing artifacts. The second post-filter also performs sharpening. The third part addresses the problem of measuring audio and video delay as well as skewness between these, also known as synchronization. This method is a black box technique which enables it to be applied on any audiovisual application, proprietary as well as open standards, and can be run on any platform and over any network connectivity. The last part addresses no-reference (NR) bitstream video quality prediction using features extracted from the coded video stream. Several methods have been used and evaluated: Multiple Linear Regression (MLR), Artificial Neural Network (ANN), and Least Square Support Vector Machines (LS-SVM), showing high correlation with both MOS and objective video assessment methods as PSNR and PEVQ. The impact from temporal, spatial and quantization variations on perceptual video quality has also been addressed, together with the trade off between these, and for this purpose a set of locally conducted subjective experiments were performed.

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MONTEIRO, Estêvão Chaves. "Shifted Gradient Similarity: A perceptual video quality assessment index for adaptive streaming encoding." Universidade Federal de Pernambuco, 2016. https://repositorio.ufpe.br/handle/123456789/17359.

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Adaptive video streaming has become prominent due to the rising diversity of Web-enabled personal devices and the popularity of social networks. Common limitations in Internet bandwidth, decoding speed and battery power available in such devices challenge the efficiency of content encoders to preserve visual quality at reduced data rates over a wide range of display resolutions, typically compressing to lower than 1% of the massive raw data rate. Furthermore, the human visual system does not uniformly perceive losses of spatial and temporal information, so a simple physical objective model such as the mean squared error does not correlate well with perceptual quality. Objective assessment and prediction of perceptual quality of visual content has greatly improved in the past decade, but remains an open problem. Among the most relevant psychovisual quality metrics are the many versions of the Structural Similarity (SSIM) index. In this work, several of the most efficient SSIM-based metrics, such as the Multi-Scale Fast SSIM and the Gradient Magnitude Similarity Deviation (GMSD), are decomposed into their component techniques and reassembled in order to measure and understand the contribution of each technique and to develop improvements in quality and efficiency. The metrics are applied to the LIVE Mobile Video Quality and TID2008 databases and the results are correlated to the subjective data included in the databases in the form of mean opinion scores (MOS), so each metric’s degree of correlation indicates its ability to predict perceptual quality. Additionally, the metrics’ applicability to the recent, relevant psychovisal rate-distortion optimization (Psy-RDO) implementation in the x264 encoder, which currently lacks an ideal objective assessment metric, is investigated as well. The “Shifted Gradient Similarity” (SG-Sim) index is proposed with an improved feature enhancement by avoiding a common unintended loss of analysis information in SSIM-based indexes, and achieving considerably higher MOS correlation than the existing metrics investigated in this work. More efficient spatial pooling filters are proposed, as well: the decomposed 1-D integer Gaussian filter limited to two standard deviations, and the downsampling Box filter based on the integral image, which retain respectively 99% and 98% equivalence and achieve speed gains of respectively 68% and 382%. In addition, the downsampling filter also enables broader scalability, particularly for Ultra High Definition content, and defines the “Fast SG-Sim” index version. Furthermore, SG-Sim is found to improve correlation with Psy-RDO, as an ideal encoding quality metric for x264. Finally, the algorithms and experiments used in this work are implemented in the “Video Quality Assessment in Java” (jVQA) software, based on the AviSynth and FFmpeg platforms, and designed for customization and extensibility, supporting 4K Ultra-HD content and available as free, open source code.
Cada vez mais serviços de streaming de vídeo estão migrando para o modelo adaptativo, devido à crescente diversidade de dispositivos pessoais conectados à Web e à popularidade das redes sociais. Limitações comuns na largura de banda de Internet, velocidade de decodificação e potência de baterias disponíveis em tais dispositivos desafiam a eficiência dos codificadores de conteúdo para preservar a qualidade visual em taxas de dados reduzidas e abrangendo uma ampla gama de resoluções de tela, tipicamente comprimindo para menos de 1% da massiva taxa de dados bruta. Ademais, o sistema visual humano não percebe uniformemente as perdas de informação espacial e temporal, então um modelo objetivo físico simples como a média do erro quadrático não se correlaciona bem com qualidade perceptível. Técnicas de avaliação e predição objetiva de qualidade perceptível de conteúdo visual se aprimoraram amplamente na última década, mas o problema permanece em aberto. Dentre as métricas de qualidade psicovisual mais relevantes estão muitas versões do índice de similaridade estrutural (Structural Similarity — SSIM). No presente trabalho, várias das mais eficientes métricas baseadas em SSIM, como o Multi-Scale Fast SSIM e o Gradient Magnitude Similarity Deviation (GMSD), são decompostas em suas técnicas-componentes e recombinadas para se obter medidas e entendimento sobre a contribuição de cada técnica e se desenvolver aprimoramentos à sua qualidade e eficiência. Tais métricas são aplicadas às bases de dados LIVE Mobile Video Quality e TID2008 e os resultados são correlacionados aos dados subjetivos incluídos naquelas bases na forma de escores de opinião subjetiva (mean opinion score — MOS), de modo que o grau de correlação de cada métrica indique sua capacidade de predizer qualidade perceptível. Investiga-se, ainda, a aplicabilidade das métricas à recente e relevante implementação de otimização psicovisual de distorção por taxa (psychovisual rate-distortion optimization — Psy-RDO) do codificador x264, ao qual atualmente falta uma métrica de avaliação objetiva ideal. O índice “Shifted Gradient Similarity” (SG-Sim) é proposto com uma técnica aprimorada de realce de imagem que evita uma perda não-pretendida de informação de análise, comum em índices baseados em SSIM, assim alcançando correlação consideravelmente maior com MOS comparado às métricas existentes investigadas neste trabalho. Também são propostos filtros de consolidação espacial mais eficientes: o filtro gaussiano de inteiros 1-D decomposto e limitado a dois desvios padrão e o filtro “box” subamostrado baseado na imagem integral, os quais retém, respectivamente, 99% e 98% de equivalência e obtém ganhos de velocidade de, respectivamente, 68% e 382%. O filtro subamostrado também promove escalabilidade, especialmente para conteúdo de ultra-alta definição, e define a versão do índice “Fast SG-Sim”. Ademais, verifica-se que o SG-Sim aumenta a correlação com Psy-RDO, indicando-se uma métrica de qualidade de codificação ideal para o x264. Finalmente, os algoritmos e experimentos usados neste trabalho estão implementados no software “Video Quality Assessment in Java” (jVQA), baseado nas plataformas AviSynth e FFmpeg e que é projetado para personalização e extensibilidade, suportando conteúdo ultra-alta definição “4K” e disponibilizado como código-fonte aberto e livre.

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Lawan, Sagir. "Adaptive intra refresh for robust wireless multi-view video." Thesis, Brunel University, 2016. http://bura.brunel.ac.uk/handle/2438/13078.

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Mobile wireless communication technology is a fast developing field and every day new mobile communication techniques and means are becoming available. In this thesis multi-view video (MVV) is also refers to as 3D video. Thus, the 3D video signals through wireless communication are shaping telecommunication industry and academia. However, wireless channels are prone to high level of bit and burst errors that largely deteriorate the quality of service (QoS). Noise along the wireless transmission path can introduce distortion or make a compressed bitstream lose vital information. The error caused by noise progressively spread to subsequent frames and among multiple views due to prediction. This error may compel the receiver to pause momentarily and wait for the subsequent INTRA picture to continue decoding. The pausing of video stream affects the user's Quality of Experience (QoE). Thus, an error resilience strategy is needed to protect the compressed bitstream against transmission errors. This thesis focuses on error resilience Adaptive Intra Refresh (AIR) technique. The AIR method is developed to make the compressed 3D video more robust to channel errors. The process involves periodic injection of Intra-coded macroblocks in a cyclic pattern using H.264/AVC standard. The algorithm takes into account individual features in each macroblock and the feedback information sent by the decoder about the channel condition in order to generate an MVV-AIR map. MVV-AIR map generation regulates the order of packets arrival and identifies the motion activities in each macroblock. Based on the level of motion activity contained in each macroblock, the MVV-AIR map classifies frames as high or low motion macroblocks. A proxy MVV-AIR transcoder is used to validate the efficiency of the generated MVV-AIR map. The MVV-AIR transcoding algorithm uses spatial and views downscaling scheme to convert from MVV to single view. Various experimental results indicate that the proposed error resilient MVV-AIR transcoder technique effectively improves the quality of reconstructed 3D video in wireless networks. A comparison of MVV-AIR transcoder algorithm with some traditional error resilience techniques demonstrates that MVV-AIR algorithm performs better in an error prone channel. Results of simulation revealed significant improvements in both objective and subjective qualities. No additional computational complexity emanates from the scheme while the QoS and QoE requirements are still fully met.

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Akamine, Welington Yorihiko Lima. "On the performance of video quality assessment methods for different spatial and temporal resolutions." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/23490.

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Dissertação (mestrado)—Universidade de Brasília, Faculdade de Tecnologia, Departamento de Engenharia Elétrica, 2017.
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O consumo de vídeos digitais cresce a cada ano. Vários países já utilizam TV digital e o tráfego de dados de vídeos na internet equivale a mais de 60\% de todo o tráfego de dados na internet. Esse aumento no consumo de vídeos digitais exige métodos computacionais viáveis para o cálculo da qualidade do vídeo. Métodos objetivos de qualidade de vídeo são algoritmos que calculam a qualidade do vídeo. As mais recentes métricas de qualidade de vídeo, apesar de adequadas possuem um tempo de execução alto. Em geral, os algoritmos utilizados são complexos e extraem características espaciais e temporais dos vídeos. Neste trabalho, realizamos uma análise dos efeitos da redução da resolução espacial no desempenho dos métodos de avaliação da qualidade do vídeo. Com base nesta análise, nós propomos um framework, para a avaliação da qualidade de vídeo que melhora o tempo de execução das métricas objetivas de qualidade de vídeo sem reduzir o desempenho na predição da qualidade do vídeo. O framework consiste em quatro etapas. A primeira etapa, classificação, identifica os vídeos mais sensíveis à redução da resolução espacial. A segunda etapa, redução, reduz a resolução espacial do vídeo de acordo com a distorção presente. A terceira etapa, predição de qualidade, utiliza uma métrica objetiva para obter uma estimativa da qualidade do vídeo. Finalmente, a quarta etapa realiza um ajuste dos índices de qualidade preditos. Dois classificadores de vídeo são propostos para a etapa de classificação do framework. O primeiro é um classificador com referência, que realiza medidas da atividade espacial dos vídeos. O segundo é um classificador sem-referência, que realiza medidas de entropia espacial e espectral, utilizando Support Vector Machine, para classificar os vídeos. Os classificadores de vídeo têm o objetivo de selecionar o melhor fator de redução da resolução espacial do vídeo. Testamos o framework proposto com 6 métricas objetivas de qualidade de vídeo e 4 bancos de qualidade de vídeo. Com isso, melhoramos o tempo de execução de todas as métricas de qualidade de vídeo testadas.
The consumption of digital videos increases every year. In addition to the fact that many countries already use digital TV, currently the traffic of internet video services are more than 60\% of the total internet traffic. The growth of digital video consumption demands a viable method to measure the video quality. Objective video quality assessment methods are algorithms that estimates video quality. Recent quality assessment methods provide quality predictions that are well correlated with the subjective quality scores. However, most of these methods are very complex and takes long periods to compute. In this work, we analyze the effects of reducing the video spatial resolution on the performance of video quality assessment methods. Based on this analysis, we propose a framework for video quality assessment that reduces the runtime performance of a given video quality assessment method without reducing its accuracy performance. The proposed framework is composed of four stages. The first stage, classification, identifies videos that are more sensitive to spatial resolution reduction. The second stage, reduction, aims to reduce the video spatial resolution according to the video distortion. The third stage, quality prediction, estimates the video quality using an objective video quality assessment method. Finally, the fourth stage normalizes the predicted quality scores according to the video spatial resolution. We design two video classifiers for the first stage of the framework. The first classifier is a full-reference classifier based on a video spatial activity measure. The second is a no-reference classifier based on spatial and spectral entropy measures, which uses a Support Vector Machine (SVM) algorithm. We use the video classifiers to identify the type of distortion in the video and choose the most appropriate spatial resolution. We test the framework using six different video quality assessment methods and four different video quality databases. Results show that the proposed framework improves the average runtime performance of all video quality assessment methods tested. We also analyze the effects of a temporal resolution reduction on the performance of video quality assessment methods. The analysis shows that video quality assessment methods based on temporal features are more sensitive to temporal resolution reduction. Also, videos with temporal distortions, like packet loss, are very sensitive to temporal resolution reduction.

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Silva, Alexandre Fieno da. "No-reference video quality assessment model based on artifact metrics for digital transmission applications." reponame:Repositório Institucional da UnB, 2017. http://repositorio.unb.br/handle/10482/24733.

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Tese (doutorado)—Universidade de Brasília, Instituto de Ciências Exatas, Departamento de Ciência da Computação, 2017.
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Um dos principais fatores para a redução da qualidade do conteúdo visual, em sistemas de imagem digital, são a presença de degradações introduzidas durante as etapas de processamento de sinais. Contudo, medir a qualidade de um vídeo implica em comparar direta ou indiretamente um vídeo de teste com o seu vídeo de referência. Na maioria das aplicações, os seres humanos são o meio mais confiável de estimar a qualidade de um vídeo. Embora mais confiáveis, estes métodos consomem tempo e são difíceis de incorporar em um serviço de controle de qualidade automatizado. Como alternativa, as métricas objectivas, ou seja, algoritmos, são geralmente usadas para estimar a qualidade de um vídeo automaticamente. Para desenvolver uma métrica objetiva é importante entender como as características perceptuais de um conjunto de artefatos estão relacionadas com suas forças físicas e com o incômodo percebido. Então, nós estudamos as características de diferentes tipos de artefatos comumente encontrados em vídeos comprimidos (ou seja, blocado, borrado e perda-de-pacotes) por meio de experimentos psicofísicos para medir independentemente a força e o incômodo desses artefatos, quando sozinhos ou combinados no vídeo. Nós analisamos os dados obtidos desses experimentos e propomos vários modelos de qualidade baseados nas combinações das forças perceptuais de artefatos individuais e suas interações. Inspirados pelos resultados experimentos, nós propomos uma métrica sem-referência baseada em características extraídas dos vídeos (por exemplo, informações DCT, a média da diferença absoluta entre blocos de uma imagem, variação da intensidade entre pixels vizinhos e atenção visual). Um modelo de regressão não-linear baseado em vetores de suporte (Support Vector Regression) é usado para combinar todas as características e estimar a qualidade do vídeo. Nossa métrica teve um desempenho muito melhor que as métricas de artefatos testadas e para algumas métricas com-referência (full-reference).
The main causes for the reducing of visual quality in digital imaging systems are the unwanted presence of degradations introduced during processing and transmission steps. However, measuring the quality of a video implies in a direct or indirect comparison between test video and reference video. In most applications, psycho-physical experiments with human subjects are the most reliable means of determining the quality of a video. Although more reliable, these methods are time consuming and difficult to incorporate into an automated quality control service. As an alternative, objective metrics, i.e. algorithms, are generally used to estimate video quality quality automatically. To develop an objective metric, it is important understand how the perceptual characteristics of a set of artifacts are related to their physical strengths and to the perceived annoyance. Then, to study the characteristics of different types of artifacts commonly found in compressed videos (i.e. blockiness, blurriness, and packet-loss) we performed six psychophysical experiments to independently measure the strength and overall annoyance of these artifact signals when presented alone or in combination. We analyzed the data from these experiments and proposed several models for the overall annoyance based on combinations of the perceptual strengths of the individual artifact signals and their interactions. Inspired by experimental results, we proposed a no-reference video quality metric based in several features extracted from the videos (e.g. DCT information, cross-correlation of sub-sampled images, average absolute differences between block image pixels, intensity variation between neighbouring pixels, and visual attention). A non-linear regression model using a support vector (SVR) technique is used to combine all features to obtain an overall quality estimate. Our metric performed better than the tested artifact metrics and for some full-reference metrics.

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Avgousti, Sotiris. "Plateforme de vidéo mobile de télé-échographie robotisée sur un réseau 4G-LTE." Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2029/document.

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L'objectif de cette thèse est le déploiement et l'évaluation d'une plate-forme de télé-échographie mobile, utilisée pour fournir un diagnostic et des soins à distance dans des milieux médicalement isolés. La plateforme intègre de nouveaux concepts qui permettent de l’utilisation de la télé-échographie robotisée sur les réseaux sans fil 3G, 4G et 5G pour satisfaire au transfert de qualité des vidéos ultrasonores pour un diagnostic médical robuste. Ce travail contribue au domaine des Sciences et Technologies de l'Information et de la Communication appliquées au secteur de la santé et en particulier à la robotique médicale téléopérée. Les principales contributions de la thèse sont : I. Un état de l’art des systèmes télé-robotiques appliqués au médical menée sur la base de publications écrites entre 2004 et 2016, II. L'évaluation objective et subjective (clinique) de la qualité vidéo a démontré que les normes H.264/AVC et HEVC peuvent atteindre une qualité vidéo sans perte de diagnostic à des débits (1024 et 2048 Kbps) bien en deçà des débits de données supportés par les réseaux 4G. Les normes de codage vidéo antérieures (Mpeg-4, Mpeg-2) ne peuvent pas être utilisées pour le diagnostic clinique à ces débits car elles présentent une perte d'information pour le diagnostic médical, III. Les experts médicaux ont apprécié la réactivité dynamique mécanique de la plate-forme en raison du faible délai présenté par les canaux LTE. La limitation la plus importante soulevée par l'expert médical, empêchant une évaluation globale clinique favorable au diagnostic, était le positionnement initial du robot sur le corps du patient et son déplacement vers l'obtention d’une échographie cardiaque, Les résultats fournissent une forte indication que la plate-forme télé-échographie robotisée peut être utilisée pour fournir un diagnostic fiable et à distance sur les réseaux sans fil émergents 4G et au-delà
The objective of this Thesis was the deployment and evaluation of an end-to-end mobile tele-echography platform used to provide remote diagnosis and care within medically isolated settings. The platform integrates new concepts that enable robotized tele-echography over commercially available 4G and beyond mobile networks for rendering diagnostically robust medical ultrasound video. It contributes to the field of Information and Communication technologies applied in the healthcare sector. The main contributions of the Thesis are: I. A systematic review on the state of the art in medical telerobotic systems was conducted based on publications of the last decade, and more specifically between the years 2004 to 2016. II. Both objective and subjective (clinical) video quality assessment demonstrated that H.264/AVC and HEVC standards can achieve diagnostically-lossless video quality at bitrates (1024 and 2048 Kbps) well within the LTE supported data rates. Earlier video coding standards (Mpeg-4 & Mpeg-2) cannot be employed for clinical diagnosis at these rates as they present loss of clinical information.III. Medical experts highly appreciated the proposed platform’s mechanical dynamic responsiveness due to the low end-to-end delay (latency) facilitated by LTE-channels. The most important limitation raised by the medical expert and prevented higher overall rating and ultimately clinical QoE was the robot initial positioning on the patient’s body and navigation towards obtaining the cardiac ultrasound. IV. Results provides a strong indication that the proposed robotized tele-echography platform can be used to provide reliable, remote diagnosis over emerging 4G and beyond wireless networks

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Kang, Chen. "Image Aesthetic Quality Assessment Based on Deep Neural Networks." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASG004.

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Avec le développement des dispositifs de capture et d'Internet, les gens accèdent à un nombre croissant d'images. L'évaluation de l'esthétique visuelle a des applications importantes dans plusieurs domaines, de la récupération d'image et de la recommandation à l'amélioration. L'évaluation de la qualité esthétique de l'image vise à déterminer la beauté d'une image pour les observateurs humains. De nombreux problèmes dans ce domaine ne sont pas bien étudiés, y compris la subjectivité de l'évaluation de la qualité esthétique, l'explication de l'esthétique et la collecte de données annotées par l'homme. La prédiction conventionnelle de la qualité esthétique des images vise à prédire le score moyen ou la classe esthétique d'une image. Cependant, la prédiction esthétique est intrinsèquement subjective, et des images avec des scores / classe esthétiques moyens similaires peuvent afficher des niveaux de consensus très différents par les évaluateurs humains. Des travaux récents ont traité de la subjectivité esthétique en prédisant la distribution des scores humains, mais la prédiction de la distribution n'est pas directement interprétable en termes de subjectivité et pourrait être sous-optimale par rapport à l'estimation directe des descripteurs de subjectivité calculés à partir des scores de vérité terrain. De plus, les étiquettes des ensembles de données existants sont souvent bruyantes, incomplètes ou ne permettent pas des tâches plus sophistiquées telles que comprendre pourquoi une image est belle ou non pour un observateur humain. Dans cette thèse, nous proposons tout d'abord plusieurs mesures de la subjectivité, allant de simples mesures statistiques telles que l'écart type des scores, aux descripteurs nouvellement proposés inspirés de la théorie de l'information. Nous évaluons les performances de prédiction de ces mesures lorsqu'elles sont calculées à partir de distributions de scores prédites et lorsqu'elles sont directement apprises à partir de données de vérité terrain. Nous constatons que cette dernière stratégie donne en général de meilleurs résultats. Nous utilisons également la subjectivité pour améliorer la prédiction des scores esthétiques, montrant que les mesures de subjectivité inspirées de la théorie de l'information fonctionnent mieux que les mesures statistiques. Ensuite, nous proposons un ensemble de données EVA (Explainable Visual Aesthetics), qui contient 4070 images avec au moins 30 votes par image. EVA a été collecté en utilisant une approche plus disciplinée inspirée des meilleures pratiques d'évaluation de la qualité. Il offre également des caractéristiques supplémentaires, telles que le degré de difficulté à évaluer le score esthétique, l'évaluation de 4 attributs esthétiques complémentaires, ainsi que l'importance relative de chaque attribut pour se forger une opinion esthétique. L'ensemble de données accessible au public devrait contribuer aux recherches futures sur la compréhension et la prédiction de l'esthétique de la qualité visuelle. De plus, nous avons étudié l'explicabilité de l'évaluation de la qualité esthétique de l'image. Une analyse statistique sur EVA démontre que les attributs collectés et l'importance relative peuvent être combinés linéairement pour expliquer efficacement les scores d'opinion moyenne esthétique globale. Nous avons trouvé que la subjectivité a une corrélation limitée avec la difficulté personnelle moyenne dans l'évaluation esthétique, et la région du sujet, le niveau photographique et l'âge affectent de manière significative l'évaluation esthétique de l'utilisateur
With the development of capture devices and the Internet, people access to an increasing amount of images. Assessing visual aesthetics has important applications in several domains, from image retrieval and recommendation to enhancement. Image aesthetic quality assessment aims at determining how beautiful an image looks to human observers. Many problems in this field are not studied well, including the subjectivity of aesthetic quality assessment, explanation of aesthetics and the human-annotated data collection. Conventional image aesthetic quality prediction aims at predicting the average score or aesthetic class of a picture. However, the aesthetic prediction is intrinsically subjective, and images with similar mean aesthetic scores/class might display very different levels of consensus by human raters. Recent work has dealt with aesthetic subjectivity by predicting the distribution of human scores, but predicting the distribution is not directly interpretable in terms of subjectivity, and might be sub-optimal compared to directly estimating subjectivity descriptors computed from ground-truth scores. Furthermore, labels in existing datasets are often noisy, incomplete or they do not allow more sophisticated tasks such as understanding why an image looks beautiful or not to a human observer. In this thesis, we first propose several measures of subjectivity, ranging from simple statistical measures such as the standard deviation of the scores, to newly proposed descriptors inspired by information theory. We evaluate the prediction performance of these measures when they are computed from predicted score distributions and when they are directly learned from ground-truth data. We find that the latter strategy provides in general better results. We also use the subjectivity to improve predicting aesthetic scores, showing that information theory inspired subjectivity measures perform better than statistical measures. Then, we propose an Explainable Visual Aesthetics (EVA) dataset, which contains 4070 images with at least 30 votes per image. EVA has been crowd-sourced using a more disciplined approach inspired by quality assessment best practices. It also offers additional features, such as the degree of difficulty in assessing the aesthetic score, rating for 4 complementary aesthetic attributes, as well as the relative importance of each attribute to form aesthetic opinions. The publicly available dataset is expected to contribute to future research on understanding and predicting visual quality aesthetics. Additionally, we studied the explainability of image aesthetic quality assessment. A statistical analysis on EVA demonstrates that the collected attributes and relative importance can be linearly combined to explain effectively the overall aesthetic mean opinion scores. We found subjectivity has a limited correlation to average personal difficulty in aesthetic assessment, and the subject's region, photographic level and age affect the user's aesthetic assessment significantly

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Solh, Mashhour M. "Depth-based 3D videos: quality measurement and synthesized view enhancement." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/43743.

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Three dimensional television (3DTV) is believed to be the future of television broadcasting that will replace current 2D HDTV technology. In the future, 3DTV will bring a more life-like and visually immersive home entertainment experience, in which users will have the freedom to navigate through the scene to choose a different viewpoint. A desired view can be synthesized at the receiver side using depth image-based rendering (DIBR). While this approach has many advantages, one of the key challenges in DIBR is generating high quality synthesized views. This work presents novel methods to measure and enhance the quality of 3D videos generated through DIBR. For quality measurements we describe a novel method to characterize and measure distortions by multiple cameras used to capture stereoscopic images. In addition, we present an objective quality measure for DIBR-based 3D videos by evaluating the elements of visual discomfort in stereoscopic 3D videos. We also introduce a new concept called the ideal depth estimate, and define the tools to estimate that depth. Full-reference and no-reference profiles for calculating the proposed measures are also presented. Moreover, we introduce two innovative approaches to improve the quality of the synthesized views generated by DIBR. The first approach is based on hierarchical blending of the background and foreground information around the disocclusion areas which produces a natural looking, synthesized view with seamless hole-filling. This approach yields virtual images that are free of any geometric distortions, unlike other algorithms that preprocess the depth map. In contrast to the other hole-filling approaches, our approach is not sensitive to depth maps with high percentage of bad pixels from stereo matching. The second approach further enhances the results through a depth-adaptive preprocessing of the colored images. Finally, we propose an enhancement over depth estimation algorithm using the depth monocular cues from luminance and chrominance. The estimated depth will be evaluated using our quality measure, and the hole-filling algorithm will be used to generate synthesized views. This application will demonstrate how our quality measures and enhancement algorithms could help in the development of high quality stereoscopic depth-based synthesized videos.

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Daronco, Leonardo Crauss. "Avaliação subjetiva de qualidade aplicada à codificação de vídeo escalável." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2009. http://hdl.handle.net/10183/18246.

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Os constantes avanços nas áreas de transmissão e processamento de dados ao longo dos últimos anos permitiram a criação de diversas aplicações e serviços baseados em dados multimídia, como streaming de vídeo, videoconferências, aulas remotas e IPTV. Além disso, avanços nas demais áreas da computação e engenharias, possibilitaram a construção de uma enorme diversidade de dispositivos de acesso a esses serviços, desde computadores pessoais até celulares, para citar os mais utilizados atualmente. Muitas dessas aplicações e dispositivos estão amplamente difundidos hoje em dia, e, ao mesmo tempo em que a tecnologia avança, os usuários tornam-se mais exigentes, buscando sempre melhor qualidade nos serviços que utilizam. Devido à grande variedade de redes e dispositivos atuais, uma dificuldade existente é possibilitar o acesso universal a uma transmissão. Uma alternativa criada é utilizar transmissão de vídeo escalável com IP multicast e controlada por mecanismos para adaptabilidade e controle de congestionamento. O produto final dessas transmissões mulimídia são os próprios dados multimídia (vídeo e áudio, principalmente) que o usuário está recebendo, portanto a qualidade destes dados é fundamental para um bom desempenho do sistema e satisfação dos usuários. Este trabalho apresenta um estudo de avaliações subjetivas de qualidade aplicadas em sequências de vídeo codificadas através da extensão escalável do padrão H.264 (SVC). Foi executado um conjunto de testes para avaliar, principalmente, os efeitos da instabilidade da transmissão (variação do número de camadas de vídeo recebidas) e a influência dos três métodos de escalabilidade (espacial, temporal e de qualidade) na qualidade dos vídeos. As definições foram baseadas em um sistema de transmissão em camadas com utilização de protocolos para adaptabilidade e controle de congestionamento. Para execução das avaliações subjetivas foi feito o uso da metodologia ACR-HRR e recomendações das normas ITU-R Rec. BT.500 e ITU-T Rec. P.910. Os resultados mostram que, diferente do esperado, a instabilidade não provoca grandes alterações na qualidade subjetiva dos vídeos e que o método de escalabilidade temporal tende a apresentar qualidade bastante inferior aos outros métodos. As principais contribuições deste trabalho estão nos resultados obtidos nas avaliações, além da metodologia utilizada durante o desenvolvimento do trabalho (definição do plano de avaliação, uso das ferramentas como o JSVM, seleção do material de teste, execução das avaliações, entre outros), das aplicações desenvolvidas, da definição de alguns trabalhos futuros e de possíveis objetivos para avaliações de qualidade.
The constant advances in multimedia processing and transmission over the past years have enabled the creation of several applications and services based on multimedia data, such as video streaming, teleconference, remote classes and IPTV. Futhermore, a big variety of devices, that goes from personal computers to mobile phones, are now capable of receiving these transmissions and displaying the multimedia data. Most of these applications are widely adopted nowadays and, at the same time the technology advances, the user are becoming more demanding about the quality of the services they use. Given the diversity of devices and networks available today, one of the big challenges of these multimedia systems is to be able to adapt the transmission to the receivers' characteristics and conditions. A suitable solution to provide this adaptation is the integration of scalable video coding with layered transmission. As the final product in these multimedia systems are the multimedia data that is presented to the user, the quality of these data will define the performace of the system and the users' satisfaction. This paper presents a study of subjective quality of scalable video sequences, coded using the scalable extension of the H.264 standard (SVC). A group of experiments was performed to measure, primarily, the efeects that the transmission instability (variations in the number of video layers received) has in the video quality and the relationship between the three scalability methods (spatial, temporal and quality) in terms of subjective quality. The decisions taken to model the tests were based on layered transmission systems that use protocols for adaptability and congestion control. To run the subjective assessments we used the ACR-HRR methodology and recommendations given by ITU-R Rec. BT.500 and ITU-T Rec. P.910. The results show that the instability modelled does not causes significant alterations on the overall video subjective quality if compared to a stable video and that the temporal scalability usually produces videos with worse quality than the spatial and quality methods, the latter being the one with the better quality. The main contributions presented in this work are the results obtained in the subjective assessments. Moreover, are also considered as contributions the methodology used throughout the entire work (including the test plan definition, the use of tools as JSVM, the test material selection and the steps taken during the assessment), some applications that were developed, the definition of future works and the specification of some problems that can also be solved with subjective quality evaluations.

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Ramadhani, Uri Arta. "Evaluation of the Profitability of Quality of Experience-based Resource Allocation Deployment in LTE Network : A Techno-economic Assessment based on Quality of Experience in Video Traffic." Thesis, KTH, Radio Systems Laboratory (RS Lab), 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-218073.

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In the current mobile telecommunication market, with slow growth in mobile subscriptions and increasing traffi demand, each mobile operator needs to manage their customer loyalty in order to maintain position in the market. To retain their customer's loyalty, the user quality of satisfaction needs to be preserved. Integrating a Quality of Experience (QoE) approach into a radio resource scheduling scheme can be a means to improve user quality of satisfaction to a service. However, the enhancement of existing resource allocation management to support a QoE-based resource scheduling scheme needs a careful consideration since it will impact the mobile operator's investment cost. A profitability assessment of QoE-based resource allocation is required as a basis for the mobile operator to forecast their potential benefit of QoE-based resource scheduling deployment. This thesis investigated the profitability of deploying QoE-based radio resource management (RRM) in terms of revenue loss compared to proportional fair (PF) scheduling, a widely used resource allocation scheme, in delivering a streaming video service. In QoE-based RRM, a buffering percentage experienced by a user was considered in the resource allocation decision process. The two scheduling schemes were simulated in different network configurations. User satisfaction was quantified in terms of mean opinion score. Given the degree of satisfaction for each user, a number of users who would be likely to churn was obtained. A cost-benefit assessment was then conducted by predicting revenue loss due to customer churn. The results from the simulation and cost analysis show that although QoE-based resource scheduling provides users with a higher degree of satisfaction for more base stations, the utilization of a QoE-based resource scheduler does not offer significant benefit to the network operator with regard to revenue loss and deployment cost when compared to a PF scheduler. This outcome indicates that if the business target is to reduce customer churn, then the operator should utilize a PF scheduler for their RRM scheme.
Den nuvarande mobiltelefonimarknaden kännetecknas av svag tillväxt av nya kunder men ett ökat nyttjande bland existerande kunder av företagens tjänster. Kundlojalitet har blivit en avgörande faktor för att uppnå en stark marknadsposition. Kundernas upplevda kvalitet utav mobiltjänsterna behöver upprätthållas på en hög nivå för att tillfredställa denna lojalitet. Att applicera en upplevad kvalitet (QoE) metod i en radio resurs kan vara ett medel till att förbättra kundernas upplevda kvalitet av mobiltj änsten. För att undersöka ifall en sådan tjänst är lönsam är det dock nödvändigt att en lönsamhetskalkyl genomförs, där investeringskostnad och systemets driftkostnad vägs mot eventuella intäkter. En lönsamhetsbedömning av QoE-baserad resursallokering krävs som grund för mobiloperatören att förutse deras potentiella fördelar med QoE-baserad resursschemaläggning. Denna uppsats undersöker lönsamheten av att implementera QoE i termer av förlorade intäkter, jämfört med proportionell rättvis (PF) schemaläggning, i att leverera en videoströmservice. I QoE-baserad RRM användes buffertprocentandel som användes av användarna i resursallokeringsprocessen. De två olika systemen simulerades genom att använda olika antal basstationer i mobilnätverkskonfigurationen. Användarnöjdhet kvantifierades genom att låta användarna betygsätta tjänsten, detta värde användes därefter till att uppskatta hur många av kunderna som sannolikt ej skulle återanvända tjänsten. En lönsamhetskalkyl genomfördes genom att prediktera förlorade intäkter med avseende på kunderna som ej skulle återanvända tjänsten. Resultaten från simulerings- och lönsamhetsberäkningen visade att även om QoE erbjuder en högre kundnöjdhet av tjänsten och tillfredsställelse för er basstationer, så leder inte en QoE-implementering till signikanta fördelar för nätverket i termer av förlorade intäkter och investeringskostnader jämfört med ett PF schemaläggare. Detta indikerar att om ett företags mål är att höja kundlojaliteten, då skall företaget applicera en PF schemaläggare istället för QoE.

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Higuchi, Marcelo Makoto. "Digital games platforms: a literature review, an empirical assessment of quality and exclusivity in video-game market and a study on project management." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3136/tde-23052018-114837/.

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Digital games are part of the creative industries, which is based on value creation through ideas and creativity. This market has gained relevance due to technology development that attracted both new firms and users. The present dissertation aims to explore three themes: (1) video game market as a two-sided market; (2) the effects of characteristics and behavior of game titles on consoles sales; and (3) project management to develop digital games. Those themes were explored through three articles: the first is a literature review and a bibliometric study of the economic concepts on two-sided market, which focused at identifying main topics, research trends and avenues for futures research. The second text is an analysis on the simultaneous influence of games\' quality and exclusivity on console sales. The last one is a qualitative, multiple-case study to understand, explore and suggest improvements to game project management in the Brazilian market. Findings include: (1) the main authors and topics, trends and developments, from and avenues for future research; (2) combinations of quality and exclusivity can affect console sales either positively or negatively, (3) quality has a predominant effect on sales over games non-exclusivity; and (4) the use of agile methodologies and Design Thinking are diffused among game developers.
Sem resumo.

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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.

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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 chirurgie
The 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

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Rodríguez, Demóstenes Zegarra. "Proposta da métrica eVSQM para avaliação de QoE no serviço de streaming de vídeo sobre TCP." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-16102014-165108/.

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Atualmente existem inúmeros serviços multimídia que são transportados através da rede IP, dos quais, o tráfego dos serviços de vídeo experimentou um maior crescimento nos últimos anos. O sucesso de aplicações de streaming de vídeo é um dos fatores pelo qual, este tráfego se incrementou. Alguns recentes estudos projetam que este tipo de serviços no ano 2016, alcançará aproximadamente o 55% do tráfego total da Internet. Considerando a importância que os serviços de vídeo alcançarão nos próximos anos, este trabalho foca-se na avaliação da qualidade de experiência (QoE) dos usuários ao utilizar estes serviços. Assim, nesta tese é proposta uma métrica de avaliação de vídeo denominada eVsQM, do inglês enhanced Video streaming Quality Metric, a qual é baseada principalmente no número, duração e localização temporal dos congelamentos de imagens (pausas) durante uma transmissão de vídeo, considerando também o tipo de conteúdo do vídeo transmitido. Esta métrica foi determinada a partir de um modelo matemático que utilizou os resultados de testes subjetivos de avaliação de vídeo, pois, este tipo de testes são os que melhor se aproximam da QoE real do usuário. Cabe destacar, que na realização dos testes subjetivos foi utilizada uma metodologia concordante com o tipo de degradação que o vídeo possui, ou seja, a pausa. No streaming de vídeo novas soluções são criadas com a finalidade de melhorar a QoE do usuário. O DASH, do inglês Dynamic Adaptive Streaming over HTTP, muda a resolução do vídeo transmitido de acordo com as características da rede. Porém, se a rede é muito flutuante existirão muitas variações de resolução e a QoE do usuário será degradada. Neste trabalho é proposto um parâmetro a ser utilizado no algoritmo DASH que funciona como um limiar para controlar a frequência destas comutações de resolução. Este parâmetro é denominado como SDF (do inglês Switching Degradation Factor) e permite que a QoE mantida em níveis aceitáveis, inclusive em situações onde a rede é muito flutuante. Adicionalmente, neste trabalho é proposto um novo modelo de faturamento nos serviços de telecomunicações, que inclua no processo de tarifação um parâmetro relacionado com a QoE, visando ter uma tarifação de serviços de comunicações mais justa do ponto de vista dos usuários. Desta forma, usuários que recebem uma menor qualidade no serviço devem pagar menos em relação aos usuários que recebem uma melhor qualidade do mesmo serviço.
Nowadays, there are several multimedia services, which are carried via IP networks. From these all services; the traffic regarding video applications had the greatest growth in the last years. The success of video streaming applications is one of the major contributors to video traffic growth. Some recent studies project that video services, will reach approximately 55% of the total Internet traffic in 2016. Considering the relevance that video services will achieve in the coming years, this work focuses on the users Quality of Experience (QoE) when using these services. Thus, this thesis proposes an evaluation metric named enhanced Video streaming Quality Metric (eVsQM), which is based primarily on the number, duration and temporal location of the image freezes (pauses) during a video transmission. Also, this metric considers the video content type and was determined from a mathematical model that used as inputs, the video quality assessment results from subjective tests due, these types of test are the most correlated with real users QoE. It is worth noting that to perform these subjective tests was used a methodology consistent with the kind of video degradation (pause). For another hand, new video streaming solutions are created for the purpose of improving the users QoE of the user. Dynamic Adaptive Streaming over HTTP (DASH) changes the video resolution according to the network characteristics. However, if the network is very fluctuant, many video resolution switching events will be performed and users QoE will be degraded. This thesis proposes a parameter to be used in DASH algorithms that works as a threshold to control the resolution switching frequency. This parameter is named Switching Degradation Factor (SDF) and is responsible to maintain the QoE in acceptable levels, inclusive in scenarios in which the network capacity is very fluctuating.

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Trioux, Anthony. "Étude et optimisation d'un système de vidéotransmission conjoint source-canal basé "SoftCast." Thesis, Valenciennes, Université Polytechnique Hauts-de-France, 2019. http://www.theses.fr/2019UPHF0018.

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Des nouveaux schémas de Codage Vidéo Linéaire (CVL) ont démontré ces dernières années un potentiel élevé pour la diﬀusion de contenus vidéo sur des canaux de transmission sans-ﬁl sévères. SoftCast représente le pionnier des schémas CVL. Diﬀérent des standards de transmission vidéo actuels et particulièrement utile en situation de broadcast, SoftCast est un système de codage conjoint source-canal où les pixels sont traités par des opérations linéaires successives (transformée DCT, allocation de puissance, modulation quasi-analogique) et directement transmis sans quantiﬁcation ni codage (entropique ou de canal). SoftCast permet ainsi d’offrir une qualité vidéo reçue directement proportionnelle à la qualité du canal de transmission, sans aucune information de retour et tout en évitant les mécanismes d’adaptation complexes des schémas classiques. Un premier objectif de ces travaux de thèse concerne l’étude des performances de bout en bout de SoftCast. Des modèles théoriques sont ainsi proposés prenant en compte les contraintes de bande passante de l’application, l’allocation de puissance, ainsi que le type de décodeur utilisé à la réception (LLSE, ZF). Une deuxième partie basée sur une campagne de tests subjectifs concerne une étude originale de la qualité vidéo et des artefacts spéciﬁques associés à SoftCast. Dans une troisième partie, des méthodes de prétraitement permettant d’accroître la qualité reçue sont proposées avec un gain moyen en PSNR de l’ordre de 3 dB. Finalement, un algorithme adaptatif modiﬁant la taille du groupe d’images (GoP) en fonction des caractéristiques du contenu vidéo transmis est proposé. Cette solution permet d’obtenir des gains supplémentaires en PSNR de l’ordre de 1 dB
Linear video coding (LVC) schemes have recently demonstrated a high potential for delivering video content over challenging wireless channels. SoftCast represents the pioneer of the LVC schemes. Diﬀerent from current video transmission standards and particularly useful in broadcast situation, SoftCast is a joint source-channel coding system where pixels are processed by successive linear operations (DCT transform, power allocation, quasi-analog modulation) and directly transmitted without quantization or coding (entropic or channel). This allows to provide a received video quality directly proportional to the transmission channel quality, without any feedback information, while avoiding the complex adaptation mechanisms of conventional schemes. A ﬁrst contribution of this thesis is the study of the end-to-end performances of SoftCast. Theoretical models are thus proposed taking into account the bandwidth constraints of the application, the power allocation, as well as the type of decoder used at the reception (LLSE, ZF). Based on a subjective test campaign, a second part concern an original study of the video quality and speciﬁc artifacts related to SoftCast. In a third part, preprocessing methods are proposed to increase the received quality in terms of PSNR scores with an average gain of 3 dB. Finally, an adaptive algorithm modifying the size of the group of pictures (GoP) according to the characteristics of the transmitted video content is proposed. This solution allows to obtain about 1 dB additional gains in terms of PSNR scores

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Slanina, Martin. "Metody a prostředky pro hodnocení kvality obrazu." Doctoral thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-233489.

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Disertační práce se zabývá metodami a prostředky pro hodnocení kvality obrazu ve videosekvencích, což je velmi aktuální téma, zažívající velký rozmach zejména v souvislosti s digitálním zpracováním videosignálů. Přestože již existuje relativně velké množství metod a metrik pro objektivní, tedy automatizované měření kvality videosekvencí, jsou tyto metody zpravidla založeny na porovnání zpracované (poškozené, například komprimací) a originální videosekvence. Metod pro hodnocení kvality videosekvení bez reference, tedy pouze na základě analýzy zpracovaného materiálu, je velmi málo. Navíc se takové metody převážně zaměřují na analýzu hodnot signálu (typicky jasu) v jednotlivých obrazových bodech dekódovaného signálu, což je jen těžko aplikovatelné pro moderní komprimační algoritmy jako je H.264/AVC, který používá sofistikovené techniky pro odstranění komprimačních artefaktů. V práci je nejprve podán stučný přehled dostupných metod pro objektivní hodnocení komprimovaných videosekvencí se zdůrazněním rozdílného principu metod využívajících referenční materiál a metod pracujících bez reference. Na základě analýzy možných přístupů pro hodnocení video sekvencí komprimovaných moderními komprimačními algoritmy je v dalším textu práce popsán návrh nové metody určené pro hodnocení kvality obrazu ve videosekvencích komprimovaných s využitím algoritmu H.264/AVC. Nová metoda je založena na sledování hodnot parametrů, které jsou obsaženy v transportním toku komprimovaného videa, a přímo souvisí s procesem kódování. Nejprve je provedena úvaha nad vlivem některých takových parametrů na kvalitu výsledného videa. Následně je navržen algoritmus, který s využitím umělé neuronové sítě určuje špičkový poměr signálu a šumu (peak signal-to-noise ratio -- PSNR) v komprimované videosekvenci -- plně referenční metrika je tedy nahrazována metrikou bez reference. Je ověřeno několik konfigurací umělých neuronových sítí od těch nejjednodušších až po třívrstvé dopředné sítě. Pro učení sítí a následnou analýzu jejich výkonnosti a věrnosti určení PSNR jsou vytvořeny dva soubory nekomprimovaných videosekvencí, které jsou následně komprimovány algoritmem H.264/AVC s proměnným nastavením kodéru. V závěrečné části práce je proveden rozbor chování nově navrženého algoritmu v případě, že se změní vlastnosti zpracovávaného videa (rozlišení, střih), případně kodéru (formát skupiny současně kódovaných snímků). Chování algoritmu je analyzováno až do plného vysokého rozlišení zdrojového signálu (full HD -1920 x 1080 obrazových bodů).

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Mantel, Claire. "Bruits temporels de compression et perception de la qualité vidéo : mesure et correction." Phd thesis, Université de Grenoble, 2011. http://tel.archives-ouvertes.fr/tel-00680787.

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Ces dernières années la diffusion vidéo "de salon" a connu trois transitions majeures : la compression vidéo aévolué de la norme MPEG2 à la norme h.264, les écrans à tube cathodique ont disparu du marché des téléviseurs quiest actuellement dominé par les écrans à cristaux liquides (LCD) et pour nir le format haute-définition (1280x720pixels ou 1920x1080) supplante de plus en plus le format SD (576x720). Ces évolutions ont modifié l'importancedes différents types de défauts de compression pour la perception de la qualité d'une vidéo. Les défauts majeursde compression vidéo sont désormais le ou et les défauts temporels. Le terme défaut temporel regroupe ici lavariation temporelle de défauts spatiaux comme l'effet de bloc et des défauts spécifiquement temporels comme lebruit de moustique.Nous nous sommes tout d'abord focalisés sur la correction du bruit de moustique. Le correcteur que nousproposons, le TVIF, est adapté aux trois caractéristiques de ce défaut : faible amplitude par rapport au contenulocal, proximité des contours et variation temporelle. Nous avons évalué l'efficacité de notre correcteur avec desmétriques objectives mais, celles-ci ne permettant pas de conclure sur les performances de notre ltre, nousavons organisé une expérience subjective de qualité. Les données recueillies lors de cette expérience indiquentque les observateurs perçoivent notre filtre comme une amélioration et que la version spatio-temporelle de notrecorrecteur est préférée à sa version spatiale. Reboucler sur les évaluations objectives nous permet de conclure queles métriques objectives ne mesurent pas adéquatement la correction du bruit de moustique, ni l'apport de lacorrection spatio-temporelle par rapport à la correction spatiale.Nous avons ensuite organisé une expérience couplant évaluation de qualité (globale et temporelle) et enregistrementsdes positions oculaires des observateurs. Cette expérience nous permet de spécifier plusieurs pointsutiles pour réaliser une métrique objective de qualité temporelle. Par exemple, le défaut le plus gênant pour laperception de la qualité globale est la variation d'effet de bloc, qui doit donc être la priorité d'une métrique dequalité temporelle. L'analyse des mouvements oculaires des observateurs en tâche libre, tâche de qualité globaleet tâche de qualité temporelle montre, entre autres, que la qualité de la vidéo diffusée n'a pas d'influence visiblesur les endroits regardés par les participants mais influence fortement la durée des fixations.

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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.

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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.

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Boujut, Hugo. "Mesure sans référence de la qualité des vidéos haute déﬁnition diffusées avec des pertes de transmission." Thesis, Bordeaux 1, 2012. http://www.theses.fr/2012BOR14578/document.

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Les objectifs de ce travail de thèse ont été: d’une part de détecter automatique-ment les images gelées dans des vidéos télédiffusées; et d’autre part de mesurer sans référencela qualité des vidéos télédiffusées (IP et DVB-T). Ces travaux ont été effectués dans le cadred’un projet de recherche mené conjointement par le LaBRI et la société Audemat WorldCastSystems.Pour la détection d’images gelées, trois méthodes ont été proposées: MV (basée vecteurde mouvement), DC (basée sur les coefﬁcients DC de la DCT) et SURF (basée sur les pointscaractéristiques SURF). Les deux premières méthodes ne nécessitent qu’un décodage partieldu ﬂux vidéo.Le second objectif était de mesurer sans référence la qualité des vidéos télédiffusées (IP etDVB-T). Une métrique a été développée pour mesurer la qualité perçue lorsque le ﬂux vidéoa été altéré par des pertes de transmission. Cette métrique "Weighted Macro-Block ErrorRate" (WMBER) est fondée sur la mesure de la saillance visuelle et la détection des macro-blocs endommagés. Le rôle de la saillance visuelle est de pondérer l’importance des erreursdétectées. Certaines améliorations ont été apportées à la construction des cartes de saillancespatio-temporelle. En particulier, la fusion des cartes de saillance spatiale et temporelle aété améliorée par rapport à l’état de l’art. Par ailleurs, plusieurs études ont montré que lasémantique d’une scène visuelle avait une inﬂuence sur le comportement du système visuelhumain. Il apparaît que ce sont surtout les visages humains qui attirent le regard. C’est laraison pour laquelle nous avons ajouté une dimension sémantique aux cartes de saillancespatio-temporelle. Cette dimension sémantique est essentiellement basée sur le détecteurde visage de Viola Jones. Pour prédire la qualité perçue par les utilisateurs, nous avonsutilisé une méthode par apprentissage supervisé. Cette méthode offre ainsi la possibilité deprédire la métrique subjective "Mean Opinion Score" (MOS) à partir de mesures objectivestelles que le WMBER, PSNR ou SSIM. Une expérience psycho-visuelle a été menée avec 50sujets pour évaluer ces travaux. Cette base de données vidéo Haute-Déﬁnition est en coursde transfert à l’action COST Qualinet. Ces travaux ont également été évalués sur une autrebase de données vidéo (en déﬁnition standard) provenant de l’IRCCyN
The goal of this Ph.D thesis is to design a no-reference video quality assessment method for lossy net-works. This Ph.D thesis is conducted in collaboration with the Audemat Worldcast Systemscompany.Our ﬁrst no-reference video quality assessment indicator is the frozen frame detection.Frozen frame detection was a research topic which was well studied in the past decades.However, the challenge is to embed a frozen frame detection method in the GoldenEagleAudemat equipment. This equipment has low computation resources that not allow real-time HD video decoding. Two methods are proposed: one based on the compressed videostream motion vectors (MV-method) and another one based on the DC coefﬁcients from thedct transform (DC-method). Both methods only require the partial decoding of the com-pressed video stream which allows for real-time analysis on the GoldenEagle equipment.The evaluation shows that results are better than the frame difference base-line method.Nevertheless, the MV and the DC methods are only suitable with for MPEG2 and H.264video streams. So a third method based on SURF points is proposed.As a second step on the way to a no-reference video quality assessment metric, we areinterested in the visual perception of transmission impairments. We propose a full-referencemetric based on saliency maps. This metric, Weighted Mean Squared Error (WMSE), is theMSE metric weighted by the saliency map. The saliency map role is to distinguish betweennoticeable and unnoticeable transmission impairments. Therefore this spatio-temporal saliencymaps is computed on the impaired frame. Thus the pixel difference in the MSE computationis emphasized or diminished with regard to the pixel saliency. According to the state of theart, several improvements are brought to the saliency map computation process. Especially,new spatio-temporal saliency map fusion strategies are designed.After our successful attempt to assess the video quality with saliency maps, we develop ano-reference quality metric. This metric, Weighted Macro-Block Error Rate (WMBER), relies on the saliency map and the macro-block error detection. The macro-block error detectionprovides the impaired macro-blocks location in the frame. However, the impaired macro-blocks are concealed with more or less success during the decoding process. So the saliencymap provides the user perceived impairment strength for each macro-block.Several psycho-visual studies have shown that semantics play an important role in visualscene perception. These studies conclude that faces and text are the most attractive. Toimprove the spatio-temporal saliency model a semantic dimension is added. This semanticsaliency is based on the Viola & Jones face detector.To predict the Mean Opinion Score (MOS) from objective metric values like WMBER,WMSE, PSNR or SSIM, we propose to use a supervised learning approach. This approach iscalled Similarity Weighted Average (SWA). Several improvements are brought to the originalSWA.For the metrics evaluation a psycho-visual experiment with 50 subjects has been carriedout. To measure the saliency map models accuracy, a psycho-visual experiment with aneye-tracker has also been carried out. These two experiments habe been conducted in col-laboration with the Ben Gurion University, Israel. WMBER and WMSE performances arecompared with reference metrics like SSIM and PSNR. The proposed metrics are also testedon a database provided by IRCCyN research laboratory

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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/.

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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.

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Calemme, Marco. "Codage de carte de profondeur par déformation de courbes élastiques." Thesis, Paris, ENST, 2016. http://www.theses.fr/2016ENST0048/document.

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Dans le format multiple-view video plus depth, les cartes de profondeur peuvent être représentées comme des images en niveaux de gris et la séquence temporelle correspondante peut être considérée comme une séquence vidéo standard en niveaux de gris. Cependant les cartes de profondeur ont des propriétés différentes des images naturelles: ils présentent de grandes surfaces lisses séparées par des arêtes vives. On peut dire que l'information la plus importante réside dans les contours de l'objet, en conséquence une approche intéressante consiste à effectuer un codage sans perte de la carte de contour, éventuellement suivie d'un codage lossy des valeurs de profondeur par-objet. Dans ce contexte, nous proposons une nouvelle technique pour le codage sans perte des contours de l'objet, basée sur la déformation élastique des courbes. Une évolution continue des déformations élastiques peut être modélisée entre deux courbes de référence, et une version du contour déformée élastiquement peut être envoyée au décodeur avec un coût de codage très faible et utilisé comme information latérale pour améliorer le codage sans perte du contour réel. Après que les principales discontinuités ont été capturées par la description du contour, la profondeur à l'intérieur de chaque région est assez lisse. Nous avons proposé et testé deux techniques différentes pour le codage du champ de profondeur à l'intérieur de chaque région. La première technique utilise la version adaptative à la forme de la transformation en ondelette, suivie par la version adaptative à la forme de SPIHT. La seconde technique effectue une prédiction du champ de profondeur à partir de sa version sous-échantillonnée et l'ensemble des contours codés. Il est généralement reconnu qu'un rendu de haute qualité au récepteur pour un nouveau point de vue est possible qu’avec la préservation de l'information de contour, car des distorsions sur les bords lors de l'étape de codage entraînerait une dégradation évidente sur la vue synthétisée et sur la perception 3D. Nous avons étudié cette affirmation en effectuant un test d'évaluation de la qualité perçue en comparant, pour le codage des cartes de profondeur, une technique basée sur la compression d'objects et une techniques de codage vidéo hybride à blocs
In multiple-view video plus depth, depth maps can be represented by means of grayscale images and the corresponding temporal sequence can be thought as a standard grayscale video sequence. However depth maps have different properties from natural images: they present large areas of smooth surfaces separated by sharp edges. Arguably the most important information lies in object contours, as a consequence an interesting approach consists in performing a lossless coding of the contour map, possibly followed by a lossy coding of per-object depth values. In this context, we propose a new technique for the lossless coding of object contours, based on the elastic deformation of curves. A continuous evolution of elastic deformations between two reference contour curves can be modelled, and an elastically deformed version of the reference contours can be sent to the decoder with an extremely small coding cost and used as side information to improve the lossless coding of the actual contour. After the main discontinuities have been captured by the contour description, the depth field inside each region is rather smooth. We proposed and tested two different techniques for the coding of the depth field inside each region. The first technique performs the shape-adaptive wavelet transform followed by the shape-adaptive version of SPIHT. The second technique performs a prediction of the depth field from its subsampled version and the set of coded contours. It is generally recognized that a high quality view rendering at the receiver side is possible only by preserving the contour information, since distortions on edges during the encoding step would cause a sensible degradation on the synthesized view and on the 3D perception. We investigated this claim by conducting a subjective quality assessment test to compare an object-based technique and a hybrid block-based techniques for the coding of depth maps

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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.

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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 HDR
In 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

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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.

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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.

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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.

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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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Belda, Ortega Román. "Mejora del streaming de vídeo en DASH con codificación de bitrate variable mediante el algoritmo Look Ahead y mecanismos de coordinación para la reproducción, y propuesta de nuevas métricas para la evaluación de la QoE." Doctoral thesis, Universitat Politècnica de València, 2021. http://hdl.handle.net/10251/169467.

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[ES] Esta tesis presenta diversas propuestas encaminadas a mejorar la transmisión de vídeo a través del estándar DASH (Dynamic Adaptive Streaming over HTTP). Este trabajo de investigación estudia el protocolo de transmisión DASH y sus características. A la vez, plantea la codificación con calidad constante y bitrate variable como modo de codificación del contenido de vídeo más indicado para la transmisión de contenido bajo demanda mediante el estándar DASH. Derivado de la propuesta de utilización del modo de codificación de calidad constante, cobra mayor importancia el papel que juegan los algoritmos de adaptación en la experiencia de los usuarios al consumir el contenido multimedia. En este sentido, esta tesis presenta un algoritmo de adaptación denominado Look Ahead el cual, sin modificar el estándar, permite utilizar la información de los tamaños de los segmentos de vídeo incluida en los contenedores multimedia para evitar tomar decisiones de adaptación que desemboquen en paradas no deseadas en la reproducción de contenido multimedia. Con el objetivo de evaluar las posibles mejoras del algoritmo de adaptación presentado, se proponen tres modelos de evaluación objetiva de la QoE. Los modelos propuestos permiten predecir de forma sencilla la QoE que tendrían los usuarios de forma objetiva, utilizando parámetros conocidos como el bitrate medio, el PSNR (Peak Signal-to-Noise Ratio) y el valor de VMAF (Video Multimethod Assessment Fusion). Todos ellos aplicados a cada segmento. Finalmente, se estudia el comportamiento de DASH en entornos Wi-Fi con alta densidad de usuarios. En este contexto, se producen un número elevado de paradas en la reproducción por una mala estimación de la tasa de transferencia disponible debida al patrón ON/OFF de descarga de DASH y a la variabilidad del acceso al medio de Wi-Fi. Para paliar esta situación, se propone un servicio de coordinación basado en la tecnología SAND (MPEG's Server and Network Assisted DASH) que proporciona una estimación de la tasa de transferencia basada en la información del estado de los players de los clientes.
[CA] Aquesta tesi presenta diverses propostes encaminades a millorar la transmissió de vídeo a través de l'estàndard DASH (Dynamic Adaptive Streaming over HTTP). Aquest treball de recerca estudia el protocol de transmissió DASH i les seves característiques. Alhora, planteja la codificació amb qualitat constant i bitrate variable com a manera de codificació del contingut de vídeo més indicada per a la transmissió de contingut sota demanda mitjançant l'estàndard DASH. Derivat de la proposta d'utilització de la manera de codificació de qualitat constant, cobra major importància el paper que juguen els algorismes d'adaptació en l'experiència dels usuaris en consumir el contingut. En aquest sentit, aquesta tesi presenta un algoritme d'adaptació denominat Look Ahead el qual, sense modificar l'estàndard, permet utilitzar la informació de les grandàries dels segments de vídeo inclosa en els contenidors multimèdia per a evitar prendre decisions d'adaptació que desemboquin en una parada indesitjada en la reproducció de contingut multimèdia. Amb l'objectiu d'avaluar les possibles millores de l'algoritme d'adaptació presentat, es proposen tres models d'avaluació objectiva de la QoE. Els models proposats permeten predir de manera senzilla la QoE que tindrien els usuaris de manera objectiva, utilitzant paràmetres coneguts com el bitrate mitjà, el PSNR (Peak Signal-to-Noise Ratio) i el valor de VMAF (Video Multimethod Assessment Fusion). Tots ells aplicats a cada segment. Finalment, s'estudia el comportament de DASH en entorns Wi-Fi amb alta densitat d'usuaris. En aquest context es produeixen un nombre elevat de parades en la reproducció per una mala estimació de la taxa de transferència disponible deguda al patró ON/OFF de descàrrega de DASH i a la variabilitat de l'accés al mitjà de Wi-Fi. Per a pal·liar aquesta situació, es proposa un servei de coordinació basat en la tecnologia SAND (MPEG's Server and Network Assisted DASH) que proporciona una estimació de la taxa de transferència basada en la informació de l'estat dels players dels clients.
[EN] This thesis presents several proposals aimed at improving video transmission through the DASH (Dynamic Adaptive Streaming over HTTP) standard. This research work studies the DASH transmission protocol and its characteristics. At the same time, this work proposes the use of encoding with constant quality and variable bitrate as the most suitable video content encoding mode for on-demand content transmission through the DASH standard. Based on the proposal to use the constant quality encoding mode, the role played by adaptation algorithms in the user experience when consuming multimedia content becomes more important. In this sense, this thesis presents an adaptation algorithm called Look Ahead which, without modifying the standard, allows the use of the information on the sizes of the video segments included in the multimedia containers to avoid making adaptation decisions that lead to undesirable stalls during the playback of multimedia content. In order to evaluate the improvements of the presented adaptation algorithm, three models of objective QoE evaluation are proposed. These models allow to predict in a simple way the QoE that users would have in an objective way, using well-known parameters such as the average bitrate, the PSNR (Peak Signal-to-Noise Ratio) and the VMAF (Video Multimethod Assessment Fusion). All of them applied to each segment. Finally, the DASH behavior in Wi-Fi environments with high user density is analyzed. In this context, there could be a high number of stalls in the playback because of a bad estimation of the available transfer rate due to the ON/OFF pattern of DASH download and to the variability of the access to the Wi-Fi environment. To relieve this situation, a coordination service based on SAND (MPEG's Server and Network Assisted DASH) is proposed, which provides an estimation of the transfer rate based on the information of the state of the clients' players.
Belda Ortega, R. (2021). Mejora del streaming de vídeo en DASH con codificación de bitrate variable mediante el algoritmo Look Ahead y mecanismos de coordinación para la reproducción, y propuesta de nuevas métricas para la evaluación de la QoE [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/169467
TESIS

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Boban, Bondžulić. "Процена квалитета слике и видеа кроз очување информација о градијенту." Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2016. http://www.cris.uns.ac.rs/record.jsf?recordId=99807&source=NDLTD&language=en.

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У овој дисертацији разматране су објективне мере процене квалитетаслике и видеа са потпуним и делимичним референцирањем на изворнисигнал. За потребе евалуације квалитета развијене су поуздане,рачунски ефикасне мере, засноване на очувању информација оградијенту. Мере су тестиране на великом броју тест слика и видеосеквенци, различитих типова и степена деградације. Поред јавнодоступних база слика и видео секвенци, за потребе истраживањаформиране су и нове базе видео секвенци са преко 300 релевантнихтест узорака. Поређењем доступних субјективних и објективних скороваквалитета показано је да је објективна евалуација квалитета веомасложен проблем, али га је могуће решити и доћи до високихперформанси коришћењем предложених мера процене квалитета сликеи видеа.
U ovoj disertaciji razmatrane su objektivne mere procene kvalitetaslike i videa sa potpunim i delimičnim referenciranjem na izvornisignal. Za potrebe evaluacije kvaliteta razvijene su pouzdane,računski efikasne mere, zasnovane na očuvanju informacija ogradijentu. Mere su testirane na velikom broju test slika i videosekvenci, različitih tipova i stepena degradacije. Pored javnodostupnih baza slika i video sekvenci, za potrebe istraživanjaformirane su i nove baze video sekvenci sa preko 300 relevantnihtest uzoraka. Poređenjem dostupnih subjektivnih i objektivnih skorovakvaliteta pokazano je da je objektivna evaluacija kvaliteta veomasložen problem, ali ga je moguće rešiti i doći do visokihperformansi korišćenjem predloženih mera procene kvaliteta slikei videa.
This thesis presents an investigation into objective image and video qualityassessment with full and reduced reference on original (source) signal. Forquality evaluation purposes, reliable, computational efficient, gradient-basedmeasures are developed. Proposed measures are tested on different imageand video datasets, with various types of distorsions and degradation levels.Along with publicly available image and video quality datasets, new videoquality datasets are maded, with more than 300 relevant test samples.Through comparison between available subjective and objective qualityscores it has been shown that objective quality evaluation is highly complexproblem, but it is possible to resolve it and acchieve high performance usingproposed quality measures.

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Fan, Yu. "Quality assessment of stereoscopic 3D content based on binocular perception." Thesis, Poitiers, 2019. http://www.theses.fr/2019POIT2266.

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La grande avancée des technologies stéréoscopiques/3D conduit à une croissance remarquable des contenus 3D dans diverses applications grâce aux effets immersifs qu’ils offrent. Cependant, ces technologies ont également créé de enjeux concernant l’évaluation de la qualité et la compression, en raison des processus complexes de la vision binocu laire. Visant à évaluer et à optimiser les performances des systèmes d’imagerie 3D quant à leur capacité de stockage et leur qualité d’expérience (QoE), cette thèse porte sur deux parties principales: 1- les seuils de visibilité spatiale du système visuel humain (SVH) et 2- l’évaluation de la qualité des images stéréoscopiques. Il est bien connu que le SVH ne peut détecter les modifications dans une image compressée si ces dernières sont inférieures au seuil JND (Just Noticeable Difference). Par conséquent, une étude approfondie basée sur une analyse objective et subjective a été menée sur les modèles 3D-JND existants. En outre, un nouveau modèle 3D-JND basé sur des expériences psychophysiques visant à mesurer l’effet de la disparité binoculaire et du masquage spatial sur les seuils visuels a été proposé. Dans la deuxième partie, nous avons exploré la mesure de la qualité 3D. Ainsi, nous avons développé un modèle avec référence prenant en compte à la fois la qualité monoculaire et cyclopéenne. Nous avons ensuite proposé une nouvelle métrique de qualité sans référence reposant sur la combinaison de statistiques locales de contraste de la paire stéréo. Les deux modèles reposent sur les propriétés de fusion et de rivalité binoculaire du SVH afin de simuler avec précision le jugement humain de la qualité 3D
The great advance of stereoscopic/3D technologies leads to a remarkable growth of 3D content in various applications thanks to a realistic and immersive experience. However, these technologies also brought some technical challenges and issues, regarding quality assessment and compression due to the complex processes of the binocular vision. Aiming to evaluate and optimize the performance of 3D imaging systems with respect to their storage capacity and quality of experience (QoE), this thesis focuses on two main parts: 1- spatial visibility thresholds of the human visual system (HVS) and 2- stereoscopic image quality assessment (SIQA). It is well-known that the HVS cannot detect the changes in a compressed image if these changes are lower than the just noticeable different (JND) threshold. Therefore, an extensive study based on objective and subjective analysis has been conducted on existing 3D-JND models. In addition, a new 3D-JND model has been proposed based on psychophysical experiments aiming to measure the effect of binocular disparity and spatial masking on the visual thresholds. In the second part, we explored new approaches for SIQA from two different perspectives. First, we developed a reference-based model accounting for both monocular and cyclopean quality. Then, we proposed a new blind quality metric relying on local contrast statistics combination of the stereopair. Both models considered the binocular fusion and binocular rivalry behaviors of the HVS in order to accurately simulate the human judgment of 3D quality

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Nabil, mahrous yacoub Sandra. "Evaluation de la qualité de vidéos panoramiques synthétisées." Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAM067/document.

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La création des vidéos panoramiques de haute qualité pour des contenus immersifs en VR est généralement faite à l'aide d'un appareil doté de plusieurs caméras couvrant une scène cible. Malheureusement, cette configuration introduit à la fois des artefacts spatiaux et temporels dus à la différence entre les centres optiques et à la synchronisation imparfaite. Les mesures de qualité d'image traditionnelles ne peuvent pas être utilisées pour évaluer la qualité de ces vidéos, en raison de leur incapacité à capturer des distorsions géométriques. Dans cette thèse, nous proposons des méthodes pour l'évaluation objective des vidéos panoramiques basées sur le flux optique et la saillance visuelle. Nous validons cette métrique avec une étude centrée sur l'homme qui combine l'annotation d'erreurs percues et l'eye-tracking.Un défi important pour mesurer la qualité des vidéos panoramiques est le manque d'une vérité-terrain. Nous avons étudié l'utilisation des vidéos originales comme référence pour le panorama de sortie. Nous notons que cette approche n'est pas directement applicable, car chaque pixel du panorama final peut avoir une à $N$ sources correspondant à $N$ vidéos d'entrée avec des régions se chevauchant. Nous montrons que ce problème peut être résolu en calculant l'écart type des déplacements de tous les pixels sources à partir du déplacement du panorama en tant que mesure de la distorsion. Cela permet de comparer la différence de mouvement entre deux images données dans les vidéos originales et le mouvement dans le panorama final. Les cartes de saillance basées sur la perception humaine sont utilisées pour pondérer la carte de distorsion pour un filtrage plus précis.Cette méthode a été validée par une étude centrée sur l'homme utilisant une expérience empirique. L'expérience visait à déterminer si les humains et la métrique d'évaluation détectaient et mesuraient les mêmes erreurs, et à explorer quelles erreurs sont les plus importantes pour les humains lorsqu'ils regardent une vidéo panoramique.Les méthodes décrites ont été testées et validées et fournissent des résultats intéressants en ce qui concerne la perception humaine pour les mesures de qualité. Ils ouvrent également la voie à de nouvelles méthodes d'optimisation de l'assemblage vidéo, guidées par ces mesures de qualité
High quality panoramic videos for immersive VR content are commonly created using a rig with multiple cameras covering a target scene. Unfortunately, this setup introduces both spatial and temporal artifacts due to the difference in optical centers as well as the imperfect synchronization. Traditional image quality metrics cannot be used to assess the quality of such videos, due to their inability to capture geometric distortions. In this thesis, we propose methods for the objective assessment of panoramic videos based on optical flow and visual salience. We validate this metric with a human-centered study that combines human error annotation and eye-tracking.An important challenge in measuring quality for panoramic videos is the lack of ground truth. We have investigated the use of the original videos as a reference for the output panorama. We note that this approach is not directly applicable, because each pixel in the final panorama can have one to N sources corresponding to N input videos with overlapping regions. We show that this problem can be solved by calculating the standard deviation of displacements of all source pixels from the displacement of the panorama as a measure of distortion. This makes it possible to compare the difference in motion between two given frames in the original videos and motion in the final panorama. Salience maps based on human perception are used to weight the distortion map for more accurate filtering.This method was validated with a human-centered study using an empirical experiment. The experiment was designed to investigate whether humans and the evaluation metric detect and measure the same errors, and to explore which errors are more salient to humans when watching a panoramic video.The methods described have been tested and validated and they provide interesting findings regarding human-based perception for quality metrics. They also open the way to new methods for optimizing video stitching guided by those quality metrics

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Derathé, Arthur. "Modélisation de la qualité de gestes chirurgicaux laparoscopiques." Thesis, Université Grenoble Alpes, 2020. https://thares.univ-grenoble-alpes.fr/2020GRALS021.pdf.

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La chirurgie laparoscopique est une pratique de plus en plus communément utilisée dans différentes spécialités chirurgicales, du fait des grands avantages pour le patient en termes de complications et de temps d’hospitalisation. En revanche, cette pratique est très différente de la chirurgie dite « ouverte », et présente ses propres difficultés, notamment dans la manipulation des instruments chirurgicaux, et la maîtrise de l’espace opératoire. Une meilleure compréhension du geste chirurgical en laparoscopie permettrait d’améliorer les outils utilisés pour la formation des jeunes chirurgiens.L’objectif de ce travail était de développer et valider une méthode visant à expliquer certains aspects clés de la pratique du geste chirurgical en termes cliniques, à partir d’une approche algorithmique. La compréhension du contexte clinique de cette thèse étant essentielle, un important travail d’explicitation et de formalisation des connaissances du chirurgien a été effectué. La deuxième partie de ce travail a consisté à développer une méthode algorithmique visant à prédire la qualité du geste chirurgical et le chirurgien pratiquant. Enfin à travers l’analyse de données décrivant la qualité et la pratique du geste chirurgical, nous avons étudié et validé la pertinence clinique de nouveaux éléments de connaissances cliniques.Nous avons travaillé sur une cohorte de 30 patients opérés par gastrectomie longitudinale au sein du département de chirurgie digestive du CHU de Grenoble. Cette technique chirurgicale est aujourd’hui communément utilisé pour traiter les patients atteints d’obésité morbide ou accompagné de comorbidités. Grâce à une réflexion commune avec notre partenaire chirurgien, nous avons pu formaliser les notions importantes de cette procédure chirurgicale. Pour chacune des chirurgies de la cohorte, nous avons effectué trois annotations distinctes : une annotation de la procédure et des actions des mains du chirurgien, une évaluation de la qualité d’exposition de la scène chirurgicale à chaque geste de dissection effectué par le chirurgien, et enfin la segmentation complète de l’image associée à chacun des gestes de dissection évalués. L’annotation de la procédure et la segmentation ont rendu possible l’extraction de métriques caractéristiques du geste et de la scène chirurgicale.Ensuite, nous avons développé un algorithme dont l’objectif était la prédiction de la qualité d’exposition à partir des métriques. Nous avons également développé un environnement dédié à l’optimisation des hyper-paramètres de notre algorithme pour maximiser les performances en prédiction. L’intérêt de cet environnement était notamment de gérer les spécificités de notre jeu de données.Dans un troisième temps, nous avons mis en place une méthode permettant de confronter l’analyse algorithmique quantitative de nos données à l’expertise clinique des chirurgiens ayant effectué les chirurgies. Pour ce faire, nous avons d’abord extrait les variables les plus importantes pour notre tâche de prédiction. Puis nous avons traduit l’information portée par ces variables sous forme d’énoncés présentant une signification clinique. Enfin nous avons extrait des échantillons vidéos représentatifs de chacun de ces énoncés. A partir de ces énoncés accompagnés de leurs échantillons vidéos, nous avons pu construire un questionnaire de validation, et le présenter à nos partenaires chirurgiens. Nous avons ainsi mené une validation clinique visant à recueillir leur avis quant à la pertinence clinique de notre approche.Nous avons donc proposé une méthode d'analyse quantitative explicitant le lien entre des observations visuelles et temporelles et des critères cliniques relatifs à des chirurgies laparoscopiques. Une meilleure compréhension de ces liens permettrait, à terme, de proposer des systèmes d'aide à la formation des chirurgiens sur cette pratique complexe.hick up
Sous cœlioscopie, le traitement chirurgical permet une meilleure prise en charge du patient, et sa pratique est de plus en plus fréquente en routine clinique. Cette pratique présente néanmoins ses difficultés propres pour le chirurgien, et nécessite une formation prolongée pendant l’internat et en post-internat. Pour faciliter cette formation, il est notamment possible de développer des outils d’évaluation et d’analyse de la pratique chirurgicale.Dans cette optique, l’objectif de ce travail de thèse est d’étudier la faisabilité d’une méthodologie proposant, à partir d’un traitement algorithmique, des analyses à portée clinique pertinente pour le chirurgien. J’ai donc traité les problèmes suivants : Il m’a fallu recueillir et annoter un jeu de données, implémenter un environnement d’apprentissage dédié à la prédiction d’un aspect spécifique de la pratique chirurgicale, et proposer une approche permettant de traduire mes résultats algorithmiques sous une forme pertinente pour le chirurgien. Dès que cela était possible, nous avons cherché à valider ces différentes étapes de la méthodologie

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Dissertations / Theses on the topic 'Video Quality Assessment'

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