Multimedia transmission is the effective way of transmitting multimedia elements (comprising voice, audio, video, data etc) from one place to the other via internet enabled protocols and other means. The term 'effective' is used because multimedia transmission is a nightmare if the conveyance is not smooth, seamless and efficient. Over time, the world has seen tremendous improvement that started from the era of the first generation of multimedia generation to the point of multimedia transmission. Much has been said and done in this area and the world has become a connected enterprise because of the transmission of multimedia. In spite of these successes that have been recorded in these areas, there are still many challenges facing multimedia transmission. What determines the progress of technology globally is the trends of evolution that multimedia transmission has gone through. An important challenge facing multimedia transmission is one that has been neglected for a long time. There has been deep neglect of the devices that are used in transmission while much emphasis has been on the protocols and the software that are being developed for multimedia transmission. Devices play a very important role in the realization of seamless transmission of media. Lately, the world seems to have realized the fact that devices that do the actual transmission needs more attention. These devices are the ones that do the distribution and the transmission of the multimedia streams or signals. This has been highlighted in a recent research study that was referenced in the Cambridge Handbook of Multimedia Learning that showed that the expectations of meeting the world's target on multimedia has been reduced by half because of problems arising from the inefficiency of multimedia devices and not really from the protocol perspective as earlier perceived. It is inline with the above that this research was titled "improving multimedia transmission through enhanced multimedia devices". Multimedia devices are the end to end units that are used in multimedia transmission. This research investigated the current devices that are being used, their deficiencies and the reasons that make them unstable for multimedia transmission. It focused on the real time multimedia transmission over the internet protocol (IP) through enhancing limited capabilities of the current multimedia devices. This will make way for new studies into newer devices that are better designed for the efficient multimedia flow. It will assure better quality end-to-end solutions in the area of multimedia distribution and transmission. This research is broad enough to cover most of the major areas of multimedia transmission and cut across several industries and technologies. These might include industries that specialize in internet telephony; design and manufacture multimedia devices and multimedia technologies. Despite the huge number of fields that this research cut across, the focus remained unchanged in highlighting this challenge and proffering a solution through enhanced end to end multimedia elements. It is hoped that this research work will contribute to the solution of this area of challenge and bring to fore the work that should be done in this regard. The advantages of improved multimedia transmission cannot be over emphasized as there will be a tremendous reduction in the cost of long distance communication globally and smoother media transmission which makes use of the readily available internet protocols. In spite of these successes that have been recorded in these areas, there are still many challenges facing multimedia transmission. What determines the progress of technology globally is the trends of evolution that multimedia transmission has gone through. An important challenge facing multimedia transmission is one that has been neglected for a long time. There has been deep neglect of the devices that are used in transmission while much emphasis has been on the protocols and the software that are being developed for multimedia transmission. Devices play a very important role in the realization of seamless transmission of media. Lately, the world seems to have realized the fact that devices that do the actual transmission needs more attention. These devices are the ones that do the distribution and the transmission of the multimedia streams or signals. This has been highlighted in a recent research study that was referenced in the Cambridge Handbook of Multimedia Learning that showed that the expectations of meeting the world's target on multimedia has been reduced by half because of problems arising from the inefficiency of multimedia devices and not really from the protocol perspective as earlier perceived. It is inline with the above that this research was titled "improving multimedia transmission through enhanced multimedia devices". Multimedia devices are the end to end units that are used in multimedia transmission. This research investigated the current devices that are being used, their deficiencies and the reasons that make them unstable for multimedia transmission. It focused on the real time multimedia transmission over the internet protocol (IP) through enhancing limited capabilities of the current multimedia devices. This will make way for new studies into newer devices that are better designed for the efficient multimedia flow. It will assure better quality end-to-end solutions in the area of multimedia distribution and transmission. This research is broad enough to cover most of the major areas of multimedia transmission and cut across several industries and technologies. These might include industries that specialize in internet telephony; design and manufacture multimedia devices and multimedia technologies. Despite the huge number of fields that this research cut across, the focus remained unchanged in highlighting this challenge and proffering a solution through enhanced end to end multimedia elements. It is hoped that this research work will contribute to the solution of this area of challenge and bring to fore the work that should be done in this regard. The advantages of improved multimedia transmission cannot be over emphasized as there will be a tremendous reduction in the cost of long distance communication globally and smoother media transmission which makes use of the readily available internet protocols. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

Multimedia transmission is the effective way of transmitting multimedia elements (comprising voice, audio, video, data etc) from one place to the other via internet enabled protocols and other means. The term 'effective' is used because multimedia transmission is a nightmare if the conveyance is not smooth, seamless and efficient. Over time, the world has seen tremendous improvement that started from the era of the first generation of multimedia generation to the point of multimedia transmission. Much has been said and done in this area and the world has become a connected enterprise because of the transmission of multimedia. In spite of these successes that have been recorded in these areas, there are still many challenges facing multimedia transmission. What determines the progress of technology globally is the trends of evolution that multimedia transmission has gone through. An important challenge facing multimedia transmission is one that has been neglected for a long time. There has been deep neglect of the devices that are used in transmission while much emphasis has been on the protocols and the software that are being developed for multimedia transmission. Devices play a very important role in the realization of seamless transmission of media. Lately, the world seems to have realized the fact that devices that do the actual transmission needs more attention. These devices are the ones that do the distribution and the transmission of the multimedia streams or signals. This has been highlighted in a recent research study that was referenced in the Cambridge Handbook of Multimedia Learning that showed that the expectations of meeting the world's target on multimedia has been reduced by half because of problems arising from the inefficiency of multimedia devices and not really from the protocol perspective as earlier perceived. It is inline with the above that this research was titled "improving multimedia transmission through enhanced multimedia devices". Multimedia devices are the end to end units that are used in multimedia transmission. This research investigated the current devices that are being used, their deficiencies and the reasons that make them unstable for multimedia transmission. It focused on the real time multimedia transmission over the internet protocol (IP) through enhancing limited capabilities of the current multimedia devices. This will make way for new studies into newer devices that are better designed for the efficient multimedia flow. It will assure better quality end-to-end solutions in the area of multimedia distribution and transmission. This research is broad enough to cover most of the major areas of multimedia transmission and cut across several industries and technologies. These might include industries that specialize in internet telephony; design and manufacture multimedia devices and multimedia technologies. Despite the huge number of fields that this research cut across, the focus remained unchanged in highlighting this challenge and proffering a solution through enhanced end to end multimedia elements. It is hoped that this research work will contribute to the solution of this area of challenge and bring to fore the work that should be done in this regard. The advantages of improved multimedia transmission cannot be over emphasized as there will be a tremendous reduction in the cost of long distance communication globally and smoother media transmission which makes use of the readily available internet protocols. In spite of these successes that have been recorded in these areas, there are still many challenges facing multimedia transmission. What determines the progress of technology globally is the trends of evolution that multimedia transmission has gone through. An important challenge facing multimedia transmission is one that has been neglected for a long time. There has been deep neglect of the devices that are used in transmission while much emphasis has been on the protocols and the software that are being developed for multimedia transmission. Devices play a very important role in the realization of seamless transmission of media. Lately, the world seems to have realized the fact that devices that do the actual transmission needs more attention. These devices are the ones that do the distribution and the transmission of the multimedia streams or signals. This has been highlighted in a recent research study that was referenced in the Cambridge Handbook of Multimedia Learning that showed that the expectations of meeting the world's target on multimedia has been reduced by half because of problems arising from the inefficiency of multimedia devices and not really from the protocol perspective as earlier perceived. It is inline with the above that this research was titled "improving multimedia transmission through enhanced multimedia devices". Multimedia devices are the end to end units that are used in multimedia transmission. This research investigated the current devices that are being used, their deficiencies and the reasons that make them unstable for multimedia transmission. It focused on the real time multimedia transmission over the internet protocol (IP) through enhancing limited capabilities of the current multimedia devices. This will make way for new studies into newer devices that are better designed for the efficient multimedia flow. It will assure better quality end-to-end solutions in the area of multimedia distribution and transmission. This research is broad enough to cover most of the major areas of multimedia transmission and cut across several industries and technologies. These might include industries that specialize in internet telephony; design and manufacture multimedia devices and multimedia technologies. Despite the huge number of fields that this research cut across, the focus remained unchanged in highlighting this challenge and proffering a solution through enhanced end to end multimedia elements. It is hoped that this research work will contribute to the solution of this area of challenge and bring to fore the work that should be done in this regard. The advantages of improved multimedia transmission cannot be over emphasized as there will be a tremendous reduction in the cost of long distance communication globally and smoother media transmission which makes use of the readily available internet protocols. / Thesis (M.Ing. (Development and Management Engineering))--North-West University, Potchefstroom Campus, 2009.

Στη διατριβή εξετάζουμε προβλήματα που σχετίζονται με τη μετάδοση δεδομένων με υψηλές απαιτήσεις σε εύρος ζώνης και προτείνουμε λύσεις, αλγόριθμους, τεχνικές βελτίωσης της απόδοσης, και εφαρμογές που τις υλοποιούν. Για την περίπτωση του προβλήματος της μετάδοσης βίντεο κατ' απαίτηση (Video on Demand - VoD), εξετάζουμε το πρόβλημα της αποδοχής ή της απόρριψης αιτήσεων για μετάδοση ταινιών χωρίς να υπάρχει γνώση των μελλοντικών αιτήσεων. Παρουσιάζουμε έναν, άμεσης απόκρισης (online), πιθανοτικό αλγόριθμο χρονοπρογραμματισμού ταινιών που εκμεταλλεύεται την γνώση για την κατανομή των προτιμήσεων των αιτήσεων για ταινίες, και αποδεικνύουμε πως έχει ανταγωνιστικό λόγο (competitive ratio) που φράσσεται άνω από σταθερά. Επίσης, δείχνουμε πως η μέθοδος μας μπορεί να επεκταθεί σε ένα προσαρμοζόμενο αλγόριθμο που δεν γνωρίζει την κατανομή των προτιμήσεων. Επίσης, προτείνουμε έναν τρόπο να εφαρμόσουμε μια υπηρεσία βίντεο κατ' απαίτηση για ένα, βασισμένο στο πρωτόκολλο IP, δίκτυο, με περιορισμένο εύρος ζώνης. Στη συνέχεια, εξετάζουμε ένα σχήμα ελέγχου και διαχείρισης του εύρους ζώνης και παρουσιάζουμε ορισμένες μεθόδους προκειμένου να αυξήσουμε την αποδοτικότητα του συστήματος και την εκμετάλλευση του διαθέσιμου εύρους ζώνης (bandwidth). Εξετάζουμε διάφορες τεχνικές και παρουσιάζουμε πειραματικά αποτελέσματα για την βελτίωση της απόδοσης. Επίσης, σχεδιάζουμε και υλοποιούμε μια υπηρεσία διαχείρισης εύρους ζώνης (Managed Bandwidth Service -- MBS). Τέλος παρουσιάζουμε μια ενοποιημένη προσέγγιση για την μετάδοση υπερμεσικών/πολυμεσικών αντικειμένων, τα οποία παρουσιάζονται με βάση προκαθορισμένα σενάρια παρουσίασης (με χωροχρονικές αλληλοεξαρτήσεις μεταξύ των διάφορων μέσων). Τα υπερμεσικά αντικείμενα δομούνται σύμφωνα με μία γλώσσα σηματοδότησης, μέσω της οποίας διατηρούνται πληροφορίες για τις χωρικές και χρονικές συσχετίσεις. Επίσης, υλοποιούμε ένα τέτοιο σύστημα μετάδοσης, που εφαρμόζουμε για εκπαίδευση από απόσταση. / In this thesis we investigate problems related to the transmission of data with high demands in terms of bandwidth, and we propose solutions, algorithms, techniques to increase performance, and applications that use them. For the case of the online video on demand problem, we investigate the problem of having to accept or reject a request for a movie without knowing the future requests. We present an online movie-scheduling scheme that exploits the knowledge of the distribution of the preference of requests for movies, and is shown to have a competitive ratio bounded above by a constant. We extend our approach by presenting an adaptive randomized scheduler which is not aware of the movie popularities. In the sequel we propose a way to implement a video on demand service over a limited bandwidth/best effort Internet based network. Ιn the sequel, we consider a bandwidth control scheme, and we present some methods to increase the efficiency of the system and the utilisation of the available bandwidth. We consider different techniques and we present experimental results for the increased performance. We, also, design and implement a Managed Bandwidth Service (MBS) . Finally, we present a unified approach for delivering hypermedia/multimedia objects, that are to be presented according to predefined scenarios (with spatial and temporal relationships between the various media). The hypermedia documents are structured using a hypermedia markup language that keeps information of the spatiotemporal relationships among document's media components. We, also, implement such a multimedia transmission system, and apply it to distance learning.

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.

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.

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.

There is an increasing demand for multimedia services in heterogeneous wireless networks. Considering the highly dynamic wireless channels and the relatively large size of the multimedia data, how to support efficient and reliable multimedia delivery is a pressing issue. In this dissertation, we investigate the multimedia delivery algorithms in heterogeneous wireless networks from three different aspects. First, we study the single-flow rate adaptation of video streaming algorithm over multiple wireless interfaces. In order to maintain high video streaming quality while reducing the wireless service cost, the optimal video streaming process with multiple links is formulated as a Markov Decision Process (MDP). The reward function is designed to consider the quality of service (QoS) requirements for video traffic, such as the startup latency, playback fluency, average playback quality, playback smoothness and wireless service cost. To solve the MDP in real time, we propose an adaptive, best-action search algorithm to obtain a sub-optimal solution. To evaluate the performance of the proposed adaptation algorithm, we implemented a testbed using the Android mobile phone and the Scalable Video Coding (SVC) codec and conducted experiments with real video flow. Then, with the multiple multimedia flows competing for limited wireless resources, we propose a utility-based scheduling algorithm for multimedia transmission in Drive-thru Internet. A utility model is devised to map the throughput to user's satisfaction level in terms of multimedia data quality, such as Peak Signal-to-Noise Ratio (PSNR) of video. The objective of the scheduling problem is to maximize the total utility. Then the optimization problem is formulated as a finite-state decision problem with the assumption that future arrival information is known, and it is solved by a searching algorithm as the benchmark. To obtain a real-time solution, a practical heuristic algorithm based on the concept of utility potential is devised. We further implemented the solution and conducted extensive simulations using NS-3. Finally, the multimedia dissemination problem in large-scale VANETs is investigated. We first utilize a hybrid-network framework to address the mobility and scalability issues in large-scale VANETs content distribution. Then, we formulate a utility-based maximization problem to find the best delivery strategy and select an optimal path for the multimedia data dissemination, where the utility function has taken the delivery delay, the Quality of Services (QoS) and the storage cost into consideration. We obtain the closed-form of the utility function, and then obtain the optimal solution of the problem with the convex optimization theory. Finally, we conducted extensive trace-driven simulations to evaluate the performance of the proposed algorithm with real traces collected by taxis in Shanghai. In summary, the research outcomes of the dissertation can contribute to three different aspects of multimedia delivery in heterogeneous wireless networks. First, we have proposed a real-time rate adaptation algorithm for video streaming with multiple wireless interfaces, to maintain the high quality while reducing the wireless services cost. Second, we have presented an optimal scheduling algorithm which can maximize the total satisfaction for multimedia transmission in Drive-thru Internet. Third, we have derived the theoretical analysis of the utility functions including delivery delay, QoS and the storage cost, and have obtained an optimal solution for multimedia data dissemination in large-scale VANETs to achieve the highest utility. / Graduate / 0984 / 0544