The reliable internet stream transport (RIST) protocol is used for streaming video over the internet and requires time synchronisation to ensure that each frame is played out at the correct time. One method to ensure time synchronisation today in RIST productions is by utilizing the network time protocol (NTP). NTP has several issues and requirements that makes it a not ideal time synchronisation method in RIST productions and this thesis proposes a dynamic average time synchronisation (DATS) method as an option for using NTP in RIST productions. The DATS method uses a two-way synchronisation scheme to estimate the time offset between a video sender node and a video receiver node which is added to an average used as the time offset value. Additionally, it is explored whether or not a Kalman filter can further increase performance in DATS. Furthermore, the Kalman filter parameters were attempted to be optimized with a genetic algorithm. With a simulated \textit{testsrc FFmpeg} stream, the performance of DATS is evaluated and compared with the NTP implementation \textit{Chrony}. The metrics used in the evaluation was the playout delay and the error in time synchronisation which were calculated by periodical messages between a sender and receiver node. The results reveal that DATS performs slightly better without a Kalman filter but is slightly less robust without it. The results also indicated that DATS is comparable to NTP in an unloaded network, but is outperformed by NTP in a congested network.

Three-dimensional technology, more commonly referred to as 3D technology, has revolutionised many fields including entertainment, medicine, and communications to name a few. In addition to 3D films, games, and sports channels, 3D perception has made tele-medicine a reality. By the year 2015, 30% of the all HD panels at home will be 3D enabled, predicted by consumer electronics manufacturers. Stereoscopic cameras, a comparatively mature technology compared to other 3D systems, are now being used by ordinary citizens to produce 3D content and share at a click of a button just like they do with the 2D counterparts via sites like YouTube. But technical challenges still exist, including with autostereoscopic multiview displays. 3D content requires many complex considerations--including how to represent it, and deciphering what is the best compression format--when considering transmission or storage, because of its increased amount of data. Any decision must be taken in the light of the available bandwidth or storage capacity, quality and user expectations. Free viewpoint navigation also remains partly unsolved. The most pressing issue getting in the way of widespread uptake of consumer 3D systems is the ability to deliver 3D content to heterogeneous consumer displays over the heterogeneous networks. Optimising 3D video communication solutions must consider the entire pipeline, starting with optimisation at the video source to the end display and transmission optimisation. Multi-view offers the most compelling solution for 3D videos with motion parallax and freedom from wearing headgear for 3D video perception. Optimising multi-view video for delivery and display could increase the demand for true 3D in the consumer market. This thesis focuses on an end-to-end quality optimisation in 3D video communication/transmission, offering solutions for optimisation at the compression, transmission, and decoder levels.

With the rapidly advancing technologies, training has been vital to keep companies competitive. Web-based training grows rapidly and attracts more attention for its most flexible manner. Virtual classroom is a form of synchronous web-based training. It provides real-time interactivity in learning process. I have developed a virtual classroom that uses Web services to control the audio/video transmission, chat box, whiteboard, and synchronous HTML presentation. Compared to an early implementation of the virtual classroom based on the Jini network, my Web-service based implementation has a significantly different control structure. My implementation has better interoperability.

"Packet loss can be detrimental to real-time interactive video over lossy networks because one lost video packet can propagate errors to many subsequent video frames due to the encoding dependency between frames. Feedback-based error control techniques use feedback information from the decoder to adjust coding parameters at the encoder or retransmit lost packets to reduce the error propagation due to data loss. Feedback-based error control techniques have been shown to be more effective than trying to conceal the error at the encoder or decoder alone since they allow the encoder and decoder to cooperate in the error control process. However, there has been no systematic exploration of the impact of video content and network conditions on the performance of feedback-based error control techniques. In particular, the impact of packet loss, round-trip delay, network capacity constraint, video motion and reference distance on the quality of videos using feedback-based error control techniques have not been systematically studied. This thesis presents analytical models for the major feedback-based error control techniques: Retransmission, Reference Picture Selection (both NACK and ACK modes) and Intra Update. These feedback-based error control techniques have been included in H.263/H.264 and MPEG4, the state of the art video in compression standards. Given a round-trip time, packet loss rate, network capacity constraint, our models can predict the quality for a streaming video with retransmission, Intra Update and RPS over a lossy network. In order to exploit our analytical models, a series of studies has been conducted to explore the effect of reference distance, capacity constraint and Intra coding on video quality. The accuracy of our analytical models in predicting the video quality under different network conditions is validated through simulations. These models are used to examine the behavior of feedback-based error control schemes under a variety of network conditions and video content through a series of analytic experiments. Analysis shows that the performance of feedback-based error control techniques is affected by a variety of factors including round-trip time, loss rate, video content and the Group of Pictures (GOP) length. In particular: 1) RPS NACK achieves the best performance when loss rate is low while RPS ACK outperforms other repair techniques when loss rate is high. However RPS ACK performs the worst when loss rate is low. Retransmission performs the worst when the loss rate is high; 2) for a given round-trip time, the loss rate where RPS NACK performs worse than RPS ACK is higher for low motion videos than it is for high motion videos; 3) Videos with RPS NACK always perform the same or better than videos without repair. However, when small GOP sizes are used, videos without repair perform better than videos with RPS ACK; 4) RPS NACK outperform Intra Update for low-motion videos. However, the performance gap between RPS NACK and Intra Update drops when the round-trip time or the intensity of video motion increases. 5) Although the above trends hold for both VQM and PSNR, when VQM is the video quality metric the performance results are much more sensitive to network loss. 6) Retransmission is effective only when the round-trip time is low. When the round-trip time is high, Partial Retransmission achieves almost the same performance as Full Retransmission. These insights derived from our models can help determine appropriate choices for feedback-based error control techniques under various network conditions and video content. "

Compressed video bitstream transmissions over wireless networks are addressed in this work. We first consider error control and power allocation for transmitting wireless video over CDMA networks in conjunction with multiuser detection. We map a layered video bitstream to several CDMA fading channels and inject multiple source/parity layers into each of these channels at the transmitter. We formulate a combined optimization problem and give the optimal joint rate and power allocation for each of linear minimum mean-square error (MMSE) multiuser detector in the uplink and two types of blind linear MMSE detectors, i.e., the direct-matrix-inversion (DMI) blind detector and the subspace blind detector, in the downlink. We then present a multiple-channel video transmission scheme in wireless CDMA networks over multipath fading channels. For a given budget on the available bandwidth and total transmit power, the transmitter determines the optimal power allocations and the optimal transmission rates among multiple CDMA channels, as well as the optimal product channel code rate allocation. We also make use of results on the large-system CDMA performance for various multiuser receivers in multipath fading channels. We employ a fast joint source-channel coding algorithm to obtain the optimal product channel code structure. Finally, we propose an end-to-end architecture for multi-layer progressive video delivery over space-time differentially coded orthogonal frequency division multiplexing (STDC-OFDM) systems. We propose to use progressive joint source-channel coding to generate operational transmission distortion-power-rate (TD-PR) surfaces. By extending the rate-distortion function in source coding to the TD-PR surface in joint source-channel coding, our work can use the ??equal slope?? argument to effectively solve the transmission rate allocation problem as well as the transmission power allocation problem for multi-layer video transmission. It is demonstrated through simulations that as the wireless channel conditions change, these proposed schemes can scale the video streams and transport the scaled video streams to receivers with a smooth change of perceptual quality.

Efficient transmission schemes are presented for streaming scalable video over a link with limited capacity. The objective is to select a transmission sequence of data units and their transmission schedule such that the overall video quality is maximized. For video with a single spatial layer, optimal transmission schemes are obtained for two general classes of hierarchical prediction structures, which include the popular dyadic structure. Based on a new characterization of the interdependence among frames in terms of trees, structural properties of an optimal transmission schedule are derived. These properties lead to the development of a jointly optimal frame selection and scheduling algorithm, which has computational complexity that is quadratic in the number of frames. Then, using the concept of virtual deadlines, an efficient sub-optimal scheme for the transmission of video with multiple spatial layers is proposed. Simulation results show that the proposed schemes substantially outperform two existing alternatives.

Efficient transmission schemes are presented for streaming scalable video over a link with limited capacity. The objective is to select a transmission sequence of data units and their transmission schedule such that the overall video quality is maximized. For video with a single spatial layer, optimal transmission schemes are obtained for two general classes of hierarchical prediction structures, which include the popular dyadic structure. Based on a new characterization of the interdependence among frames in terms of trees, structural properties of an optimal transmission schedule are derived. These properties lead to the development of a jointly optimal frame selection and scheduling algorithm, which has computational complexity that is quadratic in the number of frames. Then, using the concept of virtual deadlines, an efficient sub-optimal scheme for the transmission of video with multiple spatial layers is proposed. Simulation results show that the proposed schemes substantially outperform two existing alternatives.

Compressed video bitstream transmissions over wireless networks are addressed in this work. We first consider error control and power allocation for transmitting wireless video over CDMA networks in conjunction with multiuser detection. We map a layered video bitstream to several CDMA fading channels and inject multiple source/parity layers into each of these channels at the transmitter. We formulate a combined optimization problem and give the optimal joint rate and power allocation for each of linear minimum mean-square error (MMSE) multiuser detector in the uplink and two types of blind linear MMSE detectors, i.e., the direct-matrix-inversion (DMI) blind detector and the subspace blind detector, in the downlink. We then present a multiple-channel video transmission scheme in wireless CDMA networks over multipath fading channels. For a given budget on the available bandwidth and total transmit power, the transmitter determines the optimal power allocations and the optimal transmission rates among multiple CDMA channels, as well as the optimal product channel code rate allocation. We also make use of results on the large-system CDMA performance for various multiuser receivers in multipath fading channels. We employ a fast joint source-channel coding algorithm to obtain the optimal product channel code structure. Finally, we propose an end-to-end architecture for multi-layer progressive video delivery over space-time differentially coded orthogonal frequency division multiplexing (STDC-OFDM) systems. We propose to use progressive joint source-channel coding to generate operational transmission distortion-power-rate (TD-PR) surfaces. By extending the rate-distortion function in source coding to the TD-PR surface in joint source-channel coding, our work can use the ??equal slope?? argument to effectively solve the transmission rate allocation problem as well as the transmission power allocation problem for multi-layer video transmission. It is demonstrated through simulations that as the wireless channel conditions change, these proposed schemes can scale the video streams and transport the scaled video streams to receivers with a smooth change of perceptual quality.

Η δημοφιλής τάση για ασύρματη επικοινωνία συμβολίζει την ανάγκη μας για ανεξαρτησία και ευελιξία. Σε συνδυασμό με την έμφυτη ανάγκη του ανθρώπου για επικοινωνία, ανταλλαγή σκέψεων και εμπειριών, η τάση αυτή περιλαμβάνει τα τελευταία χρόνια την απαίτηση για ασύρματα πολυμέσα. Η ασύρματη επικοινωνία πολυμέσων έχει τη δυνατότητα να αλλάξει πολλές από τις παραμέτρους της καθημερινότητάς μας. Η πληθώρα των εφαρμογών που προσφέρονται περιορίζεται μόνο από τη δυνατότητα του ασύρματου καναλιού να διαθέσει πόρους, ενέργεια και χρόνο. Η χωρητικότητα του ασύρματου διαύλου επικοινωνίας είναι το κλειδί και η έρευνα εστιάζει στη βελτιστοποίηση της μετάδοσης εφαρμογών ροής βίντεο, αξιοποιώντας όσο το δυνατόν καλύτερα το ασύρματο κανάλι. Στα πλαίσια της διατριβής προτείνεται μια νέα αναλυτική μέθοδος δημιουργίας συνθετικών βίντεο ροών MPEG-4 που μεταδίδονται σε ένα ετερογενές ασύρματο περιβάλλον. Η κίνηση που δημιουργούν πολλαπλές ροές βίντεο μοντελοποιείται από μια αλυσίδα Μαρκόφ δύο διαστάσεων. Προκειμένου να διατηρηθεί η ποιότητα παρεχόμενης υπηρεσίας, προτείνεται ένας μηχανισμός μεταγωγής των ροών βίντεο με βάση τις πιθανότητες μετάβασης καταστάσεων του μοντέλου. Επιπλέον, παρουσιάζεται ένα αναλυτικό μοντέλο εκτίμησης της αλλοίωσης της αντιλαμβανόμενης ποιότητας κωδικοποιημένου βίντεο Η.264/AVC. Το μοντέλο αυτό αξιοποιεί τα ιδιαίτερα χαρακτηριστικά της κωδικοποίησης Η.264/AVC και ιδιαίτερα τις αλληλεξαρτήσεις μεταξύ των πλαισίων βίντεο, ώστε να εξασφαλίσει την ακριβή εκτίμηση της συνολικής αλλοίωσης. Η μελέτη περιλαμβάνει συνδυασμούς πιθανών σφαλμάτων στο ασύρματο κανάλι ώστε να αποδειχθεί η δυνατότητα εκτίμησης της αλλοίωσης από το προτεινόμενο μοντέλο σε κάθε συνθήκη του δικτύου. Στη συνέχεια, αναλύονται μηχανισμοί προγραμματισμού της μετάδοσης πακέτων βίντεο και διαφοροποίησης της σημαντικότητας των πακέτων με βάση τον αντίκτυπό τους στη συνολική αλλοίωση του βίντεο. Η σημασία κάθε πακέτου εκτιμάται από το προτεινόμενο μοντέλο εκτίμησης της αλλοίωσης. Εξασφαλίζεται, έτσι, η προσαρμογή του ρυθμού μετάδοσης του βίντεο στις διαφορετικές συνθήκες του δικτύου. Η αξιολόγηση του μοντέλου εκτίμησης επεκτείνεται ώστε να συμπεριλάβει το πρωτόκολλο 802.11e το οποίο διαθέτει μηχανισμούς διασφάλισης της ποιότητας υπηρεσίας. Τέλος, παρουσιάζονται αλγόριθμοι επιλογής βέλτιστων διαδρομών μεταξύ πηγής και παραλήπτη σε ασύρματα δίκτυα αισθητήρων πολυμέσων. Προτείνεται μια επέκταση του πρωτοκόλλου LEACH ώστε να είναι δυνατή η δρομολόγηση πακέτων βίντεο από πολλαπλές διαδρομές με στόχο τη μικρότερη δυνατή αλλοίωση της ποιότητας και την εξοικονόμηση ενέργειας στους κόμβους. / The popular trend for wireless communications marks our demand for freedom and flexibility. Recently, the inherent human need for communication and sharing of ideas and experiences has been enriched with the need for wireless multimedia. Wireless multimedia communications have the ability to alter several parameters of our daily life. The great variety of offered services is only limited by the available resources of the wireless medium. The key is the capacity of the wireless medium and this research focuses on optimizing the video traffic while fully utilizing the wireless channel. This thesis introduces a new analytical method of creating synthetic MPEG-4 video streams over heterogeneous wireless networks. The aggregate video traffic generated by multiple wireless video sources is modeled by a two-dimensional Marcov chain. In order to achieve a guaranteed quality of service, a handoff mechanism is proposed based on the state transition probabilities of the statistical model. Moreover, an analytical distortion prediction model for H264/AVC coded video is presented. In order to precisely estimate the received video distortion, the proposed model utilizes the inherent characteristics of H.264/AVC coding and in particular, the correlation among neighboring video frames. The distortion prediction model’s ability to estimate the received video distortion is studied under different channel conditions. Hence, complex combinations of errors due to the wireless channel are considered in this thesis. Moreover, an analysis of video packet scheduling algorithms and traffic differentiation schemes, based on the video packet’s impact to the overall video distortion, is included. The importance of each video packet is estimated by the proposed distortion prediction model. Therefore, the transmission rate of a video source can be adapted to the varying wireless channel conditions. The evaluation of the model has been extended in order to include the study of the 802.11e standard, which incorporates mechanisms for guaranteeing quality of service. Finally, the thesis proposes algorithms for optimised video multipath routing in wireless multimedia sensor networks. A proposed extension of the LEACH protocol is implemented that ensures multipath video packet routing. Thus, significantly improved received video distortion and power consumption in the wireless sensor nodes, is achieved.

Magasinprogrammet Go’kväll sänder i regel fem program per vecka under hela vinterhalvåret. Programmet produceras och sänds ut av SVT allmän-TV i Umeå. Till vissa delar av programmet önskas gäster som uttalar sig om aktuella ämnen. Vid några tillfällen har redaktionen upplevt att man inte kunnat plocka in de mest optimala gästerna för kommentarer på grund av rent logistiska skäl, i regel att den efterfrågade gästen i fråga inte kunnat närvara fysiskt i Umeå, ofta på grund av kort varsel, något som nuvarande programutformning kräver av alla som medverkar i direktsändning. Det som efterfrågades var en lösning för att kunna inkludera konceptet gäst via direktlänk i kortare segment av programmet. I utgångsläget fanns ingen budget eller möjlighet till stora ekonomiska investeringar just för detta ändamål. Problemformuleringen blev därför: Hur implementerar man konceptet gäst via länk med hjälp av de resurser SVT idag och inom den närmsta framtiden förfogar över? TV-verksamheten inom SVT är primärt indelad i tre olika divisioner: allmän-tv (dit hör exempelvis barn-, nöje-, fakta- och kulturprogram), nyheter (nyhetsbevakning, sport, regionala nyheter etc.) och SVTi (teknisk utveckling). Allmän-TV (ATV) produceras av SVT på fyra orter som är Stockholm, Göteborg, Malmö och Umeå. De fyra ATV-orterna har utrustning för att sända HDTV och producerar även i HD. Nyheter, och framförallt de regionala nyheterna inkluderar redan i dagsläget olika direktsända inslag från fältet i sina produktioner men skillnaden är att allt produceras i det gamla SD-formatet. I praktiken innebär detta att HD endast kan sändas mellan ATV-orterna och sedan ut i rutan utan att infrastrukturen ändras. Den stora utmaningen blev följaktligen att hitta en lösning där så mycket av befintlig infrastruktur och personalresurs som möjligt kan utnyttjas och samtidigt möta de krav på bildkvalitet som efterfrågas. Med hjälp av intervjuer och interna dokument kartlades befintliga resurser och resultatet blev att möjligheter för att lösa problemet med hjälp av befintlig infrastruktur och bemanning torde vara fullt genomförbart och möjligt att implementera snarast. / The talk-show Go'kväll (Good evening) broadcast five shows per week during the autumn, winter and spring. The show is produced and broadcasted by the non-news section (ATV) of SVT in Umeå. In some parts of the show, guests who gives comments to various recent events is wanted. Some particular times, the editorial staff has experienced that the most ideal guests could not be present in the show, mainly according to the circumstance that they have to be physically present in the studio in Umeå in order to participate in the show, often made impossible by travel logistics. The production wanted a solution for using the concept of remote located quests participating live via video link in chosen segments of the show. There was no economical budget for the project, so the question was: How to implement the concept of using remote located quests live in Go'kväll, only using present infrastructure and other resources? The TV-operations within the company of SVT is divided into three different divisions, ATV, News section (news, sport) and SVTi (Technichal development). ATV is produced and broadcasted from Stockholm, Gothenburg, Malmö and Umeå. These four facilities produce and broadcast in HD-format while the news division mainly broadcasts in SD. Practically, this means that with no change at all in infrastructure, HD can only be transmitted between and from the ATV-locations. The main challenge then, become finding a solution where as much as possible of resources in terms of infrastructure and staff could be used and also meet the requirements of video quality. By making interviews and reading internal working documents, existing resources were surveyed and the results shows that possibilities to solve the problem using existing technical infrastructure and labour exists and should be implementable instantly, if requested.