319 research outputs found

    Predictive Encoder and Buffer Control for Statistical Multiplexing of Multimedia Contents

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    International audienceStatistical multiplexing of video contents aims at transmitting several variable bit rate (VBR) encoded video streams over a band-limited channel. Rate-distortion (RD) models for the encoded streams are often used to control the video encoders. Buffering at the output of encoders is one of the several techniques used to smooth out the fluctuating bit rate of compressed video due to variations in the activity of video contents. In this paper, a statistical multiplexer is proposed where a closed-loop control of both video encoders and buffers is performed jointly. First, a predictive joint video encoder controller accounting for minimum quality, fairness, and smoothness constraints is considered. Second, all buffers are controlled simultaneously to regulate the buffering delays. This delay is adjusted according to a reference delay constraint. The main idea is to update the encoding rate for each video unit according to the average level of the buffers, to maximize the quality of each program and effectively use the available channel rate. Simulation results show that the proposed scheme yields a smooth and fair video quality among programs thanks to the predictive control. A similar buffering delay for all programs and an efficient use of the available channel rate are ensured thanks to the buffer management and to the predictive closed-loop control

    Verilog implementation of the VESA DSC compression algorithm

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    O trabalho consiste em implementar em verilog o Standard de compressão VESA DSC v1.1. O projecto está na fase de teste e optimização para cumprir restrições de timming. É esperado estar concluido nos inicios de Junho. Feito isto será feita uma comparação entre uma abordagem usando ferramentes de síntese de alto nível e a abordagem "manual" (RTL

    Dynamic bandwidth allocation in ATM networks

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    Includes bibliographical references.This thesis investigates bandwidth allocation methodologies to transport new emerging bursty traffic types in ATM networks. However, existing ATM traffic management solutions are not readily able to handle the inevitable problem of congestion as result of the bursty traffic from the new emerging services. This research basically addresses bandwidth allocation issues for bursty traffic by proposing and exploring the concept of dynamic bandwidth allocation and comparing it to the traditional static bandwidth allocation schemes

    Evaluation of unidirectional background push content download services for the delivery of television programs

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    Este trabajo de tesis presenta los servicios de descarga de contenido en modo push como un mecanismo eficiente para el envío de contenido de televisión pre-producido sobre redes de difusión. Hoy en día, los operadores de red dedican una cantidad considerable de recursos de red a la entrega en vivo de contenido televisivo, tanto sobre redes de difusión como sobre conexiones unidireccionales. Esta oferta de servicios responde únicamente a requisitos comerciales: disponer de los contenidos televisivos en cualquier momento y lugar. Sin embargo, desde un punto de vista estrictamente académico, el envío en vivo es únicamente un requerimiento para el contenido en vivo, no para contenidos que ya han sido producidos con anterioridad a su emisión. Más aún, la difusión es solo eficiente cuando el contenido es suficientemente popular. Los servicios bajo estudio en esta tesis utilizan capacidad residual en redes de difusión para enviar contenido pre-producido para que se almacene en los equipos de usuario. La propuesta se justifica únicamente por su eficiencia. Por un lado, genera valor de recursos de red que no se aprovecharían de otra manera. Por otro lado, realiza la entrega de contenidos pre-producidos y populares de la manera más eficiente: sobre servicios de descarga de contenidos en difusión. Los resultados incluyen modelos para la popularidad y la duración de contenidos, valiosos para cualquier trabajo de investigación basados en la entrega de contenidos televisivos. Además, la tesis evalúa la capacidad residual disponible en redes de difusión, por medio de estudios empíricos. Después, estos resultados son utilizados en simulaciones que evalúan las prestaciones de los servicios propuestos en escenarios diferentes y para aplicaciones diferentes. La evaluación demuestra que este tipo de servicios son un recurso muy útil para la entrega de contenido televisivo.This thesis dissertation presents background push Content Download Services as an efficient mechanism to deliver pre-produced television content through existing broadcast networks. Nowadays, network operators dedicate a considerable amount of network resources to live streaming live, through both broadcast and unicast connections. This service offering responds solely to commercial requirements: Content must be available anytime and anywhere. However, from a strictly academic point of view, live streaming is only a requirement for live content and not for pre-produced content. Moreover, broadcasting is only efficient when the content is sufficiently popular. The services under study in this thesis use residual capacity in broadcast networks to push popular, pre-produced content to storage capacity in customer premises equipment. The proposal responds only to efficiency requirements. On one hand, it creates value from network resources otherwise unused. On the other hand, it delivers popular pre-produced content in the most efficient way: through broadcast download services. The results include models for the popularity and the duration of television content, valuable for any research work dealing with file-based delivery of television content. Later, the thesis evaluates the residual capacity available in broadcast networks through empirical studies. These results are used in simulations to evaluate the performance of background push content download services in different scenarios and for different applications. The evaluation proves that this kind of services can become a great asset for the delivery of television contentFraile Gil, F. (2013). Evaluation of unidirectional background push content download services for the delivery of television programs [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31656TESI

    Video compression with complete information for pre-recorded sources

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    Thesis (Ph.D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2000.Includes bibliographical references (p. 123-130).by David Michael Baylon.Ph.D

    New interaction models for 360º video

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    Esta dissertação tem como principal objectivo a incorporação de um mecanismo de buffering num sistema de multimídia, capaz de oferecer experiências multivista adaptáveis. A incorporação deste mecanismo vem provocar melhorias na qualidade de serviço e na qualidade de experiência. O sistema recorre ao protocolo MPEG-DASH e a uma câmara convencional para detecção dos movimentos da cabeça do utilizador. O sistema incorpora ainda um mecanismo de adaptação automática da qualidade, ajustável às condições da rede. O mecanismo desenvolvido é composto por um proxy e tem o objectivo de minimizar o atraso existente na transição de vistas. O proxy será capaz de enviar três vistas em simultâneo, duas em baixa qualidade, enquanto a vista principal será enviada e apresenta ao utilizador em alta qualidade.Sempre que existe um novo pedido por parte do utilizador, o mecanismo irá comutar entre as vistas enviadas até receber a resposta por parte do servidor. Deste modo, esta dissertação pretende identificar as dificuldades que se colocam relativamente à disponibilização e transmissão eficiente deste tipo de conteúdos, assim como os compromissos necessários ao nível da qualidade de experiência do utilizador.Today, the fast technological evolution and the significant increase in the demand for multimedia content has boosted the development of the transmission mechanisms used for this purpose.This development had repercussions in several areas, such as the immersive experiences that include the 360º contents. Whether through live streaming or using on demand services, the quality of service and experience have become two points whose development has assumed high importance. The capture and reproduction of 360º content allows transmitting an immersive view of reality at a given moment. With this approach, the industry intends to provide a product with better audiovisual quality, more comfortable for the user and that allows a better interaction with the same. An example of this is the choice of the view that most appeals to us in a given event (for example, football matches or concerts). This dissertation has as main objective the incorporation of a buffering mechanism in a multimedia system, able to offer adaptive multivista experiments. The system uses the MPEG-DASH protocol for efficient use of network resources and a conventional camera for detecting the movements of the user's head, selecting the points of view that one wishes to visualize in real time. The system also incorporates an automatic quality adjustment mechanism, adjustable to the network conditions. The buffering mechanism is intended to increase the quality of experience and the quality of service, minimizing the delay in the transition of views. The mechanism will consist of a proxy capable of sending three views simultaneously. Of these views, two will be sent in low quality, while the main view will be sent and presented to the user in high quality. Whenever there is a new request from the user, the mechanism will switch between sent views until it receives the response from the server. Based on these assumptions, the dissertation intends to identify the challenges that are posed regarding the availability and efficient transmission of 360º content, as well as the necessary commitments regarding the quality of user experience. This last point is particularly significant, taking into account the network requirements and the volume of data presented by the transmissions of this type of content

    Implementation issues in source coding

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    An edge preserving image coding scheme which can be operated in both a lossy and a lossless manner was developed. The technique is an extension of the lossless encoding algorithm developed for the Mars observer spectral data. It can also be viewed as a modification of the DPCM algorithm. A packet video simulator was also developed from an existing modified packet network simulator. The coding scheme for this system is a modification of the mixture block coding (MBC) scheme described in the last report. Coding algorithms for packet video were also investigated

    QoS provisioning in multimedia streaming

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    Multimedia consists of voice, video, and data. Sample applications include video conferencing, video on demand, distance learning, distributed games, and movies on demand. Providing Quality of Service (QoS) for multimedia streaming has been a difficult and challenging problem. When multimedia traffic is transported over a network, video traffic, though usually compressed/encoded for bandwidth reduction, still consumes most of the bandwidth. In addition, compressed video streams typically exhibit highly variable bit rates as well as long range dependence properties, thus exacerbating the challenge in meeting the stringent QoS requirements of multimedia streaming with high network utilization. Dynamic bandwidth allocation in which video traffic prediction can play an important role is thus needed. Prediction of the variation of the I frame size using Least Mean Square (LMS) is first proposed. Owing to a smoother sequence, better prediction has been achieved as compared to the composite MPEG video traffic prediction scheme. One problem with this LMS algorithm is its slow convergence. In Variable Bit Rate (VBR) videos characterized by frequent scene changes, the LMS algorithm may result in an extended period of intractability, and thus may experience excessive cell loss during scene changes. A fast convergent non-linear predictor called Variable Step-size Algorithm (VSA) is subsequently proposed to overcome this drawback. The VSA algorithm not only incurs small prediction errors but more importantly achieves fast convergence. It tracks scene changes better than LMS. Bandwidth is then assigned based on the predicted I frame size which is usually the largest in a Group of Picture (GOP). Hence, the Cell Loss Ratio (CLR) can be kept small. By reserving bandwidth at least equal to the predicted one, only prediction errors need to be buffered. Since the prediction error was demonstrated to resemble white noise or exhibits at most short term memory, smaller buffers, less delay, and higher bandwidth utilization can be achieved. In order to further improve network bandwidth utilization, a QoS guaranteed on-line bandwidth allocation is proposed. This method allocates the bandwidth based on the predicted GOP and required QoS. Simulations and analytical results demonstrate that this scheme provides guaranteed delay and achieves higher bandwidth utilization. Network traffic is generally accepted to be self similar. Aggregating self similar traffic can actually intensify rather than diminish burstiness. Thus, traffic prediction plays an important role in network management. Least Mean Kurtosis (LMK), which uses the negated kurtosis of the error signal as the cost function, is proposed to predict the self similar traffic. Simulation results show that the prediction performance is improved greatly as compared to the LMS algorithm. Thus, it can be used to effectively predict the real time network traffic. The Differentiated Service (DiffServ) model is a less complex and more scalable solution for providing QoS to IP as compared to the Integrated Service (IntServ) model. We propose to transport MPEG frames through various service classes of DiffServ according to the MPEG video characteristics. Performance analysis and simulation results show that our proposed approach can not only guarantee QoS but can also achieve high bandwidth utilization. As the end video quality is determined not only by the network QoS but also by the encoded video quality, we consider video quality from these two aspects and further propose to transport spatial scalable encoded videos over DiffServ. Performance analysis and simulation results show that this can provision QoS guarantees. The dropping policy we propose at the egress router can reduce the traffic load as well as the risk of congestion in other domains
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