3 research outputs found
Recommended from our members
THINC: A Remote Display Architecture for Thin-Client Computing
Rapid improvements in network bandwidth, cost, and ubiquity combined with the security hazards and high total cost of ownership of personal computers have created a growing market for thin-client computing. We introduce THINC, a remote display system architecture for high-performance thin-client computing in both LAN and WAN environments. THINC transparently maps high-level application display calls to a few simple low-level commands which can be implemented easily and efficiently. THINC introduces a number of novel latency-sensitive optimization techniques, including offscreen drawing awareness, command buffering and scheduling, non-blocking display operation, native video support, and server-side screen scaling. We have implemented THINC in an XFree86/Linux environment and compared its performance with other popular approaches, including Citrix MetaFrame, Microsoft Terminal Services, SunRay, VNC, and X. Our experimental results on web and video applications demonstrate that THINC can be as much as five times faster than traditional thin-client systems in high latency network environments and is capable of playing full-screen video at full frame rate
Lossless compression of images with specific characteristics
Doutoramento em Engenharia ElectrotécnicaA compressão de certos tipos de imagens é um desafio para algumas normas de compressão de imagem. Esta tese investiga a compressão sem perdas de imagens com características especiais, em particular imagens simples, imagens de cor indexada e imagens de microarrays. Estamos interessados no desenvolvimento de métodos de compressão completos e no estudo de técnicas de pré-processamento que possam ser utilizadas em conjunto com as normas de compressão de imagem. A esparsidade do histograma, uma propriedade das imagens simples, é um dos assuntos abordados nesta tese. Desenvolvemos uma técnica de pré-processamento, denominada compactação de histogramas, que explora esta propriedade e que pode ser usada em conjunto com as normas de compressão de imagem para um melhoramento significativo da eficiência de compressão. A compactação de histogramas e os algoritmos de reordenação podem ser usados como préprocessamento para melhorar a compressão sem perdas de imagens de cor indexada. Esta tese apresenta vários algoritmos e um estudo abrangente dos métodos já existentes. Métodos específicos, como é o caso da decomposição em árvores binárias, são também estudados e propostos. O uso de microarrays em biologia encontra-se em franca expansão. Devido ao elevado volume de dados gerados por experiência, são necessárias técnicas de compressão sem perdas. Nesta tese, exploramos a utilização de normas de compressão sem perdas e apresentamos novos algoritmos para codificar eficientemente este tipo de imagens, baseados em modelos de contexto finito e codificação aritmética.The compression of some types of images is a challenge for some standard compression techniques. This thesis investigates the lossless compression of images with specific characteristics, namely simple images, color-indexed images and microarray images. We are interested in the development of complete compression methods and in the study of preprocessing algorithms that could be used together with standard compression methods. The histogram sparseness, a property of simple images, is addressed in this thesis. We developed a preprocessing technique, denoted histogram packing, that explores this property and can be used with standard compression methods for improving significantly their efficiency. Histogram packing and palette reordering algorithms can be used as a preprocessing step for improving the lossless compression of color-indexed images. This thesis presents several algorithms and a comprehensive study of the already existing methods. Specific compression methods, such as binary tree decomposition, are also addressed. The use of microarray expression data in state-of-the-art biology has been well established and due to the significant volume of data generated per experiment, efficient lossless compression methods are needed. In this thesis, we explore the use of standard image coding techniques and we present new algorithms to efficiently compress this type of images, based on finite-context modeling and arithmetic coding
Recommended from our members
THINC: A Virtual and Remote Display Architecture for Desktop Computing and Mobile Devices
THINC is a new virtual and remote display architecture for desktop computing. It has been designed to address the limitations and performance shortcomings of existing remote display technology, and to provide a building block around which novel desktop architectures can be built. THINC is architected around the notion of a virtual display device driver, a software-only component that behaves like a traditional device driver, but instead of managing specific hardware, enables desktop input and output to be intercepted, manipulated, and redirected at will. On top of this architecture, THINC introduces a simple, low-level, device-independent representation of display changes, and a number of novel optimizations and techniques to perform efficient interception and redirection of display output. This dissertation presents the design and implementation of THINC. It also introduces a number of novel systems which build upon THINC's architecture to provide new and improved desktop computing services. The contributions of this dissertation are as follows: - A high performance remote display system for LAN and WAN environments. This system differs from existing remote display technologies in that it focuses on the architecture of the system as a mechanism to improve performance, and not just on the remote display protocol and compression techniques. - A novel mechanism to natively support multimedia content in a remote display system in a way that is both transparent to applications and format independent. - pTHINC, a system to deliver improved remote display support for mobile devices, both in terms of performance and usability, and provide a competitive, and in some cases superior, alternative to native mobile applications. - MobiDesk, a desktop utility computing infrastructure that enables service providers to host desktop sessions in fully virtualized environments. Hosted sessions can be remotely accessed using THINC, they can be migrated across computers to provide high-availability, and can be effectively and efficiently protected from denial of service attacks. - Moving beyond remote display, we show how THINC's architecture can be used to provide continuous, low overhead recording of a desktop. Alongside, we introduce a novel way to leverage desktop accessibility services to allow users to search their recording based on captured text content. We have implemented prototypes for these systems, and evaluated their performance in a number of scenarios, and compared it to representative alternatives whenever possible. Our results demonstrate that THINC can provide superior remote display performance, and can be successfully used as a fundamental building block for new and improved desktop applications and services