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IEEE Symposium on FPGAs for Custom Computing Machines

作者： S. Govindarajan I. Ouaiss M. Kaul V. Srinivasan R. Vemuri University of Cincinnati Cincinnati OH USA

The SPARCS system is an integrated partitioning and synthesis environment for reconfigurable architectures. In this paper, we use the Joint Photographic Experts Group (JPEG) image compression algorithm as a design example to demonstrate the effectiveness of dynamic reconfiguration achieved using SPARCS. We present a typical design process using the SPARCS system consisting of temporal partitioning, spatial partitioning, and design synthesis. The results, obtained on a commercial RC architecture, show that the multiply-reconfigured version of the JPEG compression algorithm achieves reasonable improvement in execution times compared to the one-time configured version.

关键词： Reconfigurable architectures Algorithm design and analysis Partitioning algorithms Computer architecture Transform coding Discrete cosine transforms Field programmable gate arrays Image coding Process design compression algorithms

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An evaluation of quality metrics for compressed images based on human visual sensitivity

An evaluation of quality metrics for compressed images based...

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International Conference on Signal Processing Proceedings (ICSP)

作者： T. Eude A. Mayache Le2i Université de Bourgogne Dijon France

It is generally believed that the performance of current image coding techniques is not close enough to the fundamental limit on the bit rate at which high reception quality is maintained. For supporting the future applications that demand high image quality at very low bit rates, more efficient coding algorithms are expected. Among numerous approaches to reach this optimality, perceptual coding that matches the compression algorithm to the human perception mechanism has been considered as the most promising solution, and has recently become an important area of research. In addition to the investigation on perceptual coding, the need for a distortion metric for predicting the distortion has long been recognized in the image processing community. For still image evaluation, several distortion measures tied to some psycho-visual properties have been proposed. Examples of such measures are to be found in the literature. One significant problem associated with these metrics is that there is little information on how these measures perform in comparison to one another. The purpose of this paper is to provide a rigorous evaluation of four metrics which are designed for the evaluation of coded achromatic still images.

关键词： Image coding Distortion measurement Bit rate Image quality compression algorithms Humans Image recognition Image processing Psychology Performance evaluation

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compression of low entropy strings with Lempel-Ziv algorithms

Compression of low entropy strings with Lempel-Ziv algorithm...

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compression and Complexity of Sequences Proceedings

作者： S.R. Kosaraju G. Manzini Department of Computer Science Johns Hopkins University Baltimore MD USA Istituto di Matematica Computazionale CNR Italy

We compare the compression ratio of the Lempel-Ziv algorithms with the empirical entropy of the input string, We show that although these algorithms are optimal according to the generally accepted definition, we can find families of low entropy strings which are not compressed optimally. More precisely, we show that the compression ratio achieved by LZ78 (resp. LZ77) can be much higher than the zeroth order entropy H/sub 0/ (resp. the first order entropy H/sub 1/). We present a compression algorithm which combines LZ78 with run length encoding, and we show that for any string s the new algorithm achieves a compression ratio bounded by 3H/sub 0/(s). Finally, we prove that for any string s the compression ratio achieved by LZ77 is bounded by 8H/sub 0/(s).

关键词： Entropy Performance analysis Algorithm design and analysis Probability distribution compression algorithms Encoding Data compression Decoding Random sequences Computer science

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Dynamic coding of visual information

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IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY 1997年第3期7卷 489-500页

作者： Reusens, E Ebrahimi, T Kunt, M SWISS FED INST TECHNOL SIGNAL PROC LAB CH-1015 LAUSANNE SWITZERLAND

This paper introduces a novel approach to visual data compression. The approach, named dynamic coding, consists of an effective competition between several representation models used for describing data portions, The image data is represented as the union of several regions each approximated by a representation model locally appropriate, The dynamic coding concept leads to attractive features such as genericness, flexibility, and openness and is therefore particularly suited to a multimedia environment in which many types of applications are involved. Dynamic coding is a general proposal to visual data compression and many variations on the same theme may be designed. They differ by the particular procedure by which the data is segmented into objects and the local representation model selected, As an illustrative example, a video compression scheme based on the principles of dynamic coding is presented, This compression algorithm performs a joint optimization of the segmentation (restricted to a so-called generalized quadtree partition) together with the representation models associated with each data segment. Four representation models are competing namely, fractal, motion compensation, text and graphics, and background modes, Optimality is defined with respect to a rate-distortion tradeoff and the optimization procedure leads to a multicriterion segmentation.

关键词： data compression fractals image representation image segmentation image sequences motion compensation multimedia communication optimisation quadtrees rate distortion theory video coding background modes compression algorithm data segmentation dynamic cod Video coding Rate distortion theory quaternary tree compression algorithms image representation dynamic encoding image sequences Data compression image segmentation Fractals Data partitioning Motion compensation background mode visual information

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Real-time audio and video transmission of IEEE GLOBECOM '96 over the Internet

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IEEE COMMUNICATIONS MAGAZINE 1997年第4期35卷 30-33页

作者： Perkins, C Crowcroft, J University College London UK

This article is about the experiences of the authors in transmitting the proceedings of some events at IEEE GLOBECOM '96 in London, England, in the week of November 17-22, 1996. Live video and audio of all the events in the Churchill Auditorium of the Queen Elizabeth II Conference Center were captured and transmitted, in real time, as well as stored and transmitted later, for remote participants in three continents, over the Internet. Two independent systems were used simultaneously, one supplied by researchers from NTT Laboratories in Japan and the other by researchers from University College London. The former system is based on a server model of distribution, while the latter is based on the use of network-level packet multicast. Both systems employ compression algorithms, so the network capacity requirement in each case was on the order of 100 kb/s to 200 kb/s total, thus enabling remote participants without very high-end network connectivity to take part. Receivers only need software for a PC running most popular versions of Windows or a UNIX workstation to be able to receive either type of transmission, or to retrieve the recorded sessions from NTT Laboratories' servers. The multimedia transmission was carried over care fully engineered links that traversed many different subnet technologies, including point-to-point circuits, SMDS networks, ATM networks, and fast Ethernet switches. This was both to give a high level of assurance that the traffic would not experience too much interference from other traffic at the site and elsewhere, and to ensure very low packet store and forward delays. The system ran for four days continuously, and was generally very successful. In the future, it should be possible to have remote paying attendees.

关键词： Videoconference Laboratories Network servers Telecommunication traffic Continents Internet Educational institutions Web server compression algorithms Workstations

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Stationary stochastic processes and fractal data compression

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INTERNATIONAL JOURNAL OF BIFURCATION AND CHAOS 1997年第3期7卷 551-567页

作者： Barnsley, MF Deliu, A Xie, RF Iterated Systems 3535 Piedmont Rd. Seven Piedmont Center Atlanta GA 30305-1530 USA

It is shown that the invariant measure of a stationary nonatomic stochastic process yields an iterated function system with probabilities and an associated dynamical system that provide the basis for optimal lossless data compression algorithms. The theory is illustrated for the case of finite-order Markov processes: For a zero-order process, it produces the arithmetic compression method;while for higher order processes it yields dynamical systems, constructed from piecewise affine mappings from the interval [0, 1] into itself, that may be used to store information efficiently. The theory leads to a new geometrical approach to the development of compression algorithms.

关键词： Iterated Function System Stochastic Processes Markov chain Storing information Yield theories higher-order DYNAMICAL SYSTEMS Order fulfillment compression algorithms

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Consumer devices for networked audio

Consumer devices for networked audio

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IEEE International Symposium on Industrial Electronics

作者： Onufryk, PZ Snyder, JH AT&T Bell Labs Res Florham Park NJ 07932 USA

ISBN: (纸本)0780339363

Advances in networking technologies and audio compression algorithms are enabling a revolution in the way music is sold and distributed. Today, one acquires recorded music by purchasing a physical music carrier: a record, tape or CD. In the future, we will acquire music by transferring bits from a server in the network. This will create a demand for a variety of new networked audio devices, but will also introduce new challenges in copyright protection. In this paper we review some of the technologies which will be changing the audio business and describe some of the prototype audio devices being developed at AT&T Labs - Research.

关键词： Audio Music Internet servers compression algorithms Revolution Servers Networking Techniques Audio compression

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MOVIE: a building block for the design of real time simulator of moving pictures compression algorithms

MOVIE: a building block for the design of real time simulato...

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International Conference on Application Specific Array Processors

作者： R. Barzic C. Bouville F. Charot G. Le Fol P. Lemonnier C. Wagner CCETT Cesson-Sevigne France IRISA Rennes France

This paper shows how a real-time simulator of moving pictures compression algorithms can be rapidly assembled using a basic building block, here called MOVIE (MOdule for Video Experimentation). The internal architecture of the MOVIE VLSI chip can be compared to a small systolic machine made of a 32-bit I/O processor, a reduced linear array of 16-bit computation processors and data video input/output mechanisms. Externally, the chip is provided with four 16-bit bidirectional data ports and three 16-bit bidirectional data video port. Several MOVIE chips can be easily clustered to allow the size of the linear array of computation processors to be increased. The MOVIE chip is fully programmable in a high level language in order to make program developments easier.

关键词： Motion pictures Video compression Signal processing algorithms Computer architecture Very large scale integration Transform coding Digital signal processing chips compression algorithms Concurrent computing Hardware

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Universal compression algorithms based on approximate string matching

Universal compression algorithms based on approximate string...

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IEEE International Symposium on Information Theory

作者： I. Sadeh Mathematics Department Ben-Gurion University of the Negev Beersheba Israel

Two practical universal source coding schemes based on approximate string matching are proposed. One is an approximate fixed-length string matching data compression, and the other is an LZ-type quasi parsing method by approximate string matching. It is shown that in the former algorithm the compression rate converges to the theoretical bound of R(D) for ergodic and stationary processes as the average string length tends to infinity. A similar result holds for the latter algorithm in the limit of the infinite database produced by the former algorithm. The main advantages of the proposed methods are the asymptotic behavior of the encoder implementation and the simplicity of the decoder. Practical results of image and voice compression will be presented.

关键词： compression algorithms Decoding Random variables H infinity control Switches Source coding Image databases Image coding Distortion measurement Data compression

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Blocking artifacts reduction for image compression algorithms

Blocking artifacts reduction for image compression algorithm...

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Midwest Symposium on Circuits and Systems (MWSCAS)

作者： M. El-Sharkawy N. Sharma H. Gundrum Electrical Engineering Department Purdue University Indianapolis IN USA

In this paper, a new algorithm is proposed to improve the performance of the existing JPEG image compression algorithm. The algorithm proposes a recursive pruned discrete cosine transform (DCT) to reduce the bit rate and two different methods to reduce the image artifacts arising at these lower bit rates. The recursive algorithm computes the pruned DCT using a structure that allows the generation of higher order pruned DCT from two identical, lower order pruned DCT's. A variance dependent pruning method determines the pruning based on the statistical properties of the image block. A linear filtering method performs low pass filtering on the block boundaries for smoothing the discontinuities.

关键词： Image coding Discrete cosine transforms Image quality Bit rate Degradation Frequency compression algorithms Maximum likelihood detection Low pass filters Nonlinear filters

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