Lower Bounds on the Redundancy of Huffman Codes with Known and Unknown Probabilities

In this paper we provide a method to obtain tight lower bounds on the minimum redundancy achievable by a Huffman code when the probability distribution underlying an alphabet is only partially known. In particular, we address the case where the occurrence probabilities are unknown for some of the symbols in an alphabet. Bounds can be obtained for alphabets of a given size, for alphabets of up to a given size, and for alphabets of arbitrary size. The method operates on a Computer Algebra System, yielding closed-form numbers for all results. Finally, we show the potential of the proposed method to shed some light on the structure of the minimum redundancy achievable by the Huffman code

Standard and specific compression techniques for DNA microarray images

We review the state of the art in DNA microarray image compression and provide original comparisons between standard and microarray-specific compression techniques that validate and expand previous work. First, we describe the most relevant approaches published in the literature and classify them according to the stage of the typical image compression process where each approach makes its contribution, and then we summarize the compression results reported for these microarray-specific image compression schemes. In a set of experiments conducted for this paper, we obtain new results for several popular image coding techniques that include the most recent coding standards. Prediction-based schemes CALIC and JPEG-LS are the best-performing standard compressors, but are improved upon by the best microarray-specific technique, Battiato's CNN-based scheme

Eina de control d'accés a la xarxa

L'eina de control d'accés a la xarxa que es proposa en aquest article, sorgeix de la mancança d'una plataforma de gestió pels tallafocs d'una organització. L'eina en qüestió pretén facilitar la gestió treballant d'una manera organitzada, com és agrupant les regles per grups i podent assignar aquests grups als servidors. D'aquesta manera, es té una plataforma on poder veure quines regles estan donades per cada màquina de l'organització. Aquesta eina utilitza una plataforma d'automatització per comunicar-se amb els servidors i poder així, introduir les regles adients a cada màquina. Fent-la així, una eina innovadora al món de la gestió remota dels tallafocsThe network access control tool proposed in this article, appears from the lack of a management platform for an organization's firewall. The tool in matter aims to facilitate management working in a organized way, like for instance putting together rules for groups and assign these groups to the servers. This way, there is a platform where you can see which rules are given for each organization machine. This tool uses an automation platform to communicate with the servers and to be able to enter the suitable rules to each machine, thus making it an innovative tool in remote management of firewall.La herramienta de control de acceso a la red que se propone en este artículo, surge de la carencia de una plataforma de gestión para los cortafuegos de una organización. La herramienta en cuestión pretende facilitar la gestión trabajando de una manera organizada, como es agrupando las reglas por grupos y pudiendo asignar estos grupos a los servidores. De esta manera, se tiene una plataforma donde se puede ver qué reglas están dadas para cada máquina de la organización. Esta herramienta utiliza una plataforma de automatización para comunicarse con los servidores y poder así, introducir las reglas adecuadas a cada máquina. Haciéndola así, una herramienta innovadora en el mundo de la gestión remota de los cortafuegos

Strategy of microscopic parallelism for Bitplane Image Coding

Recent years have seen the upraising of a new type of processors strongly relying on the Single Instruction, Multiple Data (SIMD) architectural principle. The main idea behind SIMD computing is to apply a flow of instructions to multiple pieces of data in parallel and synchronously. This permits the execution of thousands of operations in parallel, achieving higher computational performance than with traditional Multiple Instruction, Multiple Data (MIMD) architectures. The level of parallelism required in SIMD computing can only be achieved in image coding systems via microscopic parallel strategies that code multiple coefficients in parallel. Until now, the only way to achieve microscopic parallelism in bitplane coding engines was by executing multiple coding passes in parallel. Such a strategy does not suit well SIMD computing because each thread executes different instructions. This paper introduces the first bitplane coding engine devised for the fine grain of parallelism required in SIMD computing. Its main insight is to allow parallel coefficient processing in a coding pass. Experimental tests show coding performance results similar to those of JPEG2000

Sistema de archivos remoto cifrado y de un solo archivo

El incremento en el uso de los servicios de almacenaje de datos en la nube, en los que el propietario de los datos guarda su información en los servidores de un tercero, resulta en un aumento del riesgo de que sus datos se vean comprometidos o manipulados. Almacenar datos en un medio no seguro es un problema que ya ha sido tratado con anterioridad en incontables ocasiones, e incluso si las partes principales necesarias para realizar este proyecto están al alcance de todos, no parece haber una solución disponible. El objetivo de este proyecto es el de diseñar y desarrollar una solución para mitigar este problema.The increasing use of cloud storage services, in which the data owners upload their files a third party's server, results in an increasing risk of this data getting compromised or manipulated. Storing data in a non secure medium is a problem that has been treated time and again, and although the primary necessary parts needed to implement a solution for this problem are available to everyone, we could not find a good solution for it. This project's goal is to design and develop a solution to mitigate this problem.L'increment en l'ús dels serveis d'emmagatzematge de dades al núvol, en els quals el propietari de les dades guarda la seva informació als servidors d'una tercera part, resulta en un increment del risc que les seves dades es vegin compromeses o manipulades. Emmagatzemar dades en un medi no segur és un problema que ja s'ha tratat amb anterioritat en incomptables ocasions, i tot i que les parts principals i necessàries per a realitzar aquest projecte són a l'abast de tothom, no hi ha cap solució disponible. L'objetiu d'aquest projecte és el de dissenyar i desenvolupar una solució per a mitigar aquest problema

High-Performance Lossless Compression of Hyperspectral Remote Sensing Scenes Based on Spectral Decorrelation

The capacity of the downlink channel is a major bottleneck for applications based on remotesensing hyperspectral imagery (HSI). Data compression is an essential tool to maximize the amountof HSI scenes that can be retrieved on the ground. At the same time, energy and hardware constraintsof spaceborne devices impose limitations on the complexity of practical compression algorithms.To avoid any distortion in the analysis of the HSI data, only lossless compression is considered in thisstudy. This work aims at finding the most advantageous compression-complexity trade-off withinthe state of the art in HSI compression. To do so, a novel comparison of the most competitive spectraldecorrelation approaches combined with the best performing low-complexity compressors of thestate is presented. Compression performance and execution time results are obtained for a set of47 HSI scenes produced by 14 different sensors in real remote sensing missions. Assuming onlya limited amount of energy is available, obtained data suggest that the FAPEC algorithm yields thebest trade-off. When compared to the CCSDS 123.0-B-2 standard, FAPEC is 5.0 times faster andits compressed data rates are on average within 16% of the CCSDS standard. In scenarios whereenergy constraints can be relaxed, CCSDS 123.0-B-2 yields the best average compression results of allevaluated methods

On the hardware implementation of the arithmetic elements of the pairwise orthogonal transform

The pairwise orthogonal transform (POT) is an attractive alternative to the Kahrunen-Loève transform for spectral decorrelation in on-board multispectral and hyperspectral image compression due to its reduced complexity. This work validates that the low complexity of the POT makes it feasible for a space-qualified field-programmable gate array (FPGA) implementation. A register transfer level description of the arithmetic elements of the POT is provided with the aim of achieving a low occupancy of resources and making it possible to synthesize the design on a space-qualified RTAX2000S and RTAX2000S-DSP. In order to accomplish these goals, the operations of the POT are fine-tuned such that their implementation footprint is minimized while providing equivalent coding performance. The most computationally demanding operations are solved by means of a lookup table. An additional contribution of this paper is a bit-exact description of the mathematical equations that are part of the transform, defined in such a way that they can be solved with integer arithmetic and implementations that can be easily cross-validated. Experimental results are presented, showing that it is feasible to implement the components of the POT on the mentioned FPGA

A fully embedded two-stage coder for hyperspectral near-lossless compression

This letter proposes a near-lossless coder for hyperspectral images. The coding technique is fully embedded and minimizes the distortion in the l2 norm initially and in the l∞ norm subsequently. Based on a two-stage near-lossless compression scheme, it includes a lossy and a near-lossless layer. The novelties are: the observation of the convergence of the entropy of the residuals in the original domain and in the spectral-spatial transformed domain; and an embedded near-lossless layer. These contributions enable a progressive transmission while optimising both SNR and PAE performance. The embeddedness is accomplished by bitplane encoding plus arithmetic encoding. Experimental results suggest that the proposed method yields a highly competitive coding performance for hyperspectral images, outperforming multi-component JPEG2000 for l∞ norm and pairing its performance for l2 norm, and also outperforming M-CALIC in the near-lossless case -for PAE ≥5-

Lossless compression of color filter array mosaic images with visualization via JPEG 2000

Digital cameras have become ubiquitous for amateur and professional applications. The raw images captured by digital sensors typically take the form of color filter array (CFA) mosaic images, which must be "developed" (via digital signal processing) before they can be viewed. Photographers and scientists often repeat the "development process" using different parameters to obtain images suitable for different purposes. Since the development process is generally not invertible, it is commonly desirable to store the raw (or undeveloped) mosaic images indefinitely. Uncompressed mosaic image file sizes can be more than 30 times larger than those of developed images stored in JPEG format. Thus, data compression is of interest. Several compression methods for mosaic images have been proposed in the literature. However, they all require a custom decompressor followed by development-specific software to generate a displayable image. In this paper, a novel compression pipeline that removes these requirements is proposed. Specifically, mosaic images can be losslessly recovered from the resulting compressed files, and, more significantly, images can be directly viewed (decompressed and developed) using only a JPEG 2000 compliant image viewer. Experiments reveal that the proposed pipeline attains excellent visual quality, while providing compression performance competitive to that of state-of-the-art compression algorithms for mosaic images