Papers by Max Henrique Machado Costa
Revisiting Lattice Tiling Decomposition and Dithered Quantisation
Lecture Notes in Computer Science, 2023
Hierarchical transforms are widely used in image and video coding to produce multilevel decomposi... more Hierarchical transforms are widely used in image and video coding to produce multilevel decomposition of signals. After applying these transforms, same level signals are typically uncorrelated. However, there is often still significant cross level information. Traditionally, this cross-level information is exploited at the entropy coding step, but not at the transform step. The main contribution of this work is an energy compaction technique/transform that can also exploit these cross-resolution-level structural similarities. The core idea of the technique is to include in the hierarchical transform a number of adaptive basis functions derived from the lower resolution of the signal. A full image codec was developed in order to measure the performance of the new transform. Results are presented in terms of transform coding gain, energy concentration and distortion versus rate curves compared with standard JPEG, JPEG 2000 and JPEG XR.
A new entropy power inequality
IEEE Transactions on Information Theory, Nov 1, 1985
ABSTRACT
Equivocation limits in Gaussian additive channels
NASA STI/Recon Technical Report N, Jul 1, 1983
Avaliação de sistemas de redução de taxa de bits de video com enfoque na percepção do usuario
IEEE Transactions on Information Theory, Mar 1, 1982
It turns out that the Ising model (on the infinite lattice) is It should again be noted that the ... more It turns out that the Ising model (on the infinite lattice) is It should again be noted that the entropy representation of the well-defined for some range of its local characteristics and that it previous section is equal to H(h) as shown above. In [4] H(h) is can equivalently be described as having the limiting distribution evaluated for various values of b, and an encoding scheme is as M, N + cc of the following field defined on an orthogonal proposed whose compression performance for encoding sample M X N subset of the infinite lattice. (For more detailed (and also fields of the Ising model is near optimum, i.e., is very close to the introductory) descriptions of the Ising model, see [5].) one indicated by the entropy rate. The sample space D has 2MN possible configurations w each with an assigned probability P(w). The distribution assumed is ACKNOWLEDGMENT Gibbsian, i.e., The authors wish to thank the referees for their helpful com-P(w) = CU(")/Z, (14 ments and suggestions.
Algoritmo de casamento de padrões aplicado na estimação de movimento em compressão de video
Com a aplicacao das tecnicas de estimacao e compensacao de movimento em sequencias de video, cons... more Com a aplicacao das tecnicas de estimacao e compensacao de movimento em sequencias de video, consegue-se reduzir o numero de bits gerados na codificacao e aumentar a qualidade da sequencia processada. Em contrapartida, o alto custo computacional do processo exige desempenho do codificador. O objetivo desta tese e propor um novo algoritmo de estimacao que concilia qualidade de processamento e rapidez computacional.Realiza-se uma analise do problema de codificacao e dos varios algoritmos de estimacao utilizados, enfatizando-se a questao da qualidade e da velocidade de processamento. Apresenta-se um algoritmo de estimacao inedito denominado MSEA (uma modificacao do algoritmo SEA). O algoritmo SEA (Successive Elimination Algorithm) obtem o vetor de movimento otimo fazendo uma pre-selecao de macroblocos na regiao de pesquisa. Modifica-se o algoritmo SEA introduzindo-se novos criterios de descarte executados em ordem crescente de complexidade e criando uma ordem de leitura dos macroblocos dentro da regiao de pesquisa. Tem-se um ganho expressivo na velocidade de processamento, conservando-se a solucao otima obtida pela busca exaustiva ou pelo algoritmo SEA. O algoritmo e implementado como parte de um codificador MPEG-2 e mostra-se que o MSEA atinge curvas de taxa x distorcao adequadas, a um custo computacional inferior aos de seus concorrentes. Mostra-se, tambem, a possibilidade de se mesclar o MSEA com outros algoritmos de estimacao, resultando na otimizacao das curvas de taxa x distorcao x tempo de processamento frente aos metodos de estimacao costumeiramente utilizados na pratica (busca logaritmica e busca hierarquica) Abstract
Computers & Electrical Engineering, Jul 1, 2010
This work presents a new 3D-transform coefficients scan order based on the multiplication of the ... more This work presents a new 3D-transform coefficients scan order based on the multiplication of the three dimensions sequency numbers of each coefficient. This scan process is developed to a fast embedded color video codec (also described in this article) to be executed in a set-top box on a fiber optics network. Due to its purpose, the codec is focused on reduced execution time, not on high compression rates. Low computational complexity and use of meager computational resources are also required. The Hadamard transform is used in a three-dimensional fashion, in order to avoid costly motion estimation and compensation techniques. The proposed scan procedure allows the coefficients reading in an idealistic "decreasing in the average" order. After the scan procedure, the encoding of the bits of the 3D-Hadamard coefficients is done, bit-plane-by-bit-plane, with an efficient adaptive version of Golomb's run-length encoder, which produces a fully embedded output bitstream. Even with the use of these constrained techniques, good distortion versus rate results were achieved.
We explore several local and global strategies for adaptive scan ordering of transform coefficien... more We explore several local and global strategies for adaptive scan ordering of transform coefficients in JPEG XR/HD Photo. This codec applies a global adaptive scan-order heuristic with respect to an effective localized predictor. The global ordering heuristic, although simple, performs as well as localized techniques that are computationally significantly more complex. We conclude that effective localized prediction not only minimizes but also essentially randomizes coefficient residuals, so that a global statistic is sufficient to deliver near-optimal compression performance.
A tree construction method of nested cyclic codes
This paper presents a tree-based algebraic construction of nested cyclic codes through a tree con... more This paper presents a tree-based algebraic construction of nested cyclic codes through a tree construction method. These codes can be used to encode different data packets, producing codewords that are added for transmission. Both encoding and decoding are performed by polynomial operations with no need of side information, so the proposed scheme may be useful in applications that require low computational complexity. In cases where the number of information sources is large, it is convenient to design the system in a systematic manner. Hence, the tree construction method may contribute to simplify the code design.
Hierarchical taylor-made scheduling for data traffic with prioritization over LTE networks
Long Term Evolution (LTE) is the standard developed by the 3rd Generation Partnership Project (3G... more Long Term Evolution (LTE) is the standard developed by the 3rd Generation Partnership Project (3GPP) to address the ITU's 4G requirements. For the first time, we have technology convergence in a generation of cellular communication systems. LTE promises data transmission of about 100 Mbps and its advanced version (LTE-A) goes even further with more than 1 Gbps in the downlink channel. Such very high data rates will only be achievable with appropriate network resource optimizations. Accordingly, this paper presents a flexible and adaptive scheme of multi-user scheduling considering data traffic prioritization in the LTE downlink channel. The proposed scheduling algorithm uses Proportional Fairness and Analytic Hierarchy Process (AHP) that allows to aggregate performance criteria and to improve resource allocation for users based on the general traffic.
In this paper we establish that a maximizer of a non-convex problem in positive semidefinite matr... more In this paper we establish that a maximizer of a non-convex problem in positive semidefinite matrices has a certain property using information-theoretic methods. Further, we propose a Gaussian extremality conjecture, which if true, would imply that Gaussian signaling achieves the capacity region of the Gaussian Z-interference channel. The non-convex problem mentioned above arose naturally in the reduction from the conjecture to the optimality of Gaussian signaling.
The optimality of Han-Kobayashi achievable region (with Gaussian signaling) remains an open probl... more The optimality of Han-Kobayashi achievable region (with Gaussian signaling) remains an open problem for Gaussian interference channel. In this paper we focus on the Gaussian Z-interference channel. In this paper we first show that using correlated (over time) Gaussian signals do not improve on the Han-Kobayashi achievable rate region. Secondly we compute the slope of the Han and Kobayashi achievable region around the Sato's corner point and provides outer bounds to the slope.
We investigate the vicinity of the newly established corner point for the capacity region of the ... more We investigate the vicinity of the newly established corner point for the capacity region of the Gaussian Z-interference channel. We determine the expression for the slope of the Han and Kobayashi region with Gaussian signaling just around the corner.
IEEE Transactions on Information Theory, Sep 1, 1987
Water filling for uncoded communications over parallel gaussian channels
We investigate the problem of allocating power to send uncoded information over parallel Gaussian... more We investigate the problem of allocating power to send uncoded information over parallel Gaussian channels. We examine the reason why regular "water-filling" does not work in the uncoded case, and show that a modification of the noise level of each subchannel lets "water-filling" work in this case.
Parameter Selection in Optical Networks With Variable-Code-Rate Superchannels
Journal of Optical Communications and Networking, Jun 21, 2016
Future flexible transceivers will be able to adjust modulation format, number of subcarriers, sym... more Future flexible transceivers will be able to adjust modulation format, number of subcarriers, symbol rate, and forward error correction (FEC) scheme, according to channel and network conditions. This paper uses a combination of theoretical derivations and experimental results to recommend the best set of parameters to satisfy a specific demand to be routed along the network. In particular, for a given required transparent reach and desired net bit rate, and assuming an FEC scheme with a constant gap to capacity, the paper provides a set of modulation format, number of subcarriers, symbol rate, and code rate, which requires minimum bandwidth, while offering a conveniently low bit error rate (in optical systems, typically 10-15). We observed that optimum operating points required FEC schemes with overheads ranging from almost 0 to 145%, which is an important guideline for future flexible optical communications systems.
IEEE Transactions on Information Theory, Nov 1, 1984
The preceeding equations allow the entropy power inequality and the Brunn-Minkowski Inequality to... more The preceeding equations allow the entropy power inequality and the Brunn-Minkowski Inequality to be rewritten in the equivalent form Mc4x H.M.COSTAmMBER,IEEE,AND THOMAS M. COVER FELLOW, IEEE H(X+ Y) 2 H(X'+ Y') (4)
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Papers by Max Henrique Machado Costa