Lossless Multi-Grid Chain Code with Optimized Cell Usage for Contour Description of Visual Objects

Fabiana O. P. Fernandes, Willian G. de Almeida, Flávia M. Freitas, Abraham Alcaim

DOI: 10.14209/sbrt.2010.8

Keywords: shape encoding object-based image compression MPEG-4 chain code grid cell

Abstract

In the context of object-based image compression, shape encoders that describe the contour of the objects, called chain codes, tend to be more efficient than that the one based on bitmap, which is the MPEG-4 Part 2 framework. Among the chain codes, those based on grid cells are expected to outperform the ones that employ a symbol to code each particular boundary pixel. This paper presents a lossless chain code based approach for binary shapes encoding, called OCULMGCC (Optimized Cell Usage - Lossless Multi Grid Chain Code). The OCU-LMGCC solves shortcomings in the original MGCC, optimizes the required extra parallel information to the decoder and uses a new set of coding symbols, better suited to the novel cell-switching schemes proposed. Results showed a compression gain noticeable larger than the known algorithms reported in the literature.

Download

An Adequate Objective Performance Evaluation of Dirac Video Codec Compared to H.264/AVC

André F. de Araujo, Yuzo Iano, Rangel Arthur

DOI: 10.14209/sbrt.2010.9

Keywords: Dirac video codec H.264; Video Coding Vide Compression Wavelet-based video coding

Abstract

Dirac, a relevant new open wavelet-based video codec, has been released recently. The main contribution of this paper is an adequate performance evaluation of this codec compared to the well-known H.264/AVC. This work differs significantly from previous ones which present unfair and inconclusive comparisons. Eight videos comprising three different resolutions with various degrees and kinds of motion are used to perform the simulations, as well as appropriate tuning of coding parameters for both codecs. In every case, H.264’s objective visual quality results outperform Dirac ones, but some evidences indicate Dirac might provide better subjective quality.

Download

Mean Weight Behavior for the Generalized Subband Decomposition LMS Algorithm

Javier E. Kolodziej, Orlando J. Tobias, Rui Seara

DOI: 10.14209/sbrt.2010.7

Keywords: Averaging principle least-mean-square (LMS) algorithm mean weight behavior subband adaptive filters

Abstract

This paper presents an improved stochastic model for the generalized subband decomposition least-mean-square (GSD-LMS) algorithm. This algorithm is used as an alternative to the standard LMS aiming to improve the convergence speed under correlated input data. An analytical model for the first moment of the adaptive filter weights is derived considering just the independence between weight and input data vectors. Numerical simulation results confirm the accuracy of the proposed model, outperforming other models presented previously in the literature.

Download

Providing Higher Entropy Cryptographic Keys by the Use of Biometrics

D. P. B. A. Camara, V. C. da Rocha Jr.

DOI: 10.14209/sbrt.2010.10

Keywords: Biometrics cryptography error-correcting codes security

Abstract

In this paper modifications are investigated to a previously introduced Key Regeneration system used to obtain cryptographic keys from biometric data, specifically from the iris. These modifications improve the performance of the previous system making possible the regeneration of longer and higher entropy cryptographic keys. The modified system was evaluated on two public databases: CBS-BiosecureV1 and NIST-ICE 2005. On NIST-ICE 2005 it is possible to regenerate a 287 binary digit cryptographic key with an estimated entropy of 231 bits at 0.28% False Acceptance Rate (FAR) and 6.30% False Rejection Rate (FRR). The cryptographic keys regenerated possess enough length and entropy to be used on practical cryptosystems like, for example, the AES.

Download

Improving VoIP Quality over Satellite Transmission with Dynamic Bandwidth

Franco Brandelero, Evelio M. G. Fernandez

DOI: 10.14209/sbrt.2010.101

Keywords: DVB-RCS VoIP VAD

Abstract

This work presents a dynamic bandwidth allocation scheme for DVB-RCS satellite standard aiming to avoid the conflict that arise when VoIP transmission with Voice Activity Detection (VAD) is used. A proposal is presented to improve the quality perceived by the user through bandwidth preallocation and validated by computer simulations using the Network Simulator (NS2).

Download

Fiber Bragg Grating Compression-based Tuning Device for Reconfigurable OADM

Roberson A. Oliveira, Carlos E. N. Mayer, Alexandre A. P. Pohl, Jucélio T. Pereira

DOI: 10.14209/sbrt.2010.11

Keywords: Fiber Bragg Gratings tuning device OADM

Abstract

In this work a fast Bragg grating-based tuning device, working according to the mechanical compression of the fiber, is demonstrated. The device achieves a tuning range of 10 nm and presents tuning speeds up to 15 nm/ms. The component can function as the basic element in wavelength routers and add-drop multiplexers.

Download

Analysis of multi-homed SCTP and delay-centric transmission for VoIP traffic in lossy networks

Rudolfo A. E. Runcos, Eduardo P. Ribeiro

DOI: 10.14209/sbrt.2010.95

Keywords:

Abstract

Nowadays a number of Internet access possibilities can be simultaneously available to fixed or mobile users. Adequate selection of the most appropriate communication path can improve transmission quality for Voice over IP (VoIP) applications by providing smaller delay and smaller packet loss. Stream Control Transmission Protocol (SCTP) is currently being studied as a good alternative for implementing this type of control due to its multi-homing capability. Different parameter configurations can affect performance of path selection mechanisms. In this paper the performance of delay-centric path selection method and SCTP standard mechanism to deal with path failure are analyzed. Communication performance of VoIP transmission is evaluated by comparing the session Mean Opinion Score (MOS) that is calculated using E-model from ITU-T. Simulated scenarios include packet losses and different levels of average delay on the available paths. Results show that delay-centric method combined with standard failure detection mechanism with nondefault parameters performs well for most common cases.

Download

Microstrip Antennas Array with patch superconductor at High Temperature

Hugo Michel Câmara de Azevedo Maia, Humberto César Chaves Fernandes, Leonardo Martins Caetano, Marinaldo Pinheiro de Sousa Neto

DOI: 10.14209/sbrt.2010.12

Keywords: Temperature antenna microstrip superconductor patch antenna array linear

Abstract

New results and the analysis of the resonance frequency and pattern fields of microstrip antennas array, with superconductor patch for different very high critical temperatures, are presented. The linear superconducting rectangular microstrip antennas array uses the new materials Sn5InBa4Ca2Cu10Oy at temperature of 212 K, conductivity of 1.88x105 S/m and Tl5Ba4Ca2Cu10Oy at temperature of 233 K with conductivity equal 2.0x105 S/m. The concise full wave Transverse Transmission Line (TTL) method, is used in the analysis. New results as functions of the temperature, and resonant frequency as functions of the various antenna parameters, for different superconductor are presented.

Download

Reduced Complexity Viterbi Decoding Based on the M-Algorithm and the Minimal

Daiana Nascimento Muniz, Franco A. dos S. Pezzini, Richard Demo Souza, Cecilio Pimentel

DOI: 10.14209/sbrt.2010.125

Keywords:

Abstract

In this paper we propose sub-optimum, reduced complexity decoding algorithms for convolutional codes. The algorithms are based on the minimal trellis representation for the convolutional code, and on the M algorithm. We analyze both the computational complexity, in terms of arithmetic operations, and the bit error rate performance of the proposed algorithms. Results demonstrate that large complexity reductions can be obtained while achieving a very good performance.

Download

Rounded Patch Antenna with T-Shaped Probe Feeding and Shorted Wall

F. da Silva Paixão, M. N. Kawakatsu, V. A. Dmitriev

DOI: 10.14209/sbrt.2010.13

Keywords: Patch antenna T-shaped probe feeding shorted wall broadband

Abstract

In this work, a modified patch antenna with broad bandwidth and small size is proposed and investigated. Instead of rectangular patch of a known antenna we use a rounded patch. This modification increases significantly the upper frequency edge of the operating band. This allows one to obtain a -10 dB return loss bandwidth of 72 % and to flatten the gain characteristic. In our study, we use the parametric optimization of geometry of the antenna

Download