Shape Coding Research Articles

Complex atomic spectral line shapes in the presence of an external magnetic field.

Both the theoretical basis and the computational approach for extending the capabilities of an established spectral line broadening code are presented. By following standard line broadening theory, the effects of an external magnetic field are incorporated into the plasma average and atomic Hamiltonian. An external magnetic field introduces a preferential axis that destroys the symmetry of the quasistatic electric ion microfield. An external magnetic field also modifies the angular properties of the atomic Hamiltonian-atomic energy levels are perturbed and the spectral emission line is polarized. These extensions have been incorporated in an atomic line shape code for complex atoms and applied to several problems of importance to the understanding of tokamak edge plasmas. Applications fall into two broad categories: (1) determination of local plasma properties, such as the magnetic field strength, from distinct line shape features; and (2) consideration of global plasma phenomenon, such as radiation transport. Observable features of the Zeeman effect make H(alpha) a good line for diagnosing the magnetic field. H(beta) does not make a good electron density diagnostic since the Zeeman effect is comparable to the Stark effect for a majority of tokamak edge plasma conditions. For optically thick lines, the details of the spectral line shapes are shown to significantly influence the transport of radiation throughout the system.

Population coding of shape in area V4

Population coding of shape in area V4

Population coding of shape in area V4.

Shape is represented in the visual system by patterns of activity across populations of neurons. We studied the population code for shape in area V4 of macaque monkeys, which is part of the ventral (object-related) pathway in primate visual cortex. We have previously found that many macaque V4 neurons are tuned for the curvature and object-centered position of boundary fragments (such as 'concavity on the right'). Here we tested the hypothesis that populations of such cells represent complete shapes as aggregates of boundary fragments. To estimate the population representation of a given shape, we scaled each cell's tuning peak by its response to that shape, summed across cells and smoothed. The resulting population response surface contained 3-8 peaks that represented major boundary features and could be used to reconstruct (approximately) the original shape. This exemplifies how a multi-peaked neural population response can represent a complex stimulus in terms of its constituent elements.

Evidence for Perceptual “Trapping” and Adaptation in Multistable Binocular Rivalry

When a different pattern is presented to each eye, the perceived image spontaneously alternates between the two patterns (binocular rivalry); the dynamics of these bistable alternations are known to be stochastic. Examining multistable binocular rivalry (involving four dominant percepts), we demonstrated path dependence and on-line adaptation, which were equivalent whether perceived patterns were formed by single-eye dominance or by mixed-eye dominance. The spontaneous perceptual transitions tended to get trapped within a pair of related global patterns (e.g., opponent shapes and symmetric patterns), and during such trapping, the probability of returning to the repeatedly experienced patterns gradually decreased (postselection pattern adaptation). These results suggest that the structure of global shape coding and its adaptation play a critical role in directing spontaneous alternations of visual awareness in perceptual multistability.

VLSI architecture design of MPEG-4 shape coding

This paper presents an efficient VLSI architecture design of MPEG-4 shape coding, which is the key technology for supporting the content-based functionality of the MPEG-4 video standard. The real-time constraint of MPEG-4 shape coding leads to a heavy computational bottleneck on today's computer architectures. To overcome this problem, design analysis and optimization of MPEG-4 shape coding are addressed. By utilizing the RISC-based model, computational behaviors of the MPEG-4 shape coding tool are carefully examined and analyzed. The characteristic of a large amount of bit-level data processing and data transfer of MPEG-4 shape coding motivates the optimization of bit-level data operations. Applying data-flow optimization and data reuse techniques, bit-level computation-efficient architectures, such as data-dispatch-based binary-shaped motion estimation, the delay-line model, and configurable context-based arithmetic coding, are designed to accelerate bit-level processing. These hardware blocks are integrated and scheduled in a very efficient data flow to achieve real-time performance for MPEG-4 CPL2 (core profile level 2) specification at 23.5 MHz clock rate. The system architecture is implemented using Verilog HDL and synthesized with a 0.35 /spl mu/m four-layer CMOS standard library.

Bitplane-by-bitplane shift (BbBShift) - A suggestion for JPEG2000 region of interest image coding

The JPEG2000 image coding standard defines two kinds of region of interest (ROI) coding methods-the general scaling based method and the maximum shift (maxshift) method. The former requires shape coding of the ROIs, which leads to increased complexity of codec implementations and limits the choice of ROI shapes (currently, only rectangle and ellipse shapes are defined). The latter allows for arbitrarily shaped ROI coding without explicitly transmitting any shape information to the decoder, but does not have the flexibility to select an arbitrary scaling value to define the relative importance of the ROI and the background wavelet coefficients. We propose a bitplane-by-bitplane shift (BbBShift) method, which supports both arbitrary ROI shape and arbitrary scaling without shape coding.

Display of Munsell color values, earthquakes, and other three- and four-parameter datasets in stereo 3D

A new version of the program 3D.BAS facilitates display of three- and four-parameter datasets, particularly earthquake distributions and Munsell color measurements, by using stereoscopic 3D scatterplots. With respect to earthquakes, hypocenters can be plotted on whole-earth spherical plots or on rectangular plots for specific regions. The program allows a series of earthquakes to be examined quake by quake, with coding of symbol shapes and/or colors for depths, magnitudes, time intervals, or individual identification. It also allows a variety of panning, zooming, slicing, rotation, projection, and stepping. It can handle datasets of 10 4 earthquakes, and can filter such a dataset for quakes below, between, or above specific depths or intensities, or within chosen distances on either side of an oblique line. With respect to Munsell colors, the program can plot the three constituent parameters (hue, lightness, and chroma) on a rectangular coordinate system that mimics the arrangement of a stack of pages of color chips, or on cylindrical and spherical coordinate systems (the Munsell “color cylinder” or “color sphere”).

A modified vertex-based shape coding algorithm

This paper proposes a modified shape coding algorithm called modified vertex-based shape coding (MVBSC) to encode the boundary of a visual object compactly by using a modified polygonal approximation approach which uses modified curvature scale space (CSS) theory to extract feature-points.

A hybrid scheme for low bit-rate coding of stereo images

In this paper, we propose a hybrid scheme to implement an object driven, block based algorithm to achieve low bit-rate compression of stereo image pairs. The algorithm effectively combines the simplicity and adaptability of the existing block based stereo image compression techniques with an edge/contour based object extraction technique to determine appropriate compression strategy for various areas of the right image. Unlike the existing object-based coding such as MPEG-4 developed in the video compression community, the proposed scheme does not require any additional shape coding. Instead, the arbitrary shape is reconstructed by the matching object inside the left frame, which has been encoded by standard JPEG algorithm and hence made available at the decoding end for those shapes in right frames. Yet the shape reconstruction for right objects incurs no distortion due to the unique correlation between left and right frames inside stereo image pairs and the nature of the proposed hybrid scheme. Extensive experiments carried out support that significant improvements of up to 20% in compression ratios are achieved by the proposed algorithm in comparison with the existing block-based technique, while the reconstructed image quality is maintained at a competitive level in terms of both PSNR values and visual inspections.

A Multiresolution Markov Approach to Model-Based Image Compression

Bonneau, R. J., and Meadows, H. E. A Multiresolution Markov Approach to Model-Based Image Compression, Digital Signal Processing11 (2001) 346–358Currently a large area of research is being devoted to content-based compression due to the JPEG-2000 and MPEG-7 requirements. Recently there has been much work in wavelet and fractal methods for texture and shape segmentation as well as data compression. While these methods do not give optimal least mean square noise performance for a given compression ratio, they contain implicit models for shape and texture coding as a natural part of the compression process. We thus develop an approach for wavelet fractal compression that incorporates these shape and texture models during quantization. Upon decoding, the model regions are preserved for visual or automatic inspection. Our compression models make use of the Mallat Gaussian derivative basis set and an implicit Markov shape and texture structure.

Optimal buffered compression and coding mode selection for MPEG-4 shape coding

We propose an optimal buffered compression algorithm for shape coding as defined in the forthcoming MPEG-4 international standard. The MPEG-4 shape coding scheme consists of two steps: first, distortion is introduced by down and up scaling; then, context-based arithmetic encoding is applied. Since arithmetic coding is "lossless," the down up scaling step is considered as a virtual quantizer. We first formulate the buffer-constrained adaptive quantization problem for shape coding, and then propose an algorithm for the optimal solution under buffer constraints. Previously, the fact that a conversion ratio (CR) of 1/4 makes a coded image irritating to human observers for QCIF size was reported for MPEG-4 shape coding. Therefore, careful consideration for small size images such as QCIF should be given to prevent coded images from being unacceptable. To this end, a low bit rate tuned algorithm is proposed in this paper as well. Experimental results are given using an MPEG-4 shape codec.

Adaptive context-based arithmetic coding of arbitrary contour maps

An efficient technique for encoding arbitrary contours is presented. It is based on the concept of transition points of a contour map and relies on a new four-symbol adaptive context-based arithmetic encoder (CAE) that calculates contexts in the (binary) domain of the contour map. The results obtained with this new technique, applied to the compression of image partitions, are substantially better than those previously attained, showing a clear superiority over adaptive CAE-based differential chain coding and also over the MPEG-4 shape coding.

Vertex adjustment method using geometric constraint for polygon-based shape coding

A new vertex selection scheme for polygon-based contour coding is proposed. The proposed method consists of ‘two-step procedure’. Initial vertices are selected by using the conventional iterated refinement method (IRM) or progressive vertex selection (PVS) method. A vertex adjustment process then follows where the initial vertices are updated to produce an optimal polygon in the sense of ‘error area’. In this step, the geometrical information of the partial contour and its polygon segment is used to reduce the search region for the admissible vertex position. Experimental results are presented to compare the approximation performances and the required computational burdens of the proposed and conventional methods.

Motion compensation method for moving pictures with binary shape

This paper describes a motion compensation method for arbitrarily shaped moving visual objects. To utilise both the inter-frame correlation and the texture-shape correlation, we use macroblock-based motion compensation for binary shape coding as well as texture coding. To efficiently achieve motion compensation for a moving binary shape, we introduce extra motion vectors for the shape coding in addition to the texture motion vectors, where the shape motion vectors are coded by referring to the texture motion vectors. The proposed method can successfully save more than 50% of the number of bits in comparison with the intra-only method. The effectiveness of the proposed method has been established through MPEG4 standardisation activity, and the proposed motion-compensation framework has been adopted by the MPEG-4 visual coding standard (ISO 14496-2).

ANN modeling of DNA sequences: new strategies using DNA shape code

Two new encoding strategies, namely, wedge and twist codes, which are based on the DNA helical parameters, are introduced to represent DNA sequences in artificial neural network (ANN)-based modeling of biological systems. The performance of the new coding strategies has been evaluated by conducting three case studies involving mapping (modeling) and classification applications of ANNs. The proposed coding schemes have been compared rigorously and shown to outperform the existing coding strategies especially in situations wherein limited data are available for building the ANN models.

Error resilient video coding techniques

We review error resilience techniques for real-time video transport over unreliable networks. Topics covered include an introduction to today's protocol and network environments and their characteristics, encoder error resilience tools, decoder error concealment techniques, as well as techniques that require cooperation between encoder, decoder, and the network. We provide a review of general principles of these techniques as well as specific implementations adopted by the H.263 and MPEG-4 video coding standards. The majority of the article is devoted to the techniques developed for block-based hybrid coders using motion-compensated prediction and transform coding. A separate section covers error resilience techniques for shape coding in MPEG-4.

Auditory Temporal Envelope Processing in a Patient with Left-hemisphere Damage

Abstract Auditory temporal envelope processing was investigated in a patient showing a mild speech identification impairment following left-hemisphere damage. Three tasks evaluated the patient's ability to: (1) detect a sinusoidal amplitude modulation (SAM) applied to a white noise, as a function of modulation rate (i.e. her ‘temporal modulation transfer function’ or TMTF); (2) discriminate between two white noises amplitude modulated by time-reversed temporally asymmetric envelopes; and (3) identify white noises amplitude modulated by the temporal envelope of speech stimuli. Measurements of intensity discrimination thresholds were performed as a control task. Compared to normal data, the results obtained with the brain-damaged patient showed: (1) increased thresholds for the detection of SAM; (2) increased thresholds for the discrimination of temporal asymmetry; and (3) a deficit in the identification of speechenvelope noise stimuli. In contrast, intensity discrimination thresholds were within the normal range. Taken together, the results indicate a general impairment in auditory temporal acuity, which is now specified as a deficit in the coding of envelope rate and shape, and a deficit in the ability to use temporal envelope cues in speech processing. These results support the hypothesis that left-hemisphere damage is associated with an impairment in time analysis, which may cause, in turn, speech intelligibility disorders.

Auditory temporal envelope processing in a patient with left-hemisphere damage

Auditory temporal envelope processing was investigated in a patient showing a mild speech identification impairment following left-hemisphere damage. Three tasks evaluated the patient's ability to: (1) detect a sinusoidal amplitude modulation (SAM) applied to a white noise, as a function of modulation rate (i.e. her ‘temporal modulation transfer function’ or TMTF); (2) discriminate between two white noises amplitude modulated by time-reversed temporally asymmetric envelopes; and (3) identify white noises amplitude modulated by the temporal envelope of speech stimuli. Measurements of intensity discrimination thresholds were performed as a control task. Compared to normal data, the results obtained with the brain-damaged patient showed: (1) increased thresholds for the detection of SAM; (2) increased thresholds for the discrimination of temporal asymmetry; and (3) a deficit in the identification of speechenvelope noise stimuli. In contrast, intensity discrimination thresholds were within the normal range. Taken together, the results indicate a general impairment in auditory temporal acuity, which is now specified as a deficit in the coding of envelope rate and shape, and a deficit in the ability to use temporal envelope cues in speech processing. These results support the hypothesis that left-hemisphere damage is associated with an impairment in time analysis, which may cause, in turn, speech intelligibility disorders.

Special Issue on Shape Coding for Emerging Multimedia Applications

Special Issue on Shape Coding for Emerging Multimedia Applications

Scan interleaving based scalable binary shape coding

Abstract In this paper, we propose scan interleaving based shape coding (SISC) as a spatial scalable coding algorithm for binary shape. A typical scalable video system has two or more scalable layers. These are the base layer and the associated enhancement layers. In the proposed spatial scalable binary shape coding algorithm, scan interleaving based data encoding (SI) scheme is proposed for the enhancement layer coding. And context-based arithmetic encoding (CAE) method is employed for entropy coding of binary shape data in each scalable layer. SI scheme efficiently exploits the spatial redundancy of the scalable layers. For reducing the temporal redundancy, inter-frame coding based on motion compensation is employed. The major advantages of SISC are high coding gain, low complexity, and consistency with MPEG-4 non-scalable binary shape coding. High coding gain is achieved from the method of coded-scan-line data analysis, which uses exclusive-OR operation on top and bottom reference pixels. Furthermore, by referring the lower layer motion vectors for its inter-frame coding process, SISC also saves some computational overhead of enhancement layer coding. The proposed technique is, currently, adopted in the Working Draft of MPEG-4 Version 2. SISC supports both the frame-based coding mode and the block-based coding mode. The block-based SISC, as in MPEG-4, is mainly described in this paper.