Estimation and identification for 2-D block Kalman filtering

The development of a recursive identification and estimation procedure for two-dimensional block Kalman filtering is discussed. The recursive identification scheme can be used online to update the image model parameters at each iteration based on the local statistics within a block of the observed noisy image. The covariance matrix of the driving noise can also be estimated at each iteration of this algorithm. A recursive procedure for computing the parameters of the higher order models is given. Simulation results are also provided     

A Hybrid Geometric–Statistical Deformable Model for Automated 3-D Segmentation in Brain MRI

We present a novel 3-D deformable model-based approach for accurate, robust, and automated tissue segmentation of brain MRI data of single as well as multiple magnetic resonance sequences. The main contribution of this study is that we employ an edge-based geodesic active contour for the segmentation task by integrating both image edge geometry and voxel statistical homogeneity into a novel hybrid geometric-statistical feature to regularize contour convergence and extract complex anatomical structures. We validate the accuracy of the segmentation results on simulated brain MRI scans of both single T1-weighted and multiple T1/T2/PD-weighted sequences. We also demonstrate the robustness of the proposed method when applied to clinical brain MRI scans. When compared to a current state-of-the-art region-based level-set segmentation formulation, our white matter and gray matter segmentation resulted in significantly higher accuracy levels with a mean improvement in Dice similarity indexes of 8.55% (p<0.0001) and 10.18% (p<0.0001), respectively.     

2-D Direction-of-arrival Estimation of Real-valued Sources

A new method is presented to estimate two-dimensional （2-D） Direction-of-Arrival （DOA） angles of narrowband real-valued signals impinging on a L-shape Arrays（LA）. The basic idea of the proposed method is to increase both the effective aperture size and the number of sensors by employing the conjugate invariance property of real-valued signals. Thus, the proposed method can provide a more precise DOA and detect more signals than the Cross-Correlation Matrix Method （CCMM）. Numerical simulation results are presented to support the theory.     

Maximum Entropy Power Spectrum Estimation for 2-D Multirate Systems

This paper presents maximum entropy power spectrum estimation of a 2-D information signal given that multirate low-resolution observations are available. Since the exact calculation of the 2-D maximum entropy power spectrum is not practical, we propose an efficient method utilizing slices in the 2-D discrete Fourier transform (DFT) domain and the duality in convex programming. We investigate the properties of our solution and provide numerical examples to demonstrate the performance of the new method.     

A Super-Resolution Framework for 3-D High-Resolution and High-Contrast Imaging Using 2-D Multislice MRI

A novel super-resolution reconstruction (SRR) framework in magnetic resonance imaging (MRI) is proposed. Its purpose is to produce images of both high resolution and high contrast desirable for image-guided minimally invasive brain surgery. The input data are multiple 2-D multislice inversion recovery MRI scans acquired at orientations with regular angular spacing rotated around a common frequency encoding axis. The output is a 3-D volume of isotropic high resolution. The inversion process resembles a localized projection reconstruction problem. Iterative algorithms for reconstruction are based on the projection onto convex sets (POCS) formalism. Results demonstrate resolution enhancement in simulated phantom studies, and ex vivo and in vivo human brain scans, carried out on clinical scanners. A comparison with previously published SRR methods shows favorable characteristics in the proposed approach.     

运动估计块匹配算法的分析研究

在对目前运动估计快速块匹配算法研究的基础上，描述了运动估计的基本原理；揭示了提高运动估计效率的关键技术，并对相关的算法进行了分析和比较；提出了运动估计算法今后的研究方向。     

Motion Estimation for Video Coding Standards

Motion-compensated estimation is an effective means in reducing the interframe correlation for image sequence coding. Therefore, it is adopted by the international video coding standards, ITU H.261, H.263, ISO MPEG-1 and MPEG-2. This paper provides a comprehensive survey of the motion estimation techniques that are pertinent to video coding standards.There are three popular groups of motion estimation methods: i) block matching methods, ii) differential (gradient) methods, and iii) Fourier methods. However, not all of them are suitable for the block-based motion compensation structure specified by the aforementioned standards. Our focus in this paper is to review those techniques that would fit into the standards. In addition to the basic operations of these techniques, issues discussed are their extensions, their performance limit, their relationships with each other, and the other advantages or disadvantages of these methods. At the end, an example of evaluating block matching algorithms from a system-level VLSI design viewpoint is provided.     

一种改进的UMHexagonS运动估计算法

在分析UMHexagonS运动估计算法的基础上,根据中心偏移特性在起始搜索点预测中加入了原点预测;利用预测运动矢量的运动信息把当前块的运动类型区分为慢速运动、中速运动和快速运动,并采取相应的搜索策略;考虑到常见视频序列水平、垂直方向运动相对剧烈的特性,提出了用13点中菱形模板和8点多层次大菱形模板分别代替正方形模板和多层次六边形模板;在中菱形搜索和大菱形搜索的步骤后均加入提前终止判定,减少了对不重要搜索点的搜索.仿真结果表明,改进后的新算法在保证信噪比和编码码率基本不变的情况下,使得运动估计的时间减少了10％ ～ 23％,增强了编码的实时性.     

基于约束MUSIC的二维DOA估计

本文首先分析了约束MUSIC算法的原理,然后采用这种方法,研究了均匀圆阵的二维到达波方向估计问题,并推广到平面任意阵的情况.研究结果表明,对于相关信号源的DOA估计,采用约束MUSIC法比MUSIC法具有更好的估计性能.     

一种用于运动估值的预测搜索算法

本文提出了一种运动估值算法一预测搜索算法（PSA）。该算法由于利用了运动矢量的空间、时间相关性，可以明显减小搜索范围，提高搜索效率，并能给出正确的运动矢量。文中还对预测搜索算法和全搜索算法（FSM）进行了比较。     

Selective Disparity Estimation and Variable Size Motion Estimation Based on Motion Homogeneity for Multi-View Coding

Multi-view video coding (MVC) is an ongoing standard in which variable size disparity estimation (DE) and motion estimation (ME) are both employed to select the best coding mode for each macroblock (MB). This technique achieves the highest possible coding efficiency, but it results in extremely large encoding time which obstructs it from practical use. In this paper, a fast DE and ME algorithm based on motion homogeneity is proposed to reduce MVC computational complexity. The basic idea of the method is to utilize the spatial property of motion field in prediction where DE and variable size ME are needed, and only in these regions DE and variable size ME are enabled. The motion field is generated by the corresponding motion vectors (MVs) in spatial window. Simulation results show that the proposed algorithm can save 63% average computational complexity, with negligible loss of coding efficiency.      

序列图象编码中位移估值新算法—二维遗传优化算法

本文分析了块匹配算法中几种快速搜索算法存在的问题,基于全局最优化思想提出一种新的位移估值算法——二维遗传优化算法。对帧间差值信号采用相同的编码方法时,该算法和二维对数搜索算法比较,所需编码比特数减少,恢复图象信噪比有所提高,运算复杂度也得到下降。     

A Fast Decoupled Nominal 2-D Direction-of-Arrival Estimation for Coherently Distributed Source

In this paper, we consider the problem of the nominal 2-D (azimuth and elevation) direction-of-arrival (DOA) estimation for coherently distributed source. This new approach is based on the rotation matrices of three parallel uniform linear arrays as deduced, which has decoupled the nominal 2-D DOA from those of angular spreads. The estimator makes use of the eigenvalue decomposition to beamspace data to estimate the nominal elevation DOA. And then using a new cross-correlation matrix, the nominal azimuth DOA estimates are decoupled from the elevation estimates and can be obtained with no searching. The proposed algorithm has lower computational complexity particularly when the radio of array size to the number of source is large, at the expense of negligible performance loss. Simulation results verify the effectiveness of the proposed method.     

基于四阶统计2-D切片的直扩信号多参数估计

基于四阶累积量2-D切片,提出了一种低信噪比环境直扩信号的参数估计方法。该方法可同时估计直扩信号的载波频率和扩频码周期,且还具有较强的抑制噪声的能力。计算机仿真实验验证了其有效性。     

A Power Differentiation Method of Fractal Dimension Estimation for 2-D Signals

Fractal dimension has been used for texture analysis as it is highly correlated with the human perception of surface roughness. Several methods have been proposed for the estimation of the fractal dimension of an image. One of the most popular is via its power spectrum density, provided that it is modeled as a fractional Brownian function. In this paper, a new method, called the power differentiation method (PDM), for estimating the fractal dimension of a two-variable signal from its power spectrum density is presented. The method is first applied to noise-free data of known fractal dimension. It is also tested with noise-corrupted and quantized data. Particularly, in the case of noise-corrupted data, the modified power differentiation method (MPDM) is developed, resulting in more accurate estimation of the fractal dimension. The results obtained by the PDM and the MPDM are compared directly to those obtained using four other well-known methods of fractal dimension. Finally, preliminary results for the classification of ultrasonic liver images, obtained by applying the new method, are presented.     

二维RAKE接收机中一种新的信道矢量估计算法

在二维RAKE接收机中，通常仅用导频信道来估计信道矢量，当导频功率较低时，估计误差较大。本文提出一种新的信道矢量估计算法，该算法采用导频信道与业务信道联合估计技术，通过分集组合两个信道的估计结果，使信道矢量的估计精度得到了提高，仿真结果表明，该算法能有效地降低系统的误码率。     

一种运动估计的快速搜索方法

本文提出了动态图像压缩中估计运动矢量的一种快速搜索算法。分析与实验表明，该算法的计算量大大低于二维全搜索，而匹配效果优于三步法等快速算法，目硬件实现简单。它适用于动态图像的实时编码。     

A Content-Based Search Algorithm for Motion Estimation

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Computationally Efficient Motion Estimation Algorithm for HEVC

In this paper, we present a novel computationally efficient motion estimation (ME) algorithm for high-efficiency video coding (HEVC). The proposed algorithm searches in the hexagonal pattern with a fixed number of search points at each grid. It utilizes the correlation between contiguous pixels within the frame. In order to reduce the computational complexity, the proposed algorithm utilizes pixel truncation, adaptive search range, sub-sampling and avoids some of the asymmetrical prediction unit techniques. Simulation results are obtained by using the reference software HM (e n c o d e r_l o w d e l a y_P_m a i n and e n c o d e r_r a n d o m a c c e s s_m a i n profile) and shows 55.49% improvement on search points with approximately the same PSNR and around 1% increment in bit rate as compared to the Test Zonal Search (TZS) ME algorithm. By utilizing the proposed algorithm, the BD-PSNR loss for the video sequences like B a s k e t b a l l P a s s_416 × 240@50 and J o h n n y_1280 × 720@60 is 0.0804 dB and 0.0392 dB respectively as compared to the HM reference software with the e n c o d e r_l o w d e l a y_P_m a i n profile.