An efficient encoding algorithm for vector quantization based on subvector technique

In this paper, a new and fast encoding algorithm for vector quantization is presented. This algorithm makes full use of two characteristics of a vector: the sum and the variance. A vector is separated into two subvectors: one is composed of the first half of vector components and the other consists of the remaining vector components. Three inequalities based on the sums and variances of a vector and its two subvectors components are introduced to reject those codewords that are impossible to be the nearest codeword, thereby saving a great deal of computational time, while introducing no extra distortion compared to the conventional full search algorithm. The simulation results show that the proposed algorithm is faster than the equal-average nearest neighbor search (ENNS), the improved ENNS, the equal-average equal-variance nearest neighbor search (EENNS) and the improved EENNS algorithms. Comparing with the improved EENNS algorithm, the proposed algorithm reduces the computational time and the number of distortion calculations by 2.4% to 6% and 20.5% to 26.8%, respectively. The average improvements of the computational time and the number of distortion calculations are 4% and 24.6% for the codebook sizes of 128 to 1024, respectively.     

一种基于VLIW架构的高效DCT实现方法

文中提出了一种在VLIW架构DSP上计算AVS视频标准中DCT的方法。在对DCT变换矩阵进行分解的基础上,利用复数乘法实现矩阵乘法计算,并通过合理组织数据,实现了变换矩阵打包系数的复用,减少了寄存器占用,使得算法更适于进行循环展开和软件流水,从而实现更高的并行度,执行速度得到有效提升。在计算效率上,文中提出的计算方法比AVS标准中的快速算法提高了4.28倍,并且比现有方法的计算耗时减少了31.1%。     

一种改进的矢量量化码字搜索算法

该文利用图像矢量的平均值和方差,结合了最近邻域搜索算法,构造了一种新的快速矢量量化编码算法。将一个输入矢量分为两个子矢量,分别计算原始矢量、两个子矢量的和以及方差值,利用在这些数值基础上建立的一组三角不等式来排除不可能的码字。仿真结果表明新算法在所需时间和计算复杂度方面优于改进的EENNS算法,为矢量量化算法的研究提供了一种新的思路。     

矢量量化有效排查快速编码算法

研究了一种基于均方误差（MSE）测度的矢量量化快速编码算法,算法利用小波变换的特点合理地构造矢量。结合非线性插补矢量量化技术、矢量和值差法和部分失真排除法,在搜索编码过程中,有效排除部分候选码字。实验结果表明,相对于穷尽搜索方法,计算量有明显降低,计算时间减少显著。     

CORDIC based fast algorithm for power-of-two point DCT and its efficient VLSI implementation

—In this paper, we present a coordinate rotation digital computer (CORDIC) based fast algorithm for power-of-two point DCT, and develop its corresponding efficient VLSI implementation. The proposed algorithm has some distinguish advantages, such as regular Cooley-Tukey FFT-like data flow, identical post-scaling factor, and arithmetic-sequence rotation angles. By using the trigonometric formula, the number of the CORDIC types is reduced dramatically. This leads to an efficient method for overcoming the problem that lack synchronization among the various rotation angles CORDICs. By fully reusing the uniform processing cell (PE), for 8-point DCT, only four carry save adders (CSAs)-based PEs with two different types are required. Compared with other known architectures, the proposed 8-point DCT architecture has higher modularity, lower hardware complexity, higher throughput and better synchronization.     

An adaptive spatio-temporal perception aware quantization algorithm for AVS2

Adaptive quantization proves to be an effective tool to improve coding performance. In this paper, we propose an adaptive spatiotemporal perception aware quantization algorithm to increase subjective coding performance. To measure the spatiotemporally perceptual redundancy, the perceptual complexity models are firstly established with spatial and temporal characteristics respectively. With the help of the models, the adaptive spatial and temporal quantization parameter (QP) offsets are then calculated for each coding tree unit (CTU), respectively. Finally, the perceptually optimal Lagrange multiplier of each CTU is determined with the spatial–temporal QP offset. Experimental results show that the proposed algorithm reduces 8.6% and 8.4% Bjontegaard-Delta Rate (BD-Rate) with Structural Similarity Index Metric (SSIM) in average over the second generation of Audio Video Coding Standard (AVS2) reference software RD17.0 in Low-Delay-P (LDP) and Random-Access (RA) configurations, respectively. The subjective assessment proves that the proposed algorithm can reduce the bitrates with the same subjective quality significantly.     

An efficient bit-loading algorithm for DMT applications

This letter describes an efficient bit allocation algorithm for digital subscriber loop modems that use discrete multi-tone technology. The algorithm computes the optimum bit allocation profile within all constraints and requires fewer computations than the conventional “water-filling” approach. Conventional algorithms are unable to assign data bits to higher frequency bins over long loops with high level of interference due to the power spectrum mask limitation, even if the total power budget is not expended. We propose a novel scheme to distribute data over multiple bins at correspondingly reduced power in these, otherwise unpopulated bins     

海洋合成孔径雷达图像的一种高效压缩方法

针对通用压缩算法未利用合成孔径雷达（SAR）图像特征的不足,提出一种基于概率分布的自适应海洋SAR图像压缩算法。利用海洋SAR图像的概率分布,根据目标的分布设计量化方案,使目标和背景得到不同程度的保留。利用场景的稀疏性,将阈值以上的像素映射到三元组,对其灰度和位置信息分别熵编码;利用剩余背景层灰度偏差较小的特点作位平面编码。实验结果表明,该算法能有效地压缩图像,同码率下峰值信噪比（PSNR）较JPEG2000高5dB～10dB。本文算法复杂度低,对比度保持好,适用于针对不同需求的海面舰船SAR图像压缩。     

An efficient algorithm for two-dimensional frequency estimation

This paper presents a computationally efficient eigenstructure-based 2D-MODE algorithm for two-dimensional frequency estimation. We derive the theoretical performance of the 2D-MODE estimator and show that it is asymptotically statistically efficient under either the assumption that the number of temporal snapshots is large or the signal-to-noise ratio is high. Numerical examples showing the performance of this algorithm and comparing it with the computationally efficient subspace rotation algorithms are also given. We show that the statistical performance of the 2D-MODE algorithm is better than that of the subspace rotation methods. The amount of computations required by the former is no more than a few times of that needed by the latter for either small numbers of spatial measurements or a single temporal snapshot, which are the cases of interest herein.     

一种有效的混合噪声滤波算法

以噪声特点和图像结构分析为基础,提出了一种有效的混合噪声滤除算法。算法首先通过极值判断和像素间的相容性检测,分离出脉冲噪声并以中值滤波滤除;然后对含有高斯噪声的图像以模糊滤波算法进行降噪处理。实验结果表明,本算法能有效地滤除图像中脉冲与高斯混合噪声,且较好地保护了图像细节特征。     

An efficient algorithm for mobile objects localization

A new efficient algorithm based on time of arrival to determine the position of a mobile object (MO) in a wireless environment is proposed. Since all operations in our algorithm are simple add and shift operations, it can be easily implemented in the MO's firmware or hardware to reduce the number of instructions and computational cost involved in the localization task. Simulation results show that the proposed algorithm outperforms other algorithms in terms of computational cost and implementation simplicity. Copyright © 2007 John Wiley & Sons, Ltd.     

An efficient Re-indexing algorithm for color-mapped images

The efficiency of lossless compression algorithms for fixed-palette images (indexed images) may change if a different indexing scheme is adopted. Many lossless compression algorithms adopt a differential-predictive approach. Hence, if the spatial distribution of the indexes over the image is smooth, greater compression ratios may be obtained. Because of this, finding an indexing scheme that realizes such a smooth distribution is a relevant issue. Obtaining an optimal re-indexing scheme is suspected to be a hard problem and only approximate solutions have been provided in literature. In this paper, we restate the re-indexing problem as a graph optimization problem: an optimal re-indexing corresponds to the heaviest Hamiltonian path in a weighted graph. It follows that any algorithm which finds a good approximate solution to this graph-theoretical problem also provides a good re-indexing. We propose a simple and easy-to-implement approximation algorithm to find such a path. The proposed technique compares favorably with most of the algorithms proposed in literature, both in terms of computational complexity and of compression ratio.     

An efficient PSTD algorithm for cylindrical coordinates

A pseudospectral time-domain (PSTD) algorithm is developed to overcome limitations in the conventional solution methods for Maxwell's equations in cylindrical coordinates. It is based on the fast Fourier transform (FFT) representation of spatial derivatives and a centered grid. The main contributions of this algorithm are to eliminate the singularity problem at the axis and to allow a larger time step. It uses a coarse grid close to the Nyquist sampling density provided that the geometrical modeling does not require fine cells. It reduces the required number of unknowns and the number of time steps in the finite-difference time-domain (FDTD) method and is efficient for large-scale problems     

An efficient algorithm for spare allocation problems

The spare allocation problem in redundant RAM is to replace faulty rows/columns of memory cells with spare rows/columns. To solve the problem, comparison-based search tree structures were used in traditional exact algorithms. These algorithms are not efficient for large problems because significant amounts of data have to be retained and copied in order to generate new partial solutions. Many data may need to be compared for the removal of each redundant partial solution. To overcome these drawbacks, an efficient algorithm is proposed in this paper. The algorithm transforms a spare allocation problem into Boolean functions, and the renowned BDD is used to manipulate them. Experimental results indicate that the proposed algorithm is very efficient in terms of speed and memory requirements. It may also be useful for problems which can be modeled as constraint bipartite vertex cover problems.     

An efficient algorithm for time delay estimation

We present a conceptually simple and computationally efficient algorithm, which is referred to as WRELAX for the well-known time delay estimation problem. The method is a relaxation-based minimizer of a complicated nonlinear least squares criterion, WRELAX can be applied to detecting and classifying roadway subsurface anomalies by using an ultra-wideband ground-penetrating radar. Numerical and experimental examples are provided to demonstrate the performance of the new algorithm     

An efficient scheduling algorithm for input-queued switches

This letter presents an efficient scheduling algorithm DTRR （Dual-Threshold Round Robin） for input-queued switches. In DTRR, a new matched input and output by round robin in a cell time will be locked by two self-adaptive thresholds whenever the queue length or the wait-time of the head cell in the corresponding Virtual Output Queue （VOQ） exceeds the thresholds. The locked input and output will be matched directly in the succeeding cell time until they are unlocked. By employing queue length and wait-time thresholds which are updated every cell time simultaneously, DTRR achieves a good tradeoff between the performance and hardware complexity. Simulation results indicate that the delay performance of DTRR is competitive compared to other typical scheduling algorithms under various traffic patterns especially under diagonal traffic.     

An adaptive quantization algorithm without side information for depth map coding

This paper presents a novel block-adaptive quantization scheme for efficient bit allocation without side information in depth map coding. Since the type of distortion in a depth map causes different effects in terms of the visual artifacts in a synthesized view, the proposed method adaptively assigns the number of bits according to the characteristics of the corresponding texture block. I have studied the details of the depth map and its rendered view distortion, modeled these analytically, and then proposed a new rate and distortion model for depth map coding. Finally, I derived a simple closed-form solution based on my proposed rate and distortion model, which determines the block-adaptive quantization parameter without any side information. Experimental results show that the proposed scheme can achieve coding gains of more than 0.6% and 1.4% for quarter- and full-resolution depth maps, respectively, in a multi-view-plus-depth 3D system.     

An efficient macro-cell placement algorithm

A new approximation algorithm is presented for the efficient handling of large macro-cell placement problems. The algorithm combines simulated annealing with new features based on a hierarchical approach and a divide-and-conquer technique. Numerical results show that these features can lead to a considerable increase in efficiency of the placement algorithm without loss of effectiveness.     

一种离散余弦变换域抗同步攻击的音频水印算法

设计了一种抵抗同步攻击的音频水印方案。首先证 明音频均值是一个受TSM(time scale modification)操作稳定的特征量,然后利用音频均 值生成水印,并将其嵌入4级离散余弦变换(DCT)分解低频系数的统计 均值中。为避免同步攻击引起的水印同步结构连续偏移问题,提取水印过程中采用帧长不固 定的 可变帧长分帧方法;为实现水印的盲检测,水印的嵌入、提取通过量化的方法实现;为保证 水印的不可听性,利用信噪比(SNR)控制水印的嵌入强度。实验结果表明 ,提出的方法在抵抗常规信号处理操作的同时, 还能抵抗20%的TSM操作和1/10的抖动操作,具有很好的鲁棒性。