共查询到19条相似文献,搜索用时 125 毫秒
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传统的钻石搜索算法只考虑块误差梯度下降最大的方向,从而降低了得到最佳匹配点为全局最优的概率.在钻石搜索算法的基础上,提出了多方向钻石搜索算法,用于实现视频编码中的块运动估计.该算法考虑所有的块误差梯度下降的方向,而不是只考虑梯度下降最大的那个方向,在钻石搜索法的第一步之后,对LDSP(Large Diamond Search Pattern,LDSP)外围8个点中小于中心点BDM(Block Distortion Measure,BDM)的方向上执行搜索.与全搜索、新三步搜索、四步搜索、基于块的梯度下降搜索、钻石搜索算法相比较,实验结果表明该算法在搜索速度和搜索质量上性能较好. 相似文献
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为了提高分形图像压缩编码的速度,针对在基本分形图像压缩算法中值域块编码匹配搜索时需要对变换后的定义域块一一对应,导致编码时间较长的缺点,提出了一种基于菱形搜索算法的分形图像压缩编码新算法.菱形搜索算法是一种运动估计的快速搜索算法,主要过程是在所有的候选块中搜索当前块的最优匹配块.通过运用菱形搜索算法中的大小菱形模板进行匹配搜索,实验证明文中算法在提高编码速度和降低编码复杂度是有效的. 相似文献
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4.6动态搜索窗调整算法(DSWA)通常运动矢量在搜索区域内具有中心偏置分布特性.而3SS算法在搜索区域为(±16.±16)时第一步搜索采用17×17的搜索窗,对运动块的运动矢量估计来说初始步长太大.跳出了可能性比较大的区域.导致搜索方向的不确定性.故而有可能陷于局部最小。动态搜索窗调整算法在搜索过程中可以根据搜索窗收敛因子的大小自动调整下一个搜索阶段的搜索窗的尺寸,是一种自适应的梯度搜索算法。DSWA算法的搜索窗收敛因子Rw为当前阶段搜索窗大小与上一阶段搜索富大小之比.可以表示为T和H是常数参量.是通过统计一些… 相似文献
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A new diamond search algorithm for fast block-matching motionestimation 总被引:127,自引:0,他引:127
Shan Zhu Kai-Kuang Ma 《IEEE transactions on image processing》2000,9(2):287-290
Based on the study of motion vector distribution from several commonly used test image sequences, a new diamond search (DS) algorithm for fast block-matching motion estimation (BMME) is proposed in this paper. Simulation results demonstrate that the proposed DS algorithm greatly outperforms the well-known three-step search (TSS) algorithm. Compared with the new three-step search (NTSS) algorithm, the DS algorithm achieves close performance but requires less computation by up to 22% on average. Experimental results also show that the DS algorithm is better than the four-step search (4SS) and block-based gradient descent search (BBGDS), in terms of mean-square error performance and required number of search points. 相似文献
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Li-Min Du Zi-Qiang Hou Qi-Hu Li 《Signal Processing, IEEE Transactions on》1992,40(12):3032-3042
An optimum block-adaptive learning rate (OBALR) backpropagation (BP) algorithm for training feedforward neural networks with an arbitrary number of neuron layers is described. The algorithm uses block-smoothed gradient as direction for descent and no momentum term, but produces an optimum block-adaptive learning rate which is constant within each block and is updated adaptively at the beginning of each block iteration so that it is kept optimum in a sense of minimizing the approximate output mean-square error of the block. Several computer simulations were tested on learning a deterministic chaos time-series mapping. The OBALR BP algorithm not only overcame the difficulty in choosing good values of the two parameters, but also provided significant improvement on learning speed and descent capability over the standard BP algorithm 相似文献
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一种结合遗传算法和钻石搜索的多模式快速运动估计方法 总被引:2,自引:0,他引:2
为了解决视频编码中运动矢量搜索精度与速度的矛盾,本文提出了一种基于遗传算法(GA)和钻石搜索(DS)的多模式快速运动估计方法——MMS算法.它以图像序列的时空预测矢量作为图像活动剧烈程度的判据,自适应选择搜索模式.针对平缓运动类型使用快速的DS搜索模式,针对剧烈运动类型使用GA/DS联合搜索模式.与现有的次优解快速算法相比,MMS有效地解决了在大运动矢量情况下编码器性能下降的问题,可以从整体上提升编码器的性能,接近理想的全搜索法的结果;与其它直接利用GA进行全局优化的方法相比,MMS利用DS配合GA实现加速收敛.此外,通过引入多模式处理的概念,在保证搜索精度的同时,充分发挥了次优解算法的效率,整体编码速度与DS等快速算法的结果十分接近.这一方法为有效地解决运动估计中的矛盾问题提供了一个新的处理框架.实验结果验证了算法的性能. 相似文献
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Lixin Yu Yan-Qing Zhang 《IEEE transactions on systems, man and cybernetics. Part C, Applications and reviews》2005,35(2):244-249
In this paper, an evolutionary fuzzy neural network using fuzzy logic, neural networks (NNs), and genetic algorithms (GAs) is proposed for financial prediction with hybrid input data sets from different financial domains. A new hybrid iterative evolutionary learning algorithm initializes all parameters and weights in the five-layer fuzzy NN, then uses GA to optimize these parameters, and finally applies the gradient descent learning algorithm to continue the optimization of the parameters. Importantly, GA and the gradient descent learning algorithm are used alternatively in an iterative manner to adjust the parameters until the error is less than the required value. Unlike traditional methods, we not only consider the data of the prediction factor, but also consider the hybrid factors related to the prediction factor. Bank prime loan rate, federal funds rate and discount rate are used as hybrid factors to predict future financial values. The simulation results indicate that hybrid iterative evolutionary learning combining both GA and the gradient descent learning algorithm is more powerful than the previous separate sequential training algorithm described in. 相似文献
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Yui-Lam Chan Wan-Chi Siu 《IEEE transactions on image processing》2001,10(8):1223-1238
Block motion estimation using the exhaustive full search is computationally intensive. Fast search algorithms offered in the past tend to reduce the amount of computation by limiting the number of locations to be searched. Nearly all of these algorithms rely on this assumption: the mean absolute difference (MAD) distortion function increases monotonically as the search location moves away from the global minimum. Essentially, this assumption requires that the MAD error surface be unimodal over the search window. Unfortunately, this is usually not true in real-world video signals. However, we can reasonably assume that it is monotonic in a small neighborhood around the global minimum. Consequently, one simple strategy, but perhaps the most efficient and reliable, is to place the checking point as close as possible to the global minimum. In this paper, some image features are suggested to locate the initial search points. Such a guided scheme is based on the location of certain feature points. After applying a feature detecting process to each frame to extract a set of feature points as matching primitives, we have extensively studied the statistical behavior of these matching primitives, and found that they are highly correlated with the MAD error surface of real-world motion vectors. These correlation characteristics are extremely useful for fast search algorithms. The results are robust and the implementation could be very efficient. A beautiful point of our approach is that the proposed search algorithm can work together with other block motion estimation algorithms. Results of our experiment on applying the present approach to the block-based gradient descent search algorithm (BBGDS), the diamond search algorithm (DS) and our previously proposed edge-oriented block motion estimation show that the proposed search strategy is able to strengthen these searching algorithms. As compared to the conventional approach, the new algorithm, through the extraction of image features, is more robust, produces smaller motion compensation errors, and has a simple computational complexity. 相似文献
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A fully adaptive normalized nonlinear complex-valued gradient descent (FANNCGD) learning algorithm for training nonlinear (neural) adaptive finite impulse response (FIR) filters is derived. First, a normalized nonlinear complex-valued gradient descent (NNCGD) algorithm is introduced. For rigour, the remainder of the Taylor series expansion of the instantaneous output error in the derivation of NNCGD is made adaptive at every discrete time instant using a gradient-based approach. This results in the fully adaptive normalized nonlinear complex-valued gradient descent learning algorithm that is suitable for nonlinear complex adaptive filtering with a general holomorphic activation function and is robust to the initial conditions. Convergence analysis of the proposed algorithm is provided both analytically and experimentally. Experimental results on the prediction of colored and nonlinear inputs show the FANNCGD outperforming other algorithms of this kind. 相似文献
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Fernando Ciriaco Taufik Abro Antonio Fischer de Toledo Paul Jean E. Jeszensky 《Wireless Communications and Mobile Computing》2011,11(6):767-782
This work aims at proposing the use of the evolutionary computation methodology in order to jointly solve the multi‐user channel estimation (MuChE) and detection problems at its maximum‐likelihood, both related to the direct sequence code division multiple access (DS/CDMA). The effectiveness of the proposed heuristic approach is proven by comparing performance and complexity merit figures with that obtained by traditional methods found in literature. Simulation results considering genetic algorithm (GA) applied to multipath, DS/CDMA and MuChE and multi‐user detection (MuD) show that the proposed genetic algorithm multi‐user channel estimation (GAMuChE) yields a normalized mean square error estimation (nMSE) inferior to 11%, under slowly varying multipath fading channels, large range of Doppler frequencies and medium system load, it exhibits lower complexity when compared to both maximum likelihood multi‐user channel estimation (MLMuChE) and gradient descent method (GrdDsc). A near‐optimum multi‐user detector (MuD) based on the genetic algorithm (GAMuD), also proposed in this work, provides a significant reduction in the computational complexity when compared to the optimum multi‐user detector (OMuD). In addition, the complexity of the GAMuChE and GAMuD algorithms were (jointly) analyzed in terms of number of operations necessary to reach the convergence, and compared to other jointly MuChE and MuD strategies. The joint GAMuChE–GAMuD scheme can be regarded as a promising alternative for implementing third‐generation (3G) and fourth‐generation (4G) wireless systems in the near future. Copyright © 2010 John Wiley & Sons, Ltd. 相似文献
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An error in a paper by Chang and Gray (see ibid., vol.34, no.4, p.679-90, 1986) is pointed out and corrected. The error invalidates their observation that the generalized Lloyd algorithm is a gradient descent technique but the generalized Lloyd algorithm is a member of the related class of coordinate descent techniques. Convergence rate analysis of gradient descent algorithms for vector quantizer design is provided 相似文献