共查询到15条相似文献,搜索用时 140 毫秒
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提出了一种新的参考矢量选择方法.编码前,首先计算所有码字的哈德码变换,按照第一维系数的大小对码字进行升序排序,将排序后的码字平均分为四段,选择每一段中间位置的码字作为该段的参考矢量,从而增加了子空间三角不等式删除准则的删除能力,有效减小了搜索空间,加快了搜索速度.仿真实验表明,对不同复杂程度的测试图像,算法均快于其他搜索算法. 相似文献
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等和值块扩展最近邻搜索算法(EBNNS)是一种快速矢量量化码字搜索算法,该算法首先将码书按和值大小排序分块,编码时查找与输入矢量和值距离最近的码书块中间码字,并将它作为初始匹配码字.然后在该码字附近上下扩展搜索相邻码字中距输入矢量最近的码字,最后将搜索到的最匹配码字在码书中的地址输出.同时本文对该算法进行了FPGA设计.设计时采用串并结合和流水线结构,折中考虑了硬件面积和速度.结果表明针对所用FPGA器件Xilinx xc2v1000,整个系统最大时钟频率可达88.36MHz,图像处理速度约为2.2 MPixel/s. 相似文献
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传统矢量量化编码算法码字搜索范围较大,编码时间较长.文章提出一种基于不等式的矢量量化快速码字搜索算法.该算法将方差不等式和三角不等式引入范数排序算法(NOS),有效减小了码字搜索范围.实验结果表明,重构图像峰值信噪比(PSNR)相同时,该算法编码时间较低. 相似文献
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基于Hadamard变换和自适应顺序搜索的码字快速搜索算法 总被引:2,自引:2,他引:0
提出了一种Hadamard域中改进的快速码字搜索算法.在已离线按照码字第一维分量的大小进行了排序的码书中,首先找出与输入矢量第一维分量最接近的L个初始候选码字,求出对应的L个Chebyshev距离,接着按自适应的方法在这L个码字之外进行上下搜索,并用新找到的具有更小Chebyshev距离的码字来更新这L个候选码字,以便得到全体码书中L个具有最小Chebyshev距离的最终候选码字.最后用PDS算法在这L个最终候选码字中找出Euclidean距离最小的码字作为最佳匹配码字.实验表明文中算法相比本文算法在保证PSNR性能无任何下降的前提下,明显减少了算法的计算量,有效地提高了编码速度. 相似文献
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一种改进的基于Hadamard变换的快速码字搜索算法 总被引:1,自引:0,他引:1
提出了一种矢量量化码字搜索的快速算法。该算法是在Hadamard变换域内进行的。匹配码字的判决过程首先根据Chebyshev误差测度,在码书中找出一定数量Chebyshev误差最小的码字;然后运用部分失真搜索算法(PDS),在上述码字中找出其中最匹配的码字。从理论分析和模拟实验结果表明,该算法在保证较好的性能指标和视觉效果前提下,明显减少码字搜索时间。 相似文献
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Efficient codeword search algorithm based on Hadamard transform 总被引:7,自引:0,他引:7
Zhe-Ming Lu Jeng-Shyang Pan Sheng-He Sun 《Electronics letters》2000,36(16):1364-1365
A new fast codeword search algorithm for image vector quantisation (VQ) is introduced. This algorithm performs a fast codeword search in the Hadamard transform (HT) domain using the partial distance search (PDS) technique. Experimental results show that the algorithm needs only 2-3% of the distortion calculations of the exhaustive search method 相似文献
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In this paper, two efficient codebook searching algorithms for vector quantization (VQ) are presented. The first fast search algorithm utilizes the compactness property of signal energy on transform domain and the geometrical relations between the input vector and every codevector to eliminate those codevectors that have no chance to be the closest codeword of the input vector. It achieves a full search equivalent performance. As compared with other fast methods of the same kind, this algorithm requires the fewest multiplications and the least total times of distortion measurements. Then, a suboptimal searching method, which sacrifices the reconstructed signal quality to speed up the search of nearest neighbor, is presented. This algorithm performs the search process on predefined small subcodebooks instead of the whole codebook for the closest codevector. Experimental results show that this method not only needs less CPU time to encode an image but also encounters less loss of reconstructed signal quality than tree-structured VQ does 相似文献
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Ghosh D. Shivaprasad A.P. 《Vision, Image and Signal Processing, IEE Proceedings -》1997,144(5):278-284
Adaptive vector quantisation is used in image sequence coding where the code-book is updated continuously to keep track with the changing source statistics. Hence, for real-time video coding applications, both the processes of quantising the input vectors and updating the codebook are required to be fast. Since the nearest codeword search is involved in both these processes, a fast codeword search algorithm can make the coding process time efficient. The authors describe a proposed codeword search algorithm with reduced search space. The algorithm uses the mean value and the sum of the absolute differences as the two criteria to reject unlikely codewords, thereby saving a great deal of computational time, while introducing no more distortion than the conventional full search algorithm. Simulation results obtained confirm the effectiveness of the proposed algorithm in terms of computational complexity 相似文献
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Byung Cheol Song Jong Beom Ra 《IEEE transactions on image processing》2002,11(1):10-15
Vector quantization for image compression requires expensive encoding time to find the closest codeword to the input vector. This paper presents a fast algorithm to speed up the closest codeword search process in vector quantization encoding. By using an appropriate topological structure of the codebook, we first derive a condition to eliminate unnecessary matching operations from the search procedure. Then, based on this elimination condition, a fast search algorithm is suggested. Simulation results show that with little preprocessing and memory cost, the proposed search algorithm significantly reduces the encoding complexity while maintaining the same encoding quality as that of the full search algorithm. It is also found that the proposed algorithm outperforms the existing search algorithms. 相似文献
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An efficient encoding algorithm for vector quantization based on subvector technique 总被引:4,自引:0,他引:4
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. 相似文献