一种基于H.264的快速运动估计算法

H.264是现有最重要数据压缩编码国际标准之一。同时快速运动估计算法一直是视频压缩中的研究热点。本文针对一些快速估计算法过早确定了搜索方向,容易陷入局部最小点,损失了搜索精度的情况,在原有基础上,运用菱形十字搜索算法(DCS)与阈值估计相结合的方法提高了运动估计的性能。实验结果表明,该算法可以用较小的搜索代价取得与全搜索(FS)相当的效果,并且在搜索速度方面优于钻石法(DS)。     

基于多媒体DSP TM1300的运动估计算法研究及实现

提出一种用于H.263视频编码的快速运动估计的算法——NDA，通过PC仿真后将它移植到多媒体DSP TM1300上，并对它进行了改进和优化。实际运行的测试结果表明，NDA的性能要优于TMN3．0给出的运动估计算法，接近FS。文中还给出了衡量实际运动估计算法性能的测试方法。     

一种改进型新三步搜索算法的研究与实现

针对3G无线网络对流媒体传输的需求分析,基于新三步搜索(NTSS)算法,提出了一种改进型(INTSS)算法.该算法通过采用预搜索定位搜索窗口,并且针对不同的宏块进行相应的编码处理,可以提高视频压缩效率.在Cradle3400的DSP开发板上实现并验证了算法可行性,评估了其性能.相对于传统的全搜索(FS)算法、三步法(TSS)、NTSS等算法,INTSS算法在压缩性能和效率方面均有一定程度的提高.     

基于传播算子的Root-MUSIC算法

传播算子（PM）法不需要进行复杂的特征值分解,减小了计算量,但仅在信噪比较高的情况下才有较好的波达方向估计性能,且谱峰搜索仍需要较大计算量。在此基础上提出了一种改进的算法PM-Root-MUSIC,它不需要特征值分解,同时用多项式求根代替谱峰搜索,大大减少了计算量。理论分析和计算机仿真结果表明此方法是有效的。     

基于方向自适应模板的UMHexagonS算法改进

对UMHexagonS算法的搜索步骤和特点进行了分析,提出了一种改进的方法,改进初始运动矢量预测精度,去掉UMHexagonS算法中5×5全搜索中的相对不重要点,根据初始运动矢量的方向采用梯形格点搜索代替全六边形格点搜索,这在一定程度上减少了计算量.同时能更快地搜索到最佳运动矢量.实验结果表明,在保证PSNR和码率基本不变的前提下,可以有效地降低运动估计时间.     

在VLIW处理器上实现视频图像的运动估计算法的方法

利用超长指令字(VLIW)处理器处理单指令多数据(SIMD)的优势,采用加速SIMD指令计算的数据拼接方案和多方向并行搜索方法以及适合图像数据复用的插值图像存储结构,优化实现了一个高效的ME软硬件结合的架构,分别在TMS320C64××及自行设计的LILY Processor上实现了H.264的QCIF图像数据的搜索及H.263的CIF图像数据的搜索.测试实验表明ME的搜索速度提高了3倍到15倍.     

一种用于H.264的改进UMHexagonS算法

在运动估计中,H.264以增加的编码复杂性为代价获得了非常好的性能.基于对现有文献的研究,提出了一种改进的UMHexagonS算法.首先,在UMHexagonS的非对称十字交叉搜索中增加了8个搜索点,以改善算法在垂直方向上运动的适应性;其次,为提高编码效率,将UMHexagonS算法的小矩形窗口全搜索分为两个步骤;然后,在UMHexagonS的非均匀多层次六边形网格搜索中采用了一种并行算法,进一步提高算法的运动估计性能;最后,采用三点搜索法来替代小菱形搜索,原始的小菱形搜索只作为满足提前终止最佳情况的跳转对象.仿真表明,相比于UMHexagonS算法,提出的改进算法在视频压缩编码速度和重建图像的质量都具有更好的性能.     

基于模式和时空相关性的运动估计快速算法

H.264标准中的多尺寸块运动估计,在显著提高编码性能的同时,大大增加了其计算量,使得H.264实时编码器的实现面临巨大挑战.本文充分利用视频图像的时空相关性和多尺寸块间的运动相似性,根据运动向量的中心偏置特性,提出了一种运动估计快速算法.该算法通过有效地预测搜索起点,自适应选择搜索模式以及采用二级终止搜索策略等方式,在编码性能相当的情况下,运动估计的速度比全搜索算法提高了95~247倍,比H.264推荐的快速算法提高了4.1~6.3倍.     

一种改进的UMHexagonS运动估计算法

在视频编码中,运动估计占据约70%的编码时间,是视频编码中的重要环节。整像素运动搜索UMHexagon S算法以较低的计算复杂度,达到了接近全搜索算法的率失真性能,而被H.264和AVS等标准所采纳。在分析UMHexagon S算法的基础上,对其非对称十字形搜索和非均匀多层次六边形格点搜索算法进行了改进。实验表明,在基本保持原算法性能的同时,该算法比原算法减少了60%~70%的搜索点数,降低了运动估计的计算复杂度。     

基于树形原子字典的匹配跟踪算法

为了降低匹配跟踪视频编码算法的运算复杂度,提出了一种原子字典的树形组织方法,并相应地提出了一种改进的树形字典搜索策略。此算法通过在树中寻找最优路径来搜索最佳原子,并在第一级搜索中引入了一种改进的全搜索策略,进一步降低了计算量。为了有效地捕捉预测误差帧中的曲线特征,冗余原子字典通过对各向异性的生成函数进行真正二维意义上的几何变换来构造,并尽可能地去除了性能不佳的原于以减小字典尺寸。实验结果表明,本文算法具有较高的搜索正确性及较快的收敛速度,而其计算量明显降低。     

符合人眼视觉特征的H.263编码方案

在研究视觉阈值效应和视觉掩盖效应的基础上,提出了一个符合人眼视觉特征的失真判断准则,并将其应用到Ｈ．２６３视频编码中,以达到提高编码速度的目的。实验结果表明,这种基于人眼视觉特性的失真判断方法能在保证恢复图像主观质量和压缩效率的前提下,有效地提高编码速率。     

高质量4kb/s FS-ACELP语音编码算法及性能

4kb/s有限状态代数码激励线性预测语音编码算法FS-ACELP是一种具有延时较短,合成语音质量高、算法复杂度较低的语音编码算法.在线性预测(LP)参数量化上,利用了语音帧内和帧间的相关性,对线谱对(LSP)参数使用预测式分裂式矢量量化,获得很高的量化效率.在自适应码本搜索上,采用了有限状态控制分数延时搜索的算法.在保证合成语音质量的同时,有效地降低了运算量.对于随机码本,采用了具有多模结构的代数码本,提高语音合成质量.对于激励码序列的增益,采用了预测式矢量量化,有效地提高了量化精度.经非正式听音测试,4kb/s FS-ACELP的合成语音质量超过了北美8kb/s VSELP,接近G.729 8kb/s CS-ACELP,MOS分约为3.9.     

An automatic region-based video sequence codec based on fractal compression

In order to improve the performance of fractal video coding, we explore a novel fractal video sequences codec with automatic region-based functionality. To increase the quality of decoding image, intra frame coding, deblocking loop filter and sub-pixel block matching are applied to the codec. An efficient searching algorithm is used to increase the compression ratio and encoding speed. Automatic region-based fractal video sequences coding reduces coding stream greatly. Experimental results indicate that the proposed algorithm is more robust, and provides much less encoding time and bitrate while maintaining the quality of decompression image than the conventional CPM/NCIM method and other related references. We compare the proposed algorithm with three algorithms in Refs. [24], [25], [26], and the results of all these four algorithms are compared with H.264. The bitrate of the proposed algorithm is decreased by 0.11% and the other algorithms are increased by 4.29%, 6.85% and 11.62%, respectively. The average PSNR degradations of the four algorithms are 0.71 dB, 0.48 dB, 0.48 dB and 0.75 dB. So the bitrate of the proposed algorithm is decreased and the other algorithms are increased. At the meantime the compression time is reduced greatly, about 79.19% on average. The results indicate that, on average, the proposed automatic region-based fractal video sequences coding system can save compression time 48.97% and bitrate 52.02% with some image quality degradation in comparison with H.264, since they are all above 32 dB and the human eyes are insensitive to the differences.     

一种新的视频编码的块运动估计算法

本文提出了一种连续判别的非线性预测搜索ＮＰＳＳＤ块运动估计算法,可以用于视频压缩的一些国际标准,如Ｈ．２６１,Ｈ．２６３,ＭＰＥＧ１,ＭＰＥＧ２,ＨＤＴＶ中。ＮＰＳＳＤ算法充分利用了序列图像的实际运动矢量与预测矢量之间的位移的空间分布特性－－中心偏置分布特性和时间上的相关特性,并在搜索过程中采用了中止判别和搜索判别,可以明显地减少运动搜索复杂度。仿真表明这种算法减少了搜索次数,提高了搜索效率,降低     

高质量4kb/s FS-ACELP语音编码算法及性能

4kb/s有限状态代数码激励线性预测语音编码算法FS-ACELP是一种具有延时较短、合成语音质量高、算法复杂度较低的语音编码算法.在线性预测(LP)参数量化上,利用了语音帧内和帧间的相关性,对线谱对(LSP)参数使用预测式分裂式矢量量化,获得很高的量化效率.在自适应码本搜索上,采用了有限状态控制分数延时搜索的算法,在保证合成语音质量的同时,有效地降低了运算量.对于随机码本,采用了具有多模结构的代数码本,提高语音合成质量.对于激励码序列的增益,采用了预测式矢量量化,有效地提高了量化精度.经非正式听音测试,4kb/s FS-ACELP的合成语音质量超过了北美8kb/s VSELP,接近G.729 8kb/s CS-ACELP,MOS分约为3.9.     

Foveated video compression with optimal rate control

Previously, fovcated video compression algorithms have been proposed which, in certain applications, deliver high-quality video at reduced bit rates by seeking to match the nonuniform sampling of the human retina. We describe such a framework here where foveated video is created by a nonuniform filtering scheme that increases the compressibility of the video stream. We maximize a new foveal visual quality metric. the foveal signal-to-noise ratio (FSNR) to determine the best compression and rate control parameters for a given target bit rate. Specifically, we establish a new optimal rate control algorithm for maximizing the FSNR using a Lagrange multiplier method defined on a curvilinear coordinate system. For optimal rate control, we also develop a piecewise R-D (rate-distortion)/R-Q (rate-quantization) model. A fast algorithm for searching for an optimal Lagrange multiplier lambda* is subsequently presented. For the new models, we show how the reconstructed video quality is affected, where the FSNR is maximized, and demonstrate the coding performance for H.263,+,++/MPEG-4 video coding. For H.263/MPEG video coding, a suboptimal rate control algorithm is developed for fast, high-performance applications. In the simulations, we compare the reconstructed pictures obtained using optimal rate control methods for foveated and normal video. We show that foveated video coding using the suboptimal rate control algorithm delivers excellent performance under 64 kb/s.     

A Content-Based Search Algorithm for Motion Estimation

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High Acceleration for Video Processing Applications Using Specialized Instruction Set Based on Parallelism and Data Reuse

This paper describes an application-specific instruction set for a configurable processor to accelerate motion-compensated frame rate conversion (MC-FRC) algorithms based on block motion estimation (BME). The paper shows that the key to achieve very high performance when creating new instructions is to leverage, at the same time, parallel computations, data reuse, and efficient cache use. This is supported by concrete examples that demonstrate how it can be done in the case of the two algorithms considered. The new instructions are used to implement two BME algorithms: one implements the full search (FS) block matching algorithm (BMA), while the other implements the One-Dimensional Full Search (ODFS) BMA. The obtained acceleration factors exceed one hundred for the MC-FRC algorithm embedding the FS algorithm and twenty for the ODFS algorithm. The results show that getting such global acceleration is the consequence of combining parallel computations, data reuse, and efficient cache use, not of only one of them.     

ITU standardisation of very low bitrate video coding algorithms

The ITU near term standard for very low bitrate video coding, H.263 (ITU-T SG 15/1 Rapporteurs Group for Very Low Bitrate Visual Telephony, 1995), is described. Both QCIF and a sub-QCIF format (128 × 96) are mandatory picture formats for the decoder; the CIF picture format is optional. The H.263 algorithm consists of a mandatory core algorithm and four negotiable options. With H.263 a significantly better picture quality than with H.261 can be achieved, depending on the content of the video scene and the coding parameters. Also, the cost of the H.263 video codec can be kept low if only the minimum required is implemented. The negotiable options of H.263 increase the complexity of the video codec, but also significantly improve the picture quality. H.263 is part of a set of recommendations for a very low bitrate audio visual terminal that was frozen in January 1995 and is based on existing technology. A long term activity is planned by ITU for the development of a new video coding algorithm (H.263/L) with a considerable better picture quality than H.263. This standard will be developed in joint co-operation with MPEG4.     

New adaptive partial distortion search using clustered pixel matching error characteristic.

In order to reduce the computation load, many conventional fast block-matching algorithms have been developed to reduce the set of possible searching points in the search window. All of these algorithms produce some quality degradation of a predicted image. Alternatively, another kind of fast block-matching algorithms which do not introduce any prediction error as compared with the full-search algorithm is to reduce the number of necessary matching evaluations for every searching point in the search window. The partial distortion search (PDS) is a well-known technique of the second kind of algorithms. In the literature, many researches tried to improve both lossy and lossless block-matching algorithms by making use of an assumption that pixels with larger gradient magnitudes have larger matching errors on average. Based on a simple analysis, it is found that, on average, pixel matching errors with similar magnitudes tend to appear in clusters for natural video sequences. By using this clustering characteristic, we propose an adaptive PDS algorithm which significantly improves the computation efficiency of the original PDS. This approach is much better than other algorithms which make use of the pixel gradients. Furthermore, the proposed algorithm is most suitable for motion estimation of both opaque and boundary macroblocks of an arbitrary-shaped object in MPEG-4 coding.