H.264/AVC中快速1/4像素运动估计算法

提出了一种快速1/4像素的运动估计算法.该算法基于运动补偿预测误差模型,与传统的1/4像素的分层运动估计算法不同,仅通过一步计算就能直接得到1/4像素精度的运动矢量,而且完全避免了运算量很大的分数像素内插运算和整像素搜索完成后的分数像素搜索.实验结果表明,该算法在保持图像质量的前提下极大地减少了1/4像素运动估计的运算量.     

Interpolation-Free Fractional-Pixel Motion Estimation Algorithms with Efficient Hardware Implementation

This paper presents interpolation-free fractional-pixel motion estimation (FME) algorithms and efficient hardware prototype of one of the proposed FME algorithms. The proposed algorithms use a mathematical model to approximate the matching error at fractional-pixel locations instead of using the block matching algorithm to evaluate the actual matching error. Hence, no interpolation is required at fractional-pixel locations. The matching error values at integer-pixel locations are used to evaluate the mathematical model coefficients. The performance of the proposed algorithms has been compared with several FME algorithms including the full quarter-pixel search (FQPS) algorithm, which is used as part of the H.264 reference software. The computational cost and the performance analysis show that the proposed algorithms have about 90% less computational complexity than the FQPS algorithm with comparable reconstruction video quality (i.e., approximately 0.2 dB lower reconstruction PSNR values). In addition, a hardware prototype of one of the proposed algorithms is presented. The proposed architecture has been prototyped using the TSMC 0.18 μm CMOS technology. It has maximum clock frequency of 312.5 MHz, at which, the proposed architecture can process more than 70 HDTV 1080p fps. The architecture has only 13,650 gates. The proposed architecture shows superior performance when compared with several FME architectures.     

Model-based quarter-pixel motion estimation with low computational complexity

Proposed is an interpolation-free quarter-pixel motion estimation method based on a mathematical model for video encoding. In this method, only three shift operators and four compare operators are required in each horizontal and vertical direction to find a quarter-pixel resolution motion vector. Experimental results show that the proposed method reaches almost the same performance as an interpolation-based full-search for quarter-pixel motion estimation with much less computational complexity.     

小数运动估计在可重构处理器ReMAP的映射实现

介绍一种在可重构媒体处理器ReMAP上实现小数运动估计的方法.ReMAP处理器由可重构的运算单元阵列和互联单元级联组成,具有高度可重构性和强大的并行计算能力.在ReMAP中映射实现了小数运动估计中的1/2插值、1/4插值和搜索等算法.通过算法的仿真验证分析,ReMAP可支撑小数运动估计的高性能实现,达到或接近ASIC的性能,并具有较好的应用灵活性,适于媒体处理应用.     

H.264中1/4像素运动预测的快速搜索算法

提出了一种新的1/4像素运动预测快速搜索算法,测试结果表明,此算法大大减少了搜索点数,降低了计算量,可使搜索速度明显提高.     

Sub-pixel motion estimation using kernel methods

Modern video codecs such as MPEG2, MPEG4-ASP and H.264 depend on sub-pixel motion estimation to optimise rate-distortion efficiency. Sub-pixel motion estimation is implemented within these standards using interpolated values at 1/2 or 1/4 pixel accuracy. By using these interpolated values, the residual energy for each predicted macroblock is reduced. However this leads to a significant increase in complexity at the encoder, especially for H.264, where the cost of an exhaustive set of macroblock segmentations needs to be estimated for optimal mode selection. This paper presents a novel scheme for sub-pixel motion estimation based on the whole-pixel SAD distribution. Both half-pixel and quarter-pixel searches are guided by a model-free estimation of the SAD surface using a two dimensional kernel method. While giving an equivalent rate distortion performance, this approach approximately halves the number of quarter-pixel search positions giving an overall speed up of approximately 10% compared to the EPZS quarter-pixel method (the state of the art H.264 optimised sub-pixel motion estimator).     

Analysis of spatial transform motion estimation with overlappedcompensation and fractional-pixel accuracy

The authors investigate how the performance of spatial transform motion estimation can be significantly improved by incorporating overlapped compensation and fractional-pixel accuracy. An overlapped spatial transformation (OST) motion model is developed, which successfully addresses the inability of the conventional block matching technique to compensate for complex motion and inside-block motion field discontinuities. Simulation results show that the motion compensated prediction error of this method is reduced by 1.1 dB, compared with the conventional overlapped block matching motion estimation, for the same generated motion vectors overhead. To improve the performance, the overlap must be used in both the motion estimation and compensation processes. Further improvement can be obtained using half-pixel precision motion vectors. However, this improvement is comparatively less than the gain of conventional block matching from a half-pixel search     

H.264编码器中1/4像素精度插值算法的VLSI实现

H.264视频编码标准中引入了1/4像素精度插值算法,大大提高了压缩效率,但同时使运算复杂度增加、存储带宽增大。针对以上问题,从运动估计的角度出发,采用一步插值法和数据复用技术,可使带宽减少26%,处理周期可减少45%;设计了相应的硬件结构:采用了5级流水线实现一步插值算法,通过输入缓冲单元实现了参考数据的复用;针对插值过程中产生的大量数据,采用乒乓操作结构,保证数据及时传递。该结构可以显著降低带宽,提高吞吐率,完全可以应用于实时编码器中。     

Hardware design focusing in the tradeoff cost versus quality for the H.264/AVC fractional motion estimation targeting high definition videos

This article presents an architecture for the fractional motion estimation (FME) of the H.264/AVC video coding standard focusing in a good tradeoff between the hardware cost and the video quality. The support to FME guarantees a high quality in the motion estimation process. The applied algorithmic simplifications together with the multiplierless implementation and with a well balanced pipeline allow a low cost and a high throughput solution. The architecture was also designed to avoid redundant external memory accesses when computing the FME. The design was divided in two main modules: integer motion estimation (with diamond search algorithm) and fractional refinement (half-pixel and quarter-pixel interpolation and search). The designed architecture was described in VHDL and synthesized to an Altera Stratix III FPGA. The architecture is able to reach 260 MHz when running in the target FPGA. In worst case scenario, this operation frequency allows a processing rate of 43 HD 1080p (1,920 × 1,080 pixels) frames per second, surpassing the requirements for real time processing. In comparison to related works, the developed architecture was able to achieve a good tradeoff among hardware costs, video quality and processing rate.     

一种H.264的快速运动估计算法

在研究了H.264多宏块运动估计特点的基础上,提出了一种使用宏块模式搜索截止准则的快速运动估计算法.经实验验证,采用此快速搜索算法的编码结果,搜索速度平均可提高30%.     

Low complexity motion estimation utilising spatial correlation

An efficient algorithm is proposed to reduce the computational complexity of block matching motion estimation by using the characteristics of spatial correlation. The proposed algorithm is to skip the motion vector search of inside macroblocks surrounded by identical motion vectors. Experimental results show that the proposed algorithm reduces computational complexity by 52.5% compared to conventional motion estimation at the cost of negligible performance degradation.     

基于模糊量化和2 bit深度像素的运动估计算法

提出了一种2 bit深度像素的运动估计算法。首先,将像素深度的降采样过程形式化为区间分划和区间映射2个步骤,其中前者为多对一映射,决定着运动估计性能,后者为一一映射;其次,提出一种非均匀量化方法求解区间分划的3个初始阈值,并利用隶属度函数对初始阈值细化,从而克服信号噪声等因素导致的初始阈值周围像素值的误匹配;再次,讨论了适用于2 bit深度像素运动估计的误差度量准则,进而提出了基于模糊量化和2 bit深度像素的运动估计算法;最后,借助信号自相关函数,建立比特深度转换误差—运动向量精度模型来估计该算法所能达到的预测精度。实验结果证明,对于多种类型的视频序列,尤其是场景细节和物体运动比较复杂者,该算法始终能保持较高的估计精度,运动补偿的平均峰值信噪比较之传统2 bit深度像素的运动估计提高0.27 dB。     

基于H.264的内容自适应分数像素运动估计算法

分数像素精确运动估计的改进是整个运动估计模块优化的关键,本文提出了基于H.264的内容自适应分数像素运动估计算法。首先,提出基于平坦区域宏块预测的无效分数像素运动矢量(MV)搜索省略算法(SMBP);然后,改进H.264采用的基于中心的分数像素搜索算法(CBFPS),提出基于预测矢量的增强型菱形模板(EDSP)搜索算法。实验结果表明,内容自适应分数像素运动估计算法比分数像素全搜索算法(FFPS)在峰值信噪比(PSNR)有微小降低(0.095～0.209 dB)的情况下,平均减少了75.6%的分数像素搜索点,整个运动估计模块平均节省了38.5%的计算量。     

一种新的算法可编程的运动估计协处理器

本文针对块匹配运动估计快速搜索算法的要求,设计了一种算法可编程的运动估计及运动补偿协处理器。该协处理器设计采用软硬件协同处理结构。灵活的指令集和高效的硬件并行执行单元相结合,使得该协处理器具备可编程处理器结构及树形结构运动估计VLSI结构的优点,可以兼顾运动估计算法高处理效率和灵活性的要求。设计的协处理器不拘泥于某种快速搜索算法,通过改变内部程序代码,可以实现多种快速运动估计算法,包括TSS、DS、HEXBS、MVFAST、EPZS等,同时具备很强的可扩展性。与同类设计相比,本设计具有高效、灵活、算法可配置的特点,同时设计消耗的硬件资源也大幅减小。     

亚象素运动估值快速算法

高精度的匹配和补偿可以减少预测误差，提高视频图像的压缩效果。文中提出了一种亚象素精度视频运动估值的快速算法，根据半象素精度运动估值的中间结果，直接推算出更高精度的运动估值。该算法为高精度亚象素运动估值的研究提供了算法保证。     

Fast Multi-reference Motion Estimation via Enhanced Downhill Simplex Search

Block motion estimation can be regarded as a function minimization problem in a finite-dimensional space. Therefore, fast block motion estimation can be achieved by using an efficient function minimization algorithm instead of a predefined search pattern, such as diamond search. Downhill simplex search is an efficient derivative-free function minimization algorithm. In this paper, we proposed a fast block motion estimation algorithm based on applying the downhill simplex search for function minimization. Several enhanced schemes are proposed to improve the efficiency and accuracy, including a new initialization process, a special rounding scheme, and an early-stop error function evaluation procedure. We also extend the downhill simplex search for the multi-reference frame motion estimation problem. Experimental results show superior performance of the proposed algorithm over some existing fast block matching methods on several benchmarking video sequences.     

小数像素运动估计快速算法

高精度的匹配和补偿可以减少预测误差，提高压缩视频图像的质量。提出了一种小数像素精度视频运动估计的快速算法，根据半像素精度运动估计的中间结果，直接推算出最高精度的运动估计。根据该算法可以快速得到任意小数像素精度的运动估计。     

基于H.264运动估计算法的改进与优化

在H.264视频编码标准中,运动估计是最重要也是最耗时的过程,目前H.264标准中采用UMHexagons算法,本文结合H.264的验证模型在JM8.6的源代码上对UMHexagons进行分析,利用视频图像序列运动矢量的分布规律以及当前块像素之间运动估计代价的相关性,对搜索模板和搜索步长进行改进,从而提前结束搜索,减少运动估计时间,实验结果表明:改进后的算法在保证性噪比(PSNR)变化不大的前提下,运动估计时间降低10%以上。     

A fast feature-based block matching algorithm using integralprojections

Block-by-block motion compensation algorithms are studied for video-conference/video-telephone television signals. A fast feature-based block matching algorithm using integral projections for the motion vector estimation is proposed. The proposed algorithm reduces the motion estimation computations by a factor of two by calculating the one-dimensional cost functions rather than the two-dimensional ones. Also, the low sensitivity of the proposed algorithm to the presence of additive noise is shown experimentally. Simulation results based on the original and noisy image sequences are presented     

一种改进的快速块匹配运动估计算法

为了提高运动向量估计算法的速度和精度,提出了一种改进的快速块匹配运动估计算法:依据之前宏块的运动向量,估计当前宏块各可能的运动向量对应的概率值,组成和搜索窗口同样大小的概率矩阵,并根据概率大小限制搜索的次数。仿真结果表明:与标准菱形搜索法相比,在精度略有提高的同时,有效的提高了搜索效率。