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.     

一种用于H.264的快速运动估计算法

针对H.264多预测块模式的运动估计特点,提出一种选择预测块模式的方法,逐步减少预测块搜索,提高运动估计的搜索速度。结果表明,此方法与全预测块模式搜索相比较,平均搜索速度可显著提高。     

一种预测质量可控的快速运动估计搜索算法

本文提出了一种预测质量可控的快速运动估计搜索算法.该算法利用运动矢量的空间、时间相关性,通过预测初始搜索中心位置、判定是否为静止宏块、调整搜索窗口、预测质量可控的渐进式块匹配准则搜索等步骤进行运动估计,并引入调节函数在预测质量和搜索速度之间增加了可控性.实验结果表明本算法大大减少了计算量,明显提高了运算速度,且具有很好的重建视频质量,适合于在低码率视频编码中应用.     

H.264全搜索运动估计算法的优化

在H.264中进行全搜索运动估计,需要遍历所有宏块划分模式以及该模式下所有的运动向量,非常耗时.针对此问题,本文给出了一种优化的快速全搜索算法,该算法根据帧间宏块划分的特点,通过合并子块运动信息得到较大块的运动信息,可以大大提高搜索速度.实验结果表明,优化后的全搜索算法,计算速度提高了80%以上.     

创新的高效方向性菱形-弧形快速块匹配运动估计算法

针对传统运动估计算法的缺点,本文提出了一种采用弧形、小十字、大菱形模板进行快速块匹配运动估计的新算法.该算法(NOADS)充分利用序列图像中运动矢量场中心偏置分布特性,使用小十字模板,进一步搜索根据情况自适应调整扩展为水平菱形或是垂直菱形模板,处理中心区域小运动矢量和静止运动矢量的搜索.使用大菱形-弧形模板处理大运动矢量的搜索.实验结果表明NOADS有效减少了搜索点数,提高了搜索速度,能同时适应于小运动块和大运动块的搜索,速度上比DS提高约20%,比3SS提高30% ～60%.     

搜索模式自适应快速运动估计算法

提出了一种搜索模式自适应快速运动估计算法(PAFME),首先利用变块尺寸运动估计的特点与运动矢量的时空域相关性,预测初始搜索中心;采用多种搜索模式以适应不同运动特征,提出了搜索模式自适应的选择机制,以节省不必要的搜索点加快搜索速度;又能避免陷入局部极小.实验结果表明,与H.264/AVC的参考软件JM12.4相比,该算法使整像素精度运动估计的速度提高了30%～40%,同时保持了图像质量和码率基本不变.     

一种基于自适应预测的菱形搜索算法

运动估计中菱形算法是一种高效的搜索方法,但它没有利用视频序列中运动矢量的中心偏置分布特性和相邻宏块在时间和空间上的相关性,因此还有很大的空间可以进一步提高该算法的性能.在充分利用运动矢量的中心偏置分布特性和相邻宏块运动矢量的相关性的基础上,提出了一种基于自适应预测的菱形搜索算法(APDS),与传统的起点预测方法不同的是,该算法对所有宏块搜索起点的预测并不是按照一种固定的方法求取,而是通过分析其相邻宏块运动矢量的特性来自适应求得搜索起点和决定搜索策略.实验证明,同传统的菱形法相比,这种方法提高了搜索准确度,同时大幅降低了搜索时间,是一种高效率的搜索算法.     

H.264中一种基于搜索范围自适应调整的运动估计算法

视频编码标准 H.264中的固定搜索范围设定,使得运动估计单元的计算量和存储读写带宽过大,给实时编码带来了困难.该文提出一种基于搜索范围自适应调整的运动估计算法.算法首先根据当前编码块预测运动矢量(PMV)点的绝对误差和(SAD)以及相邻已编码块的信息,判断 PMV 的预测准确程度,自适应地确定搜索范围(SR)大小;然后通过检测编码块所在区域的运动方向特性,确定 SR 内的有效搜索方向.仿真结果表明:相比于全搜索算法和 UMHexagon 算法,该文算法分别能够平均节省91%和18%左右的运动估计时间,而码率和图像 PSNR 基本保持不变.     

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。     

结合十字搜索的三角形搜索算法

提出一种新的运动估计快速块匹配算法,并结合十字搜索的三角形搜索算法(PCTS),利用序列图像运动矢量场所具有的中心偏置性和空间相关性先进行起始点预测的十字搜索,并做出提前终止判断,再利用单纯形最优化理论做三角形搜索.实验结果表明,该算法在确保搜索准确度的同时大大减少了搜索点的个数.     

An efficient gray search algorithm for the estimation of motionvectors

Motion vector estimation plays an important role in motion-compensated video coding. An efficient and fast search algorithm is proposed for the estimation of motion vectors. With the help of gray prediction, the algorithm can determine the motion vectors of image blocks quickly and correctly. Since the proposed algorithm performs better than other search algorithms [e.g. the three-step search (TSS), cross-search (CS), new three-step search (NTSS), four-step search (FSS), block-based gradient descent search (BBGDS), simple-and-efficient search (SES), prediction search (PS) and gray prediction search (GPS)], it is very beneficial in applications where the video coding speed is important     

一种用于视频编码的块运动估计算法——块特征匹配预测搜索算法

本文提出了一种块特征匹配预测搜索ＢＦＭＰＳ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,ＢＦＭＰＳ算法充分利用了序列图像的实际矢量与预测矢量之间距离的空间分布特征,中心偏置分布特性和时间上的相关特性,并采用了中止判决准则,可以明显地减少了运动搜索复杂度,ＢＦＭＰＳ算法在匹配运算中采用 简单有交的块特征匹配准则函数,相应的块匹配计算复杂度,数据读     

Neighbourhood-blocks motion vector estimation technique using pyramidal data structure

A pyramidal motion estimation technique that makes use of the motion correlation within a pyramidal level is proposed. In the proposed technique, motion vectors from neighbouring motion blocks are taken into consideration as possible candidates. This is done in lieu of scaling the motion vectors from the corresponding positions at the adjacent lower pyramidal level as the prediction motion vectors for the current pyramidal level (as performed in the conventional technique). Each of these candidate motion vectors is used as the prediction motion vector and refined, and the one that has the least matching distortion is chosen as the motion vector at the current pyramidal level. Compared to the conventional pyramidal motion estimation technique, the proposed method effectively overcomes the problem of propagation of false motion vectors. Simulation studies show that a substantial improvement is achieved in the performance, both in terms of the prediction mean square error and the number of coding bits for the motion vectors.     

A Multi-Pass True Motion Estimation Scheme With Motion Vector Propagation for Frame Rate Up-Conversion Applications

This paper presents a robust true motion estimation algorithm, designated as MPMVP (Multi-pass and Motion Vector Propagation), to enhance the accuracy of the motion vector fields in frame rate up-conversion applications. The MPMVP uses a multi-pass scheme to progressively refine approximate motion vectors to true motion vectors based upon the motion information acquired in previous passes. The multi-pass motion estimation process uses a large block size to detect the motion vectors within the objects themselves and small block sizes to detect the motion vectors along the object boundaries. Actually, the block size is progressively reduced during the search process. When the motion vector of a block is considered to be sufficiently accurate for motion estimation purposes, the block is said to be converged and the local motion vector search process terminates. A novel technique, referred to as motion vector propagation, is then applied to propagate the motion vector of the converged block to its neighboring blocks. This technique not only ensures that neighboring motion vectors within the same object have a high degree of spatial correlation, but also accelerates the convergence of the motion vectors in the neighboring blocks and therefore reduces the overall computational time and expense of the multi-pass motion vector search procedure. A novel distortion criterion is proposed to enhance the tolerance of the traditional sum-of-absolute-difference measurement technique applied in the motion estimation scheme to noise and shadow effects. The experimental results demonstrate that the proposed true motion estimation algorithm outperforms the traditional full search, 3DRS and TCSBP algorithms in terms of both the smoothness of the generated motion vector fields and the visual quality of the up-converted frames.     

Fast motion estimation using modified diamond search patterns

A fast block motion estimation algorithm is proposed using modified diamond search patterns. This algorithm utilises the directions and magnitudes of motion vectors between interblocks and uses a smaller number of search points than conventional diamond search patterns. Simulation results show that the proposed method significantly improves computational speed over other fast motion estimation algorithms without degradation of distortion.     

Fast variable-size block motion estimation for efficient H.264/AVC encoding

In this paper, an efficient algorithm is proposed to reduce the computational complexity of variable-size block-matching motion estimation. We first investigate features of multiple candidate search centers, adaptive initial-blocksizes, search patterns, and search step-sizes, to match different motion characteristics and block-sizes. To avoid being trapped in local minima, the proposed algorithm uses multiple candidate motion vectors, which are obtained from different block-sizes. To further reduce the computation cost, a threshold-based early stop strategy according to the quantization parameter is suggested. With adaptive initial block-sizes, a merge-or-skip strategy is also proposed to reduce the computation for the final block-size decision. For the H.264/AVC encoder, simulations show that the proposed algorithms can speed up about 2.6–3.9 times of the original JM v6.1d encoder, which uses fast full-search for all block-sizes, and still maintain a comparable rate-distortion performance.     

Joint estimation of forward and backward motion vectors forinterpolative prediction of video

A low-complexity iterative algorithm is introduced for joint estimation of forward and backward motion vectors in interpolative prediction of video. Starting from the initial values obtained by a commonly-used block matching independent search method, the motion vectors are iteratively refined until a locally optimal solution to the motion estimation problem for interpolative prediction is achieved. Each iteration consists of a series of two similar procedures. First, the backward motion vector is fixed and a new forward motion vector is searched to minimize the interpolation error. Then the forward motion vector is fixed and the backward motion vector is similarly refined by minimizing the interpolation error. This process is repeated until the interpolation error stops decreasing. Computer simulation results demonstrate that with this technique the prediction error in some scenes is significantly reduced.     

改进的空间下采样视频转码快速运动估计算法

提出一种基于输入码流信息和已转码码流信息的视频转码快速运动估计算法。本算法利用Alpha-激励均值滤波通过输入码流的运动矢量合成作为备选预测运动矢量之一,并利用H．264标准中帧间预测的方法通过已转码码流信息合成另一个备选预测运动矢量,共同作为EPZS运动估计算法的预测中心。结合图像的运动活跃性．自适应的调整运动估计的搜索策略。该算法比传统的运动矢量方法相比提高了1dB左右的PSNR,保持了较高的转码图像质量并与菱形搜索算法相比能够降低18％左右的转码时间。     

Iterative search strategy with selective bi-directional prediction for low complexity multiview video coding

The multiview video coding (MVC) extension of H.264/AVC is the emerging standard for compression of impressive 3D and free-viewpoint video. The coding structure in MVC adopts motion and disparity estimation to exploit temporal and inter-view dependencies in MVC. It results in a considerable increase in encoding complexity. Most of the computational burden comes from uni-directional and bi-directional prediction. In this paper, an iterative search strategy is designed to speed up the uni-directional prediction in MVC. It can work with an adaptive search range adjustment through a confidence measure of a loop constraint to obtain both motion and disparity vectors jointly. Furthermore, a selective bi-directional prediction algorithm is proposed to enhance the coding performance by analyzing the statistical characteristics of bi-directional prediction in MVC. Experimental results demonstrate that, by using the proposed fast search, the temporal and inter-view redundancies of multiview video can be eliminated sufficiently with low complexity.     

一种运动估计的快速预测搜索算法

本文提出了一种运动估计的快速预测搜索算法(PSA)。该算法首先用当前块的三个邻近块运动矢量的线性加权来得到预测矢量,然后以预测点为起始点,采用33的搜索窗进行搜索步长为1的移动窗搜索,直到搜索到达搜索域的边界或搜索的局部最小点位于搜索窗的中心时停止。该算法由于利用了序列图象的实际运动矢量与预测矢量之间距离的空间分布特性一中心偏置分布特性和时间上的相关特性,并采用了中止判决准则,可以明显地减少搜索次数。仿真表明这种算法减少了搜索范围和搜索次数,提高了搜索效率,降低了运动估计的计算复杂性。本文还详细地给出了PSA算法与其它常用快速算法的比较结果。