一种提高H.261编码性能的实现方法

研究表明了采用最小均方误差或绝对误差准则的快匹配运动估值算法对Ｈ．２６１编码器来说不是最好的。本文提出了一种改进的快匹配运动估值算法。它所采用的准则不仅考虑预测误差能量的大小，还考虑了运动矢量信息以及帧间预测误差的编码比特数目的多少。实验结果表明新的准则能够显著地改善Ｈ．２６１的编码性能。     

一种用于块运动估计的匹配准则函数块特征匹配函数

本文提出了一种新的块运动估计匹配准则函数块特征匹配(BFM)函数,可以用于视频压缩的一些国际标准,如H.261,H.263,MPEG1,MPEG2,HDTV的编解码器中。在这些视频压缩国际标准中视频系统编码器的复杂性最主要取决于运动估计算法。实时的块匹配运动估计的VLSI实现需要考虑以下几个方面:在给定搜索域内运动搜索的复杂度;每次块匹配运算的匹配计算复杂度;每次块匹配运算需要从帧存读取到运动估计处理器的数据量大小;实时硬件实现的适用性.仿真表明BFM算法非常简单有效,可以大大降低相应的块匹配计算复杂度、匹配运算时数据传输时间.BFM函数便于并行实现,从而可以有效地缩短视频编码器的编码时间。本文还详细地给出了BFM函数与其它常用匹配准则函数的比较结果.     

一种基于H．264的有效运动估计算法

运动估计算法是实时视频编解码技术的研究重点，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．为降低在视频编码标准H．264中运动估计的高计算复杂度问题，提出了采用一种基于节点模型的可变形块匹配运动估计算法来搜索最佳运动矢量．该算法充分利用了H．264运动矢量的的统计特性和相关性，并采用基于像素差值分类的运动估计匹配准则．实验表明，在编码性能损失很小的条件下，该算法有效降低了视频压缩编码中运动估计的运算复杂度．     

一种改进的块匹配准则

块匹配算法是视频图像编码的核心技术。通过块匹配算法得到当前块和匹配块之间的残差和运动矢量,并对它们进行编码,从而大大提高了编码效率。在分析常用块匹配准则的基础上,提出一种改进的准则用于视频编码中的运动估计。相对于原始像素灰度值计算均方误差,同时在该准则中加入了一个反映灰度值变化符号的惩罚项。仿真实验表明该准则是有效的。     

基于量化系数均方误差准则的运动估计算法

提出了一种基于量化系数均方误差匹配准则的DCT域运动估计视频编码算法.算法中采用了一种新的运动估计匹配准则,该准则在DCT域内计算逆量化的残差均方误差值.由于该准则已考虑到量化噪声对运动残差能量的影响,因此与传统编码算法相比较,在图像质量基本不变的前提下码率更低.仿真结果显示,基于量化系数均方误差准则的DCT域运动估计算法具有较高的编码效率.     

一种多级运动估值VLSI结构的设计

提出了一种新的多级运动估值器的结构 ,它支持低比特视频编码器的高级预测模式 ,如H.2 63和 MPEG- 4。该 VLSI结构的所有级别中共用一个基本的搜索单元 ( BSU) ,减小了芯片尺寸。另外 ,由于它为计算 8× 8块的绝对误差和 SAD提供了一种对存储器数据流的控制电路 ,因此 ,对于高级预测模式 ,可同时获得 1个宏块运动矢量和每个宏块中的 4个子块运动矢量。这种尺寸较小的运动估值电路可以获得与全搜索块匹配算法 ( FSBMA)相似的编码效果     

一种改进的PDC块匹配运动估值算法

像素差分类（PDC）块匹配运动估值算法是一种考虑独立像素特征的运动估值算法，针对PDC算法的最优匹配不唯一的问题，本文提出了一种基于块运动最小相对位移约束的方法予以改进。本文还引入了双门限法以降低PDC算法的门限敏感性。实验表明本算法不仅克服了原算法的上述缺点，用于视频压缩编码时，还可使解码信噪比和主观质量有所改善。硬件实现的复杂性仅有很小的增加。     

极低码率视频编码中运动估值技术的研究

本文针对Ｈ．２６３编码系统块匹配运动估值技术中出现的一些影响图像质量和系统编码效率的问题,提出了一种新的宏块分区运动估算算法。计算模块实验表明,采用新的算法较好地提高系统编码效率和图像质量。     

基于运动矢量插值的运动补偿算法

本文首先研究了相关性约束运动估值算法,然后提出了基于运动矢量插值的运动估值算法,实验表明新算法的预测性能明显比传统块匹配运动估值算法(BMA)好,而且预测图象的主观质量得到显著改善。     

基于运动矢量插值的运动补偿算法

本文首先研究了相关性约束运动估值算法，然后提出了基于运动矢量插值的运动估值算法，实验表明新算法的预测性能明显一比传统块匹配运动估值算法（ＢＭＡ）好，而且预测图象的主观质量得到显著改善。     

Low bit-rate video coding using wavelet vector quantisation

A method for low bit-rate video coding based on wavelet vector quantisation is proposed. Motion estimation/compensation using overlapped block matching (OBM) is employed to eliminate the blocking effects in the prediction error introduced by conventional block matching. It is shown that OBM significantly increases the efficiency of the wavelet transform coder. The motion-compensated interframe prediction error is decomposed using a wavelet transform and a method is employed for the efficient coding of the wavelet coefficients. In this technique, the coefficients are coded with a zero-tree multistage lattice vector quantiser. Simulation results are provided to evaluate the coding performance of the described coding scheme for low bit-rate video coding. It provides constant bit rate, obviating the need for buffer, with just small fluctuations in PSNR. Moreover, comparison with the RM8 implementation of the standard H261 video coder shows that the presented codec provides improvements in both peak signal-to-noise ratio and picture quality     

视频编码中的块运动估计算法分析（一）

在视频压缩的一些国际标准，如Ｈ．２６１．Ｈ．２６３．ＭＰＥＧ１．ＭＰＥＧ２．ＨＤＴＶ中，视频系统编码器的复杂性最主要取决于运动估计。本文以ＭＰＥＧ２编码为例，通过计算机模拟实验，得出了一些常用运动估计算法的对比实验结果，以及常用的几种匹配函数时的对比实验结果。     

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     

VLSI Architecture of Block Matching Algorithms for Motion Estimation in High Efficiency Video Coding

High-efficiency video coding (HEVC) is a latest video coding standard and the motion estimation unit is the most important block. The work presents the different types of Matching Criteria for Block-Based Motion Estimation technique in HEVC standard. HEVC requires fast motion estimation algorithms to have better real time performance. The hardware implementation of motion estimation helps to achieve high speed though parallel processing. An improved block matching technique is designed with reduced blocks for HEVC. The proposed method has less execution time where only blocks having motion are compared for prediction computation. The searching time complexity is dependent on the number of blocks that are having motion. The searching time of frame having small motion can be reduced to 80–85% as compared to the traditional full search algorithm. In the paper, sum of absolute difference, mean square error and mean absolute difference are computed to find the best matching algorithm for HEVC. However, SAD has less computational complexity with compare to other matching criteria. The results suggest that proposed motion estimation algorithm has better performance with compare to similar previous work.

     

Predictive RD optimized motion estimation for very low bit-ratevideo coding

Predictive rate-distortion (RD) optimized motion estimation techniques are studied and developed for very low bit-rate video coding. Four types of predictors are studied: mean, weighted mean, median, and statistical mean. The weighted mean is obtained using conventional linear prediction techniques. The statistical mean is obtained using a finite-state machine modeling method based on dynamic vector quantization. By employing prediction, the motion vector search can then be constrained to a small area. The effective search area is reduced further by varying its size based on the local statistics of the motion field, through using a Lagrangian as the search matching measure and imposing probabilistic models during the search process. The proposed motion estimation techniques are analyzed within a simple DCT-based video coding framework, where an RD criterion is used for alternating among three coding modes for each 8×8 block: motion only, motion-compensated prediction and DCT, and intra-DCT. Experimental results indicate that our techniques yield very good computation-performance tradeoffs. When such techniques are applied to an RD optimized H.263 framework at very low bit rates, the resulting H.263 compliant video coder is shown to outperform the H.263 TMN5 coder in terms of compression performance and computations simultaneously     

A low-complexity region-based video coder using backwardmorphological motion field segmentation

We introduce a novel region-based video compression framework based on morphology to efficiently capture motion correspondences between consecutive frames in an image sequence. Our coder is built on the observation that the motion field associated with typical image sequences can be segmented into component motion subfield "clusters" associated with distinct objects or regions in the scene, and further, that these clusters can be efficiently captured using morphological operators in a "backward" framework that avoids the need to send region shape information. Region segmentation is performed directly on the motion field by introducing a small "core" for each cluster that captures the essential features of the cluster and reliably represents its motion behavior. Cluster matching is used in lieu of the conventional block matching methods of standard video coders to define a cluster motion representation paradigm. Furthermore, a region-based pel-recursive approach is applied to find the refinement motion field for each cluster and the cluster motion prediction error image is coded by a novel adaptive scalar quantization method. Experimental results reveal a 10-20% reduction in prediction error energy and 1-3 dB gain in the final reconstructed peak signal-to-noise ratio (PSNR) over the standard MPEG-1 coder at typical bit rates of 500 Kb/s to 1 Mb/s on standard test sequences, while also requiring lower computational complexity.     

An error detection and recovery algorithm for compressed videosignal using source level redundancy

The motion compensation-discrete cosine transform (MC-DCT) coding is an efficient compression technique for a digital video sequence. However, the compressed video signal is vulnerable to transmission errors over noisy channels. In this paper, we propose a robust video transmission algorithm, which protects the compressed video signal by inserting redundant information at the source level. The proposed algorithm encodes every lth frame in the semi-intra frame (S-frame) mode, in which the redundant parity-check DC coefficients (PDCs) are systematically inserted into the compressed bitstream. Then, the decoder is capable of recovering very severe transmission errors, such as loss of an entire frame, in addition to detecting the errors effectively without requesting any information from external devices. The proposed algorithm is implemented based on the H.263 coder, and tested intensively in realistic error prone environment. It is shown that the proposed algorithm provides much better objective and subjective performances than the conventional H.263 coder in the error prone environment.     

H.263: video coding for low-bit-rate communication

This article provides an overview of H.263, the new ITU-T Recommendation for low-bit-rate video communication. H.263 specifies a coded representation for compressing the moving picture component of audio-visual signals at low bit rates. The basic structure of the video source coding algorithm is taken from ITU-T Recommendation H.261 and is a hybrid of interpicture prediction to reduce temporal redundancy and transform coding of the prediction residual to reduce spatial redundancy. The source coder can operate on five standardized picture formats: sub-QCIF, QCIF, CIF, 4CIF, and 16CIF. The decoder has motion compensation capability with half-pixel precision, in contrast to H.261 which uses full-pixel precision and employs a loop filter. H.263 includes four negotiable coding options which provide improved coding efficiency: unrestricted motion vectors, syntax-based arithmetic coding, advanced prediction, and PB-frames     

Motion Estimation for Video Coding Standards

Motion-compensated estimation is an effective means in reducing the interframe correlation for image sequence coding. Therefore, it is adopted by the international video coding standards, ITU H.261, H.263, ISO MPEG-1 and MPEG-2. This paper provides a comprehensive survey of the motion estimation techniques that are pertinent to video coding standards.There are three popular groups of motion estimation methods: i) block matching methods, ii) differential (gradient) methods, and iii) Fourier methods. However, not all of them are suitable for the block-based motion compensation structure specified by the aforementioned standards. Our focus in this paper is to review those techniques that would fit into the standards. In addition to the basic operations of these techniques, issues discussed are their extensions, their performance limit, their relationships with each other, and the other advantages or disadvantages of these methods. At the end, an example of evaluating block matching algorithms from a system-level VLSI design viewpoint is provided.