H.264的帧间宏块模式选择算法

H.264中定义了7种不同大小的帧间宏块模式,为了提高编码效率,编码时对每一种宏块模式都进行运动搜索,并利用率失真优化(RDO)分别计算编码代价,选择编码代价最小的模式作为帧间编码模式,但是计算量非常大,导致运动估计速度缓慢,很难实现实时编码。本文提出一种选择宏块模式的快速算法,通过宏块模式编码代价的比较,提前确定宏块模式,从而逐步减少不必要的宏块搜索和RDO计算。实验结果表明,此方法与全宏块模式搜索相比较,图像质量和码流只有少量变化,而编码速度有显著提高。     

自适应简单菱形六边形运动估计搜索算法

针对H.264的特点,提出一种快速块匹配搜索算法.该算法充分利用宏块编码模式间的关联特性和运动矢量的统计特征来降低块匹配搜索复杂度。仿真结果表明,该算法在不改变重建图像质量的条件下,大幅度减少了搜索点数,提高了搜索效率,而且避免了DS算法可能陷入局部最佳点的弊端。     

H.264的帧间宏块模式选择算法

H.264中定义了7种不同大小的帧间宏块模式，为了提高编码效率，编码时对每一种宏块模式都进行运动搜索，并利用率失真优化（RDO）分别计算编码代价，选择编码代价最小的模式作为帧间编码模式，但是计算量非常大，导致运动估计速度缓慢，很难实现实时编码。本文提出一种选择宏块模式的快速算法，通过宏块模式编码代价的比较，提前确定宏块模式，从而逐步减少不必要的宏块搜索和RDO计算。实验结果表明，此方法与全宏块模式搜索相比较，图像质量和码流只有少量变化，而编码速度显著提高。     

基于分裂聚合块模式选择的运动估计算法

为了简化H.264视频压缩编码标准中庞大的计算量,提出了一种基于分裂聚合块模式选择的运动估计算法.该算法结合H.264标准7种可变块尺寸模式,利用分裂聚合原理,为帧间运动估计提前确定块模式.保证在图像质量允许的前提下,提高编码效率,为各种多媒体需求的广泛应用奠定基础.     

H.264中的基于全零块检测的运动搜索方法

运动搜索和变换域编码是视频编码标准H.264中运算量很大的部分,为了减少视频编码的运算量,本文根据H.264运动搜索和整数变换的特征,提出了一种H.264下的全零块检测方法。在帧间编码中,该方法在运动搜索中和变换前,对运动补偿的差值数据进行全零检测,检测的门限根据绝对误差和(SAD)和量化参数而定。在运动搜索非常准确时,就可以找到全零块,就停止搜索,可以省却后面的搜索运算和全零块的整数变换以及相应的量化运算,在基本保持H.264原有编码算法的图像质量的同时,减少了运算量,缩短了码流,提高了编码器的编码效率。     

基于H.264的宏块类型空域预测研究

从实验统计数据,论证了宏块类型空域预测的可行性.在此基础上,设定严格的评判准则,提出了对当前宏块的编码类型空域预测方案,并且在H.264测试模型JM7.6上实现了该方案,模拟实验表明:采用了宏块类型空域预测的宏块编码算法,减少了H.264标准算法的无效遍历,在编码效率和图像质量不损的前提下,图像编码时间显著缩短.     

基于块截断编码和运动补偿的纯软件视频编解码算法

本文报告了一种新的纯软件视频编解码算法.利用改进的块截断编码和基于一步预测运动估计的运动补偿技术,该算法能够在现有的普通PC机上实时实现全彩色视频电话图像序列的编解码,比特率小于100 Kbps.与已有的其他同类算法相比,本文的算法在保持实时性的前提下,比特率大大下降,图像质量明显提高.     

一种改进的H.264运动估计算法

为了减少视频编码的运算量,针对运动估计的特点．提出了快速块模式选择算法。该算法利用宏块的时间和空间相关性,预先对宏块模式进行判定,从而使模式选择过程大大简化。仿真结果显示,在基本保持H．264原有编码算法的图像质量的同时,可以将编码速度提高15％以上。因此,本算法可以有效的减少编码器的计算量,提高H．264的编码效率。     

活动图像的运动平滑补偿法

本文提出了一种新的运动矢量估计和平均补偿算法。该算法的特点是利用四组匹配块对预测帧进行平滑处理。处理的结果表明，本算法可以有效地消除块效应，提高图像质量，特别是主观评价质量。     

基于跳点菱形搜索的快速运动估计算法

实时视频编码系统要求运动估计的搜索算法既快又准，现行的菱形搜索算法是公认的效率较高的算法之一。利用图像像素间的相关性，提出了一种“跳点”菱形搜索，进一步减少菱形搜索的点数和时间，而重建的图像质量跟原来的菱形算法相当。     

Motion estimation in low-delay hierarchical p-frame coding using motion vector composition

Low-delay hierarchical prediction structure is currently adopted in various new video coding standards. The only hurdle of this structure is the need of motion estimation in distant reference frames. To maintain high coding efficiency, a large search range for motion estimation can improve the coding efficiency in distant reference pictures. Computational complexity will thus be increased dramatically. In this paper, a fast motion estimation scheme for a low-delay hierarchical P-frame structure is proposed. The proposed scheme adopts a motion vector composition strategy to expedite the motion estimation process for distant reference frames in the hierarchical P structure. In addition, a motion vector composition algorithm is tailor-made with the proposed hierarchical P coding scheme to further improve the coding efficiency. Simulation results show that the proposed scheme can deliver a remarkable complexity savings and coding efficiency improvement on coding a frame in low temporal layers of the hierarchical P structure.     

H.264帧间预测编码块匹配模式的研究

H.264是一种适应于低码率传输的新一代视频压缩标准,在其编码技术中,运动估计是提高编码效率的关键。通过分析H.264编码过程,针对多模式的块匹配运动估计计算量巨大这一问题提出改进措施,并应用软件进行实验仿真。结果表明:在保证图像质量的情况下,降低了运算的复杂度,提高编码效率。     

Selective VS-MRF-ME and intra coding in H.264 based on spatiotemporal continuity of motion field

The new video coding standard, H.264 uses variable size motion estimation (VS-ME), multiple reference frame motion estimation (MRF-ME) and spatial-based intra prediction with selectable block size in inter frame coding. These tools have achieved significant coding efficiency compared to coding a macroblock (MB) only based on motion-compensation in regular size with single reference frame. However, these new features also give rise to an exhaustive computation in the coding procedure since there are so many combinations of coding modes and reference frames to be tried. In this paper, a fast motion estimation algorithm based on the selective VS-MRF-ME and intra prediction is proposed to reduce H.264 coding computational complexity. The basic idea of the method is to utilize the spatiotemporal property of motion field in predicting where VS-MRF-ME and intra prediction are needed, and only in these regions VS-MRF-ME and intra coding are enabled. The motion field is generated by motion vectors from 16×16 motion estimation on the nearest reference frame. Simulation results show that the proposed algorithm can save 50% computational complexity on average, with negligible loss of coding efficiency.     

Fast multi-frame motion estimation for H264/AVC system

Advanced video compression standard, H264/AVC, with multi-frame motion estimation, can offer better motion-compensation than the previous coding standards. However, the implementation of real-time multi-frame estimation for an H264/AVC system is difficult due to heavy computations. In this paper, a fast algorithm is proposed in an effort to reduce the searching computation for motion estimation with five reference frames. The fast multi-frame motion estimation consists of the adaptive full-search, three-step search, and diamond search methods using the content adaptive control process. Efficient control flow is proposed to select the searching algorithm dependent on video features. The adaptive algorithm can achieve better rate-distortion and lower computation for H264/AVC coding. The experiments indicate that the speed-up is 6–15 times compared with the full search method, while the image quality slightly degrades.     

一种空间域Wyner-Ziv视频编码系统的性能改进算法

分布式视频编码是建立在Slepian-Wolf和Wyner-Ziv信息编码理论基础上的全新视频编码框架,具有编码复杂度低,编码效率较高,抗误码性能好的特点.本文首先简单介绍了一种典型的分布式视频编码实现方案——空间域Wyner-Ziv视频编码,随后提出一种空间域Wyner-Ziv视频编码系统的性能改进算法,该算法在不增加编码复杂度的基础上,在解码端利用双向运动估计预测获取更高质量的边信息,同时采用基于Huber-Markov随机场约束的联合迭代解码算法重建图像.实验结果表明,在相同的输出码流情况下,本文改进算法在解码端重建图像的峰值信噪比与空间域Wyner-Ziv视频编码算法相比平均提高2dB,并且主观效果有所改善.     

A hybrid model-based image coding system for very low bit-ratecoding

This paper proposes a two-stage global motion estimation method and a hybrid coding algorithm for the model-based coding. In the first stage, global motion is estimated by the feature-based algorithm. The estimated result is further refined by the gradient method. The two-stage estimation algorithm is performed hierarchically to remove the influence of the local facial expression. In the estimation process, we also utilize the steerable pyramid to improve accuracy. The facial expression region is coded by the clip-and-paste method, and is predicted by a classified prototype coding technique. The prototype coding technique can greatly improve the coding efficiency for the facial expression. The areas, which are difficult to be described by generic models, are encoded by the proposed hierarchical motion segmentation algorithm. We segment the image to different moving areas which can be modeled by affine models in a split-and-merge manner. The segmented results with the estimated affine models can give good prediction for the unmodeled regions. Computer simulation results show that the proposed complete model-based coding scheme gives very good performance in terms of peak signal-to-noise ratio and compression ratio     

An improvement to MBASIC algorithm for 3-D motion and depthestimation

In model-based coding of facial images, the accuracy of motion and depth parameter estimates strongly affects the coding efficiency. MBASIC (model-based analysis-synthesis image coding) is a simple and effective iterative algorithm recently proposed by Aizawa et el. (see Signal Processing: Image Communication, no.1, p.139-52, 1989) for 3-D motion and depth estimation when the initial depth estimates are relatively accurate. In this correspondence, we analyze its performance in the presence of errors in the initial depth estimates and propose a modification to MBASIC algorithm that significantly improves its robustness to random errors with only a small increase in the computational load.     

Selective Disparity Estimation and Variable Size Motion Estimation Based on Motion Homogeneity for Multi-View Coding

Multi-view video coding (MVC) is an ongoing standard in which variable size disparity estimation (DE) and motion estimation (ME) are both employed to select the best coding mode for each macroblock (MB). This technique achieves the highest possible coding efficiency, but it results in extremely large encoding time which obstructs it from practical use. In this paper, a fast DE and ME algorithm based on motion homogeneity is proposed to reduce MVC computational complexity. The basic idea of the method is to utilize the spatial property of motion field in prediction where DE and variable size ME are needed, and only in these regions DE and variable size ME are enabled. The motion field is generated by the corresponding motion vectors (MVs) in spatial window. Simulation results show that the proposed algorithm can save 63% average computational complexity, with negligible loss of coding efficiency.      

Just noticeable distortion model and its applications in video coding

We explore a new perceptually-adaptive video coding (PVC) scheme for hybrid video compression, in order to achieve better perceptual coding quality and operational efficiency. A new just noticeable distortion (JND) estimator for color video is first devised in the image domain. How to efficiently integrate masking effects together is a key issue of JND modelling. We integrate spatial masking factors with the nonlinear additivity model for masking (NAMM). The JND estimator applies to all color components and accounts for the compound impact of luminance masking, texture masking and temporal masking. Extensive subjective viewing confirms that it is capable of determining a more accurate visibility threshold that is close to the actual JND bound in human eyes. Secondly, the image-domain JND profile is incorporated into hybrid video encoding via the JND-adaptive motion estimation and residue filtering process. The scheme works with any prevalent video coding standards and various motion estimation strategies. To demonstrate the effectiveness of the proposed scheme, it has been implemented in the MPEG-2 TM5 coder and demonstrated to achieve average improvement of over 18% in motion estimation efficiency, 0.6 dB in average peak signal-to perceptual-noise ratio (PSPNR) and most remarkably, 0.17 dB in the objective coding quality measure (PSNR) on average. Theoretical explanation is presented for the improvement on the objective coding quality measure. With the JND-based motion estimation and residue filtering process, hybrid video encoding can be more efficient and the use of bits is optimized for visual quality.