AVS标准制定背景与知识产权状况

主要介绍AVS的开发背景、研制过程和知识产权状况.AVS用实践证明,在视频编码这样专利丛生的领域,采用主流技术路线制定自主标准仍然是可能的.AVS标准不仅是我国构建完整的数字音视频产业链的技术源头,也是全球范围内数字音视频产业发展的重要选择.     

视频编码中的块运动估计算法

在视频压缩的一些国际标准，如Ｈ．２６１，Ｈ．２６３，ＭＰＥＧ０－１，ＭＰＥＧ－２，ＨＤＴＶ中，视频系统编码器的复杂性最主要取决于运动估计。下文以ＭＰＥＧ－２编码器为例，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，以及采用常用的几种匹配函数的对比实验结果。     

Hybrid motion estimation scheme for secondary SP-frame coding using inter-frame correlation and FMO

To cope with considerable size of secondary SP-frames, quantized-transform domain motion estimation has recently been proved to be appropriate for the coding of secondary SP-frames in H.264/AVC. Nevertheless, its computational complexity is tremendous and there are still some situations that pixel-domain motion estimation can perform better. Both techniques are therefore not implemented solely in secondary SP-frame coding. In this paper, a hybrid scheme is proposed to effectively combine two existing motion estimation techniques. The combination is based on a new measurement of inter-frame correlation using the bit-counts of the macroblocks in SP-frames, so that the hybrid scheme is dominated by employing quantized-transform domain motion estimation in the macroblocks with weaker inter-frame correlation; otherwise, it approaches to pixel-domain motion estimation. With the further help of the explicit mode in Flexible Macroblock Ordering (FMO), the proposed hybrid scheme classifies MBs into two slice groups by examining the domain used in motion estimation prior to coding motion vectors in a secondary SP-frame. The slice structure of a secondary SP-frame using the explicit FMO mode is flexible and can be changed during the encoding of each new frame. Simulation results show that our proposed scheme overwhelmingly outperforms the quantized-transform domain motion estimation scheme. As a consequence, the size of secondary SP-frames can be reduced remarkably with significant computational reduction.     

Homography-based block motion estimation for video coding of PTZ cameras

Due to the constrained movement of pan-tilt-zoom (PTZ) cameras, two frames in the video sequences captured by such cameras can be geometrically related by a relationship (homography). This geometric relationship is helpful for reducing the spatial redundancy in video coding. In this paper, by exploiting the homography between two frames with optical flow tracking algorithm, we propose a novel homography-based search (HBS) algorithm for block motion estimation in coding the sequences captured by PTZ cameras. In addition, adaptive thresholds are adopted in our method to classify different kinds of blocks. Compared with other traditional fast algorithms, the proposed HBS algorithm is proved to be more efficient for the sequences captured by PTZ cameras. And compared to our previous work in ICME (Cui et al., 2011), which only deals with pan-tilt (PT) camera and calculates the homography with mechanical devices, in this extended work we compute the homography by using information on images instead.     

A new distortion measure for motion estimation in motion-compensated hybrid video coding

In the video coding standards MPEG-x and H.26x, a motion-compensated prediction technique is used for enhancing the coding performance of bitrate reduction or peak signal to noise ratio (PSNR) improvement. This technique takes advantage of the correlation between consecutive frames in the time domain, which is relatively higher than that between adjacent blocks in the spatial domain. In order to utilize the correlation between consecutive frames, the conventional video coding standards have used the motion estimation (ME) and compensation technique, where the Sum of the Absolute Differences (SAD) is usually used as the distortion measure. The ME estimates the reference block that could minimize the residual signal between the current and reference blocks. However, the SAD is not appropriate to the specific sequences that have global or local illumination changes. In addition, the high-resolution video sequences have higher spatial correlation than the low-resolution video sequences in general. Therefore, a new distortion measure that can consider spatial and temporal correlation simultaneously may be helpful to enhance the coding performance. The proposed distortion measure searches for a reference block that minimizes the motion-compensated residual signal when the DC-component is predicted. In our proposed algorithm, the maximum BD-rate improvement is up to 13.6% for illumination-changed video sequences, and the average BD-rate improvement is 6.6% for various high-resolution video sequences in the baseline profile.     

一种减少块匹配运动估值象素点的方法

在分析了块匹配运动估值模型的基础上，指同处于块中央的象素眯在块匹配时作用 小，最了一种减少块匹配运算象素的方法。不仅如此，提出的方法可与任一基于减少匹配次数的快速算法相结合，从而得到各种事型的块匹配快速算法。最后试验结果，提出了的方法是有效的。     

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.     

AVS熵解码与DSP实现

阐述了AVS标准的进展情况及AVS标准的特点,重点介绍了AVS熵解码的原理和采用Equator公司MAP-CABSP-15处理器中的协处理器(Vlx)实现AVS熵解码的方法.     

基于改进KNN算法的AVS到H.264/AVC 快速转码方法

尽管音视频编码标准(Audio and Video Coding Standard,AVS)的编码性能可以与H.264相媲美,但是H.264的应用范围更加广泛,因此视频由AVS标准转码成H.264标准具有很大的应用前景.目前,主流的转码方法是将AVS的分块模式与H.264的分块模式映射的方式降低转码复杂度,但是技术之间的差异导致这两种标准之间的分块模式并不是一一映射的关系,因此会导致编码效率大幅度降低.提出一种基于改进KNN(K最邻近节点)算法的AVS到H.264/AVC快速转码方法.充分利用了AVS码流中的各种信息,通过改进的KNN算法建立了中间信息和H.264分块模式之间的映射模型.根据AVS中运动矢量信息的差异自适应确定H.264可能的分块模式,实验结果表明上述问题得到有效解决,该算法在保证H.264编码效率的前提下大幅降低了转码复杂度.     

Video coding using fast geometry-adaptive partitioning and an elastic motion model

Effective motion-compensated prediction is the key to high-performance video coding. To ensure continuous improvement of video coders, emerging motion-compensation technologies will need to be successfully integrated into future standards. Higher order elastic motion models and geometry-adaptive block partitioning are such advanced techniques that are good candidates for integration into future generations of video coders. However, it is vital that these techniques are additive in performance, non-interfering and maintain justifiable complexity. In this paper, we propose an efficient block-partitioning scheme that incorporates both geometry-adaptive partitioning and an elastic motion model as extensions to the standard motion estimation procedure. Our experiments suggest that geometric partitioning in combination with the use of an elastic motion model can provide enhanced performance, although the increased complexity is of some concern for real-time applications.     

一种用于MPEG-4形状编码的快速运动估计算法

该文提出了一种用于MPEG-4形状编码的快速运动估计算法。该算法利用了形状编码及形状信息的固有特性,即基于上下文的运动估计特性、相邻二值alpha块的运动矢量相关性以及形状信息的二值特性。模拟结果表明,该算法具有运算量少、处理速度快的特点,适用于MPEG-4形状编码的实时软件实现。     

Multi-resolution motion estimation and compensation based on adjacent prediction of frame difference in wavelet domain

Aiming at the higher bit-rate occupation of motion vector encoding and more time load of full-searching strategies,a multi-resolution motion estimation and compensation algorithm based on adjacent prediction of frame difference was proposed.Differential motion detection was employed to image sequences and proper threshold was adopted to identify the connected region.Then the motion region was extracted to carry out motion estimation and motion compensation on it.The experiment results show that the encoding efficiency of motion vector is promoted,the complexity of motion es timation is reduced and the quality of the reconstruction image at the same bit-rate as Multi-Reso lution Motion Estimation (MRME) is improved.     

Fast motion estimation for H.264

Several specific features have been incorporated into Motion estimation (ME) in H.264 coding standard to improve its coding efficiency. However, they result in very high computational load. In this paper, a fast ME algorithm is proposed to reduce the computational complexity. First, a mode discriminant method is used to free the encoder from checking the small block size modes in homogeneous regions. Second, a condensed hierarchical block matching method and a spatial neighbor searching scheme are employed to find the best full-pixel motion vector. Finally, direction-based selection rule is utilized to reduce the searching range in sub-pixel ME process. Experimental results on commonly used QCIF and CIF format test sequences have shown that the proposed algorithm achieves a reduction of 88% ME process time on average, while incurring only 0.033 dB loss in PSNR and 0.50% increment on the total bit rate compared with that of exhaustive ME process, which is a default approach adopted in the JM reference software.     

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     

A low-power oriented architecture for H.264 variable block size motion estimation based on a resource sharing scheme

In the Advanced Video Coding (AVC) standard, motion estimation (ME) adopts many new features to increase the coding performances such as block matching algorithm (BMA), motion vector prediction (MVP) and variable block size motion estimation (VBSME). However, VBSME is utilized in the MPEG4-AVC/H.264 standard which leads to high computational complexity and data dependency that make the hardware implementation very complex.     

Contour simplification and motion compensated coding

In order to solve the bottleneck problem of region-based coding scheme, which is the contour coding, lossy methods are introduced in this paper for both 2D and 3D (2D plus time) contour image(s). A non-linear filter by means of majority operation is designed to act as contour simplification for both pre-processing and post-processing of contour coding. An average of 20% gain in contour coding cost is achieved by using this filter while the contour location error is controlled within one pixel width. Afterwards, an efficient contour motion estimation and compensated coding method are presented. In order to exploit the high temporal redundancy of the contour image sequence, motion estimation and compensation are applied to the correspondent label image sequence. First frame is directly coded by Chain-code method. All the following frames are coded in motion compensated mode. Meanwhile, a fast implementation of full search motion estimation algorithm is also described. This algorithm is 2R times faster than traditional method (R is the total regional number). Within each frame, labels are divided into foreground labels and background labels. Only the noticeable prediction errors for the foreground labels are coded. Morphological filters are used to clean the prediction errors of the foreground labels. An efficient prediction error coding algorithm is then introduced based on one-side Chain-code method. The reconstruction of foreground and background regions in the decoder side is also described. Experimental results have demonstrated good performance for very low bitrate video coding applications.     

A simple and efficient block motion estimation algorithm based on full-search array architecture

This paper first presents an array structure using ±1 full-search (FS) architecture as the search engine of block motion estimation which takes advantage of the design regularity of FS. An efficient algorithm named modified gradient-descent search (MGDS) is then introduced based on the proposed architecture. MGDS utilizes an adaptive computation distribution mechanism to efficiently allocate computation of the employed ±1 FS array to blocks or frames of video sequences. Experimental results indicate that MGDS uniformly achieves a higher quality than FS by an amount that is dependent on motion activities of sequences.     

AVS视频解码运动矢量预测模块的硬件设计

提出了一种适用于数字音视频编解码标准(AVS)的视频解码帧间运动矢量预测的解码方法,根据AVS宏块模式的特点,以统一的基本运算单元处理所有的解码模式,模块化流水计算,降低了硬件实现的复杂度。采用ASIC结构并使用Verilog语言进行设计、模拟,并成功通过了现场可编程门阵列验证。模块的每个功能块均为专用的VLSI结构,通过系统控制器控制各部分的运行,能有效地提高时钟频率,减小芯片的面积。使用0.18μmCMOS工艺库综合,在50MHz的时钟频率下工作时电路规模仅需1.6万门左右。     

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。     

Novel two-layer motion estimation for video coding

In this paper,we proposed a novel Two-layer Motion Estimation （TME） which searches motion vectors on two layers with partial distortion measures in order to reduce the overwhelming computational complexity of Motion Estimation （ME） in video coding.A layer is an image which is derived from the reference frame such that the sum of a block of pixels in the reference frame determines the point of a layer.It has been noticed on different video sequences that many motion vectors on the layers are the same as those searched on the reference frame.The proposed TME performs a coarse search on the first layer to identify the small region in which the best candidate block is likely to be positioned and then perform local refined search on the next layer to pick the best candidate block in the located small area.The key feature of TME is its flexibility of mixing with any fast search algorithm.Experimental results on a wide variety of video sequences show that the proposed algorithm has achieved both fast speed and good motion prediction quality when compared to well known as well as the state-of-the-art fast block matching algorithms.