一种基于小波和MP变换的细粒度视频编码算法

针对目前的细粒度算法的计算复杂度大(如Matching Pursuit编码，简称MP编码)或者视频质量有各种效应(如离散小波变换编码DWT)的缺点，提出了一种基于小波变换和MP变换联合的细粒度视频编码算法。对连续的8帧视频采用一维小波变换，然后对变换后第1帧低频图像用二维小波变换，其它7帧高频图像信息采用MP变换编码，并采用基于能量的原子搜索与基于人眼视觉特性的分配策略。实验表明，该细粒度算法对帧间运动较小的视频应用，有较高的恢复质量。     

基于H．264的立体视频右图像整帧丢失错误隐藏算法

当H．264编码立体视频流在Internet上传输时，由于信道错误所引起的数据丢失常常会造成整帧图像的丢失。为了恢复丢失的整帧立体视频右图像，提出了一种基于H．264的立体视频右图像整帧丢失错误隐藏算法，该算法依据立体视频编码特点进行相关性分析，首先确定丢失帧中每个宏块的预测方式，然后采用运动补偿或视差补偿对其进行恢复，进而重现丢失帧。实验结果表明，该算法能够在较低的计算复杂度下，获得较高质量的立体视频图像。     

一种基于冗余小波变换的快速运动估计算法

由于冗余小波变换克服了离散小波变换的移变性,在冗余小波域进行运动估计可以达到很好的效果,其缺点是算法的时间复杂度过高。在分析视频序列的运动特性和已有的运动估计算法的基础上,提出一种快速的基于冗余小波变换的运动估计算法。在冗余小波域提取潜在运动区域并对图像块的运动剧烈程度进行划分,在此基础上对不同类型的图像块采取不同的搜索策略,从而减少了运动估计中不必要的搜索。实验结果表明,该方法较经典的基于冗余小波变换的运动估计算法在时间复杂度方面具有优势。     

适合网络传输的鲁棒小波低比特率视频编码

提出了一种适合包交换网络传输的基于离散小波变换的视频编码方案,通过对SPIHT小波系数编码算法进行复杂度降低、纹理分割等修改,来适应视频编码在编码效率和鲁棒性方面的要求,为解决网络数据包丢失造成的帧质量骤降,方案对数据包的重要性进行了均衡,每一个数据包中均包含帧内信息和帧间信息,利用改进的SPIHT算法生成混合比特流。试验表明,该方案运算复杂度低,对网络传输中的包丢失不敏感,并且能很好地抑制错误传播。     

结合H.263与SLCCA的新的极低比特率小波视频编码

小波对于静止图像编码取得了巨大成功,但对于视频编码只有少数较为成功的尝试,提出一种针对极低比特率应用的新的结合H.263与SLCCA的混合小波视频编码算法,在提出的算法中,首先,用基于H.263的微调运动估计减少时间冗余,用无遗漏覆盖块运动补偿保证运动补偿误差帧的连续性;第2,对运动补偿误差帧进行小波变换得到全局能量压缩;第3,用SLCCA组织和表示小波变换后的数据;最后,运动向量的水平和垂直分量分别用自适应算法编码,算法在A级测试序列Akiyo和B级测试序列Foreman（QCIF）上测试取得了良好效果。     

一种基于块匹配的运动估计改进算法

运动估计是视频压缩中帧间预测编码的关键技术之一,在各个压缩标准中都广泛使用了基于块的运动估计技术。由于运动估计通常具有较大的运算量,因此对压缩性能具有重要的影响。本文在分析了现有的六边形搜索算法(HEXBS)和视频序列图像帧相邻空间块和对应的运动向量具有高度空间相关性的基础上提出了一种改进的快速运动估计搜索算法,通过实验表明与HEXBS算法具有相似的计算复杂度,但是视频编码质量优于HEXBS算法。     

H.264/AVC中基于决策树的P帧快速模式选择

目的 H.264/AVC帧间预测编码需要对所有可能编码模式计算并比较率失真代价,众多的模式类型导致了P帧编码的计算复杂度非常高。为此提出一种针对P帧的基于决策树的快速候选模式选择算法。方法在对宏块进行16×16的帧间运动估计后,首先根据残差宏块中4×4全零系数块个数对部分宏块直接选择出候选模式;然后使用16个4×4块的变换域系数绝对值之和(SATD)值,采用决策树分类方法对其余宏块选择候选模式。结果由于只需对候选模式进行编码,因此有效降低了编码器的计算复杂度。实验结果表明,与原始全搜索编码算法相比,该算法对不同运动程度的视频序列获得了较一致的编码时间的节省,同时平均峰值信噪比的损失和平均比特率的增加均较少。结论新的P帧帧间预测候选模式选择算法,根据帧间运动估计后的残差宏块信息,采用决策树方法对候选模式集进行分类。实验结果表明,该算法能在保证视频编码质量的前提下,有效地降低编码过程中的计算量,缩短编码时间。     

基于双边信息的分布式视频压缩感知模型研究

针对传统视频编码技术计算量大和复杂度高的缺点,提出一种基于双边信息的分布式视频压缩感知算法。该算法将压缩感知技术与分布式视频编码技术相结合,把视频序列分为Key帧和CS帧,Key帧运用传统的帧内编码和解码,CS帧编码端运用压缩感知编码,解码端运用视频块内与视频块间的双边信息和梯度投影算法进行优化重构。通过双边信息的运动估计和压缩编码器的设计,实现基于双边信息的分布式视频压缩感知模型的构建。仿真结果表明该模型既可以实现高效编码,又可以实现复杂度由编码端向解码端转移,在较低的采样率下,提高视频的压缩能力和传输速度。     

一种新的基于三维小波变换的序列图像编码算法

介绍了由时间轴一维与帧内二维组合而成的准三维小波变换结合运动补偿的编码器结构，并针对运动变化较缓慢的序列图像，观察实验数据特点，提出了改进零树编码与像素点编码相结合的编码策略。计算机仿真实验证明，采用该方法，可有效降低计算复杂度，提高执行效率，同时在压缩比达到400∶1时，图像恢复质量仍在29dB 以上。     

H.266/VVC中一种改进的仿射运动估计算法

通用视频编码标准H.266/VVC通过引入多种新的编码技术,如仿射运动补偿预测、自适应运动矢量精度、多核变换等,以支持360°视频和HDR视频的编解码,从而为用户提供最优的视频质量,但是在H.266/VVC帧间预测过程中,仿射运动估计计算复杂度高导致编码时间显著增加。针对该问题,提出一种改进的仿射运动估计算法。通过对仿射高级矢量预测（AAMVP）候选列表的构建过程进行改进,并构建一种AAMVP候选列表候选项筛选准则,使得列表的候选项更接近编码块真实的运动矢量,从而缩短编码时间。同时对仿射运动估计中迭代搜索最优仿射运动矢量的迭代过程进行优化,以加快迭代搜索速度。实验结果表明,在低时延的编码器配置下,相比VVC原始算法,当BD-BR增加了0.023%时,该算法的总体编码时间平均缩短13%,在保证编码质量的前提下能够有效降低编码的计算复杂度。     

基于提升小波变换和DCT的彩色视频水印算法

针对数字视频的版权保护应用,提出了一种混合提升小波变换和DCT的视频水印算法。该算法先对水印进行混沌加密和Arnold置乱处理,借助密钥选取r帧彩色视频并将每帧视频的每一分量进行互不重叠的8×8分块,对选取的分块进行1级提升小波变换,并对低频子带进行DCT变换,以视频帧的纹理和运动特性自适应地确定量化步长的抖动调制方式嵌入水印,水印提取时无须原始视频的参与。实验表明,该算法实现简单,具有良好的透明性和鲁棒性,与其他算法相比,该算法具有更好的性能。     

Multiresolution video object extraction fitted to scalable wavelet-based object coding

To enable content based functionalities in video processing algorithms, decomposition of scenes into semantic objects is necessary. A semi-automatic Markov random field based multiresolution algorithm is presented for video object extraction in a complex scene. In the first frame, spatial segmentation and user intervention determine objects of interest. The specified objects are subsequently tracked in successive frames and newly appeared objects/regions are also detected. The video object extraction algorithm includes discrete wavelet transform decomposition multiresolution Markov random field (MRF)-based spatial segmentation with emphasis on border smoothness at different resolutions, and an MRF-based backward region classification that determines the tracked objects in the scene. Finally, a motion constraint, embedded in the region classifier, determines the newly appeared objects/regions and completes the proposed algorithm towards an efficient video segmentation algorithm. The results are applicable for generic segmentation applications, however the proposed multiresolution video segmentation algorithm supports scalable object-based wavelet coding in particular. Moreover, compared to traditional object extraction algorithms, it produces smoother and more visually pleasing shape masks at different resolutions. The proposed effective multiresolution video object extraction method allows for larger motion, better noise tolerance and less computational complexity     

基于运动估计与回溯自适应正交匹配追踪的视频压缩传感

为了解决传统视频压缩传感方法中对视频逐帧单独重构所产生的图像模糊,将压缩传感理论与MPEG标准视频编码的相关技术相结合,提出了一种基于运动估计与运动补偿的视频压缩传感方法,以消除视频信号在空域和时域上的冗余。该方法在充分考虑视频序列时域相关性的同时,首先对视频图像进行前、后向和双向预测和补偿,然后采用回溯自适应正交匹配追踪(BAOMP)算法,对运动预测残差进行重构,最后实现当前帧的重构。实验结果表明,该方法较逐帧重构的视频图像质量有较大改善,且可获得更高的峰值信噪比。     

基于非抽样小波字典的低速率视频编码

目前,大多数视频编码器所采用的核心编码技术都是基于分块DCT(discreted cosine transform)变换对帧预测误差进行编码,在极低编码速率下,这类编码器往往会产生人眼敏感的方块效应.而基于匹配跟踪冗余信号分解的视频编码器具有比H.263编码器更高的编码性能,但由于该算法需要在一个冗余字典里搜索最佳匹配误差结构的原子函数,其实现所需要的运算量比传统的编码器要高很多,因此影响了这种编码器的效率.提出了基于树形结构的非抽样小波字典的匹配跟踪算法,能够充分利用字典函数之间存在的滤波结构关系,使得整个算法实现的计算量显著下降.同时,考虑到相邻帧运动信息的连续性,最后还给出一种基于晶格结构的有效原子位置信息编码方法.实验结果表明,该算法保持了原有的编码性能,在视频编码应用中具有很好的实用价值.     

基于音频特征和低频系数较小值的水印算法

提出一种基于音频特征和DWT低频系数相对较小值的数字水印算法。分析音频帧的过零率及短时能量,选取适当的阈值初步舍弃表明信号中高频信号成分的音频帧,筛选出待处理的音频帧。将选定的音频帧拼接在一起进行小波变换,选取低频系数并分段,通过相邻3个水印比特组合的二进制之和确定水印在该段中的嵌入位置,将系数修改为相邻系数中较小的值。实验结果表明,该算法通过对音频特征的分析,能降低提取低频分量的时间复杂度,实现水印信息的盲检测,提高水印的鲁棒性。     

Video scene analysis in 3D wavelet transform domain

This paper proposes a novel scene analysis algorithm based on three-dimensional discrete wavelet transform (3D DWT). Based on the correlation among the adjacent frames, video frames can be considered as four categories: abrupt scene transition, motion scene, gradual scene transition and static scene, which are ranked from low to high according to the strength of the correlation. Through the investigation of the particular temporal and spatial distribution of each category, the correlation among adjacent frames could be described by the 3D DWT coefficients related statistical features, which are the energy of high-frequency coefficients difference, the sum of high-frequency coefficients magnitudes and the difference of low-frequency coefficients magnitudes. The energy of high-frequency coefficients difference is first used to detect the abrupt scene transition including cut and flashlight. Then all the three features are input to SVM for the purpose of analyzing the residual scenes and detecting the gradual scene transition, such as dissolve and fade. Experimental results show the method to be effective not only for the abrupt scene transition detection, but also for the gradual scene transition detection.     

A Very Low Bit Rate Video Coding Combined with Fast Adaptive Block Size Motion Estimation and Nonuniform Scalar Quantization Multiwavelet Transform

We describe a very low bit rate video coding framework in which motion correlation between successive video frames is exploited in the multiwavelet transform domain. Some complicated techniques, such as spatial prediction in intra coding, adaptive block size motion estimation, more than one previous frames for prediction in inter frames, and content adaptive binary arithmetic coding (CABAC) are used in H.26L standard. The testing results show that H.26L can greatly outperform MPEG-4 ASP in both PSNR and visual quality. However, the encoding of H.26L costs too much time for it is complex to use fast motion search in adaptive block size motion estimation, and CABAC needs much time to generate the code list for entropy coding. Whereas, only four types of symbol are generated after zero tree wavelet coding so that the entropy coding can cost less time than CABAC. Moreover, if we select 8× 8 sized block as a basic mode, which can be united into the large size mode if neighbored 8× 8 sized blocks have same reference frame and motion vector, then the fast motion estimation can be feasible. Accordingly, a fast motion search algorithm, multiwavelet transform, and a novel adaptive quantization schemer are applied to the proposed coding frame. Experimental results reveal 0.2–0.5 dB increase in coded PSNR at low bit rates over the state-of-the-art H.26L recommendation, and similar improvements over MPEG-4 at high bit rates, with a considerable improvement in subjective reconstruction quality, while simultaneously supporting a scalable representation.Jiazhong Chen was born in 1970. He received the M.S. degree in computation mathematics in 1999 and Ph.D. degree in computer system architecture in 2003 from HUST. He is now a lecturer at School of Computer science and technology of HUST. His main research interests include signal processing and wavelet analysis, image and video coding.Jingli Zhou was born in 1946. She received the B.E. degree in 1969. She is a Professor and doctor advisor at university of science and technology. She had been a visiting scholar in USA from 1995 to 1996 and has been honor of the State Department Special Allowance since 1999. Her main field of research: computer network and multimedia signal processing.Shengsheng Yu was born in 1944. Received the B.E. degree in 1967. He is a Professor and doctor advisor at university of science and technology. He had been a visiting scholar in west Germany from 1982 to 1983. His main field of research: computer network and storage, discrete signal processing and communication.Jun Xu was born in 1981. He received the B.S. degree from HUST, Wuhan, P. R. China, in 2003. He is now pursuing his M.S. degree in the School of Computer Science and Technology of HUST. His research interests are wavelet analysis, image compression and video processing and communications.