基于RDWT-子带运动补偿的可扩展视频编码方法

随着技术的发展，视频编码方法要求的不再仅是压缩效率，还包括码流的可扩展性．本文提出了一种基于RDWT-子带运动补偿的可扩展视频编码方法．首先对输入帧组进行空域DWT分解，在其后集成运动补偿过程的时域分解步骤中，使用冗余离散小波变换（RDWT）分解得到的各相位子带作为候选，选取一个最佳相位子带作为预测，提高运动补偿效率；在编码阶段，提出基于子带扫描顺序的改进3DSPIHT技术，保障码流的扩展特性．实验表明，所提出的方法获得较高编码效率的同时，提供了码流的高度可扩展特性。     

一种基于小波域规则三角形网格运动补偿的可扩展视频编码方法

可扩展视频编码是指已编码码流在解码端能够进行部分解码,且重构图像的质量与接收到的信息量成比例变化,同时空域分辨率和时域分辨率可以根据解码端的要求改变。为了提供小波编码视频码流的高度可扩展性,提出了一种基于小波域规则三角形网格运动补偿的可扩展视频编码方法。该方法首先对参考帧使用冗余离散小波变换(RDWT)进行分解,并在RDWT小波域使用网格运动模型进行运动补偿,以提高运动补偿效率;其次在编码阶段则采用基于子带扫描顺序的改进SPIHT技术来保障码流的可扩展特性。实验表明,该方法在获得较高编码效率的同时,还提供了码流的高度可扩展特性。     

一种小波域三角形网格运动补偿方法

提出一种小波域三角形网格运动补偿方法（WDTM—MC）．在参考帧的冗余离散变换小波域中进行网格节点的选择,节点数目根据图像运动剧烈程度进行调整．构建的Delaunay三角形网格节点的前向追踪过程隐含实现运动估计．WDTM—MC方法利用RDWT域的空间位置不变特性、三角形网格映射对多种运动模型的适应性以及多预测模式提高运动补偿的效率．实验表明,所提出的方法能够提高运动补偿的效率．     

可扩展视频编码中运动补偿时域滤波的改进

在基于小波变换的可扩展视频编码方案中,研究运动补偿时域滤波的优化方法.将有效的多相位子带内运动估计纳入分层运动估计策略中,用提升算法实现子带内运动补偿时域滤波,融入多假设预测以优化运动补偿技术;为了提高低码率下视频编码的可扩展性,提出更新算子的优化设计.实验结果显示,在保证运动估计精度下,合理选择时间滤波器,结合改善的提升实现中的更新操作,提高了编码系统的编码效率和可扩展性能.     

基于变换域Wyner-Ziv视频编码的相关噪声模型

在Wyner-Ziv(WZ)视频编码中,原始WZ帧数据和边信息(Side information,SI)间相关噪声模型是影响缡码效率的关键因素.现有文献通常认为边信息和当前解码WZ帧的概率分布近似符合零均值拉普拉斯分布.本文详细研究了变换域WE帧与相应边信息的残差系数的分布关系,发现其残差变换后直流系数带统计分布相比零均值拉普拉斯分布存在一定偏差,且系数带的相关噪声分布随时间和空间变换.根据变换域残差系数的分布特征,提出了一种基于变换域的相关噪声分布模型及自适应参数估计算法,利用帧内插时前向和后向运动补偿帧变换残差,在解码端估计系数带的分布参数.实验结果表明该算法有效提高了WZ视频编码的编码效率.     

分布式小波视频编码自适应嵌套量化模型

提出一种分布式小波视频编码自适应嵌套量化模型,对Wyner-Ziv帧做小波变换,利用Slepian—Wolf编码器对低频子带系数进行量化,采用SPIHT编码器对高频子带系数进行编码,通过分析Wyner—Ziv帧低频子带系数与参考帧低频子带系数的残差自适应度,判定Wyner-Ziv帧低频子带系数的量化步长,从而使运动剧烈的视频序列有较大的量化步长,而运动平缓序列的量化步长较小。实验结果表明,采用该模型能获得较好的编码效果。     

基于残差分布特性的运动补偿算法

视频编码中离散余弦变换(DCT)对自然图像有很好的去相关性，而对运动残差的去相关性较差。针对DCT对残差编码效率较低的缺陷，该文提出一种基于残差分布特性的运动补偿算法，即将残差中所有非零量化DCT系数分为I/P系数，针对不同类型的DCT系数进行分类(帧内或帧间)运动补偿。在MPEG4的编码质量对比实验中，推荐算法比标准算法提高了2 dB以上，从而表明推荐算法能有效地提高运动残差的编码效率。     

小波视频编码中运动补偿技术研究进展

近年来小波视频编码技术在快速发展，作为视频编码核心步骤的运动补偿技术更是受到了高度重视．许多用于提高编码效率和提供新功能的观点和方法被提出．在介绍小波视频编码技术特点和基本方法的基础上，着重介绍了运动补偿技术在时域和小波域实现的最新进展，并对发展趋势进行了展望．     

基于小波域的视频压缩编码MRME算法的研究

小波变换将视频帧分解为一系列的不同频带的子图像,在该方法中,高分辨率的运动矢量由低分辨率的运动矢量预测,并且在每一步都要进行矢量修正.为了进一步提高运动补偿的效率,提出了一种只对运动区域进行运动补偿的多分辨率运动补偿(MRME)算法,根据当前帧和参考帧小波系数,运动区域由自适应的运动检测算法得到,实验结果表明,这种方法在运算时间、信噪比和码长度方面都得到了令人满意的结果.     

用于视频编码的小波域三角形网格构造方法

在深入研究视频图像冗余离散变换特征的基础上,提出一种用于视频编码运动补偿技术的小波域不规则三角形网格构造方法．基于孔径问题的原理,使用冗余离散变换小波的水平和垂直子带构造三角形网格节点的选择判据,把节点的特征匹配度集成到节点前向追踪过程的判据中;通过获得的节点运动矢量和网格映射实现运动补偿功能．实验证明,该方法获得了较好运动补偿的效果．     

Multiresolution,perceptual and vector quantization based video codec

This paper presents a novel Multiresolution, Perceptual and Vector Quantization (MPVQ) based video coding scheme. In the intra-frame mode of operation, a wavelet transform is applied to the input frame and decorrelates it into its frequency subbands. The coefficients in each detail subband are pixel quantized using a uniform quantization factor divided by the perceptual weighting factor of that subband. The quantized coefficients are finally coded using a quadtree-coding algorithm. Perceptual weights are specifically calculated for the centre of each detail subband. In the inter-frame mode of operation, a Displaced Frame Difference (DFD) is first generated using an overlapped block motion estimation/compensation technique. A wavelet transform is then applied on the DFD and converts it into its frequency subbands. The detail subbands are finally vector quantized using an Adaptive Vector Quantization (AVQ) scheme. To evaluate the performance of the proposed codec, the proposed codec and the adaptive subband vector quantization coding scheme (ASVQ), which has been shown to outperform H.263 at all bitrates, were applied to six test sequences. Experimental results indicate that the proposed codec outperforms the ASVQ subjectively and objectively at all bit rates.     

Statistical, DCT and vector quantisation-based video codec

The authors present a novel hybrid statistical, DCT and vector quantisation-based video-coding technique. In intra mode of operation, an input frame is divided into a number of non-overlapping pixel blocks. A discrete cosine transform then converts the coefficients in each block into the frequency domain. Coefficients with the same frequency index at different blocks are put together generating a number of matrices, where each matrix contains the coefficients of a particular frequency index. The matrix, which contains the DC coefficients, is losslessly coded. Matrices containing high frequency coefficients are coded using a novel statistical encoder. In inter mode of operation, overlapped block motion estimation / compensation is employed to exploit temporal redundancy between successive frames and generates a displaced frame difference (DFD) for each inter-frame. A wavelet transform then decomposes the DFD-frame into its frequency subbands. Coefficients in the detail subbands are vector quantised while coefficients in the baseband are losslessly coded. To evaluate the performance of the codec, the proposed codec and the adaptive subband vector quantisation (ASVQ) video codec, which has been shown to outperform H.263 at all bitrates, were applied to a number of test sequences. Results indicate that the proposed codec outperforms the ASVQ video codec subjectively and objectively at all bitrates.     

一种基于冗余小波变换的DT网格运动估计和运动补偿方法

网格划分和网格顶点的运动估计是基于不规则网格的视频压缩技术的关键。为了进一步提高网格运动估计和运动补偿的效果,在综合比较现有冗余小波变换域运动估计方法和适用规则网格的EMRMC算法的基础上,提出了一种新的基于不规则网格的运动估计和运动补偿算法,即在冗余小波变换域提取特征点和运动潜在区,网格顶点的运动估计采用结合运动潜在区的在时域进行块匹配的运动估计和运动补偿方法,而运动补偿则通过三角形仿射变换完成。同时还给出了冗余小波变换域提取运动潜在区的计算模板。理论分析和实验结果表明,该算法在补偿效果方面较前两种方法得到了改进。     

Color video compression using color mapping into textured grayscale video frames

Color video compression has become a necessity in the advent of newer applications of color video and its increasing size for higher definitions. New approaches are used to achieve more compression over the traditional and standard compression techniques. Considerable progress has been made of color transfer-based compression techniques that do not modify standard encoders but add some pre-processing and post-processing steps. We present a novel, simple yet robust, color transfer-based compression technique that can be integrated with the standard encoders like MPEG-2, H.264/AVC, etc. We achieve the compression by discarding the color components from all frames in a video sequence except those of the Intra (I) frames. The colored intra frames are converted to gray-textured images. The method is developed based on embedding the colors of the intra frames to low visibility high frequency textures of its gray luminance image. This is achieved by decomposing the luminance of the intra frame using the non-decimated DWT or discrete wavelet frame transform and replacing the bandpass subbands by the chrominance signals. The lowpass band is same as that of the luminance signal. At the output of the decoder, the colored intra frames are recovered using the wavelet transform. Instead of calculating motion vectors, we identify and reuse the motion vectors present in the decoder. The remaining luminance frames of the video are colored with the help of identified motion vectors and the color information of the preceding frames. The proposed codec considerably improves the compression ratio achievable by the standard codec, at the cost of slight increase in computation time at the decoder end.     

基于冗余小波变换的自适应运动估计与补偿算法研究*

为进一步提高运动估计和补偿的效果,提出了一种基于冗余离散小波变换（RDWT）的自适应运动估计算法。该算法提出了一种自适应块匹配和用于划分块运动状况的自适应阈值的计算方法;对静止块不进行估计,只对运动块采用自适应搜索起点预测方法和自适应阈值算法进行运动估计与补偿。实验结果表明,该方法能在保持较高峰值信噪比的情况下提高运动估计效率,且重建图像主观质量很好,较现有RDWT域运动估计算法有明显优势。     

An improved 3D wavelet-based scalable video coding codec for MC-EZBC

With the rapid growth of modern multimedia applications, 3D wavelet-based scalable video coding (SVC) codec has received considerable attention lately because of its high coding performance and flexibility in bitstream scalability. It combines the motion-compensated temporal filtering (MCTF) together with the spatial decomposition to produce an embedded bitstream offering various levels of video quality over the heterogeneous networks. However, in the existing 3D wavelet-based SVC schemes, where the block types for block matching algorithms are limited, weighting matrices for block-wise motion compensation are fixed, and variations in activities of temporal subbands are not considered in the selection of the Lagrange multiplier for mode decision. In this paper, our major contribution is to provide some recent extensions to the well-known scalable subband/wavelet video codec Motion-Compensated Embedded Zero Block Coding (MC-EZBC) using three novel and content adaptive algorithms. Firstly, the enhanced hierarchical variable size block matching (Enhanced HVSBM) algorithm is proposed for the variable block size motion estimation. Then, the rate-distortion optimization (RDO) based adaptive Lagrange multiplier selection model for mode decision is presented. Finally, we introduce the adaptive weighting matrices design for overlapped block motion compensation (OBMC). Experimental results show that all the three proposed algorithms significantly improve the overall coding performance of MC-EZBC. Comparisons with other popular wavelet-based SVC codecs demonstrate the effectiveness of our improved codec in terms of both video quality assessment and computational complexity.