Distributed video coding with adaptive two-step side information generation for smart and interactive media

Conventional video coding standards, such as MPEGx and H.26x, use a hybrid architecture of block-based motion compensation and discrete cosine transform (DCT) within the structure of a complex encoder and a simple decoder. Contrary to conventional video codecs, Wyner-Ziv (WZ) video coding, which is a practical application of distributed video coding (DVC) based on the Slepian-Wolf and WZ theorems, exploits the source correlation at the decoder, thereby allowing for the development of simpler encoders. However, the current WZ video coding algorithms cannot match the coding performance of conventional video coding. In order to improve the coding performance of transform-domain WZ video coding, an adaptive two-step side-information generation method is thus proposed for evaluation and analysis in this study. The proposed method uses decoded WZ frames in the down-sampled spatial resolution along with already decoded coefficients to successively improve rate-distortion (RD) performance as the decoding progresses. The experimental results show that the proposed method, compared to previous WZ video coding method, shows improved coding performance, particularly under critical conditions, such as cases with high motion content.     

Adaptive deblocking filter for transform domain Wyner?Ziv video coding

Wyner-Ziv (WZ) video coding is a particular case of distributed video coding, the recent video coding paradigm based on the Slepian-Wolf and Wyner-Ziv theorems that exploits the source correlation at the decoder and not at the encoder as in predictive video coding. Although many improvements have been done over the last years, the performance of the state-of-the-art WZ video codecs still did not reach the performance of state-of-the-art predictive video codecs, especially for high and complex motion video content. This is also true in terms of subjective image quality mainly because of a considerable amount of blocking artefacts present in the decoded WZ video frames. This paper proposes an adaptive deblocking filter to improve both the subjective and objective qualities of the WZ frames in a transform domain WZ video codec. The proposed filter is an adaptation of the advanced deblocking filter defined in the H.264/AVC (advanced video coding) standard to a WZ video codec. The results obtained confirm the subjective quality improvement and objective quality gains that can go up to 0.63 dB in the overall for sequences with high motion content when large group of pictures are used.     

Statistical motion learning for improved transform domain Wyner-Ziv video coding

Wyner-Ziv (WZ) video coding is a particular case of distributed video coding (DVC), the recent video coding paradigm based on the Slepian-Wolf and Wyner-Ziv theorems which exploits the source temporal correlation at the decoder and not at the encoder as in predictive video coding. Although some progress has been made in the last years, WZ video coding is still far from the compression performance of predictive video coding, especially for high and complex motion contents. The WZ video codec adopted in this study is based on a transform domain WZ video coding architecture with feedback channel-driven rate control, whose modules have been improved with some recent coding tools. This study proposes a novel motion learning approach to successively improve the rate-distortion (RD) performance of the WZ video codec as the decoding proceeds, making use of the already decoded transform bands to improve the decoding process for the remaining transform bands. The results obtained reveal gains up to 2.3 dB in the RD curves against the performance for the same codec without the proposed motion learning approach for high motion sequences and long group of pictures (GOP) sizes.     

Motion vector refinement in a Wyner--Ziv to H.264 transcoder for mobile telephony

The authors develop a decoder/encoder system (transcoder) to solve the consumption constraint in the communications between end-user devices, when a new Wyner?Ziv (WZ)/H.264 framework is defined for being used in mobile-to-mobile environments. This approach is based on leaving to the devices only WZ video encoding and traditional video decoding; the lowest complexity algorithms in both paradigms. The system shifts the burden of complexity to the network, where an improved transcoder that reuses information between both paradigms is allocated. The WZ decoding motion vectors are used to reduce the H.264 motion estimation process. The proposed transcoder offers a complexity reduction up to 60% on average, without any rate distortion drop.     

Network-driven low complexity coding for wireless multi-view video system

For wireless multi-view video system, which has very limited capability for storage and computation at the encoder, it is essential to design a video coding scheme with low complexity. Wyner-Ziv (WZ) coding scheme shifts large computational complexities to decoder with side information reconstruction, however, its encoding efficiency is not high enough. To obtain higher encoding efficiency and lower encoding complexity for wireless multi-view video applications, a network-driven low complexity video coding method is proposed in the paper. The proposed method is designed to implement color correction, motion vector extrapolation and disparity extraction at the central node of network, so as to reduce large computational complexities of motion estimation at the encoder and disparity estimation at the decoder. Experimental results show that encoding efficiency of the proposed method is higher than those of WZ coding and H.264 intraframe coding methods. The encoding complexity of the proposed method is greatly decreased and the decoded views are of color consistency, which is favorable to high quality view rendering at the decoder.     

分布式视频编码中关键帧丢失错误保护

目的 分布式视频编码较其传统视频编码具有编码简单、误码鲁棒性高等特点,可以很好地满足如无人机航拍、无线监控等新型视频业务的需求。在分布式视频编码中,视频图像被交替分为关键帧和Wyner-Ziv帧,由于受到信道衰落和干扰等因素的影响,采用传统帧内编码方式的关键帧的误码鲁棒性远不如基于信道编码的Wyner-Ziv帧。关键帧能否正确传输和解码对于Wyner-Ziv帧能否正确解码起着决定性的作用,进而影响着整个系统的压缩效率和率失真性能。为此针对关键帧在异构网络中的鲁棒性传输问题,提出一种基于小波域的关键帧质量可分级保护传输方案。方法 在编码端对关键帧同时进行传统的帧内视频编码和基于小波域的Wyner-Ziv编码,解码端将经过错误隐藏后的误码关键帧作为基本层,Wyner-Ziv编码产生的校验信息码流作为增强层。为了提高系统的分层特性以便使系统的码率适应不同的网络条件,进一步将小波分解后图像的各个不同层的低频带和高频带组合成不同的增强层,根据不同信道环境,传输不同层的Wyner-Ziv校验数据。同时对误码情况下关键帧的虚拟噪声模型进行了改进,利用第1个增强层已解码重建的频带与其对应边信息来获得第2个和第3个增强层对应频带的更加符合实际的虚拟信道模型的估计。结果 针对不同的视频序列在关键帧误码率为1%20%时,相比较于传统的帧内错误隐藏算法,所提方案可以提高视频重建图像的主观质量和整体系统的率失真性能。例如在关键帧误码率为5%时,通过传输第1个增强层,不同的视频序列峰值信噪比（PSNR）提升可达25 dB左右;如果继续传输第2个增强层的校验信息,视频图像的PSNR也可以提升0.51.6 dB左右;如果3个增强层的校验信息都传输的话,基本上可以达到无误码情况下关键帧的PSNR。结论 本文所提方案可以很好地解决分布式视频编码系统中的关键帧在实际信道传输过程中可能出现的误码问题,同时采用的分层传输方案可以适应不同网络的信道情况。     

基于边信息的分布式视频压缩感知重建

WZ视频编码系统中的虚拟信道会因信道模型参数估计的不稳定导致系统性能下降,为了克服该问题,提出不带有虚拟信道的分布式视频压缩感知重建算法,仅靠解码端获得的压缩感知观测值对非关键帧的错误进行纠正,并利用平滑投影Landweber迭代求解联合重建模型.实验证明本文所提出算法获得了更好的率失真性能和更低的重建时间.     

基于高斯混合模型的Wyner-Ziv视频编码

针对现有Laplacian模型不能精确描述相关噪声分布,分布式视频编码(Distributed Video Coding,DVC)的率失真性能改善非常有限,文中提出一种基于高斯混合模型的分布式视频编码方法.首先分析了WZ帧与相应边信息之间相关噪声的统计特征,发现相关噪声信息的分布并不满足某种单峰分布,然后采用高斯混合模型(Gaussian Mixture Model,GMM)对噪声系数直方图进行拟合,提出基于样本特征的EM(Expectation Maximum)算法来估计模型参数.将提出的高斯混合相关噪声模型与相应的Laplacian模型进行比较,实验结果表明前者更能精确描述相关噪声的统计特征,基于该模型的DVC率失真性能优于基于Laplacian模型的DISCOVER方案,获得的平均增益接近1 dB.     

On the Operational Rate-Distortion Performance of Uniform Scalar Quantization-Based Wyner–Ziv Coding of Laplace–Markov Sources

Wyner–Ziv (WZ) coding has recently been proposed as a low encoding complexity alternative to traditional DPCM coding for compression of sources with memory, in particular, in applications like multimedia compression. The viability of this alternative approach clearly depends on the compression performance of WZ coding compared to that of DPCM coding. In an attempt to understand the performance gap between WZ coding and DPCM coding, this paper studies the operational rate-distortion performance of WZ coding, using uniform scalar quantization followed by perfect Slepian–Wolf coding, for compression of a Laplace–Markov (LM) source. It is shown that at low rates or for weakly correlated LM sources, WZ coding is indeed a competitive alternative to DPCM coding. However, at high rates the performance gap becomes non-negligible for strongly correlated LM sources. In order to reduce the gap at high rates, a hybrid approach that combines DPCM coding and WZ coding is further investigated. It is shown that the hybrid approach is indeed competitive to DPCM coding at all rates even for strongly correlated LM sources.      

Transform domain distributed video coding with spatial correlations

Distributed Video Coding is a new coding technique which has been evolving very fast recently. However the rate distortion performances of current solutions are below the expectations especially for high motion sequences even at a group of picture (GOP) size of 2. Main reason of this problem is the temporal prediction of the Wyner-Ziv (WZ) frames at the decoder. In this paper we propose a novel transform domain DVC codec architecture which splits each frame into two sub-frames and they are encoded separately as key sub-frame and WZ sub-frame. Pixel interpolation or median prediction techniques are utilized to generate the side information at the decoder. Simulation results show that a significant rate distortion improvement can be obtained with the proposed algorithm over the current DVC solutions.     

Implementation of parallel thinning algorithms using recurrentneural networks

The use of recurrent neural networks for skeletonization and thinning of binary images is investigated. The networks are trained to learn a deletion rule and they iteratively delete object pixels until only the skeleton remains. Recurrent neural network architectures that implement a variety of thinning algorithms, such as the Rosenfeld-Kak algorithm and the Wang-Zhang (WZ) algorithm, are presented. A modified WZ algorithm which produces skeletons that are intuitively more pleasing is introduced.     

基于无线噪声信道的编码端码率控制算法研究

针对分布式视频编码系统的关键帧在无线信道中传输受到噪声污染的情况,提出一种基于无线噪声信道的编码端码率控制算法。首先对解码端边信息携带的无线信道噪声进行了理论和实验分析,建立了边信息中无线信道噪声的分布模型;然后结合相关噪声模型推导出编码端的噪声联合模型,并根据分布式视频编码的率失真理论,提出了在无线信道下WZ帧不同系数带的码率控制算法,同时将新的码率控制算法引入基于无线噪声信道的Wyner-Ziv编码器中。实验表明,与现有的编码端码率控制算法相比,所提出的算法在不同无线信道噪声下可使解码重构视频的PSNR值平均提高约0.1～1.8 dB,且未增加复杂度。     

Implementation of the Generalized WZ Factorization on a Wavefront Array Processor

In this work, the potential of a block generalized WZ factorization procedure for direct hardware implementation on a special-purpose network of Wavefront Array Processor Modules (WAPm s ) is investigated. The definition of a wavefront module is given and the development of an Eigenvalue Evaluator Engine ( E 3 ) based on this module is discussed.     

分布式视频编码中基于改进FCM聚类的相关噪声模型估计

目的：在分布式视频编码中,由于相关噪声残差子带不同区域具有不同的变化特性,子带级拉普拉斯估计法对整个子带用同一参数估计并不准确,为了进一步提高噪声模型估计精度,本文提出了一种基于改进的模糊C均值（FCM）聚类的模型估计方法。方法：本文算法针对每一解码子带选取不同的特征矢量;采用改进的模糊C均值进行聚类;为了避免类别样本数较少而溢出,采用阈值控制法求取相应的模型参数;然后用重建子带更新下一解码子带的特征矢量;直到一帧中所有子带解码完成。针对模糊C均值对初始聚类中心的敏感性,本文采用首先随机生成隶属度矩阵的方法来缓解聚类陷入局部最优的问题。结果：从实验效果和算法复杂度角度考虑,将残差样本聚为8类。实验结果表明,本文聚类算法可以更加准确地模拟帧内不同区域的不同信道噪声特性,对于运动越剧烈的序列效果越好,相对于子带级拉普拉斯估计,平均增益达1dB。结论：本文提出了一种新的相关噪声估计方法,针对不同的子带选取不同的特征矢量,并重建更新。实验结果表明,本文算法能更好地描述相关噪声特性,获得系统性能的提高。     

Parallel quadrant interlocking factorization on hypercube computers

In this article we present an adaptation of the QIF (Quadrant Interlocking Factorization) algorithm, which solves systems of linear equations, for implementation in SIMD hypercube computers with distributed memory. This method is based in the WZ decomposition of the system's matrix. The parallel algorithm developed is general in the sense that there is no restriction imposed on the size of the problem and that it is independent of the dimension of the hypercube. The comparison of this algorithm with the parallel algorithms based on the LU factorization show that the execution time is divided by a factor of two, approximately.     

Accurate pseudopotential description of the GW bandstructure of ZnO

We present the GW band structure of ZnO in its wurtzite (WZ), zincblende (ZB) and rocksalt (RS) phases at the Γ point, calculated within the GW approximation. We have used a Zn²⁰⁺ pseudopotential which is essential for the adequate treatment of the exchange interaction in the self-energy. The accuracy of the pseudopotential used is also discussed. The effect of the p–d hybridization on the GW corrections to the band gap is correlated by comparing the ZB and RS phase.     

Interactive scheduling for mobile multimedia service in M2M environment

Computational load of motion estimation in advanced video coding (AVC) standard is significantly high and its more true for HDTV sequences. In this paper, video processing algorithm is mapped onto a learning method to improve machine to machine (M2M) architecture, namely, the parallel reconfigurable computing (PRC) architecture, which consists of multiple units, First, we construct a directed acyclic graph (DAG) to represent the video coding algorithms comprising motion estimation. In the future trillions of devices are connected (M2M) together to provide services and that time power management would be a challenge. Computation aware scheme for different machine is reduced by dynamically scheduling usage of multi-core processing environment for video sequence depending up complexity of the video. And different video coding algorithm is selected depending upon the nature of the video. Simulation results show the effectiveness of the proposed method.     

Novel approaches for synthesizing video textures

Video texture, a novel type of medium, can produce a new video with a continuously varying stream of images from a recorded video. A classic approach to generate video textures is to apply principal components analysis (PCA) for dimensionality reduction (i.e. extraction of frame signatures) and autoregressive (AR) process for prediction purposes. In this paper we investigate the use of other dimensionality reduction techniques to generate accurate video textures. Based on our experiments, the quality of video textures can be improved further. We also propose a new approach for generating video textures using probabilistic principal components analysis (PPCA) and Gaussian process dynamical model (GPDM) to synthesize video textures which contain frames that never appeared before and with similar motions as original videos. Furthermore, we propose two ways of generating online video textures by applying the incremental Isomap and incremental Spatio-temporal Isomap (IST-Isomap). Both approaches can produce good online video texture results. In particular, IST-Isomap, that we propose, is more suitable for sparse video data (e.g. cartoon).     

基于内容的视频检索系统在电子政务中的应用

实现信息化政务办公需要解决的一个问题是视频文档信息的检索与浏览。文中给出一个政务视频信息浏览和检索系统的方案,系统支持抽象层的视频信息浏览和基于示例图像的视频信息检索。系统分成两个主要部分:(1)视频内容结构化处理和抽象部分;(2)基于示例图像的视频信息检索部分。在部分(1)中,给出了一个基于颜色及目标轮廓变化特征进行非监督视频结构化和视频内容抽象的方法;在部分(2)中,首先对图像库中图像进行特征降维,然后进行聚类处理,这样降低了通过示例图像检索视频内容过程中相似性匹配运算的时间,提高了效率。     

基于AP聚类和频繁模式挖掘的视频摘要生成方法

为了有效支持视频数据库浏览和检索,通过视频摘要来对视频进行紧凑表达变得十分重要.提出了一种新颖的基于近邻传播聚类AP(Affinity Propagation)和频繁镜头模式挖掘的视频摘要自动生成算法.视频频繁镜头模式被定义为在一定时间窗口内经常出现的镜头系列.首先通过近邻传播聚类,将相似镜头聚合到一起;然后采用频繁镜头模式挖掘的方法对视频聚类内容进行挖掘,去掉视频中冗余内容部分;最后通过覆盖视频语义信息的频繁镜头模式生成视频摘要.实验结果表明,视频摘要算法取得了良好的效果.