分布式视频编码中拉普拉斯-柯西混合分布相关噪声模型研究

该文通过研究变换域分布式视频编码中原始Wyner-Ziv(WZ)帧与相应边信息的残差系数特性,发现大残差和小残差系数统计分布与传统的拉普拉斯分布存在一定偏差。为了减少这种差异,提出一种拉普拉斯-柯西混合分布(LCMD)相关噪声模型及其参数估计算法。该混合模型利用改进的拉普拉斯分布描述小残差系数的分布,采用柯西分布描述大残差系数。实验结果表明该文提出的混合模型能较精确地描述WZ帧和边信息间的残差系数分布,从而有效地改善了变换域分布式视频编码的率失真性能,并减少系统解码端计算复杂度。     

基于伪随机码置乱的分布式视频残差编码端码率控制算法

提出一种基于伪随机码置乱的分布式视频残差编码端码率控制算法,利用伪随机码对残差视频帧的像素进行置乱处理,将信源图像与其边信息图像之间的差别均匀化,实现帧级别上的码率估计,即每一帧用同一码率发送。如果收端译码失败,利用提出的一种量化序号估计算法能显著提高译码成功率,解决码率低估问题。同时发端视频残差帧的特性能近似表示收发两端信号之间的相关性,因此,发端无需产生一个预测的边信息。仿真结果表明,该算法发端复杂度低、译码成功率高、系统延迟小、率失真性能良好。     

基于多假设运动补偿去噪的迭代边信息改进算法

在分布式视频压缩系统中,边信息的质量对编码效率有至关重要的作用。利用已解码图像信息提高边信息质量是近年来研究的热点之一。根据边信息和已解码信息与原始信息之间的噪声关系,该文提出了一种基于多假设运动补偿去噪的迭代边信息改进算法。首先对原始边信息进行多假设运动补偿去噪,生成质量更好而不仅是相似的补偿图像,然后利用每个码平面的解码信息对边信息进行迭代改进。实验结果表明,该算法能减少码流,显著提高Wyner-Ziv (WZ)帧质量,从而有效的改善分布式视频压缩的率失真性能。     

一种应用于ARQ系统的新型Turbo码译码方案

在介绍了FEC和ARQ技术的优缺点及分析了Turbo码迭代译码特点的基础上，提出了一种应用于ARQ系统中的Turbo码新型迭代译码方案，在不增加译码复杂度的前提下，首发帧和重发帧交替迭代，充分利用两帧的信息，在AWGN信道和相干瑞利信道下的仿真结果表明，新方案能显著改善译码性能。     

一种改进的虚拟相关信道参数估计方法

分布式视频编码框架中,准确地估计WZ帧与辅助边信息之间的统计特性,也即对它们之间的虚拟＂相关信道＂准确设计模型,并估计其参数,对于提高编码压缩效率,进而准确进行码率控制十分重要.讨论了模拟信道的模型选取和参数优化,研究了视频序列中常用的Laplace模型和Gauss模型,提出了一种带校正系数的虚拟相关信道参数估计方法,验证了虚拟相关信道更接近残差数据的真实分布.     

一种咬尾卷积译码的修正算法

在LTE系统中,物理广播信道和物理下行控制信道均采用了咬尾卷积编码,咬尾卷积编码拥有很多优良的性能.针对咬尾卷积译码,提出了一种基于Viterbi译码的修正算法——正逆序结合译码算法,根据分支度量确定误码在数据帧的分布,最后确定采用正序还是逆序译码结果.仿真结果表明,Viterbi的修正方法有效地降低了系统误码率,而且具有普适性,适合应用于LTE系统.     

一种区分极化码编码的PDCCH帧和噪声帧的算法

在第五代移动通信系统中,采用极化码编码下行控制信息,并通过物理下行控制信道（Physical Download Control Channel,PDCCH）发送给用户设备,用户设备通过极化码盲检获得属于自己的控制信息。在通常情况下,用户设备接收到的帧包括极化码字帧和噪声帧,若将其全部进行译码,则存在不必要的开销。针对此问题,提出了一种基于阈值检验的区分极化码字帧和噪声帧的方法。该方法根据收端接收到的极化码字各个节点呈现出不同的硬判可靠度,为各个节点设置不同的硬判错误率阈值,对所有帧按照未通过阈值检验的节点个数进行由小到大进行排序,选取较小的帧进入后续的译码盲检,从而在盲检前剔除一定数量的噪声帧,显著降低用户设备端的盲检译码能耗。仿真验证表明,在复杂度相同的情况下,与已有的区分算法相比,该方案能将漏检率降低90%以上。     

分布式视频编码中频域帧的非均衡编码

对基于低密度累积校验码(LDPCA)的分布式视频编码(DVC)方案,提出一种非均衡的WZ(频域)帧编码方法.根据视频序列的低频和高频成分所包含信息的不同重要性,对不同频率成分采用不同的编码方法.提取出WZ帧的低频和高频成分;然后分别对低频和高频成分进行基于块的非均衡编码.与传统的低频和高频成分统一编码方法相比,非均衡编码方法具有更好的解码性能.     

基于Turbo-TCM与时空分组码的级联系统的次优译码算法

针对瑞利信道中存在的严重的多径衰落,本文实现了Turbo-TCM方案与时空分组码的级联系统,以期利用空间分集改善系统的误码率性能。针对级联系统的译码,本文给出了一种具有低译码时延的次优译码算法,该算法的特点是各模块独立译码,先算比特对数似然比再进行二进制Turbo码译码。最后通过计算机仿真给出了使用该次优译码算法的Turbo－TCM方案与时空分组码的级联系统的译码性能。仿真结果说明,当发射天线数目一定时,随着接收天线数目的增加,译码性能的增益随之增加而帧长对译码性能的影响则随之减小。     

分布视频编码中基于帧间相关性的自适应关键帧选取算法

针对分布式视频编码(DVC)系统中固定周期关键帧选取(PKFS)方法忽视了帧间相关性的缺陷,提出了一种自适应关键帧选取(AKFS)算法。利用图像特征点检测与匹配的方法,将相邻图像的非匹配点作为帧间相关性的近似,把累积或平均非匹配点数超过阈值的帧判定为关键帧。在此基础上,提出改进的帧内插方案,以适应不同长度序列组的边信息生成;将零运动强度的关联帧合并为一帧图像参与编解码,进一步提高了系统的压缩效率。实验结果表明,对于不同运动特性的序列,本文提出的算法可以明显提升边信息帧的重建质量,使系统的率失真性能提高0.9～2.0 dB,并有效降低了编码传输码率。     

Advanced side information creation techniques and framework for Wyner–Ziv video coding

Recently, several distributed video coding (DVC) solutions based on the distributed source coding (DSC) paradigm have appeared in the literature. Wyner–Ziv (WZ) video coding, a particular case of DVC where side information is made available at the decoder, enable to achieve a flexible distribution of the computational complexity between the encoder and decoder, promising to fulfill novel requirements from applications such as video surveillance, sensor networks and mobile camera phones. The quality of the side information at the decoder has a critical role in determining the WZ video coding rate-distortion (RD) performance, notably to raise it to a level as close as possible to the RD performance of standard predictive video coding schemes. Towards this target, efficient motion search algorithms for powerful frame interpolation are much needed at the decoder. In this paper, the RD performance of a Wyner–Ziv video codec is improved by using novel, advanced motion compensated frame interpolation techniques to generate the side information. The development of these type of side information estimators is a difficult problem in WZ video coding, especially because the decoder only has available some reference, decoded frames. Based on the regularization of the motion field, novel side information creation techniques are proposed in this paper along with a new frame interpolation framework able to generate higher quality side information at the decoder. To illustrate the RD performance improvements, this novel side information creation framework has been integrated in a transform domain turbo coding based Wyner–Ziv video codec. Experimental results show that the novel side information creation solution leads to better RD performance than available state-of-the-art side information estimators, with improvements up to 2 dB; moreover, it allows outperforming H.264/AVC Intra by up to 3 dB with a lower encoding complexity.     

Efficient reconstruction scheme for transform domain Wyner-Ziv video coding

To minimize the errors of the reconstructed values and improve the quality of decoded image,an efficient reconstruction scheme for transform domain Wyner-Ziv (WZ) video coding is proposed.The reconstruction scheme exploits temporal correlation of the coefficient bands,the WZ decoded bits stream and the side information efficiently.When side information is outside the decoded quantization bin,the reconstructed value is derived using expectation of the WZ decoded bit stream and the side information.When side information is within the decoded quantization bin,the reconstructed value is derived using the biased predictor.Simulation results show that the proposed reconstruction scheme gains up to 1.32 dB compared with the commonly used boundary reconstruction scheme at the same bit rates and similar computation cost.     

An improved side information generation for distributed video coding

This paper presents a side information (SI) scheme for distributed video coding based on multilayer perceptron. The suggested scheme predicts a Wyner–Ziv (WZ) frame from two decoded key frames. The network is trained offline using patterns from different standard video sequences with varied motion characteristics to achieve generalization. The proposed scheme is simulated along with other standard video coding schemes. Performance comparisons have been made with respect to training convergence, rate distortion (RD), peak signal to noise ratio (PSNR), number of requests per SI frame, decoding time requirement, etc. In general, it is observed that the proposed scheme has a superior SI frame generation capability as compared to its competent schemes.     

Adaptive Correlation Noise Model for DC Coefficients in Wyner‐Ziv Video Coding

An adaptive correlation noise model (CNM) construction algorithm is proposed in this paper to increase the efficiency of parity bits for correcting errors of the side information in transform domain Wyner‐Ziv (WZ) video coding. The proposed algorithm introduces two techniques to improve the accuracy of the CNM. First, it calculates the mean of direct current (DC) coefficients of the original WZ frame at the encoder and uses it to assist the decoder to calculate the CNM parameters. Second, by considering the statistical property of the transform domain correlation noise and the motion characteristic of the frame, the algorithm adaptively models the DC coefficients of the correlation noise with the Gaussian distribution for the low motion frames and the Laplacian distribution for the high motion frames, respectively. With these techniques, the proposed algorithm is able to make a more accurate approximation to the real distribution of the correlation noise at the expense of a very slight increment to the coding complexity. The simulation results show that the proposed algorithm can improve the average peak signal‐to‐noise ratio of the decoded WZ frames by 0.5 dB to 1.5 dB.     

无反馈分布式视频编码中Wyner-Ziv帧的顽健重构算法

在无反馈分布式视频编码系统中,提出了一种Wyner-Ziv帧的顽健重构算法。针对比特面解码错误带来的视频质量下降问题,对DC系数和AC系数使用不同重构方法,特别是对于解码失败的DC系数量化值,利用编码端原始图像的相关信息自适应地调整边信息量化值和解码失败量化值对重构的贡献,从而完成重构。实验结果表明,与最小均方误差重构算法相比,该算法可以有效提高解码视频的平均PSNR(peak signal-to-noise ratio),且解码视频图像的主观质量有明显改善。     

Side information generation with auto regressive model for low-delay distributed video coding

In this paper, we propose an auto regressive (AR) model to generate the high quality side information (SI) for Wyner-Ziv (WZ) frames in low-delay distributed video coding, where the future frames are not used for generating SI. In the proposed AR model, the SI of each pixel within the current WZ frame t is generated as a linear weighted summation of the pixels within a window in the previous reconstructed WZ/Key frame t − 1 along the motion trajectory. To obtain accurate SI, the AR model is used in both temporal directions in the reconstructed WZ/Key frames t − 1 and t − 2, and then the regression results are fused with traditional extrapolation result based on a probability model. In each temporal direction, a weighting coefficient set is computed by the least mean square method for each block in the current WZ frame t. In particular, due to the unavailability of future frames in low-delay distributed video coding, a centrosymmetric rearrangement is proposed for pixel generation in the backward direction. Various experimental results demonstrate that the proposed model is able to achieve a higher performance compared to the existing SI generation methods.     

Side information refinement using motion estimation in dc domain for transform-based distributed video coding

The key to good decoding performance in distributed video coding systems lies in the efficient prediction of frames using side information. Previously, this process has been performed without considering the progressive nature of the synthesis of the final frame. Observing the fact that incorrectly predicted areas of the current frame can be detected at different levels of final frame synthesis, an algorithm is proposed for refinement of side information synthesis based on an additional stage of motion estimation. The additional stage is performed on correctly decoded DC frames and is used to significantly improve the motion prediction of the final resolution frames, which leads to enhanced performance of the overall system.     

Robust Video Transmission With Distributed Source Coded Auxiliary Channel

We propose a novel solution to the problem of robust, low-latency video transmission over lossy channels. Predictive video codecs, such as MPEG and H.26x, are very susceptible to prediction mismatch between encoder and decoder or “drift” when there are packet losses. These mismatches lead to a significant degradation in the decoded quality. To address this problem, we propose an auxiliary codec system that sends additional information alongside an MPEG or H.26x compressed video stream to correct for errors in decoded frames and mitigate drift. The proposed system is based on the principles of distributed source coding and uses the (possibly erroneous) MPEG/H.26x decoder reconstruction as side information at the auxiliary decoder. The distributed source coding framework depends upon knowing the statistical dependency (or correlation) between the source and the side information. We propose a recursive algorithm to analytically track the correlation between the original source frame and the erroneous MPEG/H.26x decoded frame. Finally, we propose a rate-distortion optimization scheme to allocate the rate used by the auxiliary encoder among the encoding blocks within a video frame. We implement the proposed system and present extensive simulation results that demonstrate significant gains in performance both visually and objectively (on the order of 2 dB in PSNR over forward error correction based solutions and 1.5 dB in PSNR over intrarefresh based solutions for typical scenarios) under tight latency constraints.      

A Wyner-Ziv Video Coding method utilizing mixture correlation noise model

In Wyner-Ziv (WZ) Distributed Video Coding (DVC), correlation noise model is often used to describe the error distribution between WZ frame and the side information. The accuracy of the model can influence the performance of the video coder directly. A mixture correlation noise model in Discrete Cosine Transform (DCT) domain for WZ video coding is established in this paper. Different correlation noise estimation method is used for direct current and alternating current coefficients. Parameter estimation method based on expectation maximization algorithm is used to estimate the Laplace distribution center of direct current frequency band and Mixture Laplace-Uniform Distribution Model (MLUDM) is established for alternating current coefficients. Experimental results suggest that the proposed mixture correlation noise model can describe the heavy tail and sudden change of the noise accurately at high rate and make significant improvement on the coding efficiency compared with the noise model presented by DIStributed COding for Video sERvices (DISCOVER).