分布式视频编码技术研究进展

介绍了分布式视频编码与传统视频编码方法思路的不同及各自适用的应用场景,阐述了分布式视频编码的理论基础和目前普遍采用的编解码框架,分析了分布式视频编码中的Wyner-Ziv编解码器设计、辅助边信息生成、虚拟"相关信道"建模等几项关键技术存在的问题及各自解决方案的最新研究进展,最后总结了分布式视频编码的发展与研究方向,并介绍了分布式编码在视频领域的其它应用.     

分布式视频编码关键技术及研究进展

系统地阐述了分布式视频编码(distributed video coding,DVC)技术框架的基本原理和近五年的发展历程;列举了国内外多个研究小组的基本思想研究现状;分析了分布式视频编码技术的发展趋势;揭示了技术的关键和研究热点;展望了该技术在信息安全、可伸缩编码、多描述编码以及光场编码中的应用前景.     

基于5/3运动补偿时间提升的可伸缩视频编码

运动补偿时间滤波是一种有效的可伸缩视频编码方案，采用5/3提升小波实现能进一步提高其编码性能。在给出了5/3运动补偿时间提升的计算公式之后，提出了将其实现的有限内存算法，避免了帧组带来的边界效应，也去掉了对视频序列长度的限制。为了提高低码率时5/3时间提升的性能，提出了运动矢量的压缩表示方法，使得真正编码的运动矢量总数不超过每个原始帧一个。针对不相连像素问题，根据像素的不同连接状态设计了不同的运动处理模式。实验结果表明，该方法的性能优于Haar提升滤波0.3dB~0.7 dB，在中高码率时与H.264/AVC也是可以比较的。     

Scalable video coding using motion-compensated temporal filtering and intra-band wavelet based compression

Scalable video compression is a crucial task that allows for high flexibility of video streams to different networks in various applications. Current video coding techniques exploit temporal correlation using motion-compensated predictive or filtering approaches. Particularly, motion-compensated temporal filtering (MCTF) is a useful framework for scalable video compression schemes. In this paper, we propose a new scalable video coding method that combines open-loop motion-compensated prediction with an embedded intra-band wavelet based compression. Our major objective is to provide a wavelet based video coding system that circumvents the drawbacks of conventional closed-loop prediction systems, without sacrificing compression performance. To improve the coding efficiency, we adaptively weight the target bitrate according to the temporal frame position in the temporal pyramid. Comparisons with state-of-the-art scalable video coding solutions confirm an overall coding efficiency gain of the proposed method specially at high bitrates.     

Phase-based side information generation in distributed video coding

Multimedia Tools and Applications - In distributed video coding, the quality of side information (SI) directly affects the final compression efficiency and rate-distortion performance. In the...     

分布式视频编码中关键帧编码方式的改进

在分布式视频编码中关键帧间的时间相关性没有被利用, 据此提出一种基于频带划分的关键帧编码模式的选择方法。关键帧经过DCT后得到的系数带划分为低频带和高频带, 低频带部分采用Wyner-Ziv编解码, 然后对高频带进一步进行编码模式的选择, 分别进行Wyner-Ziv编解码和传统的帧内编解码, 且在解码端完成编码模式的选择, 通过反馈信道向编码端传送编码模式的选择。仿真结果表明, 在不增加编码端复杂度的情况下, 所提出的方法改善了解码后视频的质量, 使系统的峰值信噪比（PSNR）提高约1~5 dB。     

BLAST-DVC: BitpLAne SelecTive distributed video coding

This paper presents a BitpLAne SelecTive (BLAST) distributed video coding (DVC) system. In the proposed system, the significance of each bitplane is measured at the decoder based on an estimated distortion-rate ratio that makes use of a correlation model for the original source information and the side information. Only the syndrome bits of the bitplanes that have estimated distortion-rate ratios higher than a target distortion-rate ratio, are transmitted and are used to decode the associated bitplanes. The remaining bitplanes are estimated using a minimum-distance symbol reconstruction scheme which makes use of the side information and the LDPCA-decoded bitplanes. Coding results and comparisons with existing DVC schemes and with H.264 intra- and inter-frame coding are presented to illustrate the performance of the proposed system.     

使用对极几何的多视角分布式视频编码

为了降低多视角分布式视频编码中解码器复杂度,解决视角间边信息的获取精度等问题,将一种新的基于对极几何的视差估计算法用于多视角分布式视频编码系统。提出的系统通过对视角间的冗余信息使用对极几何约束,采用新的视差搜索开始点,限制垂直方向的搜索范围以加快搜索速度。实验结果表明,提出的系统相对于运动JPEG（MJPEG）编码的主要运算绝对差值和（SAD）计算次数减少10倍,相对H.263+减少7倍。同时提出系统相对MJPEG编码有6～7 dB增益,相对H.263+有3 dB增益。     

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。     

基于分布式视频编码的井下传感器节点设计

煤矿井下的环境复杂,通信方式和通信范围受应用场景的约束性较大,在煤矿安全生产中引入无线多媒体传感器网络技术(WMSN)可以提高安全生产监管效率,在突发事件中为应急救援工作提供有力的信息指导。为此基于DISCOVER分布式视频编码(DVC)方案,设计了以S3C6410为主处理器芯片的视频传感器节点。给出了节点的硬件框图以及软件流程图。测试表明,该节点运行良好,可以对煤矿安全生产过程进行有效监控,在一定程度上预防煤矿事故的发生。     

基于depth-map和分布式视频编码的多视点视频传输方法

针对多视点视频传输系统数据量庞大的问题,提出一种基于深度图(depth-map)和分布式视频编码(DVC)的不等错误保护(UEP)传输方法。该方法首先基于多个视点提取深度图;然后,在传输过程中传输一个视点及其深度图;最后,经过网络传输,在解码端由一个视点图及其深度图生成其他视点。由于视点图和深度图在解码端的重要程度不同,对需要传输的视点图和深度图采用不同的分布式视频编码方法,进行不平等的错误保护。仿真实验结果表明,所提传输方法比传统的分布式多视点视频编码传输系统具有更好的抗误码性能,提高了传输可靠性,图像的峰值信噪比(PSNR)约提高1.5dB。     

Efficient compression and network adaptive video coding for distributed video surveillance

The availability of cheap network based video cameras and the prevalence of wireless networks has lead to a major thrust towards deployment of large scale Distributed Video Surveillance (DVS) systems. This has opened up an important area of research to deal with the issues involved in DVS system for efficient collection and transmission of large scale video streams from the cameras at the guarded sites, to the end users in possibly constrained network conditions. In this paper, we propose a framework based on content-based video classification and scalable compression scheme to provide a robust bandwidth efficient video transmission for DVS. The scheme builds on a Discrete Wavelet Transform (DWT) based Color-Set Partitioning for Hierarchical Trees (CSPIHT) coding to obtain a scalable bitstream. Wavelet domain segmentation and compression assists in development of a DVS architecture. The architecture includes a novel module for dynamic allocation of Network bandwidth based on the current available resources and constraints. Different frame constituents are optimally coded based on their relative significance, perceptual quality, and available estimate of network bandwidth. Experimental result over different video sequences and simulations for Network conditions demonstrate the efficient performance of the approach.     

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.     

Enhanced reconstruction algorithm for unidirectional distributed video coding

Distributed video coding (DVC) is an emerging video coding technology that utilises the distributed source coding principles to build very low cost video encoders, yet with remarkable error resilience. In the most common DVC framework, the reconstruction function plays a vital role that has a direct impact on the output video quality. In this study, a novel algorithm is proposed for the reconstruction function, particularly focusing on a unidirectional DVC architecture. The proposed technique exploits the variations of the bit error rate of the Wyner-Ziv decoded bit stream and the assumed noise model in the side information stream. The simulation results show that the proposed algorithm yields a significant improvement of the objective and subjective video quality at no additional bit rate cost.     

半反馈和单向分布式视频编码算法研究

由于基于理想反馈重传策略的分布式视频编码方案非实际可行的系统;另外,由于边信息和分布式帧之间的近似度对分布式视频压缩效率影响较大,但相关研究较少,为此,为了研究切实可行的分布式视频编码系统,通过统计分析边信息与分布式帧的相似度,提出了一种基于PSNR的半反馈分布式视频编码方案。为满足无反馈信道的应用场合,进一步提出了基于PSNR的单向分布式视频编码方案。实验结果表明,该方案在编码复杂度增加不大的条件下,不仅切实可行,同时有效地降低了译码复杂度,且能灵活控制传输码率,但视频解码质量稍逊于理想的反馈重传分布式视频编码。     

基于LDPC的码率自适应分布式视频编码

为了在分布式视频编码（DVC）中取得更好的压缩性能,将校验节点的合并和分裂进行有机结合,提出了一种码率自适应LDPC（RALDPC）编码新方法。该方法首先基于PEG算法构造高压缩比LDPC码字;然后由行均匀分裂得到低压缩比码字;最后通过合并或分裂校验矩阵对应的行来适度调整码率。为保证码字性能,还提出了校验节点合并的3个限制条件,并基于RALDPC提出了一种码率自适应DVC编码方案。实验结果表明,与当前基于Turbo码的DVC方案相比,在原信息和边信息高度或中度相关时,编码性能提高了0.1～0.7dB。     

Transform-domain distributed video coding with rate-distortion-based adaptive quantisation

This study presents a transform-domain distributed video coding (DVC) system with a rate-distortion (R-D)-based Adaptive QuanTisation (AQT) scheme. In the proposed system, the transform-domain Wyner-Ziv frame is divided into partitions and is adaptively quantised based on estimated local R-D characteristics for each partition. The R-D estimation is performed based on a correlation model between the original source information and the side information and can be applied at the decoder without adding complexity to the encoder. Coding results and comparisons with existing DVC schemes and with H.264/AVC interframe and intraframe coding are presented to illustrate the performance of the proposed system.     

一种改进预测结构的多视点视频编码

多视点视频编码是视频编码的研究热点之一。针对联合多视点视频编码（Joint Multi-view Video Coding,JMVC）采用的分层B帧预测结构编码复杂度高,随机访问性能较差等缺点,提出了一种改进的预测结构。所提出的预测结构对B视点中以前一帧作为其时间参考的帧仅采用时间预测,对所有P视点的非关键帧均不进行视点间预测,有效地降低了计算复杂度,提高了随机访问性能。通过选取合适的I视点位置,以减少结构简化带来的编码效率损失。实验结果表明,与分层B帧预测结构相比,所提出的预测结构在保证编码效率损失不大的情况下,显著降低了平均编码时间。改进的预测结构也具有更好的随机访问性能。     

Lossless video coding based on pixel-wise prediction

The state-of-the-art H.264/AVC was designed for lossy video coding in the beginning. Recently, the H.264/AVC FRExt was developed by removing transformation and quantization for lossless coding. In this paper, we propose an efficient intra lossless coding method based on a pixel-wise prediction. The proposed algorithm introduces an additional intra prediction mode that employs the LOCO-I predictor of JPEG LS. We found that the proposed lossless coding algorithm achieved approximately 22.0, 2.6, and 10.7% bit saving in terms of compression ratio, compared to the H.264/AVC FRExt, lossless intra 4:4:4, and Takamura’s lossless coding methods, respectively.