基于层次B帧预测结构的自适应图像组算法

与目前普遍应用的IB…BP预测结构相比,在相同参考帧数目前提下,层次B帧预测结构对大部分序列,在相同码率情况下,其图像客观质量PSNR平均提高了1 dB左右。但是,对不同运动特性的图像序列,选择不同图像组大小的层次B帧预测结构编码,编码性能差异较大。基于此,提出了基于层次B帧预测结构的自适应图像组大小编码技术,并给出了具体的图像组大小判断方法和编码过程。实验结果表明,相对于固定图像组大小的层次B帧预测编码技术,对所测序列,本文提出的方法编码性能提高了0.60 dB左右。     

基于MCTF的时域可分级视频编码技术

现代可分级视频编码的时域可分级性是采用运动补偿时域滤波技术(Motion-Compensated Temporal Filtering,MCTF)来实现的,MCTF将若干连续的视频帧组成一个图像组进行小波分解以提供时域可分级性。由于不同视频序列的时域特征变化,传统的图像组大小固定的时域分解影响编码效率。本文提出了一种图像组大小自适应调整的时域小波分解算法,利用帧间预测效果来决定视频序列的时域特性,根据时域特性用于小波分解的图像组大小做自适应的调整。实验结果表明,新算法的编码性能比图像组大小固定的结构大大提高。     

针对高清视频压缩的自适应预处理系统设计与实现

受限于达芬奇数字信号处理器DM6467只能接收固定的视频格式,设计并完成了一种基于FPGA结合DM6467的视频压缩自适应预处理系统.该系统可根据输入的视频图像自适应地完成输入视频分辨率的检测与采集,并将RGB格式视频转换为芯片可直接使用的YUV色度空间,完成对色度空间下采样.然后利用分帧传输技术将图像分成各个子帧,并对各子帧进行RAW格式组帧.最后将重组数据传输至DM6467中编码.实验结果表明该系统可对任意格式、分辨率的视频进行采集与编码,且采用的分帧传输方式极大地降低了图像采集延时.     

基于局部亮度直方图的自适应视频帧类型决策算法

视频帧类型决策是影响视频编码效率的关键因素之一。为提升x265视频编码器的编码性能,该文提出基于局部亮度直方图的自适应视频帧类型决策算法。首先,在64×64大小的编码树单元(CTU)级别上统计各帧局部亮度直方图,用帧间局部亮度直方图差异表征帧间场景变换程度;其次,引入帧内编码帧(I帧)检测窗,在检测窗内通过比较帧间场景变换程度自适应确定I帧;最后,根据帧间场景变换程度与迷你图像组(MiniGOP)大小之间的相关性确定MiniGOP大小,从而自适应确定普通P和B帧(GPB帧)及双向预测编码帧(B帧)。实验结果表明,与x265标准中的相关算法相比,所提算法能够有效降低x265的编码复杂度,可在减少近5%编码时间的前提下,实现视频I帧、GPB帧和B帧的高效自适应决策。     

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。     

高清晰度DVD＋DVR系统的实时实现技术

文章利用MPEG-2空间域编解码的结构,提出了一种实时实现DVD播放功能和电视信号/复合视音频信号的编码、存储和随机解码播放技术的数字录像机(DVR)多媒体系统。该系统的编码采用量化参数与各帧图像归一化活动系数相乘的自适应量化阶来调整图像的量化水准,使DVD+DVR回放的图像质量保持了MPEG-2的高清晰度。     

高分辨率CCD压缩视频的快速存取及实现

针对航测高分辨率CCD巨量压缩视频数据的存取,提出了一种基于文件结构的快速存取系统方案,并给出了该方案在实际存储器中的实现结构。该存取系统主要由图像基本信息和详细信息组成。图像基本信息包括帧号、缩略图、编码长度和地址。通过图像帧号获得图像的基本信息,实现快速浏览;并可进一步读取任意帧图像的详细编码信息。同时,构造了基于小波变换的缩略图方法,并通过对相关存取结构的设计,给出了整个存取系统在存储器中的实现。通过对该系统的研究实现,可高效快捷的实现对任意帧图像数据的快速存取和查找,大大提高了工作效率。     

低速率移动视频监控系统设计与实现

针对日前三大电信运营商普遍采用按用户使用流量来收取通信资费的计费模式,需要移动视频监控系统尽可能地减少对网络带宽的占用.对此,文章设计实现了一套移动视频监控系统,该系统融合了自适应帧内编码与自适应多帧参考技术.从而使系统在取得较好的视频监控图像视觉质量的情况下,能有效地降低对网络带宽的占用.     

基于帧间去相关的超光谱图像压缩方法

针对超光谱图像的特点和硬件实现的实际需要,提出了一种基于小波变换的前向预测帧间去相关超光谱图像压缩算法。通过图像匹配和帧间去相关,消除超光谱图像帧间的冗余,对残差图像的压缩采用基于小波变换的快速位平面结合自适应算术编码的压缩算法,按照率失真准则控制输出码流,实现了对超光谱图像的高保真压缩。通过实验证明了该方案的有效性,基于小波变换的快速位平面结合自适应算术编码的压缩算法速度优于SPIHT,而且易于硬件实现。     

H.264图像复杂度自适应的I帧码率控制算法

该文针对H.264帧内编码码率控制(RC)效果不佳的问题,提出了一种新颖的图像复杂度自适应I帧RC算法。首先用Sobel算子检测I帧亮度像素的梯度,建立44块的边缘方向直方图,得到每个44块最可能的帧内预测模式和相应重构块,最终获得与实际编码相近的残差图像。用残差的平均绝对值表达I帧编码复杂度,并提出了一种经验型码率-量化(R-Q)模型,同时考虑缓冲区状态和序列特性为I帧分配合适的目标比特,最后为每一个图像组(GOP)得到了合适的I帧量化参数(QP)。实验结果表明,该文算法能更准确地控制I帧输出码率,有效阻止缓冲区溢出和跳帧,得到更加平稳的视频质量,序列PSNR波动减少了60%以上。     

一种基于最小路径的通信网络可靠性分析

介绍了通信网络可靠性研究的现状，然后，从网络最小路径的角度出发，在考虑网络延时的基础上，建立了可靠性评估模型，并分析了通信网络的可靠性性能。最后，通过模拟计算，得到了针对给定网络的网络延时条件的范围，以及分析了计算结果与网络可靠性评价的相关关系。     

Reliability Indices for Topological Design of Computer Communication Networks

Incorporating network reliability parameter in the design of reliable computer communication networks makes the computations prohibitive. Interdependence among network topological parameters does not permit the design of a maximally reliable network using any one of the parameters and thus, there arises a real need for a composite reliability index which gives a more realistic assessment of network reliability. After discussing experimental results regarding the effects of various topological parameters on network reliability, we present two heuristic reliability indices which give a fair indication of overall reliability. A design procedure for reliable computer communication network based on local search technique incorporating these reliability indices is suggested. Having only one composite reliability index which is very simple to evaluate saves computation while designing maximally reliable computer networks as compared to the existing techniques based on several reliability measures.     

一种基于神经网络的通信网节点重要性评价方法

准确地评估通信网中节点的重要性,对于通信网的设计、维护管理以及提高整个通信网的可靠性都有重要作用。现有的一些评估方法通常只是考虑单一的影响因素,其评估结果不准确。提出一种基于自组织神经网络的通信网节点重要性评估模型,将通信网中节点的度、节点的网络凝聚度、节点对通信网生成树的影响程度和节点对通信网可靠性的影响程度作为节点重要性的评价指标,对通信网中的节点进行重要性等级的划分。实验结果表明该模型能够全面地评估节点的重要性。     

Empirical prediction of overall reliability in computer communication networks

Incorporation of an overall reliability parameter in the design of reliable computer communication networks makes the computation prohibitive. A composite reliability index based on the network topological parameters has been presented [1], which is very simple to evaluate and gives computation while designing maximally reliable computer networks as compared to the techniques based on several reliability measures. In this paper, we use the tabulated results of Soi and Aggarwal [1] and develop empirical formulae which can be used for quick estimation of overall reliability of a computer network for a specified value of the link reliability.     

Reliability Modeling and Analysis of Computer Networks

The reliability analysis of computer communication networks is generally based on Boolean algebra and probability theory. This paper discusses various reliability problems of computer networks including terminal-pair connectivity, tree connectivity, and multi-terminal connectivity. This paper also studies the dynamic computer network reliability by deriving time-dependent expressions for reliability measures assuming Markov behavior for failures and repairs. This allows computation of task and mission related measures such as mean time to first failure and mean time between failures. A detailed analysis of the bridge network is presented.     

Reliability of directed networks using the factoring theorem

The authors present a framework in which the factoring theorem can be used in conjunction with other network reductions and simplifications to determine the reliability of source-to-sink communication in a directed network. On published test networks, the proposed microcomputer implementation of this framework solves the two-terminal reliability problem substantially faster than existing implementations of other current algorithms     

软交换在下一代铁路通信网络容灾备份中的应用

随着通信技术的发展,铁路运输领域的通信网络也逐渐向下一代通信网络演进。在各种自然灾害以及突发事件中,如何保证铁路通信网络的可靠性显得越发重要。这里针对软交换技术在下一代铁路通信网络容灾备份中的应用进行了探讨,介绍了软交换技术的基本原理,分析了主流方案的技术优势以及适用局限性。     

Maximizing the Mean Number of Communicating Vertex Pairs in Series-Parallel Networks

A communication network can be modelled as a probabilistic graph where each of b edges represents a communication line and each of n vertices represents a communication processor. Each edge e (vertex v) functions with probability Pe (pv). If edges fail independently with uniform probability p and vertices do not fail, the probability that the network is connected is the probabilistic connectedness and is a standard measure of network reliability. The most reliable maximal series-parallel networks by this measure are those with exactly two vertices of degree two. However, as p becomes small, or n becomes large, the probability that even the most reliable series-parallel network is connected falls very quickly. Therefore, we wish to optimize a network with respect to another reliability measure, mean number of communicating vertex pairs. Experimental results suggest that this measure varies with p, with the diameter of the network, and with the number of minimum edge cutsets. We show that for large p, the most reliable series-parallel network must have the fewest minimum edge cutsets and for small p, the most reliable network must have maximum pairs of adjacent edges. We present a construction which incrementally inproves the communicating vertex pair mean for many networks and demonstrates that a fan maximizes this measure over maximal series parallel networks with exactly two edge cutsets of size two.     

Computer-communication network reliability: Trends and issues

People working in Computer-communication networks usually distinguish between the entire system and the communications subnet. The former includes the latter plus the terminals, devices and computer intercommunication via the subnet. This logically includes the resident processes that control or interface with the subnet. Greater computer communication network reliability can obviously be achieved by maximizing the reliability of its constituent components i.e. hardware, software, and communication network. The network reliability can be improved by exploiting the redundancies that are either inherent due to network topology or can be provided in the network. This paper presents a comprehensive discussion of issues involved and trends prevailing in producing reliable hardware; reliable software; and reliable computer communication network while reviewing techniques available for preventing, detecting, diagnosing, correcting and recovering from malfunctions.     

A recursive method for network reliability measures evaluation

A new recursive method for evaluation of reliability measure of the communication networks is given in this paper. The main idea of this method is based on the generation of aggregated networks related to the partitions on subsets of node set. Having found the probabilities of the networks states composing the aggregated network, reliability measures can be obtained by summing up the suitable probabilities of the aggregated networks.