无线多媒体传感器网络与编码技术

无线多媒体传感器网络(WMSNs)是一种允许从物理环境中获取视频、音频、静止图像和标量传感器数据的无线嵌入式设备组成的网络.大信息量的多媒体数据的采集与处理,在军事、民用和商业领域中具有广阔的应用前景.针对WMSNs,主要从信源及其编码技术出发,就最新的国内外研究状况进行了调查、归纳和总结,并且就其中各方面有待研究的问题进行了详细讨论.     

基于无线传感器网络的视频编码技术研究

文章对无线传感器网络中视频编码技术的现状以及所面临的问题和挑战进行了分析,同时探讨了适合无线传感器网络的分布式视频编码技术的编解码方案与优点,最后对无线传感器网络中视频编码技术的研究作了展望。     

无线多媒体传感器网络研究

无线多媒体传感器网络(WMSNs)是在传统无线传感器网络(WSNs)的基础上发展起来的具有音频、视频、图像等多媒体信息感知功能的新型传感器网络,具有广阔的应用前景。该文介绍了WMSNs的概念,分析了WMSNs区别于传统WSNs的个性化特点。对节点系统、MAC协议、路由协议、多媒体信息处理等关键技术的国内外研究现状、面临的问题和可行的解决方案进行了深入探讨。最后对WMSNs亟待解决的问题和发展趋势进行了总结。     

一种分簇无线传感器网络中的分布式信源编码算法

针对密集型无线传感器网络中信息存在大量冗余的问题,该文提出了一种适用于分簇无线传感网络的分布式信源编码算法.该算法以边信息作为初始参考信源,利用信源间的相关性来决定各信源的编码顺序和参考信源,然后由各信源相对于参考信源进行相关编码,接收端则根据编码顺序和参考信源进行相关译码.该文同时针对模值编码的方式,给出了一种低复杂度的译码算法.理论分析和仿真结果表明,将该算法应用于分簇路由协议中可以有效地降低节点的发送比特数,从而降低网络的能耗以延长网络寿命.     

无线传感器网络中的分布式压缩感知技术

本文对无线传感器网络中分布式压缩感知的几个关键技术进行了详细阐述。首先,简要论述了压缩感知方法的基本原理;其次,分析了无线传感器网络中的分布式压缩感知技术与单个信号的压缩感知技术的区别,针对无线传感器网络中联合稀疏模型的建立、分布式信源编码以及联合稀疏信号的重构技术等问题进行了详细讨论;分析了在无线传感器网络的实际应用中,联合稀疏模型、分布式信源编码方式及联合稀疏信号重构方法的性能。最后,对无线传感器网络中分布式压缩感知技术的未来研究方向进行了展望。      

无线传感器网络视频传输技术研究

对无线传感器网络中的视频传输问题进行了研究。无线传感器网络中传输视频数据的难点,在于如何在节点资源有限的网络中确保视频业务的质量。分析并比较了基于单层协议的视频传输技术和基于多层设计的视频传输技术2类视频传输技术,得出结论：2者各有优缺点,单层协议设计与优化简单、扩展性强,但整体性能不一定最佳;跨层优化设计难度较大,但设计得当,性能优于单层协议。     

基于无线组播特性的网络编码在传感器网络中的应用研究

网络编码作为一种新技术在无线传感器网络中有很好的应用前景.通过网络编码,中间节点可以将接收到的信息进行编码后再发送出去,从而提高网络的吞吐量和鲁棒性.文中分析研究了基于无线组播特性的网络编码,及其在无线传感器网络中的应用,包括节省网络能量消耗、提高网络链接鲁棒性[1].     

Ad Hoc上的新协议——流实时传输协议

在Ad Hoc网络中传输多媒体数据会受到网络拓扑变化和无线信道干扰的限制.多流实时传输协议MRTP(multi-flow real-time transport protocol)是一种可以分配和传输多个视频数据流的新协议.它结合多描述编码和多径传输,能提高无线对等网络上视频传输的效率和质量.     

无线自组织网络的网络编码技术

网络编码作为一种新的技术在宽带无线自组织网络中有很好的应用,通过网络编码,中间节点可以将接收信息进行编码并发送出去,提高了网络吞吐量和健壮性。为不对现有网络的软硬件设备和相应的协议做很大的修改,可以选择在高层实现网络编码。无线传感器网络、无线格状网（Mesh）等无线自组织网络都可以使用网络编码技术显著提高多跳链路的传输性能。目前网络编码的研究热点集中在网络编码节点选取方案、网络编码算法的设计、网络编码复杂度分析、网络编码的性能分析、网络编码与系统安全性分析、网络编码在无线分布式网络中的应用等方面。     

无线通信中的网络编码技术

网络编码是一种提高网络吞吐量和性能的新技术,预计将成为未来网络的一项关键技术.本文概述了无线网络中的网络编码技术,无线网络被认为是网络编码最可能得到应用的领域之一,网络编码技术使无线媒质的广播属性可以得到充分利用,无线网络和传感器网络为网络编码的应用提供了巨大的机会.本文结合不同无线场景介绍了网络编码的各种编码方法,包括传统的网络编码、物理层网络编码、模拟网络编码以及复数域网络编码,并对未来发展给出了展望.     

Low-complexity video coding via power-rate-distortion optimization

Wireless multimedia sensor networks (WMSNs) have been potentially applicable for several emerging applications. The resources, i.e., power and bandwidth available to visual sensors in a WMSN are, however, very limited. Hence, it is important but challenging to achieve efficient resource allocation and optimal video data compression while maximizing the overall network lifetime. In this paper, a power-rate-distortion (PRD) optimized resource-scalable low-complexity multiview video encoding scheme is proposed. In our video encoder, both the temporal and interview information can be exploited based on the comparisons of extracted media hashes without performing motion and disparity estimations, which are known to be time-consuming. We present a PRD model to characterize the relationship between the available resources and the RD performance of our encoder. More specifically, an RD function in terms of the percentages for different coding modes of blocks and the target bit rate under the available resource constraints is derived for optimal coding mode decision. The major goal here is to design a PRD model to optimize a “motion estimation-free” low-complexity video encoder for applications with resource-limited devices, instead of designing a general-purpose video codec to compete compression performance against current compression standards (e.g., H.264/AVC). Analytic results verify the accuracy of our PRD model, which can provide a theoretical guideline for performance optimization under limited resource constraints. Simulation results on joint RD performance and power consumption (measured in terms of encoding time) demonstrate the applicability of our video coding scheme for WMSNs.     

Perceptually driven video error protection using a distributed source coding approach

In video communication systems, the video signals are typically compressed and sent to the decoder through an error-prone transmission channel that may corrupt the compressed signal, causing the degradation of the final decoded video quality. In this context, it is possible to enhance the error resilience of typical predictive video coding schemes using as inspiration principles and tools from an alternative video coding approach, the so-called Distributed Video Coding (DVC), based on the Distributed Source Coding (DSC) theory. Further improvements in the decoded video quality after error-prone transmission may also be obtained by considering the perceptual relevance of the video content, as distortions occurring in different regions of a picture have a different impact on the user's final experience. In this context, this paper proposes a Perceptually Driven Error Protection (PDEP) video coding solution that enhances the error resilience of a state-of-the-art H.264/AVC predictive video codec using DSC principles and perceptual considerations. To increase the H.264/AVC error resilience performance, the main technical novelties brought by the proposed video coding solution are: (i) design of an improved compressed domain perceptual classification mechanism; (ii) design of an improved transcoding tool for the DSC-based protection mechanism; and (iii) integration of a perceptual classification mechanism in an H.264/AVC compliant codec with a DSC-based error protection mechanism. The performance results obtained show that the proposed PDEP video codec provides a better performing alternative to traditional error protection video coding schemes, notably Forward Error Correction (FEC)-based schemes.     

IP网络信源信道联合编码策略

面向IP网络,讨论了一种信源编码的失真估计模型,并用典型的视频编码器作了验证.提出了一种基于包的信道编码方法,并将该方法引入信道编码的失真估计中,对一种信道编码的失真估计模型作了改进.以前述内容为基础,提出了两种信源信道联合编码策略,实验结果表明,这两种策略得到的最优结果在很大程度上提高了视频重建质量.     

数字电视视频标准基本参数的诠释

比较了数字电视视频的格式与制式的概念、标准与规范的概念以及数字电视清晰度(分辨率)的概念，指出数字电视的分辨率不同于显像管本身的分辨率；诠释了数字电视的扫描格式、宽高比以及编码方式等基本参数，详尽地论述了数字视频信号编码中的复合编码和分量编码、数字视频传输中的信源编码和信道编码。     

A joint source and channel coding algorithm for error-resilient SPIHT-coded video bitstreams

We propose an analytical rate-distortion optimized joint source and channel coding algorithm for error-resilient scalable encoded video for lossy transmission. A video is encoded into multiple independent substreams to avoid error propagation and is assigned forward error correction (FEC) codes and source bits using Lagrange optimization. Our method separates video coding and packetization into different tiers which can be easily incorporated into any coding structure that generates a set of independent compressed bit-streams. To demonstrate the performance, we use the 2-state Markov model to describe the burst loss channel and Reed-Solomon codes as forward error correction codes. Simulation results show that the proposed channel incorporated rate-distortion optimization approach have better performance.     

视频流传输中的差错复原视频编码技术

视频压缩技术在采用预测技术、变换编码技术和可变长熵编码技术以减少冗余信息的同时,也降低了视频流的容错能力.传输信道中的差错,不仅严重损害了视频服务质量,甚至会使通信系统崩溃,因此,在有错信道上进行视频传输,差错复原视频编码技术就显得尤为重要.对差错复原视频编码技术进行了概括和总结,首先指出在视频传输过程中存在的由于传输错误而引发的比特流同步丢失及错误蔓延问题,然后研究了解决这些问题的差错复原视频编码方法,最后指出:可伸缩视频编码和多描述视频编码是差错复原视频编码的发展方向;多描述编码同多路径技术相结合,能显著提高压缩视频信号的错误恢复能力和传输信道的性能.     

Multiview coding and error correction coding for 3D video over noisy channels

We consider the joint source–channel coding problem of stereo video transmitted over AWGN and flat Rayleigh fading channels. Multiview coding (MVC) is used to encode the source, as well as a type of spatial scalable MVC. Our goal is to minimize the total number of bits, which is the sum of the number of source bits and the number of forward error correction bits, under the constraints that the quality of the left and right views must each be greater than predetermined PSNR thresholds at the receiver. We first consider symmetric coding, for which the quality thresholds are equal. Following binocular suppression theory, we also consider asymmetric coding, for which the quality thresholds are unequal. The optimization problem is solved using both equal error protection (EEP) and a proposed unequal error protection (UEP) scheme. An estimate of the expected end-to-end distortion of the two views is formulated for a packetized MVC bitstream over a noisy channel. The UEP algorithm uses these estimates for packet rate allocation. Results for various scenarios, including non-scalable/scalable MVC, symmetric/asymmetric coding, and UEP/EEP, are provided for both AWGN and flat Rayleigh fading channels. The UEP bit savings compared to EEP are given, and the performances of different scenarios are compared for a set of stereo video sequences.     

分布式信源编码错误漂移消除机制的研究

传统视频编码标准由于具有较高的视频压缩效率而得到广泛使用,但是该方法存在错误漂移的现象,而分布式信源编码是当前解决这一现象行之有效的方法。目前提出的错误漂移消除机制采用固定间隔的方法,即每隔几帧选取一帧用于阻止错误漂移,但是该方法在选取视频帧的时候没有考虑被选取视频帧与前后帧的相关性,缺乏灵活性,针对这一问题提出了基于相关性的错误漂移消除选取机制。实验结果证明,该方法可以获得较好的解码效果。     

基于感知的视频编码方法综述

基于感知的视频编码方法是目前视频编码的研究热点.该文综合论述了基于感知的视频编码方法,重点阐述了基于感知的3维视频编码方法.首先,对目前利用人类视觉系统中的亮度、对比敏感度、中心凹等视觉感知特性的单视点视频编码方法进行分析并指出其存在的问题.然后,对基于立体感兴趣区域和双目敏感度特性的3维视频感知编码方法进行了分析和论述.最后,就基于感知的视频编码方法的进一步发展提出了若干技术与研究方向的展望.     

MPEG-4标准起草工作近况

本文简略报道国际活动图像专家组近年对多媒体通信草拟新标准MPEG 4的进展情况。其中音频编码包括语音、音乐 (自然的和合成的 ) ,比特率从 2至 6 4kb /s。视频编码包括甚低比特率 5～ 6 4kb /s和较高比特率 6 4kb /s至 2Mb /s。视频编码可将图像中每一对象分开编码为不同的比特流层 ,又可操纵对象的尺度、位置等 ,具有以内容为基础的交互式功能。除了核心编码器外 ,对输入视频序列的每一帧分成若干个任意形状的“视频对象平面” ,编码成各个分开的“视频对象层”。另外 ,利用“子图形”编码技术 ,将图像的背景以及前景中的每一对象分开编码成视频序列后传输 ,可以改善视像质量。