IP网络丢包情况下音视频实时通讯研究

分析了IP网络中音视频实时通讯抗网络丢包的技术现状,并探讨了采用前向纠错方法实现抗丢包的实现机制。对于开发各种网络状况自适应的视频会议系统具有一定参考价值。     

A Low-Complexity Cross-Layer Optimization Algorithm for Video Communication Over Wireless Networks

Recent years have witnessed a rapid increment in video applications over wireless networks including on-demand video streaming and video phoning. This growth has also brought the need to find a good compromise in the conflict between resource limitations affecting mobile devices and the desire for high-quality multimedia services. It is possible to face this problem adopting a cross-layer strategy that jointly tunes the parameters of each layer in the network protocol stack. In this optimization strategy, complexity is one of the most significant issues because of the limited computational resources and power supply. The paper presents a low-complexity cross-layer algorithm that is able to jointly tune the parameters of different protocol layers by adopting simple but effective models. The quality of the reconstructed video sequence, the produced bit rate, and the service class associated to each packet are seen as functions of the percentage of null DCT coefficients. This modeling permits to find a closed-form solution to the joint optimization problem that can be computed with a limited number of operations and grants, at the same time, a good visual quality in the reconstructed sequence.     

浅谈广西水文视频会商系统的建设

广西区水文水资源局中心主会场配置一台高级视频终端POLYCOM HDX 8000XL,各地分会场配置POLYCOMHDX7002XL,通过以太网端口接入本地局域网,通过广域网连接到中心主会场的POLYCOMRMX2020多点控制单元(MCU),实现广西壮族自治区内10个地市的视频会议.该系统支持多点视频会议功能和数据会议功能,可应用于防汛异地会商、行政会议、教学培训等方面.本文重点介绍了该视频会商系统的组网技术和功能的实现.     

Remote Video Monitoring Over the WWW

Remote video monitoring has become increasingly important for monitoring the security of destined locations. Traditional security monitoring systems using coaxial cables and VCR recording systems are expensive and ineffective. With the rapid growth of the Internet, it is now possible to use it as an intermediate transmission medium to support real-time video transmission. This paper proposes a web-based remote monitoring system known as iSecure. Apart from the essential live or stored video transmission, intelligent monitoring and web-based monitoring are also supported. As the transmission of live video data through the packet switched network environment of the Internet can result in packet loss and quality degradation, the iSecure system has implemented an adaptive transmission and recovery mechanism to enhance the quality of real-time video transmission. Intelligent monitoring for elevator security and face-based door access control applications has been incorporated. The iSecure system can be used as a framework for developing other intelligent remote monitoring applications.     

基于网络丢包的网络视频质量评估

针对传统的视频质量评估模型对于在包交换网络中传输的压缩视频（网络视频）进行质量评估的局限性,如对视频质量进行评估时实时性差、没考虑人眼的视觉感知等问题,提出了一种基于网络丢包的网络视频质量评估模型。该模型采用了统计学理论,它可根据视频编码、封装传输的特点,通过可量化的评价指标来评定视频质量受网络丢包的影响程度,以评估网络视频质量。利用该模型进行网络视频质量评估,不仅资源开销小、实时性好,而且特别适合对实时传输的视频流进行视频质量评估。为了验证该模型的正确性与可靠性,采用它与MPQM模型分别对受系列丢包率影响的视频序列进行了评估实验。实验结果表明,该模型的评价结果能较好地吻合MPQM模型的评价结果,且符合人眼的视觉效果。     

H．263在无线信道上传输的抗干扰机制

随着多媒体业务的发展，基于无线网络的视频传输备受关注，但无线网络的发展由于带宽受限、误码高而受到了制约。本文基于H．263＋提出了一种抗干扰机制来提高视频信号的健壮性，同时并不引入额外带宽负担，最后采用ITU-T的差错模型仿真WCDMA信道来检验抗干扰性能。实验结果表明，采用该方法的重构图像的主客观质量都有很     

Remote Collaboration Over Video Data: Towards Real-Time e-Social Science

The design of distributed systems to support collaboration among groups of scientists raises new networking challenges that grid middleware developers are addressing. This field of development work, ‘e-Science’, is increasingly recognising the critical need of understanding the ordinary day-to-day work of doing research to inform design. We have investigated one particular area of collaborative social scientific work – the analysis of video data. Based on interviews and observational studies, we discuss current practices of social scientific work with digital video in three areas: Preparation for collaboration; Control of data and application; and Annotation configurations and techniques. For each, we describe how these requirements feature in our design of a distributed video analysis system as part of the MiMeG project: our security policy and distribution; the design of the control system; and providing freeform annotation over data. Finally, we review our design in light of initial use of the software between project partners; and discuss how we might transform the spatial configuration of the system to support annotation behaviour.     

智能视频算法评估综述

智能视频监控在公共安全和民用领域已经显现出有效与广阔的应用前景,备受国内外学者和众多实际工程领域专家的高度关注,制定有效、公正的智能视频算法评估准则是其应用过程中的一个重要环节.文中对当前国际上智能视频算法的评估工作进行了比较全面的综述,重点是运动检测、目标跟踪的性能评估.最后指出了智能视频算法评估的发展方向.     

Video Decompression Estimation and Playout Scheme Over the Internet

This paper examines problems associated with display of live continuous media. Under the assumption that the network cannot guarantee the required bounds on delay and jitter and the operating system scheduling is non-realtime, there is a need to accommodate the delay and jitter in the end systems in order to maintain a desirable Quality of Service (QoS). We propose a method of video playback which requires accurate estimation of display cycle time of video frames and the delay suffered by frames in the packet network. We apply various deterministic forecasting methods used in time series analysis on experimental data collected from video transmission. Suitable methods are recommended for display cycle time and delay estimation.     

IP网络环境下基于PI控制的实时视频流连续播放控制算法

为了克服IP网络环境下网络扰动对流媒体连续播放的影响,从接收端的角度来解决流媒体连续播放问题,提出一种基于PI控制的实时视频流连续播放控制算法.该方法在接收端使用根轨迹法设计PI控制器,通过控制播放速率,调节缓冲区的长度,实现了媒体的连续播放.为了真实地反映网络传输对接收端播放的影响,本文构建了一种基于TFRC协议的实时视频流传输控制框架.NS2仿真实验表明该方法与其他方法相比,播放质量明显提高,缓冲区出现欠载和溢出的机率明显降低,视频帧端到端平均时延明显缩小,实时性能明显增强.     

紫外光通信系统中的视频传输研究

本文介绍了紫外通信系统中的视频传输领域,详细介绍了国内外紫外光通信的发展形势.以及紫外光视频传输中遇到的问题和解决方案.基于TI生产的DM6437开发板,使用H.264作为视频压缩算法,进行了初步的研究和实验.     

An Adaptive Motion-Based Unequal Error Protection Approach for Real-Time Video Transport Over Wireless IP Networks

In this work, we consider the delivery of digital video over future 3G wireless IP networks and we propose a low-complexity adaptive motion-based unequal error protection (UEP) video coding and transmission system which efficiently combines three existing error-resilience techniques by exploiting knowledge of the source material as well as the channel operating conditions. Given this information, the proposed system can adaptively adjust the operating parameters of the video source encoder and the forward error correction (FEC) channel encoder to maximize the delivered video quality based upon both application-layer video motion estimates and link-layer channel estimates. We demonstrate the efficacy of this approach using the ITU-T H.264 video source coder. The results indicate that a significant performance improvement can be achieved with enhanced resilience to inaccurate channel feedback information and with substantially reduced computational complexity compared to competing approaches.     

一种宽带IP网视频传输方案

给出了宽带IP网视频传输系统的基本框架,并在此基础上实现了视频传输的一些关键技术,提出了一种新的QoS规范的定性描述方法和分组丢弃策略.     

Remote Control Over Noisy Communication Channels: A First-Order Example

In this note, we consider a set up in which the plant and controller are local to each other, but are together driven by a remote reference signal that is transmitted through a noisy discrete channel. Our goal is to design codeword lengths of block source and channel encoders, and a controller to meet a model matching performance objective. Such design problems are difficult in general, as there is a strong interplay between control objectives and communication constraints, which forces the synthesis of controllers and encoder-decoder pairs to be done simultaneously. Current approaches typically fix one, while the other is designed to meet some objective. We first construct a model matching performance metric that captures the tradeoffs between coding the reference command to achieve more accuracy at the remote site and designing a controller to meet performance. We then simultaneously synthesize the controller and encoder codeword lengths that meet the specified objective for a first-order plant and model case. Finally, we illustrate performance sensitivity to the poles of the plant and model, and to the channel noise     

3G终端加密技术在DSP上实现

Helix加密/鉴别算法是一种伴随消息认证码的高速流密码加密算法,它具有加密速度快、抗攻击力强的特点,特别适用于小型系统的数据加密,易于DSP实现.随着移动通信多种业务的发展,迫切需要信息的密文传输.本文就Helix加密/鉴别算法在TMS320C5510 DSP上实现给出比较完整的分析和描述,利于将Helix加密/鉴别算法引用到实际应用中.     

一种基于层次分析法的视频摘要评价模型

视频摘要是对视频内容进行浓缩的一项技术,对于快速了解视频内容至关重要。如何对视频摘要的效果进行评价,是值得研究的一个问题。论文基于层次分析法构建了视频摘要评价模型,将视频摘要质量作为最终评价目标,以内容合理性和结构合理性作为准则,以内容完整性、特殊重要性、整体流畅性等作为测度层,从而建立了视频摘要评价指标体系。最后,通过对随机生成、基于特写人脸的摘要生成以及融合视音频特征的摘要生成三种算法对所提评价方法进行了实验验证,表明该方法能够有效反映出视频摘要的质量。     

An Admission Control Scheme Based on Online Measurement for VBR Video Streams Over Wireless Home Networks

This paper presents an online measurement-based admission control scheme on the basis that the aggregate VBR video traffic is lognormally distributed. The proposed scheme consists of two components: measurement process and admission decision. The measurement process applies a linear Kalman filter to estimate statistical parameters of aggregate VBR video traffic. The estimated statistical parameters are used to calculate the effective bandwidth for admission decision. Variable bit rate (VBR) video traffic with high data rate is expected to occupy a dominant proportion of bandwidth for future wireless broadband home networks. To guarantee quality-of-service (QoS) of such VBR video streams, while achieving a high level of channel utilization, an efficient admission control scheme is urgently required, especially for emerging wireless multimedia indoor services, such as HDTV, online video game, etc. The proposed scheme is computationally efficient and accurate without much prior traffic information. Simulation results verify its effectiveness and show that it performs well for both a small number of connections and a large number of connections.     

H.264视频编解码技术在视频无线通信系统中的应用

为了进一步提高压缩性能,重点进行了H.264编解码器的优化.依据应用需求,对H.264编码中运算复杂度最高的运动估计模块进行了算法改进.在对参考代码JM10.2解码器的性能进行复杂度分析的基础上,提出了一种基于码头分组的快速变长熵解码方法.     

移动视频通信业务的应用研究

移动视频通信业务是通过移动网络和移动终端为移动用户提供的一种新型通信服务。本文主要研究了基于3G和VoLTE技术的移动视频通信业务的应用。分别从技术、资费、用户体验、互通性四个方面对两种移动视频通信业务进行了分析和对比。