Delivering audiovisual content with MPEG-21-enabled cross-layer QoS adaptation

Future multimedia communication systems have to support the user‘s needs, the terminal capabilities, the content specification and the underlying networking technologies. The related protocols and applications must be designed from this integration perspective in a cross-layer centric manner. In this paper, we propose an implementation of a streaming service (e.g.,Television over IP service) with a unified QoS management concept that enables an IP driven integration of different system components (terminal, user, content, and network). The MPEG-21 framework is used to provide a common support for implementing and managing the end-to-end QoS. The main focus of this paper is on the architecture design, protocols specification and implementation evaluation. Performance evaluations using PSNR and SSIM objective video quality metrics show the benefit of the proposed MPEG-21-enabled cross-layer adaptation.     

基于贝叶斯网络的无线Ad Hoc网络视频传输方法

针对AdHoc网络的视频传输,提出了一种新的网络带宽预测及控制方案．该方案基于跨层、接收端反馈以及贝叶斯网络等技术．对视频传输过程进行公式化描述,从而推导出影响视频传输质量的几个主要因素,这些因素可以通过跨层机制或接收端反馈的方式获取．根据这些影响因素,确定变量集和贝叶斯网络拓扑结构,从而构建贝叶斯网络预测模型．预测结果作为AdHoc网络带宽,根据该带宽值来控制视频编码器,动态调节输出的实时视频流码率．为验证该方案,对整个视频通信系统进行了仿真．结果显示,跟传统的传输方案相比较,夺方案能更好地利用网络带宽,减少了数据包的丢失,提高了实时视频质量．     

Distributed media cooperation for enhanced video communication

INTRODUCTION According to yearly statistics the demand for multimedia traffic over computer networks is con- stantly on the increase (Nielsen//NetRatings, http:// www.nielsen-netratings.com/). Therefore, it is inevi- table that situations where different media streams will need to share communication resources will be- come commonplace. In such cases, it would be of interest to optimize the overall performance of the network. In other words, resources should be allo- cated across the com…     

一种视频会议系统的研究与实现

介绍了使用局域网组播技术和Directshow多媒体开发框架实现多方视频会议系统的方法。系统引入了会议管理服务器以控制多媒体数据在网络中的接入和访问,使网络不会由于多媒体数据的激增而发生拥塞,从而保证服务质量。系统使用了面向对象的方法和UML语言,分析和设计了各个模块。系统的视频部分采用了MPEG-4编解码技术,音频数据留采用了G.729编解码方法。根据该设计方案,完成了该系统的设计和开发,实现了多人同时通讯的模拟视频会议功能。     

Joint routing and rate allocation for multiple video streams in ad-hoc wireless networks

INTRODUCTION Ad-hoc networks are attractive owing to their self-organizing nature and absence of a fixed infra- structure. They are particularly suited for communi- cation in disaster-affected areas, coordinating military operations, and sensing environmental conditions With the growing availability of supporting hardware and decreasing equipment cost, ad-hoc networking based applications are proliferating. Meshes of wire- less nodes are being deployed in cities and housing communities to…     

RTP-based broadcast streaming of high definition H.264/AVC video: an error robustness evaluation

In this work, we present an evaluation of the performance and error robustness of RTP-based broadcast streaming of high-quality high-definition (HD) H.264/AVC video. Using a fully controlled IP test bed (Hillestad et al., 2005), we broadcast high-definition video over RTP/UDP, and use an IP network emulator to introduce a varying amount of randomly distributed packet loss. A high-performance network interface monitoring card is used to capture the video packets into a trace file. Purpose-built software parses the trace file, analyzes the RTP stream and assembles the correctly received NAL units into an H.264/AVC Annex B byte stream file, which is subsequently decoded by JVT JM 10.1 reference software. The proposed measurement setup is a novel, practical and intuitive approach to perform error resilience testing of real-world H.264/AVC broadcast applications. Through a series of experiments, we evaluate some of the error resilience features of the H.264/AVC standard, and see how they perform at packet loss rates from 0.01 % to 5%. The results confirmed that an appropriate slice partitioning scheme is essential to have a graceful degradation in received quality in the case of packet loss. While flexible macroblock ordering reduces the compression efficiency about 1 dB for our test material, reconstructed video quality is improved for loss rates above 0.25%.     

Channel adaptive rate control for energy optimization

Low energy consumption is one of the main challenges for wireless video transmission on battery limited devices. The energy invested at the lower layers of the protocol stack involved in data communication, such as link and physical layer, represent an important part of the total energy consumption. This communication energy highly depends on the channel conditions and on the transmission data rate. Traditionally, video coding is unaware of varying channel conditions. In this paper, we propose a cross-layer approach in which the rate control mechanism of the video codec becomes channel-aware and steers the instantaneous output rate according to the channel conditions to reduce the communication energy. Our results show that energy savings of up to 30% can be obtained with a reduction of barely 0.1 dB on the average video quality. The impact of feedback delays is shown to be small. In addition, this adaptive mechanism has low complexity, which makes it suitable for real-time applications.     

Channel adaptive rate control for energy optimization

Low energy consumption is one of the main challenges for wireless video transmission on battery limited devices. The energy invested at the lower layers of the protocol stack involved in data communication, such as link and physical layer, represent an important part of the total energy consumption. This communication energy highly depends on the channel conditions and on the transmission data rate. Traditionally, video coding is unaware of varying channel conditions. In this paper, we propose a cross-layer approach in which the rate control mechanism of the video codec becomes channel-aware and steers the instantaneous output rate according to the channel conditions to reduce the communication energy. Our results show that energy savings of up to 30% can be obtained with a reduction of barely 0.1 dB on the average video quality. The impact of feedback delays is shown to be small. In addition, this adaptive mechanism has low complexity, which makes it suitable for real-time applications.     

JPEG2000及其网络应用前景展望

随着Internet的发展,网络上的数字图像成为信息重要载体,传统的JPEG静止图像压缩标准已经不能满足新应用的需要.为此,国际标准化组织制定了新的图像压缩标准JPEG2000.该文介绍了JPEG2000的基本原理,在与JPEG标准比较的基础上分析了JPEC2000的主要特点,并基于网络对JPEG2000应用前景作出展望.     

Multiple description coding with spatial-temporal hybrid interpolation for video streaming in peer-to-peer networks

INTRODUCTION Multimedia services over the Internet are be- coming popular due to the widespread deployment of broadband access. However, the conventional cli- ent-server architecture severely limits the number of simultaneous users, especially for bandwidth inten- sive applications such as video streaming. P2P net- works, on the other hand, offer a solution to the scalability problem. As a node joins a P2P network, it not only consumes resources but also contributes its bandwidth or comp…     

RTP-based broadcast streaming of high definition H.264/AVC video: An error robustness evaluation

In this work, we present an evaluation of the performance and error robustness of RTP-based broadcast streaming of high-quality high-definition (HD) H.264/AVC video. Using a fully controlled IP test bed (Hillestad et al., 2005), we broadcast high-definition video over RTP/UDP, and use an IP network emulator to introduce a varying amount of randomly distributed packet loss. A high-performance network interface monitoring card is used to capture the video packets into a trace file. Purpose-built software parses the trace file, analyzes the RTP stream and assembles the correctly received NAL units into an H.264/AVC Annex B byte stream file, which is subsequently decoded by JVT JM 10.1 reference software. The proposed measurement setup is a novel, practical and intuitive approach to perform error resilience testing of real-world H.264/AVC broadcast applications. Through a series of experiments, we evaluate some of the error resilience features of the H.264/AVC standard, and see how they perform at packet loss rates from 0.01% to 5%. The results confirmed that an appropriate slice partitioning scheme is essential to have a graceful degradation in received quality in the case of packet loss. While flexible macroblock ordering reduces the compression efficiency about 1 dB for our test material, reconstructed video quality is improved for loss rates above 0.25%.     

基于内容描述的可伸缩视频码流提取框架

可伸缩视频编码通过码流提取获得子码流以适应不同的网络带宽和处理终端。本文提出一种基于内容描述的视频码流提取框架,根据预处理获得视频内容的描述指导可伸缩视频的码流提取,从而获得更符合视频内容的子码流。实验表明这种方法快速有效,能够在不损失编码效率的前提下保证视觉质量。     

SVC的RTP封装及其在NS2包调度中的应用研究

随着流媒体技术的发展,实时传输协议RTP被广泛用于各种多媒体传榆系统中,为实时应用提供端到端的传输。可伸缩视频编码（SVC）因其时域、空间和质量的可分级,能够为用户提供可分级性更强的视频流,满足不同终端设备用户的需求。本文针对SVC视频流应用于NS2网络传输仿真而设计了一套可伸缩视频编码的RTP卦装方案,并将其应用于NS2仿真环境,实现了真实视频流的实时调度与传输。实验结果验证了该RTP卦装方案的正确性和有效性。     

Multipoint videoconferencing with scalable video coding

INTRODUCTION Modern videoconferencing systems allow two o more participants to communicate with each other in real-time using both audio and video. Conventionally when more than two participants are present, a sta configuration is generally employed, wherein a Mul tipoint Conferencing Unit (MCU), or bridge, is util ized to connect to all participants and coordinat communications between them. The general archi tecture is shown in Fig.1. Fig.1 Multipoint videoconferencing system Network…     

Media-specific rate allocation in heterogeneous wireless networks

INTRODUCTION With the development of novel wireless tech- nologies and increasing available bandwidth, multi- media applications over wireless networks become attractive for both businesses and end users. Fast de- ployment of Wi-Fi HotSpots, increase in wireless coverage of remote habitable areas (Wi-Max, or wireless mesh networks), improved data services over the 2G cellular systems and the long awaited debut of 3G wireless services offer many potential and inter- operable communicatio…     

JPEG压缩后图像小波特征分析

以认证水印为研究背景,提取图像第三层小波分解近似子带系数作为水印信息。考察了不同品质的JPEG压缩对图像小波近似子带系数影响,实验结果表明：小波近似子带系数值在大于标准压缩品质因子JPEG压缩前后有较好的鲁棒性,且其差值小于等于某个较小的阈值。     

Adaptive peer-to-peer streaming with MutualCast

INTRODUCTION Many applications, such as software distribution, Internet TV/video streaming, video conferencing, multiplayer gaming, personal media distribution and P2P web content duplication, distribute the same content from one source node to many destination nodes. For these applications, IP multicast is an ideal network layer solution. A distribution tree rooted at the source can be formed to reach an arbitrary number of receivers. During content distribution, every single piece of…     

一种基于JPEG2000的半脆弱数字水印

利用JPEG2000编解码系统提供的小波变换和EBCOT技术,提出了一种用于JPEG2000图像认证的半脆弱数字水印算法。该算法把水印嵌入到量化后小波系数的高频部分中,对JPEG2000编解码系统的影响小。文章最后给出算法的仿真实验结果并加以分析,实验结果表明该算法对一般的JPEG2000压缩具有较强的鲁棒性,对常见的攻击如:剪切、噪声等具有脆弱性。     

一种基于JPEG2000的半脆弱数字水印

利用JPEG2000编解码系统提供的小波变换和EBCOT技术,提出了一种用于JPEG2000图像认证的半脆弱数字水印算法。该算法把水印嵌入到量化后小波系数的高频部分中,对JPEG2000编解码系统的影响小。文章最后给出算法的仿真实验结果并加以分析,实验结果表明该算法对一般的JPEG2000压缩具有较强的鲁棒性,对常见的攻击如：剪切、噪声等具有脆弱性。     

A fast motion estimation algorithm for mobile communications

The limitation of processing power, battery life and memory capacity of portable terminals requires reducing encoding complexity in mobile communications. Motion estimation (ME) is the most computationally intensive module in a typical video codec, which determines not only the encoder’s performance but also the reconstructed video quality. In this paper, a fast ME algorithm for H.264/AVC baseline profile coding is proposed based on the analysis of motion vector field and error surface, and the statistical distributions of different type macroblocks (MBs). Simulation results showed that: in comparison with MVFAST, the proposed algorithm can decrease the computational load over 7.2% with no requirement of expanding memory capacity while maintaining the same video quality as MVFAST. Furthermore, its simplicity makes it easy to be implemented on hardware.