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.     

ATM网络的视频编码技术

异步转换模式（ＡＴＭ）的提出对编码技术产生了重大的影响。本文概述了ＡＴＭ下可变比特率（ＶＢＲ）视频编码的优点及存在的问题，扼要介绍了各种信元丢失的预防及补偿方法，着重分析了分层编码技术，并对目前提出的各种可变比特率分层编码算法进行了概括性的评述，指出了有待研究的一些问题。     

面向Internet传输的多描述可分级视频编码

带宽变化和丢包错误是当前Internet视频传输面临的主要问题,解决的有效途径是对信源采用可分级编码和多描述编码。研究表明,这两种编码方法具有互补性,联合起来使用能提供更好的质量自适应视频传输。传统的联合方案是用多描述编码保护可分级编码的基层信息,该文对此进行了拓展,提出了一种改进的多描述可分级联合视频编码方案。在该方案中,首先用多描述编码方法处理第一级可分级编码的基层信息,然后对得到的多描述进行第二级可分级编码。与传统方案相比,该方案的优点是可以同时兼顾压缩视频流的效率和鲁棒性。     

Multi-Source Spinal Coding for Coded Caching Multicast Transmissions in Wireless Networks

Recently,coded caching has been treated as a promising technique to alleviate the traffic burden in wireless networks.To support high efficient coded caching multicast transmissions,the time-varying heterogeneous channel conditions need to be considered.In this paper,a practical and novel multi-source spinal coding(MSSC)scheme is developed for coded caching multicast transmissions under heterogeneous channel conditions.By exploring joint design of network coding and spinal coding(SC),MSSC can achieve unequal link rates in multicast transmissions for different users.Moreover,by leveraging the rateless feature of SC in our design,MSSC can well adapt the link rates of all users in multicast transmissions without any feedback of time-varying channel conditions.A maximum likelihood(ML)based decoding process for MSSC is also developed,which can achieve a linear complexity with respect to the user number in the multicast transmission.Simulation results validate the effectiveness of the MSSC scheme.Compared to the existing scheme,the sum rate of MSSC in multicast transmissions is improved by about 20%.When applying MSSC in coded caching systems,the total transmission time can be reduced by up to 48% for time-varying channels.     

智能移动终端对移动网络流量影响研究

深入分析了智能移动终端对移动网络信令流量和数据流量的影响,并从移动网络、应用开发以及操作系统平台三个层面提出移动网络流量控制方案,为今后改善和规范智能移动终端操作系统、应用开发与测试等提供借鉴和参考。     

移动实时视频系统中的差错控制技术

论文给出了一种H.264实时视频系统中具有较强差错恢复能力的视频编码算法以及编解码算法的实现流程图。并在JVT提供的H.264标准测试模型JM10.2上通过优化代码进行了仿真,达到了较好的效果。     

Modeling of the Coding Gain of Joint Coding for Multi-Program Video Transmission

In digital multi-program video transmission, several video programs are compressed (e.g., using MPEG-2), multiplexed, and transmitted over a constant bit rate (CBR) channel. Joint coding, or statistical multiplexing, which is now widely used in digital television broadcasting, dynamically allocates the available channel capacity among programs according to picture content. This scheme is much more efficient than independent coding where each channel is allocated a fixed bit rate. In this paper, we present a model which can relate the decoded picture quality to bit rate, for both independent and joint coding. The model takes into account statistical variations of video program complexity, and incorporates experimental data drawn from formal subjective picture quality assessments. We use the model to calculate the coding gain of joint coding relative to independent coding, in terms of bandwidth savings.     

A Joint Source-Coding Power-Control Approach Combined With Adaptive Channel Coding for Video Transmission Over CDMA Networks

We propose a joint source-coding power-control approach combined with joint source-channel coding employing the class of rate-compatible codes for video transport over code-division multiple-access networks. We show that this cross-layer approach can provide improved spectral efficiency and network use while exhibiting graceful degradation characteristics with an increasing number of users.     

Performance of Multilayered Video Encoding and Delivery over Lossy Channels Using a Joint Source-Channel Coding Approach

In this paper, the performance of selected error-control schemes based on forward error-control (FEC) coding for H.263+ video transmission over an additive white Gaussian noise (AWGN) channel is studied. Joint source and channel coding (JSCC) techniques that employ single-layer and 2-layer H.263+ coding in conjunction with unequal error protection (UEP) to combat channel errors are quantitatively compared. Results indicate that with appropriate joint source and channel coding, tailored to the respective layers, FEC-based error control in combination with 2-layer video coding techniques can lead to more acceptable quality for wireless video delivery in the presence of channel impairments. Yong Pei is currently a tenure-track assistant professor in the Computer Science and Engineering Department, Wright State University, Dayton, OH. Previously he was a visiting assistant professor in the Electrical and Computer Engineering Department, University of Miami, Coral Gables, FL. He received his B.S. degree in electrical power engineering from Tsinghua University, Beijing, in 1996, and M.S. and Ph.D. degrees in electrical engineering from Rensselaer Polytechnic Institute, Troy, NY, in 1999 and 2002, respectively. His research interests include information theory, wireless communication systems and networks, and image/video compression and communications. He is a member of IEEE and ACM. James W. Modestino (S′67- M′73- SM′81- F′87) was born in Boston, MA, on April 27, 1940. He received the B.S. degree from Northeastern University, Boston, MA, in 1962, and the M.S. degree from the University of Pennsylvania, Philadelphia, PA, in 1964, both in electrical engineering. He also received the M.A. and Ph.D. degrees from Princeton University, Princeton, NJ, in 1968 and 1969, respectively. He has held a number of industrial positions, including positions with RCA Communications Systems Division, Camden, NJ; General Electronic Laboratories, Cambridge, MA; AVCO Systems Division, Wilmington, MA; GTE Laboratories, Waltham, MA; and MIT Lincoln Laboratories, Lexington, MA. From 1970 to 1972, he was an Assistant Professor in the Department of Electrical Engineering, Northeastern University. In 1972, he joined Rensselaer Polytechnic Institute, Troy, NY, where until leaving in 2002 he was an Institute Professor in the Electrical, Computer and Systems Engineering Department and Director of the Center for Image Processing Research. He has been responsible for teaching and research in the communication, information and signal processing systems area. His specific research interests include communication in fading dispersive channels; detection, estimation and filtering in impulsive or burst noise environments; digital signal, image and video processing; and multimedia communication systems and networks. In 2002 he joined the Department of Electrical and Computer Engineering at the University of Miami, Coral Gables, FL, as the Victor E. Clarke Endowed Scholar, Professor and Chair. He has held visiting positions with the University of California at San Diego, LaJolla, CA (1981–1982); GE Research and Development Center, Schenectady, NY (1988–1989); and Massachusetts Institute of Technology, Cambridge, MA (1995–1996). Dr. Modestino is a past member of the Board of Governors of the IEEE Information Theory Group. He is a past Associate Editor and Book Review Editor for the IEEE TRANSACTIONS ON INFORMATION THEORY. In 1984, he was co-recipient of the Stephen O. Rice Prize Paper Award from the IEEE Communications Society and in 2000 he was co-recipient of the best paper award at the International Packet Video Conference.     

面向3G环境下的移动视频编码技术

 随着移动通信迈入3G时代,在众多的3G增值业务中,移动视频业务无疑将会成为3G业务的核心应用,以视频编码技术为代表的多媒体技术是支撑移动业务运营的基础技术。本文首先介绍了面向3G环境下的移动视频业务的发展现状及其面临的技术问题;然后从可分级编码、视频转码、多描述编码、基于视觉特性的编码几个方面论述了针对移动视频的编码技术;最后对面向3G环境下的移动视频编码技术进行了总结和展望。     

一种网络编码和信道编码的联合设计

网络编码技术可以大幅度提高网络的吞吐量和鲁棒性,因此已成为近年来的研究热点。在研究无线网络中物理层网络编码技术的基础上,提出了多址信道中一种联合网络编码和信道编码的设计方案。该设计利用LDPC码和网络编码的线性特性以及软输入软输出模块设计,不仅减少了编译码的复杂度,而且在高的信噪比情况下可以获得良好的性能。仿真结果表明,该设计方案不仅容易实现,而且性能接近网络信道容量的上限,相比传统的设计技术至少能够提高1．6倍的增益。     

自适应选择联合补偿预测模式的立体视频编码算法

运动补偿预测．视差补偿预测以及两者相结合的联合补偿预测是研究立体视频编码的关键技术。不同预测模式不仅考虑了左右视频通道各自的时间相关性、而且考虑到了左右视频通道之间的空间相关性。本文提出了一种自适应选择预测模式的立体视频编码算法,并在预测模式确定后通过选取不同的加权值来达到联合补偿预测的目的。实验结果表明,本文提出的算法在改善编码性能的同时,提高了编码速度。     

Quasi-Static Scheduling of CAL Actor Networks for Reconfigurable Video Coding

The upcoming Reconfigurable Video Coding (RVC) standard from MPEG (ISO / IEC SC29WG11) defines a library of coding tools to specify existing or new compressed video formats and decoders. The coding tool library has been written in a dataflow/actor-oriented language named CAL. Each coding tool (actor) can be represented with an extended finite state machine and the data communication between the tools are described as dataflow graphs. This paper proposes an approach to model the CAL actor network with Parameterized Synchronous Data Flow and to derive a quasi-static multiprocessor execution schedule for the system. In addition to proposing a scheduling approach for RVC, an extension to the well-known permutation flow shop scheduling problem that enables rapid run-time scheduling of RVC tasks, is introduced.     

Efficient Stereoscopic Video Coding Using Joint Disparity-Motion Estimation

The goal of this paper is to determine dense disparity and motion fields jointly and efficiently, given a sequence of stereoscopic images. At each time instant, the motion field of left sequences is estimated by using the current disparity field, the next disparity field, and the motion field of right sequences. The improved concepts for the proposed joint estimation are based on an edge-preserving regularization, an ambiguous vector region detection, and a median filtering for block-based vector generation. The reported approach is verified by processing a set of stereo sequences. Results are given with real stereoscopic data.     

窄带OFDM移动视频传输编码系统设计

城市移动视频监控作为一种新的安保方案,具有广阔的市场,但由于城市无线传输的多径效应,因此对传输系统有较高的要求。而正交频分复用（OFDM）具有优良的抗无线衰落效应,因此设计采用了基于OFDM技术。然后在参考了的欧洲数字视频广播（DVB）标准和数字音频广播（DAB）标准的基础上,重新设计一套编码系统的帧结构、信道编码和调制方式,以使之能够适应城市多径效应环境下的移动视频信号的传输。最后给出了编码输出信号的频谱图。     

基于MPEG-4的视频联合信源信道编码

该文提出了一种用于提高MPEG-4码流在噪声信道下的抗误码性能的联合信源信道编码方法。该方法将MPEG-4基本层按重要性进行码流重排后进行交织打包,并根据率失真函数将基本层纹理信息进一步划分为多个子层。编码器根据反映信道状态的反馈信息动态地调整传输的子层数目和每个子层的纠错强度(信道编码速率),使得系统失真最小。仿真结果表明,该方法明显优于未保护的MPEG-4方法,在相同信道带宽及丢包率条件下比等纠错保护的MPEG-4编码方法获得更加稳定的性能。同时由于该方法根据反馈的出错分组数进行传输子层数和纠错强度的联合优化,与Puri等人提出的按照确定信道条件设计目标函数进行优化的MDFEC方法相比,更能够适应信道条件的变化,从而获得更高的性能。     

SSIM-based Error Resilient Video Coding Over Packet-Switched Networks

The visual quality is a critical factor in prediction video coding over packet-switched networks. However, the traditional MSE-based error resilient video coding cannot correlate well with the perceptual characteristics of the human visual system (HVS). This paper proposes a structural similarity (SSIM) based error resilient video coding scheme to improve the visual quality of compressed videos over packet-switched networks. In the proposed scheme, a SSIM-based end-to-end distortion model is developed to estimate the perceptual distortion due to quantization, error concealment, and error propagation. Based on this model, an adaptive mode selection strategy is presented to enhance the communication robustness of compressed videos. Experiments show that the proposed scheme significantly improves the visual quality for H.264/AVC video coding over packet-switched networks.     

A Testbed for Energy Profile Characterization of IP Services in Smartphones over Live Networks

Mobile phones are becoming pervasively used to access Internet and multimedia contents due to their increasing processing power and its wide range of featured wireless communication technologies (Infrared, Bluetooth, NFC, GSM, UMTS, HSPA, WiMax, LTE). In this paper we also introduce mobile devices as a pervasive testbed platform to characterize the energy consumption profile of Internet services. The most innovative advantage provided by our solution is the testbed’s flexibility and simplicity, making it possible to carry out extensive testing campaigns using actual mobile devices in live networks with real services.