Optimal video placement for hierarchical video-on-demand systems

We have been implementing a VOD system over ATM networks based on a hierarchical three-level network architecture. One of the most important design problems is how to organize video programs stored at different level of servers. In this paper, we propose an optimal video placement strategy which gives the optimal number of video copies should be stored at each level of server such that the cost function can be minimized while a lower bound of the request rejection probability for each video is guaranteed. Our major contribution is that we model the time-variant request arrivals as a non-homogeneous Poisson process     

The design and architecture of a video library system

The authors describe a video-on-demand system that uses personal computers with LANs, making it possible to offer video services with low cost and a wide range of applications. This design approach brings down the cost and may find a wider scope of application in the future. Our research focuses on the underlying software architecture for video library services. We assume the existence of an adequate operating system (OS), network and disk support. We survey related VOD research, introduce services supporting video library, and cover the system architecture and design. We discuss the architecture of our video library server and clients; describe our system implementation, and examine future directions     

构建城域网络视频点播系统方案分析

分析了应用于宽带城域网的商用化视频点播系统的技术要点，提出了视频服务器的评价标准，并设计了适合于宽带城域网应用的分层分布式视频点播系统的结构。     

VOD系统设计

讨论了低成本的宽带网VOD系统设计方案。由于宽带网VOD系统是一个实时系统，就必须要认真考察诸如网络带宽、I／O带宽、网络结构、视频服务器、存储结构及软件系统等关键技术要素，这样才能设计出一个有效、经济、实用的宽带网VOD系统。文章最后给出了一个宽带网VOD系统的配置实例。     

基于IP技术的VOD系统

本文简要介绍了ＶＯＤ行业的标准组织ＤＡＶＩＣ定义的ＶＯＤ系统通用参考模型,指出了在ＩＰ网上构建ＶＯＤ系统的优点并给出组网实例,同时讨论了如视频流传输、会话层及ＶＯＤ系统服务器等ＩＰ网上建立ＶＯＤ系统所涉及的技术。     

Approximation of loss calculation for hierarchical networks with multiservice overflows

This paper studies loss calculation in hierarchical networks with multiservice overflows which have different call arrival rates, mean holding times, bandwidth requirements and share a common link. The loss calculation involves two challenging problems: 1) the computation of the two moment characterizations of multiservice overflow traffic over the shared link, 2) the calculation of the loss probabilities for multiservice non-Poisson overflow traffic in hierarchical systems. An efficient approximation method, known as multiservice overflow approximation (MOA), is proposed to enable multiservice networks designs with hierarchical architecture. Two contributions are included in the MOA method. First, an approximation based on blocking probabilities matching is proposed to compute the variances of multiservice overflows over the shared link. Second, a modified Fredericks & Hayward's approximation is used to calculate the loss probabilities of multiservice non-Poisson over flow traffic. The performance of the MOA method is evaluated in a two-tier hierarchical cellular network and compared with an existing approximation method based on multi-dimensional Markov-modulated Poisson process (MMPP). Verified by simulations, the MOA method achieves better accuracy in the general heterogeneous cases at lower computational cost than the MMPP method.     

Joint source coding and data rate adaptation for energy efficient wireless video streaming

Rapid growth in wireless networks is fueling demand for video services from mobile users. While the problem of transmitting video over unreliable channels has received some attention, the wireless network environment poses challenges such as transmission power management that have received little attention previously in connection with video. Transmission power management affects battery life in mobile devices, interference to other users, and network capacity. We consider energy efficient transmission of a video sequence under delay and quality constraints. The selection of source coding parameters is considered jointly with transmitter power and rate adaptation, and packet transmission scheduling. The goal is to transmit a video frame using the minimal required transmission energy under delay and quality constraints. Experimental results are presented that illustrate the advantages of the proposed approach.     

DVFS-aware motion estimation design scheme based on bandwidth–rate–distortion optimization in application processor systems

In this paper, a novel dynamic voltage–frequency scaling-aware (DVFS-aware) bandwidth- efficient motion estimation (ME) scheme is presented for mobile application processor (AP) systems. Under volatile operating performance conditions due to the power management mechanism, we model the coding bandwidth (BW) and coding performance for the video processor as a convex function of the working frequency. In this paper, we present a bandwidth–rate–distortion (B–R–D) optimized framework that will guarantee the smallest possible rate–distortion cost among coding BW constraints applied in video coding design. By formulating the coding bandwidth-constrained ME problem as an optimization problem, known convex optimization theory can be applied to yield optimal resource-constrained compression. Using varied CIF (352×288)- and HP (1280×720)-sized video sequences with different motion activities over our proposed DVFS-aware video coding approach, the excellent results in terms of coding performance and coding bandwidth savings are obtained. With negligible quality loss, the proposed scheme under coding BW constraints achieves 45–65% coding BW usage reduction over HD-sized 30 frame/s video coding.     

An Efficient Transmission Scheme for Minimizing User Waiting Time in Video-On-Demand Systems

To take the advantage of skewed popularity of videos, efficient video-on-demand (VOD) systems are more likely to deliver the most popular videos through periodic broadcasting and the least popular videos through on-demand multicasting. While videos delivered through multicasting usually share a pool of server channels, broadcasting of each video demands one or more channels dedicated to it. Given a total number of available channels, distributing them for individual broadcasting and the multicasting pool to achieve the optimal average user waiting time is a nonlinear optimization problem. This letter addresses this problem by proposing a hybrid transmission scheme, which uses dynamic programming approach to ensure optimally for any given number of channels and request arrival rate     

Two algorithms for multi‐constrained optimal multicast routing

Multimedia applications, such as video‐conferencing and video‐on‐demand, often require quality of service (QoS) guarantees from the network, typically in the form of minimum bandwidth, maximum delay, jitter and packet loss constraints, among others. The problem of multicast routing subject to various forms of QoS constraints has been studied extensively. However, most previous efforts have focused on special situations where a single or a pair of constraints is considered. In general, routing under multiple constraints, even in the unicast case is an NP‐complete problem. We present in this paper two practical and efficient algorithms, called multi‐constrained QoS dependent multicast routing (M_QDMR) and (multicasting routing with multi‐constrained optimal path selection (M_MCOP)), for QoS‐based multicast routing under multiple constraints with cost optimization. We provide proof in the paper that our algorithms are correct. Furthermore, through extensive simulations, we illustrate the effectiveness and efficiency of our proposals and demonstrate their significant performance improvement in creating multicast trees with lower cost and higher success probability. Copyright © 2003 John Wiley & Sons, Ltd.     

智慧城市安防高清视频资源共享系统及应用

首先介绍智慧城市安防视频资源共享系统的主要技术路线分析和各子系统的组成,然后详细阐述该系统的高标清视频兼容、社会图像监控资源接入方式、存储设备的选择等关键技术分析,最后结合公安实战需求,总结该系统在智能化方面的综合应用.     

Efficient non-data-aided carrier and clock recovery for satelliteDVB at very low signal-to-noise ratios

This paper deals with the analysis and design of efficient non-data-aided clock and carrier (frequency/phase) synchronization algorithms intended for use in satellite digital video broadcasting systems employing turbo-coding techniques to enhance the power efficiency. The above issue appears quite challenging in view of both the extremely low signal-to-noise ratio, typical of turbo-codes operation, and the very short time allocated to the acquisition of synchronization parameters. These constraints rule out most conventional clock/carrier recovery schemes and demand a careful search for specific, highly efficient algorithms. We propose and analyze a clock/carrier synchronization scheme capable of operating at values of E_b/N _o as low as 1 dB with lock-in delay not exceeding 50 ms     

Partial encryption of compressed images and videos

The increased popularity of multimedia applications places a great demand on efficient data storage and transmission techniques. Network communication, especially over a wireless network, can easily be intercepted and must be protected from eavesdroppers. Unfortunately, encryption and decryption are slow, and it is often difficult, if not impossible, to carry out real-time secure image and video communication and processing. Methods have been proposed to combine compression and encryption together to reduce the overall processing time, but they are either insecure or too computationally intensive. We propose a novel solution called partial encryption, in which a secure encryption algorithm is used to encrypt only part of the compressed data. Partial encryption is applied to several image and video compression algorithms in this paper. Only 13-27% of the output from quadtree compression algorithms is encrypted for typical images, and less than 2% is encrypted for 512×512 images compressed by the set partitioning in hierarchical trees (SPIHT) algorithm. The results are similar for video compression, resulting in a significant reduction in encryption and decryption time. The proposed partial encryption schemes are fast, secure, and do not reduce the compression performance of the underlying compression algorithm     

Low-complexity video coding for receiver-driven layered multicast

The “Internet Multicast Backbone,” or MBone, has risen from a small, research curiosity to a large-scale and widely used communications infrastructure. A driving force behind this growth was the development of multipoint audio, video, and shared whiteboard conferencing applications. Because these real-time media are transmitted at a uniform rate to all of the receivers in the network, a source must either run at the bottleneck rate or overload portions of its multicast distribution tree. We overcome this limitation by moving the burden of rate adaptation from the source to the receivers with a scheme we call receiver-driven layered multicast, or RLM. In RLM, a source distributes a hierarchical signal by striping the different layers across multiple multicast groups, and receivers adjust their reception rate by simply joining and leaving multicast groups. We describe a layered video compression algorithm which, when combined with RLM, provides a comprehensive solution for scalable multicast video transmission in heterogeneous networks. In addition to a layered representation, our coder has low complexity (admitting an efficient software implementation) and high loss resilience (admitting robust operation in loosely controlled environments like the Internet). Even with these constraints, our hybrid DCT/wavelet-based coder exhibits good compression performance. It outperforms all publicly available Internet video codecs while maintaining comparable run-time performance. We have implemented our coder in a “real” application-the UCB/LBL videoconferencing tool vic. Unlike previous work on layered video compression and transmission, we have built a fully operational system that is currently being deployed on a very large scale over the MBone     

中心式VOD视频点播系统及其关键技术实现

介绍了一种基于IP骨干网的中心式VOD视频点播结构，并与分布式结构进行了比较，指出了它的主要优缺点。讨论了中心式VOD系统所面临的若干关键技术，最后简述了VOD over IP的操作过程。     

An efficient computation-constrained block-based motion estimationalgorithm for low bit rate video coding

We present an efficient computation constrained block-based motion vector estimation algorithm for low bit rate video coding that yields good tradeoffs between motion estimation distortion and number of computations. A reliable predictor determines the search origin, localizing the search process. An efficient search pattern exploits structural constraints within the motion field. A flexible cost measure used to terminate the search allows simultaneous control of the motion estimation distortion and the computational cost. Experimental results demonstrate the viability of the proposed algorithm in low bit rate video coding applications. The resulting low bit rate video encoder yields essentially the same levels of rate-distortion performance and subjective quality achieved by the UBC H.263+ video coding reference software. However, the proposed motion estimation algorithm provides substantially higher encoding speed as well as graceful computational degradation capabilities.     

Minimal cost coverage planning for single frequency networks

OFDM based single frequency networks (SFNs) have been standardized for terrestrial broadcasting systems, for digital audio broadcasting (DAB) as well as for digital video broadcasting (DVB). Due to the multipath tolerance of the OFDM scheme, the receiver is able to combine signals coming from several transmitters, despite of the varying propagation delays, i.e., heavy artificial multipath propagation. In order to take full advantage of the diversity gain provided by the SFN architecture, proper network design is required. We focus on the cost efficient design of an SFN providing broadcasting services over a predefined service area with requirements both on the received signal quality and on the allowable interference level experienced by existing services in the same spectrum. We formulate the problem as a discrete optimization problem, where the network design parameters such as power, antenna heights and transmitter locations are the decision variables. The general stochastic optimisation algorithm simulated annealing has been adapted for solving the above problem. The novelty of our method is that cost factors and interference constraints are embedded in the optimisation procedure. Through numerical examples we demonstrate that significant reduction in network cost can be achieved by our approach     

The role of local storage in supporting video retrieval services onATM networks

This paper studies a reference network architecture for video information retrieval, based on hierarchical storage of the video segments and asynchronous transfer mode (ATM) transport capability on the long distance network. The storage associated to local switching nodes can be exploited in two complementary ways, either for caching the most requested video programs, and for decoupling the transmission speed on the long distance network from the natural playout speed of the video segments. We show that both approaches lead to a substantial increase of the load carried on the long distance network with a given service requirement. Moreover, we show that a greater efficiency is obtained when a suitable integration of the two approaches is considered     

IPTV transport architecture alternatives and economic considerations

Telecommunications companies are under increased pressure due to competition from multiple system operators, and the changing communications and entertainment needs of residential consumers. These pressures are driving the telecommunications companies to design and deploy metro networks capable of delivering broadcast video and VOD services through IP-based broadband connectivity (known as IPTV). One important architectural consideration for these IPTV networks is the core layer 1 transport infrastructure that supports economical delivery of these high-bandwidth services. This article surveys some of the major layer 1 optical transport network alternatives including DWDM, SONET, and Ethernet-on-fiber as well as its passive WDM/DWDM (PWDM) variation. The article analyzes the architectural and cost performance metrics for these transport options, and explores the economic crossover points with regard to the key network and service parameters such as bandwidth demand, number of subscribers, network topology, and operational constraints. DWDM technology, when coupled with native Ethernet aggregation, is found to have significant applicability for IPTV transport networks. DWDM offers value in capital cost and operations, while delivering the required bandwidth and performance. Ethernet aggregation capability within the transport infrastructure adds scalability, flexibility, and cost advantage for the multiservice network applications of the future.     

分布式视频点播系统中代理视频服务器的效率模型

针对传统的成本代价模型无法体现出系统网络和存储资源利用率的问题,考察代理服务器上单位时间内单位容量的服务用户数,并考虑了不同级网络成本的差异,提出了效率模型。通过对常用多播协议的比较,利用效率模型对代理服务器的性能进行了详细讨论。仿真实验表明,效率模型对分布式视频点播系统的设计和评估非常有效。