Storage and synchronization for distributed continuous media

Advances in local area ATM networking make it possible to integrate digital audio and video, or continuous media (CM), into distributed computing environments. The temporal nature of CM introduces new requirements for acceptable end-to-end delay and jitter. This and an increased demand for bandwidth affect the design of modern, general purpose, operating systems. This paper addresses distributed system support for CM applications, focusing on the design and implementation of facilities for secondary storage and synchronization. We describe the relevant issues, along with details of our research project and its relationship to existing work. We emphasize experimentation and present results obtained with a prototype in an ATM testbed. These provide fresh insights into the role of operating system support for multimedia.     

A framework for synchronous delivery of time-dependent multimedia data

Multimedia data often have time dependencies that must be satisfied at presentation time. To support a general purpose multimedia information system, these timing relationships must be managed to provide utility to both the data presentation system and the multimedia author. Timing management encompasses specification, data representation, temporal access control, playout scheduling, and run-time intermedia synchronization. In this paper we describe the components of our framework for supporting time-dependent multimedia data encompassing these areas and how they are assembled into a unified system.     

Visualization of time-dependent data with feature tracking and event detection

This paper presents an innovative method to analyze and visualize time-dependent evolution of features. The analysis and visualization of time-dependent data are complicated because of the immense number of data involved. However, if the scientist's main interest is the evolution of certain features, it suffices to show the evolution of these features. The task of the visualization method is to extract the features from all frames, to determine the correspondences between features in successive frames, to detect significant events or stages in the evolution of the features, and, finally, to visualize the results. The method described here performs all these steps, and it is applied to a number of applications.     

Continuous data aggregation and capacity in probabilistic wireless sensor networks

Due to the existence of many probabilistic lossy links in Wireless Sensor Networks (WSNs) (Liu et al., 2010)  [25], it is not practical to study the network capacity issue under the Deterministic Network Model (DNM). A more realistic one is actually the Probabilistic Network Model (PNM). Therefore, we study the Snapshot Data Aggregation (SDA) problem, the Continuous Data Aggregation (CDA) problem, and their achievable capacities for probabilistic WSNs under both the independent and identically distributed (i.i.d.) node distribution model and the Poisson point distribution model in this paper. First, we partition a network into cells and use two vectors to further partition these cells into equivalent color classes. Subsequently, based on the partitioned cells and equivalent color classes, we propose a Cell-based Aggregation Scheduling (CAS) algorithm for the SDA problem in probabilistic WSNs. Theoretical analysis of CAS and the upper bound capacity of the SDA problem show that the achievable capacities of CAS are all order optimal in the worst case, the average case, and the best case. For the CDA problem in probabilistic WSNs, we propose a Level-based Aggregation Scheduling (LAS) algorithm. LAS gathers the aggregation values of continuous snapshots by forming a data aggregation/transmission pipeline on the segments and scheduling all the cell-levels in a cell-level class concurrently. By theoretical analysis of LAS and the upper bound capacity of the CDA problem, we prove that LAS also successfully achieves order optimal capacities in all the cases. The extensive simulation results further validate the effectiveness of CAS and LAS.     

基于Linux的文件系统对连续媒体的支持

从操作系统角度考虑了底层文件系统对连续媒体的支持,并详细介绍了Linux下设计和实现的BLOB(Binary Large Obiject)文件系统的设计思想及其实现技术细节,并讨论它对连续媒体的支持情况。     

浅谈连续数据保护解决方案在医院中应用

由于在医院中会有很多对于病案、物资、药剂等需要进行统计的东西,尽管也应用了HIS、LIS、RIS等的多个信息管理的系统,建立生产中心机房和灾备中心机房。虽然这些举措切实增强了工作效率和便于医生进行决策,提高了医院整体的管理效率。那么为了更好的全面防御故障与灾难,以及确保医院的业务运行不中断,医院决定采用美国飞康公司所生产的CDP连续数据保护方案,这个方案能够提供一系列的措施来全面保护医院一关键业务系统：     

基于流数据技术的连续查询处理

提出了一个流查询处理方案,同时满足普通用户和高级用户(有计算机语言基础),并从几个重要的指标来闸述如何提高查询效率,减少系统瓶颈,并在原型系统中得到了验证。     

连续媒体网络发布的体系结构研究

该文针对连续媒体的网络发布，研究了活跃服务的体系结构，在采用软状态协议和轻量级会话体系结构基础上，设计了一个课件访问控制协议SCACP，并研究了代理洪水抑制，访问控制带宽限制，系统容错和错误恢复，会话的分裂和重组等问题。     

Efficient striping techniques for variable bit rate continuous media file servers

The performance of striped disk arrays is governed by two parameters: the stripe unit size and the degree of striping. In this paper, we describe techniques for determining the stripe unit size and degree of striping for disk arrays storing variable bit rate continuous media data. We present an analytical model to determine the optimal stripe unit size in redundant and non-redundant disk arrays. We then use the model to study the effect of various system parameters on the optimal stripe unit size. To determine the degree of striping, we first demonstrate that striping a continuous media stream across all disks in the array causes the number of clients supported to increase sub-linearly with increase in the number of disks. To overcome this limitation, we propose a technique that partitions a disk array and stripes each media stream across a single partition. We then propose an analytical model to determine the optimal partition size and maximize the number of clients supported by the array.     

基于流数据技术的连续查询处理

网络提供了一个无限的、变化的信息源,使得数据库由传统的静态存储变成了动态的存储,数据变成了流数据,查询变成了连续查询。为了有一个完善的系统来处理大量的数据及查询,提出了一个流查询处理方案,同时满足普通用户和高级用户(有计算机语言基础),并从几个重要的指标来阐述了如何提高查询效率,减少了系统瓶颈,并在原型系统中得到了验证。     

The Continuous Media Web: a distributed multimedia information retrieval architecture extending the World Wide Web

The World Wide Web, with its paradigms of surfing and searching for information, has become the predominant system for computer-based information retrieval. Media resources, however information-rich, only play a minor role in providing information to Web users. While bandwidth (or the lack thereof) may be an excuse for this situation, the lack of surfing and searching capabilities on media resources are the real issue. We present an architecture that extends the Web to media, enabling existing Web infrastructures to provide seamless search and hyperlink capabilities for time-continuous Web resources, with only minor extensions. This makes the Web a true distributed information system for multimedia data. The article provides an overview of the specifications that have been developed and submitted to the IETF for standardization. It also presents experimental results with prototype applications.     

QoS-based evaluation of file systems and distributed system services for continuous media provisioning

This paper presents a QoS-based performance analysis of file systems and distributed object services for Continuous Media (CM) provisioning, as well as the details and implementation experiences of a continuous media file system and associated CM servers. For this we have implemented QoS-driven CM servers and the Presto continuous media file system (PFS) in the context of a distributed multimedia application development environment, and validate the performance of PFS against that of the conventional Unix file system through an experimental evaluation. Using our CM server prototype, we next examine the effect of continuous media data delivery on the three different kinds of network protocols such as CORBA, UDP/IP, and TCP/IP, with respect to QoS provisioning and throughput.     

Multi-path continuous media streaming: what are the benefits?

Quality of service (QoS) in delivery of continuous media (CM) over the Internet is still relatively poor and inconsistent. Although many such applications can tolerate some degree of missing information, significant losses degrade an application’s QoS. In this paper, we investigate the potential benefits of mitigating this problem through the exploitation of multiple paths existing in the network between a set of senders and a receiver of CM. Our focus in this work is on providing a fundamental understanding of the benefits of using multiple paths to deliver CM over best-effort wide-area networks. Specifically, we consider pre-recorded CM applications and use the following metrics in evaluating the performance of multi-path streaming as compared to single-path streaming: (a) data loss rate, (b) conditional error burst length distribution, and (c) lag1-autocorrelation. The results of this work can be used in guiding the design of multi-path CM systems streaming data over best-effort wide-area networks.     

连续媒体服务的磁盘调度算法—EDLSF

主要对连续媒体服务中I／O子系统的磁盘调度问题进行讨论。提出了一种新的调度算法－EDLSF（Earliest Deadine and Least Seek First)来解决连续媒体的访问。EDLSF算法综合考虑了磁盘服务时间和实时特点,通过分析、比较EDLISF算法和其它调度算法在提供并发访问数量上的多少,说明EDLSF算法是能够较好处理连续媒体请求的算法。     

基于时间戳的FTL实现的连续数据恢复方法

基于FLASH的存储系统复写旧数据时需要通过地址映射层(flash translation layer,FTL)分配新的写入地址,因此旧的数据在一段时间内仍存在于系统中,在这样的系统上实现连续数据保护(continuous data protection,CDP),只需找到旧的映射信息,不需额外保存数据的更新信息。利用FLASH的带外区(out of band,OOB)记录时间戳,在FTL的映射项中增加时间戳信息,在不跟踪映射表每次更新的情况下,达到数据快速恢复的目的。该方法降低了对存储系统性能的影响,实现了快速的数据恢复响应。     

Design of Multi-User Editing Servers for Continuous Media

Based on a fifteen month investigation of a post production facilities for both the entertainment industry and broadcasters, we identified a number of challenges with the design and implementation of a server in support of multiple editing stations. These include, how to: share the same content among multiple editors, support continuous display of the edited content for each editor, support complex editing operations, compute the set of changes (deltas) proposed by an editor, compare the deltas proposed by multiple editors, etc. It is beyond the focus of this paper to report on each challenge and its related solutions. Instead, we focus on one challenge, namely how to support continuous display of the edited content for each editors, and techniques for physical organization of data to address this challenge.     

连续数据保护中的数据一致性保障技术研究综述

连续数据保护是当前灾难恢复领域的新方向,它克服了传统数据备份和快照技术的缺陷,从新的角度对关键数据进行保护。首先对连续数据保护的工作过程进行了阐述,对其中存在的几类数据一致性问题进行了剖析,并结合当前国内外的连续数据保护技术中涉及的数据一致性保障措施进行了概括和归纳,分析其不足之处,并指出连续数据保护数据一致性保障技术的未来发展方向。     

An Efficient Data Layout Scheme for Multi-Disks Continuous Media Servers

Recently, zoning technique has been widely applied to disks to increase their capacities. Under the technique, an interesting feature of a disk is that there are a number of various bandwidths on it. Herein, a novel data layout scheme called cluster-pairing on efficiently exploiting this feature for continuous media (CM) servers is proposed. We first applied track-pairing method between a pair of homogeneous disks, and then partitioned each disk into a same number of clusters to facilitate the retrieval of region-based data placement. The proposed method can take the advantages of track-pairing and region-based data placement schemes to fully utilize the various bandwidths from zoned-disks and meanwhile reduce the seek time overhead. According to the simulation results, the disk throughput after applying our approach can be promoted by 35% to 65% than that of the traditional data striping strategies, 10% to 30% than that of region-based data placement method, and about 10% than that of track-pairing scheme. And the wasted storage space is less than 1% which is negligible in terms of the improvement of the disk throughput.     

Digital media: Bridges between data particles and artifacts

The field of visual communication is currently facing a period of transition to digital media. Two tracks of development can be distinguished; one utilitarian, the other artistic in scope. The first area of application pragmatically substitutes existing media with computerized simulations and adheres to standards that have evolved out of common practice. The artistic direction experimentally investigates new features inherent in computer imaging devices and exploits them for the creation of meaningful expression. The intersection of these two apparently divergent approaches is the structural foundation of all digital media. My focus will be on artistic explorations, since they more clearly reveal the relevant properties. The metaphor of adata particle is introduced to explain the general universality of digital media. The structural components of the data particle are analysed in terms of duality, discreteness and abstraction. These properties are found to have significant impact on the production process of visual information: digital media encourage interactive use, integrate different classes of symbolic representation, and facilitate intelligent image generation.     

Design of Scalable Continuous Media Servers

Multimedia applications place high demands for quality-of-service (QoS), performance, and reliability on systems. These stringent requirements make design of cost-effective and scalable systems difficult. Therefore efficient adaptive and dynamic resource management techniques in conjunction with data placement techniques can be of great help in improving performance, scalability, and reliability of such systems. This is the focus of our paper.