Modeling Distributed Multimedia Synchronization with DSPN

Multimedia synchronization is the essential technology for the integration of multimedia in distributed multimedia systems.The multimedia synchronization model has been recognized by many researchers as a premise of the implementation of multimedia synchronization.In distributed multimedia systems,the characteristic of multimedia synchronization is dynamic,and the key medium has the priority in multimedia synchronization.The previously proposed multimedia synchronization models cannot meet these requirements.So a new multimedia dynamic synchronization model-DSPN,based on the timed Petri-net has been designed in this paper.This model can not only let the distributed multimedia system keep multimedia synchronization in a more precise and effective manner according to the runtime situation of the system,but also allow the user to interact with the presentation of multimedia.     

PREMO:多媒体同步的标准模型

本文描述了PREMO的基于事件的同步机制,该机制是多媒体表现标准中媒体间同步的核心,是以活动对象间互操作为基础的。分析表明,PREMO的这种同步机制综合了其它各种同步模型,是多媒体表现中实现复杂同步模式的强大工具。     

A standard model for multimedia synchronization: PREMO synchronization objects

This paper describes an event-based synchronization mechanism, which is at the core of the inter-media synchronization in the upcoming standard for multimedia presentation, PREMO. The synchronization mechanism of PREMO is a powerful tool, based on a small number of concepts, and on cooperation among active objects, and represents a synthesis of various synchronization models described in the literature. This model can serve as a basis for the implementation of complex synchronization patterns in multimedia presentations, both purely event-based, as well as time-based.     

多媒体复合同步模型

多媒体同步是多媒体研究应用的一个重要方面,文中在分析了多媒体制作,播放的特点后,提出了一种新的多媒体的同频模型－复合同步模型。     

A synchronization algorithm for distributed multimedia environments

Network synchronization plays a significant role in transmitting multimedia objects over computer networks. Even packets from a single channel must be synchronized due to the problems in a packet switching environment, such as network jitter, frequency, and time offsets. We present an algorithm that determines the set of packets generated periodically by various participants arriving at a node. The basic advantage of the proposed algorithm is that the receiver estimates the reference times (expected arrival times of the packets) and achieves synchronization, without knowledge of the packet delays. The accuracy is improved and the complexity is reduced by predicting the time/frequency offsets between the clocks at the source and the mixer. The error is calculated by the Chernoff bound, demonstrated by simulation, and shown to be acceptable in practical applications.     

Clock synchronization for distributed media applications

Current video wall technology relies on custom processing hardware to drive the individual display channels. This hardware is both expensive to design and to maintain. Given that modern off‐the‐shelf computers have a significant amount of computing power, future video displays can be driven with this hardware at a lower cost. By using mass‐produced computers and a standard commercial operating system, the benefits of economies of scale can be brought to the custom video wall market. This paper describes a Windows library that provides the synchronized timing support necessary to drive a video wall with consumer hardware. The goal is to provide a key building block for the media software that will process the incoming video stream. This library exports several interfaces to the host software and provides support for synchronized timers, a synchronized clock, and reliable multicast messaging. The library uses common Windows APIs and protocols for maximum interoperability and portability. Through empirical testing, we are able to show that synchronization between any two machines in the system can be maintained to within 12 ms when run on Windows XP SP2. This synchronization is also shown to be consistent even when there is a heavy load on the processor. As a result, this library will successfully allow a commercial video wall to be driven from media software running on consumer hardware and software. Copyright © 2007 John Wiley & Sons, Ltd.     

一种面向多对象多媒体应用的同步控制方法

多对象多媒体应用允许多路媒体同时呈现,其同步控制比较复杂,可分为传输过程中与呈现过程中的同步。然而现有的同步方法忽略了媒体在最后呈现过程中的同步,也没有考虑各媒体对象之间的同步要求差异。针对以上问题,为视频点播提出了一种在应用层上控制多对象多媒体同步呈现质量的方法。在采用多级缓冲门限实现媒体内同步反馈控制的基础上,依据主要媒体对象的呈现时间戳,在每一个呈现场景内调整次要媒体对象的呈现速率,从而实现媒体间的同步呈现。实验结果表明该方案能够有效地提高同步质量,且媒体间的同步性能平均提高28.45%。     

实时多媒体流同步机制的研究

实时多媒体流同步是网络环境下流媒体应用的基本要求和主要难点之一。文章介绍了多媒体同步的基本概念，分析了在IP网络环境下实时多媒体流在各个环节失去同步的原因，并针对这些原因提出了相应的解决方法。     

一种分布式多媒体数据仓库模型

多媒体数据采掘是从大型多媒体数据库中提取高层的多媒体信息及知识。介绍一种分布式多媒体数据仓库模型──ＣＭＳ模型的体系结构及存储结构,并构造了具有综合处理各种媒体数据,能够对这些媒体数据进行修改、查询的军用多媒体数据仓库原型系统。     

An integrated runtime QoS-aware middleware framework for distributed multimedia applications

Future-generation distributed multimedia applications are expected to be highly scalable to a wide variety of heterogeneous devices, and highly adaptive across wide-area distributed environments. This demands multiple stages of run-time support in QoS-aware middleware architectures, particularly, probing the performance of QoS parameters, instantiating the initial component configurations, and adapting to on-the-fly variations. However, few of the past experiences in related work have shown comprehensive run-time support in all of the above stages – they often design and build a middleware framework by focusing on only one of the run-time issues. In this paper, we argue that distributed multimedia applications need effective run-time middleware support in all these stages to be highly scalable and adaptive across a wide variety of execution environments. Nevertheless, the design of such a middleware framework should be kept as streamlined and simple as possible, leading to a novel and integrated run-time middleware platform to unify the probing, instantiation and adaptation stages. In addition, for each stage, the framework should enable the interaction of peer middleware components across host boundaries, so that the corresponding middleware function can be performed in a coordinated and coherent fashion. We present the design of such an integrated architecture, with a case study to illustrate how it is simple yet effective to monitor and configure complex multimedia applications.     

Nondeterministic Temporal Relations in Multimedia Data

Synchronization is an important issue in multimedia systems which integrate a variety of temporally related media objects.One part of synchronization is the representation of temporal information.Wish the emerging interactive multimedia,deterministic temporal models are replaced by nondeterministic ones with more expressiveness.This paper classifies temporal models by their expressiveness,and evealuates relevant nondeterministic temporal relations in multimedia data.Additionally,an interval-based nondeterministic model based on a complete temporal operator set is proposed providing high-leval abstractions and a high degree of expressiveness for interactive multimedia systems.     

Experiences in implementing a distributed object platform for multimedia applications

Two current trends in distributed computing are the emergence of standardized distributed object platforms such as CORBA, and the increasing use of continuous media data types. This paper describes and evaluates a platform which supports both standard CORBA interactions and continuous media interactions in a fully integrated environment. The platform is implemented as a self‐contained support infrastructure (GOPI core) and a separate ‘personality’ that sits on top of the infrastructure and provides a CORBA API. The platform user can create both request/reply oriented and stream oriented bindings with quality of service specifications that are honoured (as far as possible) by the infrastructure. A framework for quality of service management which involves the monitoring and adaptation of quality levels is also supported. The level of performance attained by the platform provides evidence of the feasibility of natively supporting continuous media in a distributed object platform environment. Copyright © 2000 John Wiley & Sons, Ltd.     

SCADA系统冗余模式下数据同步的实现模型

SCADA系统作为一体化的工业自动控制系统，不仅要完成实时采集数据和远程控制等基本功能，而且其自身的稳定性和健壮性需要给予特别考虑。本文在介绍了SCADA系统软件基本结构后。重点讨论了冗余模式下实时数据和历史数据的同步问题。并给出了一种实现模型。     

A support platform for distributed multimedia applications

Abstract

Considerable progress has been made in the development of technologies to support distributed multimedia computing, such that there is now a wide range of pilot applications under development. The design of support systems which help in the development of multimedia applications is therefore an emerging area of research. This paper discusses the requirements of distributed multimedia applications with respect to their support environments. A number of experimental systems are then described which intend to provide the necessary facilities for multimedia applications. Particular focus is placed on the Lancaster system which provides multimedia support for open distributed systems.     

The expressive task specification and adaptive image data handling for mobile applications

An efficient multimedia data handling is a fundamental requirement of mobile multimedia applications. To accommodate this requirement, issues of the available technologies as well as mobile multimedia data access and transfer processes, and the characteristics of the medium to be handled should all be taken into consideration. For this end, these aspects are investigated. The results of the investigation lead to the conclusion that an expressive task specification and adaptive multimedia data handling should be provided. With an expressive task specification, a demand for accessing multimedia object can be described flexibly to enable a minimum handling overhead (thus high performance) and an optimal compromise between performance, cost and quality. Adaptive media handling functionality adapts the service performance according to the medium to be accessed, the available resources and compromise preference of a mobile client, etc. This paper presents the new concepts and methods for these two aspects.