Quality-based evaluation of multimedia synchronization protocolsfor distributed multimedia information systems

Distributed, networked multimedia information systems will be a critical component of technology-based information infrastructures in the future. We present an infrastructure for supporting multimedia applications. We discuss various characteristics of multimedia data and the effect of the network on the required quality of presentation for multimedia data. We present a suite of synchronization protocols to support the quality of presentation. The crux of these protocols is the scheduling of multimedia information for synchronized delivery, over broadband networks with limited resources, and is identified as an NP-hard problem. We introduce two parameters which can be used to measure the performance of end-to-end synchronization protocols in a network supporting distributed multimedia applications. We propose and implement several heuristic scheduling algorithms, and compare their performance. We deduce the appropriateness of these algorithms in different types of distributed multimedia environments     

An EFSM-based multimedia synchronization model and the authoringsystem

Multimedia synchronization is one of the key issues to be resolved in order to have smooth multimedia presentations. The demand of bringing multimedia information systems into distributed environments makes multimedia synchronization more difficult. We apply extended finite state machines (EFSM) to formally specify multimedia synchronization among multiple media streams. Using the EFSM model, the intra-medium synchronization is handled by an actor, which is formally represented as an EFSM. The inter-media synchronization is handled by a synchronizer, which is also represented as an EFSM. Both centralized and distributed synchronization cases can be specified. The synchronizer and actors achieve the corresponding multimedia presentations cooperatively. We also propose some policies to rectify the random delays caused by networks in the distributed presentation case. These policies, which can be formally specified in the corresponding EFSMs, are classified as intra-stream and inter-stream synchronization policies. Using the EFSM-based model, an authoring system and an associated experimental execution environment has been developed on SUN SPARC workstations     

实时多媒体通信的同步模型研究

本文在对同步信息进行分类和分析的基础上,分析了ＯＣＰＮ模型的局限性,提出了改进的多媒体同步模型ＲＯＣＰＮ。通过在节点中引入媒体表现时间和同步时间,将媒体的表现与媒体间的同步行为分开,该模型解决了ＯＣＰＮ模型关于媒体内同步与媒体间同步不可兼得的问题。模拟实验表明,使用ＲＯＣＰＮ模型的多媒体流其媒体流内同步指标和媒体流间同步指标均明显优于使用ＯＣＰＮ模型的多媒体流,尤其当对象丢失率较高时,ＲＯＣＰＮ模     

A multimedia synchronization model and its implementation intransport protocols

An implementation of a synchronization mechanism in transport protocol to support multimedia applications over a packet or cell switched network is proposed. In designing such a mechanism for practical use, ease of implementation and capability of handling random delay of packets are two key issues for success. Since the random delay of packet or cell switched networks makes synchronization among media more complicated after the transmission across the network, a model which considers the random transmission delay is hence required to specify the temporal relationship among media. Therefore, a real-time synchronization model is presented to satisfy this requirement in the paper. Based on the proposed synchronization model, a transport protocol, namely the multimedia synchronization transport protocol (MSTP), is designed and implemented. We have implemented a prototype system using the MSTP protocol and built a simulation system for the wide area network (WAN) environment in order to evaluate the performance of the MSTP protocol     

A temporal reference framework for multimedia synchronization

The synchronization problem for audio/visual reproduction has consumed engineers time since the advent of recorded audio and images and the first multimedia productions. As computers have evolved to support programmed reproduction of multimedia information, the complexity but not the character or interest have changed. In the digital domain, synchronization problems exist due to data distribution and communications, random events caused by human-computer interaction, and general computer and communications performance limitations. This rich research domain has led to numerous approaches to the modeling and execution of multimedia synchronization scenarios. Unfortunately, these approaches are difficult to compare and evaluate due to their varied theoretical bases and modeling techniques. We develop a uniform, theoretical foundation for discussing multimedia synchronization and temporal specification. We propose a temporal reference framework and use it to compare existing temporal specification schemes and their relationships to multimedia synchronization. The ensuing comparison of existing specification and synchronization techniques demonstrates the utility of the framework     

Toward a formal specification of multimedia synchronization scenarios

This paper introduces time stream Pétri nets (Ts treamPn), a model for the formal specification of multimedia synchronization scenarios. This new model extends time Pétri nets to formally describe the timed behaviour of multimedia objects and streams in asynchronous distributed systems. The proposed approach uses time intervals to label the arcs exiting from the places of the net, and typed transitions to define different firing rules. This model allows a complete and accurate specification of synchronization constraints between multimedia streams and can be used at different levels of granularity.     

Media synchronization in multimedia Web using a neuro-fuzzyframework

We consider the problem of multimedia synchronization in a Web environment. The workload generated by the multimedia server during a Web session exhibits variations that are quite different from the traffic fluctuation offered by a single media stream, e.g., a variable bit rate (VBR) video. We propose a set of parameters that can be used to characterize the workload generated by the multimedia server in a Web-type browsing environment. The workload characterization scheme is subsequently used in designing a server-based synchronization scheme. The problem of scheduling multimedia information to ensure media synchronization in a Web environment is identified as a multicriteria scheduling problem, which is NP-hard. The ability of fuzzy control to deal with multivariables makes it a good alternative for the multicriteria scheduling problem considered. Consequently, we propose a neuro-fuzzy scheduler (NFS) that makes an intelligent compromise among multicriteria by properly combining some scheduling heuristics. Performance of the NFS is compared with several known heuristics and a branch and bound algorithm. The results show that the proposed NFS ran dynamically adjust to the varying workload quite well     

New architecture for enforcing multimedia synchronization in videoconferencing applications

This paper presents a formally defined architecture allowing the design and the corresponding implementation of a set of modules that fulfill the quality of service requirements of PNSVS (Petri Net Synchronized Videoconference System), an application designed to run on top of an asynchronous environment. It describes the mechanisms and architecture allowing the system to enforce the temporal synchronization between the audio and video streams, the presentation quality, and the end to end delay. This synchronization method relies on a formal model extending time Petri nets: the Time Stream Petri Net (TSPN) model, that will be used to completely specify the time constraints of the application streams. From this, the communication architecture is improved by introducing a new partial order transport service that maximizes the PNSVS quality of service. The partial order transport principle is presented together with the pre-synchronization sub-layer, which makes the partial order transport service match the applicative synchronization requirements. Moreover, it will be shown that each layer of this synchronization architecture can be formally modeled by a well defined set of TSPN models.     

A programming model and system infrastructure for real-timesynchronization in distributed multimedia systems

One of the major requirements of distributed multimedia applications is the need to maintain often complex, real-time synchronization constraints. More specifically, it is necessary to be able to manage arbitrary intra- and inter-media synchronization across activities in the distributed environment. Furthermore, it is important that such developments are integrated into emerging object-oriented standards for distributed computing. This paper presents an object-oriented programming model and associated implementation to meet these requirements. The main concepts behind the proposed approach are, firstly, the use of reactive objects for real-time control and synchronization and, secondly, quality of service controlled bindings for predictable communication between objects. The flexibility of the approach is demonstrated by three contrasting examples of real-time synchronization. The implementation extends the real-time capabilities of the Chorus micro-kernel by introducing the concepts of rtports, rthandlers and quality of service controlled connections. The paper demonstrates how reactive objects and bindings are realized on this infrastructure     

Distributed multimedia systems

A distributed multimedia system (DMS) is an integrated communication, computing, and information system that enables the processing, management, delivery, and presentation of synchronized multimedia information with quality-of-service guarantees. Multimedia information may include discrete media data, such as text, data, and images, and continuous media data, such as video and audio. Such a system enhances human communications by exploiting both visual and aural senses and provides the ultimate flexibility in work and entertainment, allowing one to collaborate with remote participants, view movies on demand, access on-line digital libraries from the desktop, and so forth. In this paper, we present a technical survey of a DMS. We give an overview of distributed multimedia systems, examine the fundamental concept of digital media, identify the applications, and survey the important enabling technologies     

Large-capacity multimedia systems

The exponential growth of Internet use may result in a reduction of the grade of service of telecommunication networks. Capacity increase is the challenge to telecom operators. Communication satellites “see” a large customer population and provide a large: amount of-mainly entertainment-information. Interactive services are possible with enhanced communication satellite systems. Such satellite concepts and technologies are the subject of this article     

Millimeter waves for short-range multimedia communication systems

A framework for the performance characterization of short-range communications systems is developed with the intention of investigating the feasibility of new multimedia wireless services at millimeter waves (MMWs). Both narrow- and wide-band systems are considered for mobile and/or fixed users. This paper aims at defining and evaluating proper metrics to characterize the service quality for the user and jointly takes the propagation characteristics, the transmission techniques, and the multiple access protocols into account. The definition of service-oriented metrics is emphasized. Three different real scenarios operating at MMW are investigated with a unified perspective: intelligent transport systems, wide-band local-area networks, and local multipoint distribution systems for interactive video services. The role played by the MMW band in the development of these services is discussed. In each scenario, accurate propagation analysis is carried out and suitable countermeasure techniques are pointed out in order to join suitable service-quality levels. The methodology considered is based on both analytical and semianalytical tools for performance evaluation     

Power control for wireless multimedia CDMA systems

In a wireless multimedia communication system where different types of traffic such as speech, data, and video have different data rates, good power control for individual traffic can ensure quality of service (QoS) and achieve a better throughput at the same time. The authors propose a closed-form power control function based on a parameter called the traffic exponent that simplifies the power control processing and improves the overall CDMA system performance     

QoS for multimedia applications in satellite systems

We present a policy for handling multimedia traffic over satellite air interfaces. It extends the advantages of ATM to satellite by the statistical multiplexing of variable-rate traffic sources. Effectiveness is assessed within a multimedia satellite platform called EuroSkyWay, based on Ka-band payload and on-board processing     

An architecture for real-time multimedia communication systems

A multimedia communication system includes both the communication protocols used to transport the real-time data and the distributed computing system (DCS) within which any applications using the protocols must execute. The architecture presented attempts to integrate these communications protocols with the DCS in a smooth fashion in order to ease the writing of multimedia applications. Two issues are identified as being essential to the success of this integration: the synchronization of related real-time data streams, and the management of heterogeneous multimedia hardware. The synchronization problem is tackled by defining explicit synchronization properties at the presentation level and by providing control and synchronization operations within the DCS which operate in terms of these properties. The heterogeneity problems are addressed by separating the data transport semantics (protocols themselves) from the control semantics (protocol interfaces)     

Discrete-time model for multimedia correlated sources

A multimedia source model is presented. To capture the intermedia synchronisation requirements of the streams in the multimedia flow, the model is defined as the superposition of heterogeneous correlated monomedia arrival processes. Transition probability matrices and correlation functions are calculated to allow any designer to investigate network performance by means of well-known analytical techniques