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Selected Areas in Communications, IEEE Journal on

Issue 1 • Date Jan. 1996

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Displaying Results 1 - 21 of 21
  • Guest Editorial Synchronization Issues in Multimedia Communications

    Publication Year: 1996
    Cited by:  Papers (2)
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    Freely Available from IEEE
  • MultiSync: a synchronization model for multimedia systems

    Publication Year: 1996 , Page(s): 238 - 248
    Cited by:  Papers (10)  |  Patents (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1360 KB)  

    Synchronization among various media sources is one of the most important issues in multimedia communications and various audio/video (A/V) applications. For continuous playback (such as lip synchronization) under a time-sharing multiprocessing operating system (such as UNIX), the synchronization quality of traditional synchronization mechanisms employed on single processes may vary according to the workload of the system. When the system encounters an overload situation, the synchronization usually fails and, even worse, results in two fatal defects in human perception: the audio discontinuity (audio break) and the out-of-synchronization (synchronization anomaly). In order to overcome these problems, a novel media synchronization model employed on multiple processes (or threads) in a multiprocessing environment is proposed. The problem of asynchronism due to system overload is solved by assigning a higher priority to more important media and adopting a delay-or-drop policy to treat the lower priority ones. Some experimental results are presented to show the effectiveness of the proposed model and the implementation mechanisms under a UNIX, X-Windows environment. On the basis of the proposed model, a continuous media playback (CMP) module, which acted as the key component of some popular multimedia systems such as multimedia authoring system, multimedia E-mail system, multimedia bulletin board system (BBS), and video-on-demand (VoD) System, was implemented View full abstract»

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  • An EFSM-based multimedia synchronization model and the authoring system

    Publication Year: 1996 , Page(s): 138 - 152
    Cited by:  Papers (20)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1608 KB)  

    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 View full abstract»

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  • Doing FLIPS: flexible interactive presentation synchronization

    Publication Year: 1996 , Page(s): 114 - 125
    Cited by:  Papers (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1436 KB)  

    Multimedia presentation technology has enormous potential for a myriad of applications including academic classrooms, industrial training, and business presentations. As presentation technology advances, it is possible to incorporate a wider range of media including variable duration media such as simulations and animations. At the same time, users are able to take more control over presentations by controlling the rate and selection of media being played. To make full use of these advances, multimedia systems must support flexible presentations that incorporate many variations in the way they are played. This paper identifies three requirements for flexible presentations and derives four requirements for synchronization of flexible presentations. The paper presents flexible interactive presentation synchronization (FLIPS), a model for specifying coarse synchronization for flexible presentations. FLIPS supports a wide range of temporal synchronization specifications. It also provides algorithms for attaining a consistent and coherent presentation state in response to user interaction (e.g. skipping to a different slide or selection) and other state-changing events. Applications of the FLIPS model are discussed View full abstract»

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  • Multimedia group synchronization protocols for integrated services networks

    Publication Year: 1996 , Page(s): 162 - 173
    Cited by:  Papers (28)  |  Patents (13)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1224 KB)  

    Unlike traditional data traffic, real time multimedia traffic requires synchronization. Temporal relationships among media must be maintained. Yet delay jitter and the absence of a global clock may disrupt these temporal relationships. This paper introduces new group synchronization protocols for real-time, multimedia applications, including teleconference, teleorchestration and multimedia on demand services. The proposed protocols achieve synchronization for all configurations (one-to-one, one-to-many, many-to-one, and many-to-many), and does so without prior knowledge of the end-to-end delay distribution, or the distribution of the clock drift. The only a-priori knowledge the protocols require is an upper bound on the end-to-end delay. The paper concludes with simulation experiments showing that the protocols work effectively in both LAN and WAN environments View full abstract»

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  • Synchronization of multimedia data for a multimedia news-on-demand application

    Publication Year: 1996 , Page(s): 264 - 278
    Cited by:  Papers (12)  |  Patents (14)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1536 KB)  

    We present a complete software control architecture for synchronizing multiple data streams generated from distributed media-storing database servers without the use of a global clock. Independent network connections are set up to remote workstations for multimedia presentations. Based on the document scenario and traffic predictions, stream delivery scheduling is performed in a centralized manner. Certain compensation mechanisms at the receiver are also necessary due to the presence of random network delays. A stream synchronization protocol (SSP) allows for synchronization recovery, ensuring a high quality multimedia display at the receiver. SSP uses synchronization quality of service parameters to guarantee the simultaneous delivery of the different types of data streams. In the proposed architecture, a priority-based synchronization control mechanism for MPEG-2 coded data streams is also provided. A performance modeling of the SSP is presented using the DSPN models. Relevant results such as the effect of the SSP, the number of synchronization errors, etc., are obtained View full abstract»

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  • A temporal reference framework for multimedia synchronization

    Publication Year: 1996 , Page(s): 36 - 51
    Cited by:  Papers (25)  |  Patents (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1628 KB)  

    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 View full abstract»

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  • Clock hierarchies: an abstraction for grouping and controlling media streams

    Publication Year: 1996 , Page(s): 174 - 184
    Cited by:  Papers (3)  |  Patents (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1392 KB)  

    Synchronization plays an important role in multimedia systems at various levels of abstraction. We propose a set of powerful abstractions for controlling and synchronizing continuous media streams in distributed environments. The proposed abstractions are based on a very general computation model, that allows media streams to be processed (i.e. produced, consumed or transformed) by arbitrarily structured networks of linked components. Further, compound components can be composed of existing ones to provide higher levels of abstractions. The clock abstraction is provided to control individual media streams, i.e., streams can be started, paused or scaled by issuing the appropriate clock operations. Clock hierarchies are used hierarchically group related streams, where each clock in the hierarchy identities and controls a certain group, or subgroup of streams. Control and synchronization requirements can be expressed in a uniform manner by associating group members with control or synchronisation attributes. An important property of the concept of clock hierarchy is that it can be combined in a natural way with component nesting View full abstract»

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  • A new multimedia synchronization model

    Publication Year: 1996 , Page(s): 73 - 83
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1116 KB)  

    The paper presents a hierarchical synchronization model for the description of the time relations and regimes necessary for the presentation of multimedia or animated data which have either natural or implied time dependencies. The model generalizes some previous multimedia synchronization models by unifying time and event based synchronization concepts and offering a consistent framework in which to handle dynamic media presentation functionality View full abstract»

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  • Exception handling and fault-tolerance in multimedia synchronization

    Publication Year: 1996 , Page(s): 196 - 211
    Cited by:  Papers (3)
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    This paper contributes toward exception handling and fault-tolerance in multimedia presentation. Our study is based on the well-known four phases in fault-tolerant computing: fault detection, damage assessment, error recovery, and continued service. We define a fault in multimedia synchronization and a simple fault detection mechanism. Using the concept of a partner set of a media stream, we assess the damage caused to media presentation due to a fault. From the point of error recovery and reducing synchronization failures, we introduce the ideas of a k-cycle virtual fault. A k-cycle virtual fault suggests the possibility of a failure in the future after k presentation cycles. Detection of a possible presentation failure in the future gives lead time to take corrective measures to avoid the failure. In order to handle exception conditions during a synchronization failure, we define pinned and sliding semantics of media presentation. These two semantics allow us to define different levels of quality of presentation during a failure. Finally, we present the detailed design of a fault-tolerant presentation architecture and prove its properties. We discuss how the ideas of virtual fault and damage assessment can be used in generating useful information for the underlying data transfer protocol so that synchronization failures can be reduced View full abstract»

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  • Synchronization representation and traffic source modeling in orchestrated presentation

    Publication Year: 1996 , Page(s): 104 - 113
    Cited by:  Papers (9)
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    Multimedia applications comprise several media streams, which are semantically synchronized at different time instants. The application behavior is stored along with the multimedia database using representation mechanisms such as OCPN (object composition Petri nets) or dynamic timed Petri nets (DTPN). It is imperative that one translates the application behavior to the corresponding schedulable entities, such as packets, so that the performance engineering of any system can be done, using the traffic model arising out of the (media related) application behavior as opposed to individual media level behavior. This requires that a function be defined, which takes the stored temporal representation as input and produces packets as output, preserving the semantic relationships among the streams. The authors propose a methodology based on probabilistic, attributed context free grammar (PACFG) to address this issue. They demonstrate the appropriateness of this methodology by applying it to the OCPN/DTPN representation of a typical multimedia application vis-a-vis orchestrated presentation View full abstract»

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  • A programming model and system infrastructure for real-time synchronization in distributed multimedia systems

    Publication Year: 1996 , Page(s): 249 - 263
    Cited by:  Papers (8)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1752 KB)  

    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 View full abstract»

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  • Human perception of jitter and media synchronization

    Publication Year: 1996 , Page(s): 61 - 72
    Cited by:  Papers (146)  |  Patents (2)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2252 KB)  

    Multimedia synchronization comprises both the definition and the establishment of temporal relationships among media types. The presentation of `in sync' data streams is essential to achieve a natural impression, data that is `out of sync' is perceived as being somewhat artificial, strange, or even annoying. Therefore, the goal of any multimedia system is to enable an application to present data without no or little synchronization errors. The achievement of this goal requires a detailed knowledge of the synchronization requirements at the user interface. The paper presents the results of a series of experiments about human media perception that may be used as `quality of service' guidelines. The results show that skews between related data streams may still give the effect that the data is `in sync' and gives some constraints under which jitter may be tolerated. The author uses the findings to develop a scheme for the processing of nontrivial synchronization skew between more than two data streams View full abstract»

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  • A media synchronization survey: reference model, specification, and case studies

    Publication Year: 1996 , Page(s): 5 - 35
    Cited by:  Papers (165)  |  Patents (8)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (3500 KB)  

    Researchers have addressed multimedia synchronization from various perspectives. The major issues include how to specify and how to implement synchronization. Especially in the specification area a variety of techniques have been published and implemented. This survey summarizes briefly synchronization requirements, presents a multimedia synchronization reference model, shows details of various specification approaches and applies the reference model to compare existing prominent approaches as case studies View full abstract»

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  • Client-server synchronization and buffering for variable rate multimedia retrievals

    Publication Year: 1996 , Page(s): 226 - 237
    Cited by:  Papers (13)  |  Patents (23)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1248 KB)  

    We consider the use of large buffers and feedback as a mechanism to maintain loosely coupled synchronization between a multimedia server and a client. The multimedia stream is modeled as a fluid flow through rate controlled valves and buffers with multiple thresholds. These thresholds are used to control the rates upstream. The quality of service for the multimedia connection is characterized in terms of the jitter in the received media stream due to buffer underflow and overflow. This quality of service is used to exercise rate and admission control in the presence of congestion. The feedback mechanism is, implemented in GRAMS (gopher-style real time ATM multimedia system), an adaptive multimedia client-server system. Experimental statistics are gathered for the purpose of traffic engineering. We employ a fluid flow and first passage time analysis to understand the traffic process through the pipelines and the buffers and to estimate the amount of signaling required by the feedback mechanism View full abstract»

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  • Continuity and synchronization in MPEG

    Publication Year: 1996 , Page(s): 52 - 60
    Cited by:  Papers (26)  |  Patents (25)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (796 KB)  

    The requirement of continuous retrieval, and the presence of multiple media streams whose display must proceed in a mutually synchronized manner are the distinguishing features that are unique to digital multimedia. In the emerging international multimedia encoding standard MPEG, continuity and synchronization are handled at different layers of the multimedia stream. The authors discuss how they are specified and propose techniques for their implementation within a distributed multimedia environment View full abstract»

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  • A general-purpose multimedia synchronization mechanism based on causal relations

    Publication Year: 1996 , Page(s): 185 - 195
    Cited by:  Papers (12)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1364 KB)  

    Designing distributed multimedia applications raises temporal and spatial synchronization issues related to processing, transport, storage, retrieval and presentation of data, sound, still images and video. Within this framework, the paper aims to define a general-purpose multimedia synchronization mechanism, known as the conditional delivery mechanism, capable of addressing both intraand inter-stream synchronization issues. The proposed mechanism, based on the identification of causal relations among information units of one or several streams, is designed to ensure that these causal relations, expressed at the user's level, are satisfied when delivering the streams. The conditional delivery mechanism is analyzed in depth and both informal and formal specifications of the mechanism are provided. The formal specification refers to an extension of the standard formal description technique LOTOS (RT-LOTOS for real-time LOTOS). Validation results of the conditional delivery mechanism are finally presented for a distance and interactive training application View full abstract»

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  • Using timed CSP for specification verification and simulation of multimedia synchronization

    Publication Year: 1996 , Page(s): 126 - 137
    Cited by:  Papers (11)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1160 KB)  

    Timed communicating sequential processes (TCSP) language is used to specify fine-grain and coarse-grain multimedia synchronization. A lip synchronization system is an example of fine-grain synchronization. Several groupware scenarios are examples of coarse-grain synchronization. The formal specifications are used as the basis of verification and simulation. Safety and liveness timing requirements of the synchronization system are stated in terms of temporal logic formulas. Correctness analysis of the specification is shown using the temporal formulas and TCSP proof theory. It is shown that TCSP is powerful enough to be used in multimedia system design and verification. Next, simulation of multimedia synchronization is discussed. Various simulation models are developed for fine- and coarse-grain synchronization systems. It is shown that simulation modeling can lead to early detection of possible synchronization violations. The buffering requirements of a given synchronization mechanism can be effectively studied using simulation View full abstract»

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  • Modeling logical and temporal synchronization in hypermedia systems

    Publication Year: 1996 , Page(s): 84 - 103
    Cited by:  Papers (27)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (2076 KB)  

    The paper introduces a unified formal model for the complete and accurate specification of both temporal and logical (i.e., link) synchronization within hypermedia distributed and weakly synchronous systems. This new model extends time Petri nets with hierarchical design capabilities and new firing rules. These new firing rules enlighten the notion of hypermedia synchronization through powerful combinations of temporal and logical synchronization. Moreover, the proposed model offers an easy and concise modeling technique of asynchronous events in hypermedia systems View full abstract»

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  • A multimedia synchronization model and its implementation in transport protocols

    Publication Year: 1996 , Page(s): 212 - 225
    Cited by:  Papers (14)  |  Patents (1)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (1496 KB)  

    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 View full abstract»

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  • Distributed source-destination synchronization using inband clock distribution

    Publication Year: 1996 , Page(s): 153 - 161
    Cited by:  Papers (5)  |  Patents (3)
    Save to Project icon | Request Permissions | Click to expandQuick Abstract | PDF file iconPDF (920 KB)  

    This paper presents a new distributed methodology for source destination synchronization for interactive teleconferencing. The method is based on a reference clock, which is synthesized from a distributed global clock. The global clock is generated by periodically exchanging inband synchronization signals with neighboring nodes. The timing jitter achieved with this method can be arbitrarily close to the jitter obtained by the centralized synchronous methods which usually use an out-of-band, hard-wired reference clock. The global clock synchronization algorithm, used in this work, guarantees frequency locking of all the network nodes to the slowest clock in the system. As a result, the slowest clock can be used as an implicit reference clock for source-destination synchronization protocols, such as synchronous frequency encoding technique (SFET) and synchronous residual time stamp (SRTS). This inband synchronization method does not require the explicit knowledge of which clock is actually the slowest in the system. Therefore, if the slowest clock fails, then another clock on a different node will be the slowest, and the nodes will use it as a reference clock for the source-destination synchronization protocol. The existing out-of-band reference clock techniques do not have this strong fault tolerant property View full abstract»

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Aims & Scope

IEEE Journal on Selected Areas in Communications focuses on all telecommunications, including telephone, telegraphy, facsimile, and point-to-point television, by electromagnetic propagation.

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Editor-in-Chief
Muriel Médard
MIT