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1.
In this paper, we investigate a playout scheduling framework for supporting the continuous and synchronized presentations
of multimedia streams in a distributed multimedia presentation system. We assume a situation in which the server and network
transmissions provide sufficient support for the delivery of media objects. In this context, major issues regarding the enforcement
of the smooth presentation of multimedia streams at client sites must be addressed to deal with rate variance of stream presentations
and delay variance of networks. We develop various playout-scheduling algorithms that are adaptable to quality-of-service
parameters. The proposed algorithms permit the local adjustment of unsynchronized presentations by gradually accelerating
or retarding presentation components, rather than abruptly skipping or pausing the presentation materials. A comprehensive
experimental analysis of the proposed algorithms demonstrates that our algorithms can effectively avoid playout gaps (or hiccups)
in the presentations. This scheduling framework can be readily used to support customized multimedia presentations. 相似文献
2.
Denise J. Ecklund Vera Goebel Thomas Plagemann Earl F. Ecklund Jr. 《Multimedia Systems》2002,8(5):431-442
In this paper, we present a separable, reusable middleware solution that provides coordinated, end-to-end QoS management
over any type of service component, and can use existing (legacy) QoS management solutions (by using wrappers) in a distributed
multimedia system. Our middleware solution incorporates strategic and tactical QoS managers, and supports protocols and messages
between tactical managers and managed application components, and between QoS managers in the management hierarchy. Strategic
QoS managers take a global view of QoS provided by a set of application components within the manager's policy domain. Tactical
QoS managers provide local control over application components. We introduce the concept of QoS policy domains to scope the
authority of a strategic QoS manager. We describe how the management hierarchy is dynamically configured and reconfigured
based on runtime needs of the application. 相似文献
3.
One of the challenges in the design of a distributed multimedia system
is devising suitable specification models for various schemas in
different levels of the system.
Another important research issue is
the integration and synchronization of heterogeneous multimedia
objects. In this paper, we present our models for multimedia schemas
and transformation algorithms. They transform high-level
multimedia objects into schemas that can be used to
support the presentation and communication of the multimedia objects.
A key module in the system is the Object Exchange Manager (OEM). In this paper,
we present the design and implementation of the OEM module,
and discuss in detail the interaction
between the OEM and other modules in a
distributed multimedia system. 相似文献
4.
The next generation of interactive multimedia documents can contain both static media, e.g., text, graph, image, and continuous
media, e.g., audio and video, and can provide user interactions in distributed environments. However, the temporal information
of multimedia documents cannot be described using traditional document structures, e.g., Open Document Architecture (ODA)
and Standard Generalized Mark-up Language (SGML); the continuous transmission of media units also raises some new synchronization
problems, which have not been met before, for processing user interactions. Thus, developing a distributed interactive multimedia
document system should resolve the issues of document model, presentation control architecture, and control scheme. In this
paper, we (i) propose a new multimedia document model that contains the logical structure, the layout structure, and the temporal
structure to formally describe multimedia documents, and (ii) point out main interaction-based synchronization problems, and
propose a control architecture and a token-based control scheme to solve these interaction-based synchronization problems.
Based on the proposed document model, control architecture, and control scheme, a distributed interactive multimedia document
development mechanism, which is called MING-I, is developed on SUN workstations. 相似文献
5.
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. 相似文献
6.
Due to recent advances in network, storage and data compression technologies, video-on-demand (VOD) service has become economically
feasible. It is a challenging task to design a video storage server that can efficiently service a large number of concurrent
requests on demand. One approach to accomplishing this task is to reduce the I/O demand to the VOD server through data- and
resource-sharing techniques. One form of data sharing is the stream-merging approach proposed in [5]. In this paper, we formalize a static version of the stream-merging problem, derive an upper bound on the
I/O demand of static stream merging, and propose efficient heuristic algorithms for both static and dynamic versions of the
stream-merging problem. 相似文献
7.
Nikitas M. Sgouros 《Multimedia Systems》2003,8(6):470-481
Interactive performance systems allow multiple, networked users to take part in a performance either as players or audience
members and influence the performance's development in real time. Among the most prominent research issues concerning the
development of these systems are the provision of effective interaction capabilities and adequate means of expression to the
audience. This article describes a set of methods for the detection, analysis, synchronization and rendering of audience behavior
in real-time during such an event. Furthermore, it describes ways in which audience feedback is utilized to dynamically index
the contents of a performance so as to embed this event in large-scale multimedia services. All these methods have been applied
in the creation of MISSION, a multi-user game involving both players and audience. This article presents and analyzes the
design of the system and the results of user trials with it. 相似文献
8.
As the number of video streams to be supported by a digital video delivery system (DVDS) increases, an improved understanding
of the necessity for reliable and cost-efficient support for a considerable number of video streams (in the magnitude of tens
of thousands), and the dependency largely on software capabilities emerges. Even in the presence of an optimal hardware configuration,
or model, and associated costs, using software to exploit the underlying hardware capabilities is of paramount importance.
Although a number of DVDSs have become operational, their ability to deliver the required services mainly depends on the small
number of streams supported and the hardware trade-offs. It is imperative that current software developments account for
the eventual scalability of the number of video streams without commensurate increase in hardware. In this paper, we present
strategies for the management of video streams in order to maintain and satisfy their space and time requirements. We use
a DVDS architectural model with functionally dichotomized nodes: a single-node partition is responsible for data retrieval,
while the remaining partition of nodes accepts user requests, determines object locations, and routes requests through the
network that connects both partitions. We present a detailed analysis of the issues related to queuing I/O requests and data
buffering. The discussion includes the requirements for arranging and scheduling I/O requests and data buffers, with the objective
of guaranteeing the required data availability rates for continuous media display. 相似文献
9.
High-speed networks and powerful end-systems enable new types of applications, such as video-on-demand and teleconferencing.
Such applications are very demanding on quality of service (QoS) because of the isochronous nature of the media they are using.
To support these applications, QoS guarantees are required. However, even with service guarantees, violations may occur because
of resources shortage, e.g., network congestion. In this paper we propose new adaptation approaches, which allow the system
to recover automatically, if possible, from QoS violations (1) by identifying a new configuration of system components that might support the initially
agreed QoS and by performing a user-transparent transition from the original configuration to the new one, (2) by redistributing
the levels of QoS that should be supported, in the future, by the components, or (3) by redistributing the levels of QoS that
should be supported immediately to meet end-to-end requirements based on the principle that (local) QoS violation at one component
may be recovered immediately by the other components participating in the support of the requested service. The proposed approaches,
together with suitable negotiation mechanisms, allow us (1) to reduce the probability of QoS violations which may be noticed
by the user, and thus, to increase the user confidence in the service provider, and (2) to improve the utilization of the
system resources, and thus to increase the system availability. 相似文献
10.
In packet audio applications, packets are buffered at a receiving site and their playout delayed in order to compensate for
variable network delays. In this paper, we consider the problem of adaptively adjusting the playout delay in order to keep
this delay as small as possible, while at the same time avoiding excessive “loss” due to the arrival of packets at the receiver
after their playout time has already passed. The contributions of this paper are twofold. First, given a trace of packet audio
receptions at a receiver, we present efficient algorithms for computing a bound on the achievable performance of any playout delay adjustment algorithm. More precisely, we compute upper and lower bounds (which are shown to be tight for the
range of loss and delay values of interest) on the optimum (minimum) average playout delay for a given number of packet losses
(due to late arrivals) at the receiver for that trace. Second, we present a new adaptive delay adjustment algorithm that tracks
the network delay of recently received packets and efficiently maintains delay percentile information. This information, together
with a “delay spike” detection algorithm based on (but extending) our earlier work, is used to dynamically adjust talkspurt
playout delay. We show that this algorithm outperforms existing delay adjustment algorithms over a number of measured audio
delay traces and performs close to the theoretical optimum over a range of parameter values of interest. 相似文献
11.
Over the last few years, there has been a tremendous increase in the number of interactive multimedia presentations prepared
by different individuals and organizations. In this paper, we present an algebra for creating and querying interactive multimedia
presentation databases. This algebra operates on trees whose branches reflect different possible playouts of a set of presentations.
The algebra not only extends all the classical relational operators to such databases, but also introduces a variety of novel
operators for combining multiple presentations. As our algebra supports merging parts or all of existing presentations, this
algebra can also be used as an authoring tool for creating multimedia presentations. We prove a host of equivalence results
for queries in this algebra, which may be used to build query optimizers for interactive presentation databases. 相似文献
12.
Igor D.D. Curcio Antonio Puliafito Salvatore Riccobene Lorenzo Vita 《Multimedia Systems》1998,6(6):367-381
The relative simplicity of access to digital communications nowadays and the simultaneous increase in the available bandwidth
are leading to the definition of new telematic services, mainly oriented towards multimedia applications and interactivity
with the user. In the near future, a decisive role will be played in this scenario by the providers of interactive multimedia
services of the on-demand type, which will guarantee the end user a high degree of flexibility, speed and efficiency. In this
paper, some of the technical aspects regarding these service providers are dealt with, paying particular attention to the
problems of storing information and managing service requests. More specifically, the paper presents and evaluates a new storage
technique based on the use of disk array technology, which can manage both typical multimedia connections and traditional
requests. The proposed architecture is based on the joint use of the partial dynamic declustering and the information dispersal
algorithm, which are employed for the allocation and retrieval of the data stored on the disk array. We also define efficient
strategies for request management in such a way as to meet the time constraints imposed by multimedia sessions and guarantee
good response times for the rest of the traffic. The system proposed is then analyzed using a simulation approach. 相似文献
13.
In this paper, we present two novel disk failure recovery methods that utilize the inherent characteristics of video streams
for efficient recovery. Whereas the first method exploits the inherent redundancy in video streams (rather than error-correcting
codes) to approximately reconstruct data stored on failed disks, the second method exploits the sequentiality of video playback
to reduce the overhead of online failure recovery in conventional RAID arrays. For the former approach, we present loss-resilient
versions of JPEG and MPEG compression algorithms. We present an inherently redundant array of disks (IRAD) architecture that combines these loss-resilient compression algorithms with techniques for efficient placement of video streams
on disk arrays to ensure that on-the-fly recovery does not impose any additional load on the array. Together, they enhance
the scalability of multimedia servers by (1) integrating the recovery process with the decompression of video streams, and
thereby distributing the reconstruction process across the clients; and (2) supporting graceful degradation in the quality
of recovered images with increase in the number of disk failures. We present analytical and experimental results to show that
both schemes significantly reduce the failure recovery overhead in a multimedia server. 相似文献
14.
We describe a collection of algorithms designed to support reliable synchronization and group membership services for distributed
multimedia applications. In particular, we consider those applications that require interactivity, isochronous rendering of
multimedia data, and high reliability. We show that the algorithms we propose (i) provide reliable support for the synchronization
of multimedia data streams, despite the occurrence of possible communication failures, (ii) maintain a consistent view of
the relative group membership of all the nonfaulty application components, (iii) guarantee time-bounded delay of component
failure detection and join, and (iv) meet effectively possible scalability requirements of the applications. 相似文献
15.
HweeHwa Pang 《Multimedia Systems》1997,5(6):386-399
Multimedia applications that are required to manipulate large collections of objects are becoming increasingly common. Moreover,
the size of multimedia objects, which are already huge, are getting even bigger as the resolution of output devices improve.
As a result, many multimedia storage systems are not likely to be able to keep all of their objects disk-resident. Instead,
a majority of the less popular objects have to be off-loaded to tertiary storage to keep costs down. The speed at which objects
can be accessed from tertiary storage is thus an important consideration. In this paper, we propose an adaptive data retrieval
algorithm that employs a combination of staging and direct access in servicing tertiary storage retrieval requests. At retrieval
time, an object that resides in tertiary storage can either be staged to and then played back from disks, or the object can
be accessed directly from the tertiary drives. We show that a simplistic policy that adheres strictly to staging or direct
access does not exploit the full retrieval capacity of both the tertiary library and the secondary storage. To overcome the
problem, we propose a data retrieval algorithm that dynamically chooses between staging and direct access, based on the relative
load on the tertiary versus secondary devices. A series of simulation experiments confirms that the algorithm achieves good
access times over a wide range of workloads and resource configurations. Moreover, the algorithm is very responsive to changing
load conditions. 相似文献
16.
Efficient admission control algorithms for multimedia servers 总被引:3,自引:0,他引:3
In this paper, we have proposed efficient admission control algorithms for multimedia storage servers that are providers
of variable-bit-rate media streams. The proposed schemes are based on a slicing technique and use aggressive methods for admission
control. We have developed two types of admission control schemes: Future-Max (FM) and Interval Estimation (IE). The FM algorithm uses the maximum bandwidth requirement of the future to estimate the bandwidth requirement. The IE
algorithm defines a class of admission control schemes that use a combination of the maximum and average bandwidths within
each interval to estimate the bandwidth requirement of the interval. The performance evaluations done through simulations
show that the server utilization is improved by using the FM and IE algorithms. Furthermore, the quality of service is also
improved by using the FM and IE algorithms. Several results depicting the trade-off between the implementation complexity,
the desired accuracy, the number of accepted requests, and the quality of service are presented. 相似文献
17.
A multimedia application involves information that may be in a form of video, images, audio, text and graphics, need to be
stored, retrieved and manipulated in large databases. In this paper, we propose an object-oriented database schema that supports
multimedia documents and their temporal, spatial and logical structures. We present a document example and show how the schema
can adress all the structures described. We also present a multimedia query specification language that can be used to describe
a multimedia content portion to be retrieved from the database. The language provides means by which the user can specify
the information on the media as well as the temoral and spatial relationships among these media. 相似文献
18.
Multimedia systems must be able to support a certain quality of service (QoS) to satisfy the stringent real-time performance
requirements of their applications. HeiRAT, the Heidelberg Resource Administration Technique, is a comprehensive QoS management
system that was designed and implemented in connection with a distributed multimedia platform for networked PCs and workstations.
HeiRAT includes techniques for QoS negotiation, QoS calculation, resource reservation, and resource scheduling for local and
network resources. 相似文献
19.
Without user interactions, multimedia presentations are just fancy slide shows with sound and video supports. User interactions
by themselves do not change the temporal relationships among multimedia objects, such as texts, graphics, images, audio, and
video, but affect the playback schedules. In this paper, we propose a synchronization mechanism to guarantee the quality of
multimedia presentation with user interactions. In our protocol, each presentation site requests media transmission from the
required media servers at certain time intervals prior to the playback deadlines, where these time intervals are the response
times to cover possible experienced end-to-end delays and packet losses, and waits for an initial setup time to ensure intermedia
synchronization before starting the presentation. Users may interact with the presentation. This synchronization mechanism
solves the problems incurred by user interactions by determining the new presentation scenario produced by the interactive
operation, calculating the corresponding setup time, and then rendering the new playback and retrieval schedules. 相似文献
20.
Adaptive multimedia synchronization in a teleconference system 总被引:3,自引:0,他引:3
In this paper, we present an adaptive buffering scheme for implementing intra-stream and inter-stream synchronization in
real-time multimedia applications. The essence of the proposed scheme is to dynamically enforce equalized delays to incoming
media streams, in order to piece-wise smooth the network delay variations and to synchronize the streams at the sink. An adaptive
control mechanism based on an event-counting algorithm is employed to calibrate the PlayOut Clocks (POCs), which manages the
presentations of multimedia data. The algorithm does not rely on globally synchronized clock and makes minimal assumption
on underlying network delay distribution. Also, the user defined quality of service (QoS) specifications can be directly incorporated
into the design parameters of the synchronization algorithm. The proposed synchronization scheme has been experimentally implemented
in a teleconference system which consists of separately controllable audio, video, and data channels. The modular structure
of the synchronization control provides the flexibility to maintain an arbitrary synchronization group in conjunction with
a distributed conference management scheme. This paper also shows the experimental results of the test implementation and
the suitability of the proposed scheme with respect to the multimedia traffic across an FDDI/Ethernet network. 相似文献