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1.
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
2.
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
3.
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
4.
The elicitation or communication of user requirements comprises an early and critical but highly error-prone stage in system
development. Socially oriented methodologies provide more support for user involvement in design than the rigidity of more
traditional methods, facilitating the degree of user–designer communication and the ‘capture’ of requirements. A more emergent
and collaborative view of requirements elicitation and communication is required to encompass the user, contextual and organisational
factors. From this accompanying literature in communication issues in requirements elicitation, a four-dimensional framework
is outlined and used to appraise comparatively four different methodologies seeking to promote a closer working relationship
between users and designers. The facilitation of communication between users and designers is subject to discussion of the
ways in which communicative activities can be ‘optimised’ for successful requirements gathering, by making recommendations
based on the four dimensions to provide fruitful considerations for system designers. 相似文献
5.
Due to their large bandwidth demand and synchronization requirements, multimedia applications, in general, consume buffers
of huge size, which prevents potential customers from using multimedia services. We recognize the problem and propose a hierarchical
architecture to reduce the buffer size. The architecture can be applied to both 1- and - applications. We establish the architecture by first determining neighbor sets and then applying a grouping algorithm and
a renegotiation process. This architecture can also meet the synchronization requirements of multimedia applications. We evaluate
the performance of the architecture through simulations and compare it with that of a direct connection architecture. The result shows that the hierarchical architecture reduces the buffer size significantly without
serious penalty to the total bandwidth and without introducing extra hot spots. 相似文献
6.
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
7.
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
8.
Ivan Herman Nuno Correia David A. Duce David J. Duke Graham J. Reynolds James Van Loo 《Multimedia Systems》1998,6(2):88-101
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. 相似文献
9.
Multimedia streams such as audio and video impose tight temporal constraints for their presentation. Often, related multimedia
streams, such as audio and video, must be presented in a synchronized way. We introduce a novel scheme to ensure the continuous
and synchronous delivery of distributed stored multimedia streams across a communications network. We propose a new protocol for synchronized playback and compute the buffer
required to achieve both, the continuity within a single substream and the synchronization between related substreams. The
scheme is very general and does not require synchronized clocks. Using a resynchronization protocol based on buffer level
control, the scheme is able to cope with server drop-outs and clock drift. The synchronization scheme has been implemented
and the paper concludes with our experimental results. 相似文献
10.
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
11.
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
12.
K. Selçuk Candan Eric Lemar V.S. Subrahmanian 《The VLDB Journal The International Journal on Very Large Data Bases》2000,9(2):131-153
Abstract. Though there has been extensive work on multimedia databases in the last few years, there is no prevailing notion of a multimedia
view, nor there are techniques to create, manage, and maintain such views. Visualizing the results of a dynamic multimedia
query or materializing a dynamic multimedia view corresponds to assembling and delivering an interactive multimedia presentation
in accordance with the visualization specifications. In this paper, we suggest that a non-interactive multimedia presentation
is a set of virtual objects with associated spatial and temporal presentation constraints. A virtual object is either an object, or the result of a query.
As queries may have different answers at different points in time, scheduling the presentation of such objects is nontrivial.
We then develop a probabilistic model of interactive multimedia presentations, extending the non-interactive model described
earlier. We also develop a probabilistic model of interactive visualization where the probabilities reflect the user profiles,
or the likelihood of certain user interactions. Based on this probabilistic model, we develop three utility-theoretic based
types of prefetching algorithms that anticipate how users will interact with the presentation. These prefetching algorithms
allow efficient visualization of the query results in accordance with the underlying specification. We have built a prototype
system that incorporates these algorithms. We report on the results of experiments conducted on top of this implementation.
Received June 10, 1998 / Accepted November 10, 1999 相似文献
13.
Streaming media from the Internet is a successful application for end-users. With the upcoming success of mobile devices
and home networking environments, cooperation among users will become more important in the future. To achieve such cooperation,
explicit middleware standards have been defined. On the other hand, Internet conferencing applications do not handle collaborative
streaming sessions with individual control for each user. We propose a new concept for cooperation exemplary for collaborative
media streaming using IETF multimedia session control protocols together with a proxy architecture. This concept enables both
synchronization among clients and flexible control to individual users. 相似文献
14.
An adaptive protocol for synchronizing media streams 总被引:8,自引:0,他引:8
Stream synchronization is widely regarded as a fundamental problem in the field of multimedia systems. Solutions to this
problem can be divided into adaptive and rigid mechanisms. While rigid mechanisms are based on worst case assumptions, adaptive
ones monitor the underlying network and are able to adapt themselves to changing network conditions. In this paper, we will
present an adaptive stream synchronization protocol. This protocol supports any kind of distribution of the sources and
sinks of the streams to be synchronized. It is based on a buffer-level control mechanism, allowing immediate corrections
when the danger of a buffer overflow or underflow is recognized. Moreover, the proposed protocol is flexible enough to support
a wide variety of synchronization policies, which can be dynamically changed while synchronization is in progress. Finally,
the message overhead of this protocol is low, because control messages are only exchanged when network conditions change. 相似文献
15.
The Personal Presence System (PPS) is an experimental research prototype platform to support advanced broadband applications,
including multimedia conferencing and distance learning. It supports the user's presentation control of advanced network elements
(multimedia bridges). The multimedia bridge provides for a single contact point per user, who receives only one combined video
stream, which minimizes access bandwidth. This architecture solves the -squared transmission problem of multipoint video conferencing and makes customer terminal equipment simpler and cheaper than
high-end desktop workstations. The PPS provides each user with flexible presentation control of a feature-rich video bridge.
The PPS also supports advanced features such as object extraction and multimedia object associations. 相似文献
16.
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
17.
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
18.
19.
Kaoru Nakazono 《Multimedia Systems》1998,6(5):359-366
The preservation of QoS for multimedia traffic through a data network is a difficult problem. We focus our attention on video
frame rate and study its influence on speech perception.
When sound and picture are discrepant (e.g., acoustic ‘ba’ combined with visual ‘ga’), subjects perceive a different sound
(such as ‘da’). This phenomenon is known as the McGurk effect. In this paper, the influence of degraded video frame rate on
speech perception is studied.
It is shown that, when frame rate decreases, correct hearing is improved for discrepant stimuli and is degraded for congruent
(voice and picture are the same) stimuli. Furthermore, we studied the case where lip closure was always captured by the synchronization
of sampling time and lip position. In this case, frame rate has little effect on mishearing for congruent stimuli. For discrepant
stimuli, mishearing is decreased with degraded frame rate. These results indicate that the stiff motion of lips resulting
from low frame rate cannot give enough labial information for speech perception. In addition, the effect of delaying the picture
to correct for low frame rate was studied. The results, however, were not as definitive as expected, because of compound effects
related to the synchronization of sound and picture. Finally, we inspected the still pictures of normal Japanese speech and
determined a lower limit of frame rate from the view point of assisting hearing. 相似文献
20.
As multimedia applications spread widely, it is crucial for programming and design support systems to handle “time” in multimedia
documents effectively and flexibly. This paper presents a set of interactive system support tools for designing and maintaining
the temporal behavior of multimedia documents. The tool set provides mechanisms for anomaly detection, temporal query processing,
and interactive scheduling. It is based on a fast incremental constraint solver we have developed, which can be adapted by
any constraint-based system. The incremental constraint solver provides immediate feedback to the user, supporting a highly
interactive design process. Combined with existing optimal layout generation mechanisms proposed in the literature, our tools
effectively utilize the flexibility provided by constraint-based systems. 相似文献