Synchronization and handoff management schemes for wireless multimedia systems

This paper presents handoff management schemes for synchronization algorithms for wireless multimedia systems. The synchronization and handoff management schemes allow mobile hosts to receive time-dependant multimedia streams without delivery interruption while moving from one cell to another. They also maintain the correct ordering of the media components, through the execution of the wireless multimedia application by a means of timestamped messages passed among mobile hosts, base stations and servers. The timestamp values are used to compute the delay for each multimedia unit for each server. Furthermore, the proposed schemes always search for a quasi-receiver among the base stations with which the mobile hosts can communicate to synchronize multimedia units. We discuss the algorithms and present a set of simulation experiments that evaluate the performance of our schemes, using message complexity and buffer usage at each frame arrival time. Our results indicate that our schemes exhibit no underflow or overflow within the bounded delivery time.     

动态上下文环境下的实时分布式多媒体系统框架

伴随着多媒体采集和处理设备成本的不断降低,以及处理目标的不断复杂化,多媒体信息系统正朝着大规模数据分析和管理系统靠拢,因此如何有效支持实时分布式多媒体信息所需的实时采集、压缩、传输、处理、描述、反馈与存档,以及后期的浏览与检索,已经成为多媒体计算研究的重要问题。为了有效支持实时分布式多媒体信息的实时采集、传输、处理、描述、存档等的需要,在分析动态上下文环境下实时分布式多媒体系统对底层采集、压缩和传输以及信息的表达和存储的普遍需求的基础上,提出并实现了一个通用的实时分布式媒体信息处理框架,以便为实时分布多媒体系统提供基础服务支持。该框架包括软件平台和信息系统两部分。前者用于将逻辑功能与物理设备隔离开来,完成实时采集、压缩、传输和解压等功能;后者通过统一信息表达格式,将数据与特定的采集处理模块隔离开来,同时还提供了信息管理的功能,以便于用户后期检索。这两部分共同将多媒体系统所需要的实时采集、处理、压缩、描述、反馈与存档以及离线浏览与检索等服务融入一致、统一的框架中。基于该框架的会议系统的相关实验表明,该框架具有良好的开放性、可配置性和可扩展性。     

手机二维码在多媒体教室设备管理中的应用

针对我校多媒体教室管理中存在的问题,设计开发一套多媒体教室设备管理系统。该系统采用C/S架构,基于Android平台,利用手机二维码技术,实现快速查询多媒体教室的软硬件信息以及设备操作手册,极大地提升了多媒体教室管理效率。      

A multi-layer experimental study of multimedia and QoS communication in wireless mesh networks

A significant issue in Mesh networks is to support multimedia transmissions while providing Quality of Service (QoS) guarantees to mobile users. For real-time multimedia streaming, unstable throughput or insufficient bandwidth will incur unexpected delay or jitter, and it remains difficult to provide comprehensive service guarantees for a wireless mesh environment. In this paper, we target the problem of providing multimedia QoS in wireless mesh networks. We design and implement a campus test-bed for supporting multimedia traffic in mobile wireless mesh networks, and investigate in detail some possible improvements on a number of layers to enable multimedia transmission over wireless networks with QoS support. We first study a number of improvements of some existing routing protocols to support multimedia transmissions. Some new admission control and rate control mechanisms are studied and their performance gains are verified in our experiments. In our new cross-layer adaptive rate control (CLARC) mechanism, we adaptively change the video encoder’s output bit rate based on the available network bandwidth to improve the quality of the received video. We also design a mobile gateway protocol to connect the MANET to Internet and a wireless LAN management protocol to automatically manage WLAN to provide some QoS.     

Optimization for adaptive bandwidth reservation in wireless multimedia networks

In future wireless multimedia networks, user mobility management for seamless connection regarding realtime multimedia applications is one of the most important problems. In this paper we propose an opportunity-cost concept-based approach for adaptive bandwidth reservation with admission control for handover calls utilizing network traffic information. Excessive reservation guarantees low blocking probability of handover calls at the cost of high blocking probability of new calls. According to our survey, however, it may degrade bandwidth utilization while no prioritization for handover admissions degrades quality of service (QoS) for ongoing calls. We consider both QoS assurance and bandwidth utilization in order to optimize the amount of bandwidth to reserve for handover admissions. We believe that our scheme could be utilized as a guideline for cost-effective radio resource allocation in mobile multimedia networks.     

基于一体化智能型多媒体教室设备系统的选型

随着多媒体技术的不断发展,越来越多的新设备和新技术融入到多媒体教室的建设和管理中,因此,一体化智能型多媒体教室设备系统的选型在多媒体建设中起着关键的作用。多媒体教室不仅是现代教学的基础设施,更是评估各高职院校办学硬条件的必要指标。文章通过对我校一体化智能型多媒体教室设备系统选型的分析,探讨符合我校教学、管理需求的,实用、高效的一体化智能型多媒体教室设备系统的选型。     

A measurement-based approach for dynamic QoS adaptation in DiffServ networks

This paper presents a practical approach to managing multimedia traffic in DiffServ network, using network monitoring feedback and control. We exploit the flexibility of multimedia traffic and process network level parameters to adapt the traffic according to the current state of the network. The latter is determined based on reports sent by bandwidth monitors installed on each node of a DiffServ Domain. The bandwidth monitors interact with a policy server which, depending on the network state, decides the policy(ies) that should be enforced by the DiffServ network. The implementation of the selected policies typically leads to accepting, remarking, or dropping the multimedia traffic entering the network. Multimedia streams may be assigned different levels of QoS, as interpreted by the marker at the DiffServ edge router and marked according to network state. To achieve such dynamic QoS adaptation for multimedia applications, we have implemented and evaluated a policy-based management system. Performance evaluation shows that multimedia applications adapt better to network conditions using our approach.     

An object-oriented multimedia database system for a news-on-demand application

We describe the design of a multimedia database management system for a distributed news-on-demand multimedia information system. News-on-demand is an application that uses broadband network services to deliver news articles to subscribers in the form of multimedia documents. Different news providers insert articles into the database, which are then accessed by users remotely, over a broadband, asynchronous transfer-mode (ATM) network. The particulars of our design are an object-oriented approach and strict adherence to international standards, in particular the Standard Generalized Mark-up Language (SGML) and Hy-Time. The multimedia database system has a visual query facility, which is also described in this paper. The visual query interface provides three major facilities for end users: presentation, navigation, and querying of multimedia news documents. The main focus, however, is the querying of multimedia objects stored in the database.     

MyOwnLife: incremental and hierarchical classification of a personal image collection on mobile devices

Browsing multimedia collection on mobile devices raises the needs for new multimedia indexing solutions. In this paper, we focus on the management of personal image collections. We propose a method to simplify the browsing task on such a collection. The contributions reside in an incremental hierarchical algorithm, a method to provide a textual representation of the groups obtained and an algorithm to build a geo-temporal view of the collection. The proposed incremental hierarchical algorithm builds a temporal tree from the time stamp of each image. We opt here for a combination of a supervised clustering and an incremental algorithm based on mixture model. Good properties of the hierarchy are determined automatically thanks to the Integrated Likelihood Criterion (ICL). Based on the events obtained, a textual representation is proposed and then used to improve our temporal classification, combining geographical and temporal information. Results are validated on several real user collections with our prototype MyOwnLife.     

Building Manageable Multimedia Network Services

The paper addresses the problem of designing and realizing manageable multimedia network services. We argue that open interface between the service delivery and the service management systems can be defined using design patterns, i.e., generic object models. As an example, we introduce a generic object model that makes instances of a network service accessible to the management system. The model includes a set of cooperating objects that can be customized for particular service and management requirements. By applying this model to the design of mcast, an ATM multicast service, we enable the management system to monitor and control mcast sessions. To validate our approach, we have implemented mcast and the management functions on two different platforms: (1) on a high-performance emulation platform, which allows us to study the system's dynamic behavior and scaling properties in various scenarios; (2) on a broadband testbed, on which network services can be fully implemented, including the transport between multimedia devices. We outline a specific technique that allows us to run the same code, without changes, on both platforms.     

Joint Source/Channel Coding to Maximize Perceptual Video Quality on Packet Networks

The QoS-guarantee in real-time communication for multimedia applications is significantly important. An architectural framework for multimedia networks based on substreams or flows are effectively exploited for combining source and channel coding for multimedia data. In this paper, firstly, we designed a source coding scheme based on wavelet transform to exploit the human visual systems's spatial and temporal characteristics of video data. Secondly, we designed a classification scheme to partition video data into multiple substreams which have their own quality of service (QoS) requirements. Finally, we designed a management (reservation and scheduling) scheme for substreams to support better perceptual video quality such as the bound of end-to-end jitter. We have shown that our joint source/channel coding scheme is better than two other schemes by simulation and a real video experiment.     

基于IP网络的自适应QoS管理方案研究

目前实时音频、视频多媒体应用已经开始进入IP网络,但还有许多问题没有得到很好地解决,其中一个关键问题是多媒体服务的QoS问题、TCP／IP协议本身只提供一种“Best-effort”级别的服务,对QoS支持很少,“Best-effort”级别的服务往往会导致实时应用出现延迟抖动、分组丢失率高,从而极大的影响了实时应用的运行效果,因此必须研究可行的、高效的基于IP网络的QoS控制机制。IP网络QoS已成为分布式多媒体和网络通信的重要研究热点和难点课题。本文在IEＴＦ Intserv与Diffserv相结合的体系结构基础上,提出了一种适用于IP网络的自适应QoS管理框架,与Intserv或Diffserv模型不同的是,该QoS管理框架引入优先级节和自适应概念,QoS俦权处理采用基于多媒体优先级节的算法,在传输控制上采用了自适应QoS控制算法。它在应用层上完成,因此独立于底层网络协议。本文首先讨论了基本概念和函数,然后提出一种基于优先级节的自适应QoS管理框架和优先级调度流程。提出一种基于IP的自适应QoS协商机制,基本思想是基于RSVP（资源预留协议）。在提出QoS请求时进行QoS映射,然后启动适应性函数和资源管理函数进行协商,直到获得一组在当前资源状况下最佳的QoS指标。最后,本文还讨论了此方案的有效性并在自行开发的实验平台GUT上进行的QoS实验。实验表明应用该方法可以根据网络当前状态自适应地整多媒体实时应用的QoS需求。     

中国多媒体技术研究：2009

本文是中国多媒体技术研究与应用的年度文献综述之十二。该文从2009年9种核心刊物的3023篇中选取396篇多媒体技术相关的文章进行了分类、统计,以展现出2009年中国多媒体技术发展的现状。今年采用的分类方案在去年的基础上做了一些调整,以适应多媒体技术发展的趋势。通过与前4年统计结果的对比可以看出,数字水印、数据管理与检索、多播、交互模式与接口、虚拟现实交互等多媒体基础技术是2009年论文反映出的研究热点,同时,多媒体应用日趋多样化,与社会生活的结合程度越来越紧密。该文还对近5年的中国多媒体技术文献统计结果作了比较,从中可看到多媒体技术,特别是一些热点技术的发展趋势。该文不仅能给从事多媒体技术研究与应用的人员提供系统的文献索引,也能为技术规划和管理人员提供参考。     

中国多媒体工程：2010

本文是中国多媒体技术研究与应用的年度文献综述之十三。该文从2010年9种核心刊物的2916篇中选取380篇多媒体技术相关的文章进行了分类、统计,以展现出2010年中国多媒体技术发展的现状。今年采用的分类标准在去年的基础上做了一些细微调整,以适应多媒体技术发展的趋势。通过与前四年统计结果的对比可以看出,数字水印、数据管理与检索、流媒体多播、交互模式与接口、生物特征身份识别等多媒体基础技术是2010年论文反映出的研究热点,同时,多媒体应用日趋多样化,与社会生活的结合程度越来越紧密。该文还对近5年的中国多媒体技术文献统计结果做了比较,从中可看到多媒体技术,特别是一些热点技术的发展趋势。该文不仅能给从事多媒体技术研究与应用的人员提供系统的文献索引,也能为技术规划和管理人员提供参考。     

符合MIKEY规范的密钥更新协议MIKEY-Rekey

MIKEY协议是一种可应用于实时的、多媒体通信的密钥管理协议。该文基于MIKEY协议和文献[6]中的组密钥管理结构,提出了一种综合周期和批量密钥更新策略的密钥更新协议MIKEY-Rekey协议,协议设计考虑到了两种更新策略的融合、同步问题的对策和PDU的设计等问题。     

Supporting interactive presentation for distributed multimedia applications

In this paper we present IMP, a platform to support the authoring and run-time management of interactive multimedia applications in distributed environments. The multi-level platform model encourages slot-in extensibility to cater for the evolving environment. We illustrate with our prototype platform built above the Cambridge multimedia environment. The authoring model emphasises reusability, tailorability and use of environment features in a uniform way. We have shown the validity of our approach by constructing a variety of application types.     

Group Decision Making on Urban Planning Using Desktop Multimedia Conferencing

Recent developments on multimedia systems and networking technology show that using desktop multimedia conferencing for group decision making on wide area networks such as the Internet is possible. In this paper we review the design, hardware and software requirements and organizational issues in a desktop multimedia conferencing system. We draw on our experiences from multiple multimedia conferences on the Internet and in particular we focus on a case study on urban planning using desktop multimedia conferencing on the Internet. Further we discuss implications for further research on desktop multimedia conferencing.     

Design and performance evaluation considerations of a multimediamedical database

Multimedia information management and communications systems for medical applications have been undergoing design and development. The aim of these activities has been the development of distributed computer systems providing storage, processing, and communication services required by the medical community. One of the main critical issues of such systems is the handling of multimedia information (i.e., text, images, graphics, and voice) in a uniform way and the fast access to images through the network. We present the design architecture and concepts used in our multimedia database system, along with its performance evaluation. The evaluation focuses on the response times of a multimedia medical database server, as seen by remote workstations for various retrieval and image transfer requests. For this purpose, a queueing network model was developed and simulated. Communications between the workstations and the database server are governed by the client-server model using TCP/IP and appropriate application protocols on a 10 Mb/s Ethernet LAN     

中国多媒体技术研究: 2011

本文是中国多媒体技术研究与应用的年度文献综述之十四。本文从2011年9种核心刊物的2 841篇中选取349篇多媒体技术相关的文章进行了分类、统计,以展现出2011年中国多媒体技术发展的现状。由于分类标准在去年进行过细微调整,较好地适应了多媒体发展的趋势,因此今年仍然采用去年的分类标准。通过分类统计结果可以看出,数字水印、数据管理与检索、QoS控制、流媒体多播、交互模式与接口、生物特征身份识别等多媒体基础技术连续两年都是论文反映出的研究热点,同时,多媒体应用在数目和种类上都日益丰富,与社会生活的结合程度越来越紧密。该文还比较了近5年中国多媒体技术文献统计结果,以得出多媒体技术,特别是特点技术的发展趋势。该文既能为从事多媒体技术研究与应用的人员提供系统的文献索引,也能为技术规划和管理人员提供参考。     

An Extended Relational Data Model for Multimedia DBMSs

We have extended the canonical relational data model to enable the management of multimedia objects. In an attempt to provide a smooth paradigm shift to multimedia information system development, we have enhanced the relational data model framework with techniques for modeling, storing and manipulating multimedia data. In particular, we have provided a graphical conceptual model for structuring a multimedia document and mapping rules for translating it into an extended relational data schema. Extensions have regarded the management of foreign keys, active components, mechanisms for the management of spatial and temporal relations, and finally functions for handling multimedia presentations. As a consequence, we have also provided extensions to the SQL language to handle these new mechanisms.