地市级气象高清视频会商系统的构建与应用

本文介绍了地市级气象高清视频会商系统的结构、组成及主要应用。在气象信息网络平台的基础上,通过MCU级联,实现了区一地一县三级视频会商,画面的分辨率达到了1080P的高清标准。该系统在日常天气会商、业务会议及远程培训中已发挥了重要作用,在实际应用中取得了良好的效果。     

IP可视电话视频会议系统设计与实现

从H．323协议族和MCU系统的软硬件结构设计出发,讨论了一种基于H．323协议的IP可视电话视频会议系统。它是一个针对特殊需求而设计的嵌入式系统,在网络层采用分组交换技术,以提高网络资源的利用率;硬件采用双板结构,将音／视频编／解码、数据封装等支撑硬件放在母板上,将网络通信等功能放在子板上;板间通信采用了流机制,软件系统采取了数据驱动的方式。上述方案能够为视频会议系统提供高可靠性、低廉的成本以及较好的可移植性,对类似的小型视频会议系统的研究和开发提供了一定的参考价值。     

The Vidboard: A video capture and processing peripheral for a distributed multimedia system

This paper describes a network-based video capture and processing peripheral, called the Vidboard, for a distributed multimedia system centered around a 1-Gbit/s asynchronous transfer mode (ATM) network. The Vidboard is capable of generating full-motion video streams having a range of presentation (picture size, color space, etc.) and network (traffic, transport, etc.) characteristics. The board is also capable of decoupling video from the real-time constraints of the television world, which allows easier integration of video into the software environment of computer systems. A suite of ATM-based protocols has been developed for transmitting video from the Vidboard to a workstation, and a series of experiments are presented in which video is transmitted to a workstation for display.     

A cost-effective cloud computing framework for accelerating multimedia communication simulations

Multimedia communication research and development often requires computationally intensive simulations in order to develop and investigate the performance of new optimization algorithms. Depending on the simulations, they may require even a few days to test an adequate set of conditions due to the complexity of the algorithms. The traditional approach to speed up this type of relatively small simulations, which require several develop–simulate–reconfigure cycles, is indeed to run them in parallel on a few computers and leaving them idle when developing the technique for the next simulation cycle. This work proposes a new cost-effective framework based on cloud computing for accelerating the development process, in which resources are obtained on demand and paid only for their actual usage. Issues are addressed both analytically and practically running actual test cases, i.e., simulations of video communications on a packet lossy network, using a commercial cloud computing service. A software framework has also been developed to simplify the management of the virtual machines in the cloud. Results show that it is economically convenient to use the considered cloud computing service, especially in terms of reduced development time and costs, with respect to a solution using dedicated computers, when the development time is longer than one hour. If more development time is needed between simulations, the economic advantage progressively reduces as the computational complexity of the simulation increases.     

Experiments on block-matching techniques for video coding

Video compression is becoming increasingly important with the advent of compression standards and broadband networks. Recently, several block-based motion-estimation algorithms to exploit the temporal redundancies in a video sequence have been reported in the literature. Some of these algorithms tend to be either computationally expensive or to converge to a local optimum. In this paper, we present results for various block-matching techniques and propose a low-complexity block-matching motion-estimation algorithm that is useful for hybrid video coding schemes, including MPEG video. This algorithm consists of a layered structure search, and, unlike other fast block-matching methods, it does not converge to a local optimum. The proposed method employs a novel matching criterion, namely, the modified pixeldifference classification (MPDC), that offers simplicity with other potential advantages.     

Security and privacy for multimedia database management systems

This paper describes security and privacy issues for multimedia database management systems. Multimedia data includes text, images, audio and video. It describes access control for multimedia database management systems and describes security policies and security architectures for such systems. Privacy problems that result from multimedia data mining are also discussed.

An approximate model for performance evaluation of real-time multimedia communication systems

A Markov Modulated Poisson Process (MMPP) is a doubly stochastic Poisson process which has recently received a lot of attention due to its ability to model a highly correlated arrival stream while retaining analytical tractability. In this paper, the cell arrival process from integrated voice and data sources is approximated by a two-state MMPP with batch arrivals (BMMPP). We propose a new matching technique which leads to more accurate performance prediction than other recent work for both delay estimation and evaluation of tail probabilities. While using BMMPP in the model does not noticeably increase the computational complexity over MMPP, it allows better representation of traffic sources with significantly higher burstiness. Another major contribution of the proposed model is its simplicity which makes the model suitable for real-time traffic control. An extended version of the model for integrated video, voice and data sources is also given with numerical examples again showing that the accuracy is quite satisfactory.     

Real-time data analytics and event detection for IoT-enabled communication systems

Enterprise Communication Systems are designed in such a way to maximise the efficiency of communication and collaboration within the enterprise. With users becoming mobile, the Internet of Things (IoT) can play a crucial role in this process, but is far from being seamlessly integrated into modern online communications. In this paper, we present a semantic infrastructure for gathering, integrating and reasoning upon heterogeneous, distributed and continuously changing data streams by means of semantic technologies and rule-based inference. Our solution exploits semantics to go beyond today’s ad-hoc integration and processing of heterogeneous data sources for static and streaming data. It provides flexible and efficient processing techniques that can transform low-level data into high-level abstractions and actionable knowledge, bridging the gap between IoT and online Enterprise Communication Systems. We document the technologies used for acquisition and semantic enrichment of sensor data, continuous semantic query processing for integration and filtering, as well as stream reasoning for decision support. Our main contributions are the following, (i) we define and deploy a semantic processing pipeline for IoT-enabled Communication Systems, which builds upon existing systems for semantic data acquisition, continuous query processing and stream reasoning, detailing the implementation of each component of our framework; (ii) we present a rich semantic information model for representing and linking IoT data, social data and personal data in the Enterprise Communication scenario, by reusing and extending existing standard semantic models; (iii) we define and develop an expressive stream reasoning component as part of our framework, based on continuous query processing and non-monotonic reasoning for semantic streams, (iv) we conduct experiments to comparatively evaluate the performance of our data acquisition and semantic annotation layer based on OpenIoT, and the performance of our expressive reasoning layer in the scenario of Enterprise Communication.     

全互联视频会议实时数据传输路由算法设计

针对NAT环境下参与用户网络类型、网络状况往往不一致的情况,提出一种动态节点转发的实时多媒体数据传输技术.采用数据发送节点基于最优节点路由算法将数据发送给多媒体系统中的某些节点,然后由这些节点及下一批被选中接收的节点将数据经过多次转发,发送给系统中的其他节点,最终实现系统中各节点多媒体数据全互联.     

A live video streaming system for intuitive human-system interaction

In this paper, we propose an intuitive live video streaming system based on virtual reality technologies among people who are far apart. This system is a kind of server-client system, and can provide remote users with virtual 3D audiovisual fields in real time via a very-high-speed network. The server captures audio and video data from its clients, compiles them into a 3D audiovisual scene at a virtual conference, and broadcasts it to the clients. At the present stage, our system captures 2 videos and creates one 3D video at a time. Our system can play 3D audiovisual contents on Windows XP systems as well as on CAVE systems. Currently, our system can play the 3D video contents at about 2.36 fps under a LAN environment. This work was presented in part at the 12th International Symposium on Artificial Life and Robotics, Oita, Japan, January 25–27, 2007     

Packet loss resilience using unequal forward error correction assignment for video transmission over communication networks

Forward error correction (FEC) methods have been developed for packet loss resilience in application layer for real-time video transmission over communication networks. In this paper, an efficient packet loss resilience method is proposed using closed form solution for unequal FEC assignment based on a new packet distortion model. We first derive the packet distortion model by investigating the error concealment property and error propagation effect in H.264. To select the source and channel rate minimizing the overall distortion, we present a model-based rate allocation algorithm using the packet distortion model and rate-distortion function. Then we propose the closed form solution for unequal FEC assignment, which uses the packet distortion model and considers channel status information. Simulation results show that the proposed method gives substantial improvement for the received video quality in packet-lossy Internet and wireless network environments, while it requires much less computational complexity compared to the previous scheme.     

全互联视频会议实时数据传输路由算法设计*

针对NAT环境下参与用户网络类型、网络状况往往不一致的情况,提出一种动态节点转发的实时多媒体数据传输技术。采用数据发送节点基于最优节点路由算法将数据发送给多媒体系统中的某些节点,然后由这些节点及下一批被选中接收的节点将数据经过多次转发,发送给系统中的其他节点,最终实现系统中各节点多媒体数据全互联。     

MINDEX: An efficient index structure for salient-object-based queries in video databases

Several salient-object-based data models have been proposed to model video data. However, none of them addresses the development of an index structure to efficiently handle salient-object-based queries. There are several indexing schemes that have been proposed for spatiotemporal relationships among objects, and they are used to optimize timestamp and interval queries, which are rarely used in video databases. Moreover, these index structures are designed without consideration of the granularity levels of constraints on salient objects and the characteristics of video data. In this paper, we propose a multilevel index structure (MINDEX) to efficiently handle the salient-object-based queries with different levels of constraints. We present experimental results showing the performance of different methods of MINDEX construction.     

多媒体技术的应用现状与发展趋势

南阳理工学院河南473004随着计算机技术的飞速发展,以计算机为基础的多媒体技术被广泛应用并渗透到社会生活的各个方面。本文重点论述了多媒体的定义,多媒体技术的应用,及其发展前景。     

Comparative analysis of a twin-class M-QAM transmission system for wireless video applications

This paper presents a unique set of techniques to support reliable and efficient video transmission over mobile channels. The transmission system is comprised of an M level Quadrature Amplitude Modulation (QAM) technique. A twin class uniform and non-uniform partitioned M-QAM system is used to transport a compressed video bitstream which is partitioned to match the bit-error sensitivity of the transmitted symbol in terms of mapping in the constellation diagram and picture quality. Video partitioning based on a separation of the Variable Length Coded (VLC) Discrete Cosine Transforms (DCT) coefficients within each block is considered for constant bitrate transmission (CBR). Various scenarios for splitting the bitstream are investigated and their results are compared and analysed thoroughly. The performance of the transmission system is evaluated under Additive White Gaussian Noise (AWGN) conditions. The simulation results showed that the video partition strategy results in a significantly higher quality of the reconstructed video data.     

KAIST image computing system (KICS): A parallel architecture for real-time multimedia data processing

An efficient parallel architecture is proposed for high-performance multimedia data processing using multiple multimedia video processors (MVP; TMS320C80), which are fully programmable general digital signal processors (DSP). This paper describes several requirements for a multimedia data processing system and the system architecture of an image computing system called the KAIST Image Computing System (KICS). The performance of the KICS is evaluated in terms of its I/O bandwidth and the execution time for some image processing functions. An application of the KICS to the real-time Moving Picture Expert Group 2 (MPEG-2) encoder is introduced. The programmability and the high-speed data-access capability of the KICS are its most important features as a high-performance system for real-time multimedia data processing.     

A window-assisted video partitioning strategy for partitioning and caching video streams in distributed multimedia systems

In this paper, we address the issue of efficiently streaming a set of heterogenous videos under the constraint of service latency over a scalable multimedia systems. We propose a novel strategy, referred to as window-assisted video partitioning (WAVP), for rendering cost-effective multimedia services. The objective is to minimize the service cost and maximize the number of requests that can be successfully served under resources constraints (cache capacity and link bandwidth). We formulate the problem of video partitioning as an optimization of both bandwidth resources and cache space, and derive the optimal schedule window for different video portions under consideration of time constraints, the popularities and the sizes of the video portions. In WAVP, video are partitioned into multiple portions and delivered according to by adaptive schedule windows. We prove that WAVP strategy not only optimize the service cost but also be able to serve requests under the time constraints without causing too much delay. We conduct mathematical analysis and derive certain performance bounds that quantify the overall performance of the strategy. It shows that the service cost can be optimized by adjusting the schedule window and resources utilization can be improved as video streams are partitioned into multiple portions. We evaluate the performance under several influencing parameters such as available bandwidth, cache capacity, and partition gradients. Simulation results show that our proposed method can not only significantly reduce the service cost under tight time constraints and with low partition overhead, but also balance the utilization of network resources to achieve high acceptance ratio with low average service cost.     

Comparative analysis of a twin-class M-QAM transmission system for wireless video applications

This paper presents a unique set of techniques to support reliable and efficient video transmission over mobile channels. The transmission system is comprised of an M level Quadrature Amplitude Modulation (QAM) technique. A twin class uniform and non-uniform partitioned M-QAM system is used to transport a compressed video bitstream which is partitioned to match the bit-error sensitivity of the transmitted symbol in terms of mapping in the constellation diagram and picture quality. Video partitioning based on a separation of the Variable Length Coded (VLC) Discrete Cosine Transforms (DCT) coefficients within each block is considered for constant bitrate transmission (CBR). Various scenarios for splitting the bitstream are investigated and their results are compared and analysed thoroughly. The performance of the transmission system is evaluated under Additive White Gaussian Noise (AWGN) conditions. The simulation results showed that the video partition strategy results in a significantly higher quality of the reconstructed video data.     

Evaluating video layout strategies for a high-performance storage server

We propose a systems approach to providing video service that integrates the multiresolution data generated by scalable compression algorithms with the high-bandwidth, high-capacity storage provided by disk arrays. We introduce two layout strategies for storing multiresolution video data on magnetic disk arrays, which vary in the degrees of parallelism and concurrency they use to satisfy requests. Our simulation results show that the storage of multiple video resolutions allows a video file server to satisfy considerably more user requests than a server that stores a single resolution of video data.