一种用于提高流媒体传输性能的标记方法

在DiffServ网络中常用的标记法由于无法区分出数据流中每一个包在应用层的重要程度,因此不能有效提高视频流的传送质量。针对MPEG特点,采用在数据源与边界路由器两次标记的策略,通过基于NS 2的仿真系统对这种新标记策略进行对比,在带宽受限的情况下能有效的提高视频流的传输质量。     

Feig快速DCT算法及其处理器的体系结构设计

离散余弦变换是ＪＰＥＧ和ＭＰＥＧ中的关键技术之一。当前ＭＰＥＧ的普遍应用是在解码中使用，一个解码的例子是ＶＣＤ，ＩＤＣＴ是静止／运动补偿帧解码的关键部分。为了要得到较好的性能，ＩＤＣＴ通常被硬件逻辑实现而嵌入产品中，但该方法有一个缺陷。那就是ＩＤＣＴ的硬件逻辑实现不能完成ＭＰＥＧ所需要的其它功能，如音频解码，视频／音频的比特流可变长度解码等等。文中提出的Ｆｅｉｇ快速ＤＣＴ算法的并行顺序指令流实现Ｉ     

Adaptive filtering of MPEG system streams in IP networks

Congestion and large differences in available link bandwidth create challenges for the design of applications that want to deliver high quality video over the Internet. We present an efficient adaptive filter for MPEG System streams that can be placed in the network (e.g., as an active service). This filter adjusts the bandwidth demands of an MPEG System stream to the available bandwidth without transcoding while maintaining synchronization between the streams embedded in the MPEG System. The filter is network-friendly: it is fair with respect to other (TCP) competing streams and it avoids generating bursty traffic. This paper presents the system architecture and an evaluation of our implementation in three different operating environments: a networking testbed in a laboratory environment, a home-user scenario (DSL line with 640 Kbit/s), and a wide area network covering the Atlantic (server in Europe, client in the US). Moreover we examine the network-friendliness of the adaptation protocol and the relationship between the quality of the received continuous media and the protocol's aggressiveness. Our architecture is based on efficient MPEG System filtering to achieve high-quality video over best-effort networks.Effort sponsored in part by the Advanced Research Projects Agency and Rome Laboratory, Air Force Materiel Command, USAF, under agreement number F30602-96-1-0287. The U.S. Government is authorized to reproduce and distribute reprints for Governmental purposes notwithstanding any copyright annotation thereon.The views and conclusions contained herein are those of the authors and should not be interpreted as necessarily representing the official policies or endorsements, either expressed or implied, of the Advanced Research Projects Agency, Rome Laboratory, or the U.S. Government.     

交互式分割视频运动对象的研究与实现

在 MPEG- 4视频编码标准中 ,为了实现基于视频内容的交互功能 ,视频序列的每一帧由视频对象面来表示 ,而生成视频对象面 ,需要对视频序列中运动对象进行有效分割 ,并跟踪运动对象随时间的变化 .在视频分割方法中 ,交互式分割视频对象能满足分割的效率与质量指标要求 ,因此提出了一种交互分割与自动跟踪相结合的方式来分割视频语义对象 ,即在初始分割时 ,依据用户的交互与形态学的分水线分割算法相结合提取视频对象轮廓 ,并用改进的轮廓跟踪方法有效提高视频对象轮廓的精度 ;对后续帧的跟踪 ,采用六参数仿射变换跟踪运动对象轮廓的变化 ,用平移估算的运动矢量作为初始值 ,计算六参数仿射变换的参数 .实验结果表明 ,该方法能有效地分割并跟踪视频运动对象     

An Integrated Framework for Efficient Transport of Real-Time MPEG Video over ATM Best Effort Service

This paper describes a framework for the transport of real-time multimedia traffic generated by MPEG-2 applications over ATM networks using an enhanced UBR best effort service (UBR+). Based on the factors affecting the picture quality during transmission, we propose an efficient and cost-effective ATM best effort delivery service. The proposed framework integrates three major components: 1) a dynamic frame-level priority assignment mechanism based on MPEG data structure and feedback from the network (DexPAS), 2) a novel audio-visual AAL5 SSCS with FEC (AV-SSCS), and 3) an intelligent packet video discard scheme named FEC-PSD, which adaptively and selectively adjusts cell drop levels to switch buffer occupancy, video cell payload type and forward error correction capability of the destination. The overall best-effort video delivery framework is evaluated using ATM network simulation and MPEG2 video traces. The ultimate goal of this framework is twofold: First, minimizing loss of critical video data with bounded end-to-end delay for arriving cells and second, reducing the bad throughput crossing the network during congestion. Compared to previous approaches, performance evaluation shows a good protection of Predictive coded (P-) and Bi-directional Predictive coded (B-) frames at the MPEG video slice layer.     

Objective quality assessment of MPEG-2 video streams by using CBP neural networks

The increasing use of compression standards in broadcasting digital TV has raised the need for established criteria to measure perceived quality. Novel methods must take into account the specific artifacts introduced by digital compression techniques. This paper presents a methodology using circular backpropagation (CBP) neural networks for the objective quality assessment of motion picture expert group (MPEG) video streams. Objective features are continuously extracted from compressed video streams on a frame-by-frame basis; they feed the CBP network estimating the corresponding perceived quality. The resulting adaptive modeling of subjective perception supports a real-time system for monitoring displayed video quality. The overall system mimics perception but does not require an analytical model of the underlying physical phenomenon. The ability to process compressed video streams represents a crucial advantage over existing approaches, as avoiding the decoding process greatly enhances the system's real-time performance. Experimental evidence confirmed the approach validity. The system was tested on real test videos; they included different contents ranging from fiction to sport. The neural model provided a satisfactory, continuous-time approximation for actual scoring curves, which was validated statistically in terms of confidence analysis. As expected, videos with slow-varying contents such as fiction featured the best performances.     

自动分割及跟踪视频运动对象的一种实现方法

随着MPEG-4压缩标准的制定,分割及跟踪视频运动对象的研究显得极其重要。在MPEG-4视频编码标准中,为了实现基于视频内容的交互功能,其视频序列的每一帧由视频对象面（VOP）来表示。为了生成视频对象面,需要对视频序列中的运动对象进行有效的分割;并跟踪运动对象随时间的变化,为此提出并实现了一种用于分割及跟踪视频运动对象的时空联合方法。该方法首先采用连续帧间差的4次统计量假设检验,确定运动对象的位置,自动地分离出运动区域与背景区域;在运动区域内,采用数学形态学的分水线算法来精确地提取运动对象的轮廓;最后,将提取到的运动对象作为模板,对后续的视频序列,用Hausdorff距离度量,来跟踪并提取后续帧中运动对象。实验结果表明,该方法能有效地分割和跟踪视频运动对象,且能有效减少计算复杂度,其调整参数也较少。     

Enhancing aggregate QoS for video streaming

The IETF's Differentiated Services architecture is designed to provide different types or levels of service for Internet traffic. One of its key features is that traffic flows are aggregated so that routers in the core network only need to distinguish a relatively small number of aggregate flows, even if those flows consist of hundreds or thousands of individual flows. However, network-level QoS differentiation may not satisfy the requirements of many QoS-sensitive applications such as live video streaming, where end-to-end delay and reliability must be guaranteed.

This paper investigates application-level service differentiation for MPEG video streaming in a Diff-Serv-aware MPLS network infrastructure, along with routing support at the network layer. Based on the fact that MPEG video has become one of the most popular formats for Internet (wired and wireless) users, our approach enhances aggregate QoS for video streaming by employing existing application-level knowledge of the MPEG video structure; therefore it requires neither a new video compression algorithm nor additional bandwidth. Several MPEG video dispersion models are proposed and analyzed. Simulation results show that two such strategies are superior to the other tested. In addition, a new routing scheme is proposed to support searching the ‘best’ paths for efficient multi-path video streaming. Through extensive simulations, we demonstrate that our approaches improve the aggregate QoS of MPEG video streams, as well as overall network efficiency.     

Connection admission control of MPEG streams in ATM network using hierarchical fuzzy logic controller

Asynchronous transfer mode (ATM) operates in a connection-oriented mode; if sufficient resources are not available for transporting data over a network, the connection is refused. Connection admission control (CAC) deals with the question of whether or not an ATM switch can accept a new connection. This paper presents the design of a fuzzy logic controller (FLC) for CAC of Motion Picture Experts Group (MPEG) audio and video streams in an ATM network. Our approach is different from the plain use of sample input–output data for automating FLC design as frequently reported in the literature. One of the differences is that we do not use any sample data that happen to be available. Instead, we perform intensive simulations of the system, to generate sample data which are then processed to obtain unique entries for the selected combination of the values of the input variables. We compared the performance of our fuzzy-CAC to conventional CACs such as those based on average bandwidth, peak bandwidth and equivalent bandwidth and we found our scheme to produce better results.     

A Quality-Driven Cross-Layer Solution for MPEG Video Streaming Over WiMAX Networks

Extensive efforts have been focused on deploying broadband wireless networks. Providing mobile users with high speed network connectivity will let them run various multimedia applications on their wireless devices. Satisfying users with different quality-of-service requirements while optimizing resource allocation is a challenging problem. In this paper, we discuss the challenges and possible solutions for transmitting MPEG video streams over WiMAX networks. We will briefly describe the MPEG traffic model suggested by the WiMAX Forum. A cross-layer solution for enhancing the performance of WiMAX networks with respect to MPEG video streaming applications is explained. Our solution uses the characteristics of MPEG traffic to give priority to the more important frames and protect them against dropping. Besides, it is simple and compatible with the IEEE 802.16 standards and thus easily deployable. It is shown that the proposed solutions will improve the video quality over WiMAX networks.     

一种无线实时流媒体增强型自适应FEC控制机制

无线网络动态的信道特性和带宽有限等特点,使得在无线环境下为流媒体应用提供QoS保证面临更大的挑战。提出一种用于无线实时流媒体传输的增强型自适应前向纠错控制策略,以提高接收方的播放质量。该策略采用跨层设计的方法,根据当前的网络状态,自适应地调整MPEG视频帧的发送速率,在视频源数据和冗余数据之间动态分配网络带宽。仿真结果表明,该策略能使接收方获得最大的可播放帧率,有效提高流媒体传输的可靠性和实时性。     

A new paradigm for analysis of MPEG compressed videos

The increasing use of multimedia streams nowadays necessitates the development of efficient and effective methodologies for manipulating databases storing these streams. Moreover, content-based access to multimedia databases requires in its first stage to parse the video stream into separate shots then apply a method to summarize the huge amount of data involved in each shot. This work proposes a new paradigm capable of robustly and effectively analyzing the compressed MPEG video data. First, an abstract representation of the compressed MPEG video stream is extracted and used as input to a neural network module (NNM) that performs the shot detection task. Second, we propose two adaptive algorithms to effectively select key frames from segmented video shots produced by the segmentation stage. Both algorithms apply a two-level adaptation mechanism in which the first level is based on the dimension of the input video file while the second level is performed on a shot-by-shot basis in order to account for the fact that different shots have different levels of activity. Experimental results show the efficiency and robustness of the proposed system in detecting shot boundaries and flashlights occurring within shots and in selecting the near optimal set of key frames (KFs) required to represent each shot.     

Impact of video scheduling on bandwidth allocation for multiplexed MPEG streams

We present efficient schemes for scheduling the delivery of variable-bit-rate MPEG-compressed video with stringent quality-of-service (QoS) requirements. Video scheduling is being used to improve bandwidth allocation at a video server that uses statistical multiplexing to aggregate video streams prior to transporting them over a network. A video stream is modeled using a traffic envelope that provides a deterministic time-varying bound on the bit rate. Because of the periodicity in which frame types in an MPEG stream are typically generated, a simple traffic envelope can be constructed using only five parameters. Using the traffic-envelope model, we show that video sources can be statistically multiplexed with an effective bandwidth that is often less than the source peak rate. Bandwidth gain is achieved without sacrificing the stringency of the requested QoS. The effective bandwidth depends on the arrangement of the multiplexed streams, which is a measure of the lag between the GOP periods of various streams. For homogeneous streams, we give an optimal scheduling scheme for video sources at a video-on-demand server that results in the minimum effective bandwidth. For heterogeneous sources, a sub-optimal scheduling scheme is given, which achieves acceptable bandwidth gain. Numerical examples based on traces of MPEG-coded movies are used to demonstrate the effectiveness of our schemes.     

无线城域网中MPEG视频传输的上行调度算法

针对现有无线城域网中MPEG视频传输的实时轮询服务算法的不足,提出了一种更为有效的媒体接入控制上行调度算法。该算法无需基站周期地提供带宽请求机会,而是在视频应用的连接建立以后,主动周期地分配固定带宽来传输视频数据的特定部分,剩余部分的带宽通过携带请求的方式获得,以此保证更好的服务质量。仿真中使用典型的视频测试源,结果表明,新算法在近似现有算法的信道利用率的情况下,具有更小的视频帧延迟和抖动。     

视频采集与编码技术在视频监控终端中的应用

考虑到开发的难易程度、生产成本和软件升级等因素,本文介绍了一种基于ARM处理器和嵌入式Linux操作系统的无线视频监控终端的设计和实现方法;分析了在嵌入式Linux操作系统下基于V4L的视频采集的新思路与基于MPEG-4的视频编码的优点,阐述了整个终端系统开发的难点及相应的解决方案;给出了无线监控终端的实现方案、视频采...     

RCSP and stop-and-go: a comparison of two non-work-conserving disciplines for supporting multimedia communication

To support emerging real-time applications, high-speed integrated services networks must provide end-to-end performance guarantees on a per-connection basis in a networking environment. Resource management algorithms must accommodate traffic that may get burstier as it traverses the network due to complex interactions among packet streams at each switch. To address this problem, several non-work-conserving packet-service disciplines have been proposed. Non-work-conserving servers may be idle and hold packets under certain conditions, to reconstruct, fully or partially, the traffic pattern of the original source inside the network and prevent the traffic from becoming burstier. We compare two non-work-conserving service disciplines. Stop-and-go uses a multilevel framing strategy to allocate resources in a single switch and to ensure traffic smoothness throughout the network. Rate controlled static priority (RCSP) decouples the server functions with two components: (1) a regulator to control traffic distortion introduced by multiplexing effects and load fluctuations in previous servers, and 2) a static priority scheduler to multiplex the regulated traffic. We compare the two service disciplines in terms of traffic specification, scheduling mechanism, buffer space requirement, end-to-end delay characteristics, connection admission-control algorithms, and achievable network utilization. The comparison is first done analytically, and then empirically by using two 10-min traces of MPEG compressed video.     

Video transport in ATM networks: a systems view

This paper presents a systems view of video transport issues in asynchronous transfer mode (ATM) networks. Since video is a critical component of future distributed multimedia applications, we consider technical approaches necessary to realize a flexible, robust, and efficient ATM framework for video delivery. The overall system-design problem is discussed for a general distributed multimedia computing scenario, and key video-related design issues are identified. This is followed by a more detailed discussion of selected ATM video topics, including: (1) variable bit-rate (VBR) statistical multiplexing and dynamic usage parameter control (VBR+), (2) ATM cell-loss concealment in MPEG decoders, and (3) new transport protocols (“MTP”) for video and multimedia. Supporting simulation or experimental results from ongoing research are given where available.     

SCTP传输MPEG4视频流的性能分析

为了在IP分组网络上传输N0.7信令，IETF信令传输工作组专门制定了流量控制传输协议(SCTP)。该文对SCTP与TCP进行了比较，分析了CCTP适合于信令和多媒体传输的特性，研究了用SCTP传输MPEG4视频流的性能，并进行了仿真和分析。最后讨论了SCTP其它的一些可能的应用。     

An algorithm to estimate mean vehicle speed from MPEG Skycam video

With low computation cost, motion vectors can be readily extracted from MPEG video streams and processed to estimate vehicle motion speed. A statistical model is proposed to model vehicle speed and noise. In order to achieve high estimation accuracy and also study the limitations of the proposed algorithm, we quantitatively evaluated four parameters used in our algorithm: temporal filter window size T, video resolution R _v (CIF/QCIF), motion vector frame distance m, and video bit-rates. Our experiments showed that the mean vehicle speed can be estimated with high accuracy, up to 85 to 92% by proper spatial and temporal processing. The proposed algorithm is especially suitable for Skycam-based application, where the traditional tracking-based or virtual-loop-based approaches perform poorly because of their requirements of high-resolution images. Although extensive work has been done in extracting motion information directly from MPEG video data in compressed domain, to our best knowledge, this paper is the very first work in which stationary motion (speed) of moving objects can be estimated with high accuracy directly from MPEG motion vectors. Furthermore the proposed method is not limited to vehicle speed estimation by nature and it can be applied to other applications where the stationary motion assumption is satisfied.

Adaptive delivery of immersive 3D multi-view video over the Internet

The increase in Internet bandwidth and the developments in 3D video technology have paved the way for the delivery of 3D Multi-View Video (MVV) over the Internet. However, large amounts of data and dynamic network conditions result in frequent network congestion, which may prevent video packets from being delivered on time. As a consequence, the 3D video experience may well be degraded unless content-aware precautionary mechanisms and adaptation methods are deployed. In this work, a novel adaptive MVV streaming method is introduced which addresses the future generation 3D immersive MVV experiences with multi-view displays. When the user experiences network congestion, making it necessary to perform adaptation, the rate-distortion optimum set of views that are pre-determined by the server, are truncated from the delivered MVV streams. In order to maintain high Quality of Experience (QoE) service during the frequent network congestion, the proposed method involves the calculation of low-overhead additional metadata that is delivered to the client. The proposed adaptive 3D MVV streaming solution is tested using the MPEG Dynamic Adaptive Streaming over HTTP (MPEG-DASH) standard. Both extensive objective and subjective evaluations are presented, showing that the proposed method provides significant quality enhancement under the adverse network conditions.