Extending critical bandwidth allocation techniques for stored video delivery across best‐effort networks

In this paper, we propose two new techniques for the delivery of compressed prerecorded video streams across best‐effort networks like the Internet. Current approaches for the delivery of stored video across best‐effort networks typically alter the quality of the video frames, the frame rate delivered to the user, or a combination of both. By using network feedback, these algorithms continually adjust the video quality to fit within the available network resources. These approaches, however, do not take advantage of the a priori information available from stored video streams, namely the frame sizes that the movie consists of. We will show how monitoring the a priori information and actively monitoring a client‐side buffer can help smooth the video frame rate delivered to the user, providing a more consistent quality of video. Copyright © 2001 John Wiley & Sons, Ltd.     

Dynamic bandwidth allocation and buffer dimensioning under equal segment scheme to support video‐on‐demand services

This paper focuses on the optimization of network bandwidth allocation and buffer dimensioning to transport pre‐stored MPEG video data from source to playback destination across ATM networks. This is one of the most important issues in the support of video‐on‐demand (VoD) service. This paper provides a novel scheme in the dynamic allocation of bandwidth to segments of video using ABR mode. The dynamic bandwidth allocation is based on a new concept, called playback tunnel which is obtained from the traffic characteristics of the pre‐stored MPEG video trace to determine the optimum of transmission bandwidth as well as the buffer capacity to ensure that the playback buffer neither underflows nor overflows. The proposed scheme is tested with real‐life MPEG video traces. The obtained results have shown its significant performance improvement in terms of the capacity of playback buffer, the start‐up playback delay, the size of video segment and the network multiplexing gain. Copyright © 2001 John Wiley & Sons, Ltd.     

An analytic study of a scalable video buffer

In this contribution, we investigate the performance of the output buffer of an ‘on-demand’ video streaming server. The server maintains a local database of stored video clips and movies which can be streamed to the users upon request. We assume that the stored video is encoded in a scalable way, which means that the data streams contain a base layer ensuring a minimum of guaranteed quality and a stack of additional enhancement layers progressively improving the quality of the video. For the purpose of performance analysis, we assume that a video stream is split up in logical units called frames. Every frame consists of a number of packets, each containing information of one layer only. When the output buffer gets congested, one may choose to drop the transmission of some of the layers in a frame, thus reducing the frame transmission time and expediting the restoration of the buffer size to normal levels. A discrete-time finite capacity queueing model with buffer size dependent transmission times is proposed. Using a probability generating function approach, we focus on the characteristics of idle and busy periods. We obtain performance measures such as the frame loss ratio and the average frame transmission time. The latter measure relates to the quality of the video stream. We conclude with some numerical examples, including a realistic case study.     

Optimal video placement for hierarchical video-on-demand systems

We have been implementing a VOD system over ATM networks based on a hierarchical three-level network architecture. One of the most important design problems is how to organize video programs stored at different level of servers. In this paper, we propose an optimal video placement strategy which gives the optimal number of video copies should be stored at each level of server such that the cost function can be minimized while a lower bound of the request rejection probability for each video is guaranteed. Our major contribution is that we model the time-variant request arrivals as a non-homogeneous Poisson process     

Supporting stored video: reducing rate variability and end-to-endresource requirements through optimal smoothing

Variable-bit-rate (VBR) compressed video can exhibit significant multiple-time-scale bit-rate variability. In this paper we consider the transmission of stored video from a server to a client across a network, and explore how the client buffer space can be used most effectively toward reducing the variability of the transmitted bit rate. Two basic results are presented. First, we show how to achieve the greatest possible reduction in rate variability when sending stored video to a client with given buffer size. We formally establish the optimality of our approach and illustrate its performance over a set of long MPEG-1 encoded video traces. Second, we evaluate the impact of optimal smoothing on the network resources needed for video transport, under two network service models: deterministic guaranteed service (Chang 1994; Wrege et al. 1996) and renegotiated constant-bit-rate (RCBR) service (Grossglauser et al. 1997). Under both models, the impact of optimal smoothing is dramatic     

Hierarchical storage management in a distributed VOD system

The article describes the storage management algorithms in the Berkeley Video-on-Demand System, a hierarchical storage management system designed to support transparent access to thousands of hours of video material. Storage management algorithms handle continuous media objects stored on video servers within a hierarchical distributed video-on-demand system. Media objects stored permanently on tertiary storage devices are moved to video servers when needed. Algorithms manage the distributed cache in the video servers and select a video server on which to place a requested object. The object-placement algorithm uses server load, network load, and service-wait times to optimize system performance     

嵌入式视频采集存储电路的设计

该文介绍了嵌入式Linux的视频采集压缩存储功能的实现。以三星S3C2440为核心处理器,移植嵌入式Linux操作系统。利用Linux下视频采集库函数V4L2实现视频采集,利用开源编解码器xvid实现视频压缩,并将压缩的视频存储到SD卡中。     

视频实时采集系统的FPGA设计

设计了一种基于FPGA的视频实时采集系统，视频数据通过视频解码器、双口RAM、内存控制器，然后存入片外SDRAM中。根据视频处理算法的要求和SDRAM的特点，对视频数据的存储格式及读写时序进行了优化，提高了系统的数据传输速率，能够满足后续视频处理系统的需要。     

Smoothing, statistical multiplexing, and call admission control forstored video

Variable bit-rate (VBR) compressed video is known to exhibit significant, multiple-time-scale rate variability. A number of researchers have considered transmitting stored video from server to a client using smoothing algorithms to reduce this rate variability. These algorithms exploit client buffering capabilities and determine a “smooth” rate transmission schedule, while ensuring that a client buffer neither overflows nor underflows. We investigate how video smoothing impacts the statistical multiplexing gains available with such traffic, and we show that a significant amount of statistical multiplexing gains can still be achieved. We then examine the implication of these results on network resource management and call admission control when transmitting smoothed stored video using VBR service with statistical quality-of-service (QoS) guarantees. Specifically, we present a uniform call admission control scheme based on a Chernoff bound method that uses a simple, novel traffic model requiring only a few parameters. This scheme provides an easy and flexible mechanism for supporting multiple VBR service classes with different QoS requirements. We evaluate the efficacy of the call admission control scheme over a set of MPEG-1 coded video tracts     

Parallel video servers: a tutorial

In conventional video-on-demand (VoD) systems, compressed digital video streams are stored in a video server for delivery to receiver stations over a communication network. This article introduces a framework for the design of parallel video server architectures and addresses three central architectural issues: video distribution architectures, server striping policies, and video delivery protocols     

视频采集系统SDRAM控制器的FPGA实现

介绍基于FPGA的SDRAM控制器的设计及其在视频采集系统中的应用。视频数据流通过该控制器接收，然后存入片外SDRAM中。针对视频数据流特点和SDRAM特性对该控制器进行了优化，实现了任意长度的突发读写而不需要修改模式寄存器，加快了SDRAM读写的速度。     

基于NIOSⅡ的视频叠加电路设计与实现

介绍基于NIOSⅡ嵌入式视频叠加电路的设计与实现。嵌入式NIOSⅡCPU控制电路接收矢量视频信号及标准PAL制视频信号,使其相叠加后存储于双端口RAM．上位机通过PXI总线接口将双端口RAM中数字视频信号采集至内存,并通过软件将叠加后的视频信息回放。实验证明,该电路能有效完成视频叠加,并成功应用于某测试系统。     

全局视频环境:一种新型的视频点播系统分发环境

介绍了一种具有可扩展性的视频点播系统:GloVE(全球视频环境).在这种系统中,用户共同建造了一个共享的协作视频存储空间,并以此作为主要的视频信息来源供用户使用.在这种方式下,GloVE服务器不需要限制并发用户的数量.当视频信息存在于协作视频存储空间时,信息可直接从存储空间传送至用户,而不用通过VOD服务器.GloVE支持没有组播流传送功能的视频服务器,同时支持任意格式存储的视频信息.     

Traffic shaping, bandwidth allocation, and quality assessment forMPEG video distribution over broadband networks

This article provides an overview of residential video delivery systems and presents the applications, benefits, and challenges of using VBR MPEG video encoding in broadband video distribution networks. The network resources required to transmit stored variable-rate MPEG can be reduced by properly analyzing and smoothing the video stream before transmission. A scheduling technique is presented which selects a traffic contract for a pre-encoded MPEG video stream with the criteria of minimizing network resources and maintaining video quality. Several effective bandwidth metrics are discussed and used to model the potential savings in network resources for the shaped streams     

Balancing MPEG Transcoding with Storage in Multiple-Quality Video-on-Demand Services

To match the requirements of heterogeneous mobile devices, video objects may be transcoded, which requires considerable CPU resources. Alternatively, multiple versions of the same video may be stored on servers, but this requires a lot of disk space. We formulate the trade-off between the versions that are stored on disk and the need for transcoding. We propose an optimal solution to this formulation based on dynamic programming. Experiments show that our scheme allows up to 68% more clients to be admitted than conventional schemes when a reasonable amount of storage is available.     

基于异常检测与双流编码的视频监控系统设计

介绍了一种基于异常检测与双流编码的无线智能视频监控系统的设计方案.该系统首先基于对采集视频的分析,实现非法入侵等异常事件的自动检测,同时通过对同一路视频采用两个编码器进行双流编码,产生两路不同质量和码率的视频流.在此基础上,基于异常事件检测的结果,在有异常事件时触发高质量图像的本地保存和低码率图像的实时无线传输.在蜂窝...     

Matrix encoding for data hiding using multilayer video coding and transcoding solutions

This paper proposes a multitier data hiding solution in MPEG video using matrix encoding. In the first tier of the proposed solution, raw video is encoded into two layers using multilayer Signal to Noise Ratio (SNR) encoding. During the multilayer encoding process, the quantization scales and coding parameters are stored. In the second tier, message bits are embedded in the stored quantization scales using matrix encoding. In the third and last tier, the raw video is encoded again into two layers using the modulated quantization scales and coding parameters of the first encoder. The proposed multitier solution is extended by replacing the multilayer encoder with a multilayer transcoder to accommodate situations in which the video exists in pre-coded format only. By the use of multilayer encoder or transcoding, we show that the message payload can be doubled without adversely affecting the coding quality or bitrate of the host video. We also show that message embedding using matrix encoding can be extended to modulate motion vectors. The paper also proposes two solutions for motion vector modulation based on the availability of the raw video. In comparison to existing work, the proposed solutions have higher message payloads, lower degradation in video quality and result in reduced excessive bitrate.     

基于S3C6410的USB视频压缩、回放系统

阐述了在嵌入式Linux下,将市面上常见的USB摄像头作为视频输入设备,将其输出的JPEG格式图像数据通过S3C6410内部的硬件H.264编码器压缩成视频文件的方法,并基于此方法,设计了一个基于S3C6410和USB摄像头的视频采集、压缩、存储系统,采用了高级语言与汇编语言相结合的方法,在USB摄像头每秒最快输出15帧640×480图像的情况下,系统整体可以达到13 f/s(帧/秒)的录制效果。该系统具有取材方便、成本低、存储时间长、实用性强等特点。     

监播系统中视频关键帧抽取器的设计与实现

为满足发展迅猛的广电行业对电视频道节目内容的实时监测,提出并设计了一种针对全媒体监播系统的模拟信号关键帧抽取器.该设备采用运行嵌入式Linux系统的ARM处理器S3C2440作为主处理器,同时FPGA芯片EP3C25作为协处理器,极大地提高了设计灵活性和系统的实时处理性能.抽取的视频图像通过视频解码器ADV212压缩后,最终存储到本地SATA硬盘.在验证部分中,闭环测试的试验结果证明了这种设备的正确性和工程实用性.     

基于FPGA的视频图像画面分割器设计

为了解决在一个屏幕上收看多个信号源的问题,对基于FPGA技术的视频图像画面分割器进行了研究。研究的主要特色在于构建了以FPGA为核心器件的视频画面分割的硬件平台,首先,将DVI视频信号,经视频解码芯片转换为数字视频图像信号后送入异步FIFO缓冲。然后,根据画面分割需要进行视频图像数据抽取,并将抽取的视频图像数据按照一定的规则存储到图像存储器。最后,按照数字视频图像的数据格式,将四路视频图像合成一路编码输出,实现了四路视频图像分割的功能,提高了系统集成度,并可根据系统需要修改设计和进一步扩展功能,增加了系统的灵活性,适用于多种不同领域。