优化的存储模式-VBR视频安置在MZ磁盘组上

研究了大量视频在磁盘组上的安置和接纳计算方法。基于视频的特性、视频的流行性及磁盘的特性,提出了一个优VBRMZVBRMZ化的存储模式及相应的接纳算法,和其它现存算法相比,结果显示它能支持更多的流数、在作品流行性变化的情况下有更好的适应能力。     

优化的存储模式——VBR视频安置在MS磁盘组上

研究了大量VBR视频在MZ磁盘组上的安置和接纳计算方法，基于视频的VBR特性，视频的流行性及MZ磁盘的特性，提出了一个优化的存储模式及相应的接纳算法，和其它现存算法相比，结果显它能支持更多的流数，在作品流行性变化的情况下更好的适应能力。     

视频服务器存储子系统的I/O优化

视频服务器存储子系统的I／O性能决定了视频服务器的总体性能。本文提出的一种新的实时磁盘调度算法（LLF－Window)能有效地服务各种编码格式的视频流，并对传统的SCSI总线不均衡调度机制进行了改造，实验结果表明，新的磁盘调度算法和改造后的SCSI总线调度机制有效地改进了视频服务器存储子系统的I／O性能，保证了视频流的连续播放。     

面向单记录的混合负载下物化视图异步增量维护任务生成

针对已有的混合负载（HTAP）下物化视图异步增量维护任务生成算法主要面向多记录,无法面向单记录生成HTAP物化视图异步增量维护任务,导致磁盘IO开销的增加,进而降低HTAP物化视图异步增量维护性能的问题,提出面向单记录的HTAP物化视图异步增量维护任务的生成方法。首先,建立面向单记录的HTAP物化视图异步增量维护任务生成的效益模型;然后,基于Q-learning设计面向单记录的HTAP物化视图异步增量维护任务的生成算法。实验结果表明,所提算法在实现面向单记录生成HTAP物化视图异步增量维护任务的基础上,将平均每秒读写操作次数（IOPS）、平均CPU利用率（2核）和平均CPU利用率（4核）至少分别降低了8.49次、1.85个百分点和0.97个百分点。     

基于磁盘系统的多用户视频准入算法

分析了基于磁盘系统的视频服务器的准入策略,提出了基于磁盘系统的为保证视频服务器接纳更大数目用户的准入算法,即在每个服务周期中每个用户要求检索到的数据块的数目与其对应的回放速率成比例,视频服务器通过过量预约资源来允许更大数量的客户数。这种算法允许视频服务器接纳更大数目的用户,满足多用户媒体回放的稳态性和迁移态连续性的要求。     

国防科大计算机学院工学博士学位论文摘要

连续媒体数据存储与回取技术的研究作者：刘衡竹（１９９９．６）导师：陈福接教授　　随着存储技术、通讯技术和视频压缩技术的高速发展,使得通过ＢＩＳＤＮ进行视频点播（Ｖｉｄｅｏ－Ｏｎ－Ｄｅｍａｎｄ）服务成为可能。ＶＯＤ服务器以压缩、数字化的形式存储视频数据,并为多个用户并发提供回取和传输服务。为了实现视频数据的优化存储与回取,本文对ＭＰＥＧ流的结构及传输特性进行了讨论,分析了现有磁盘系统的读取过程和延时特性,建立了用于对连续媒体回取过程进行分析的磁盘传输延迟模型。定义了与具体算法无关的用于连续媒体回取…     

视频服务器中变比特率视频流的I/O调度

讨论了视频服务器中变化特率（ＶＢＲ）视频流的Ｉ／Ｏ调度问题．其中重点讨论了Ｉ／Ｏ调度中的接纳控制算法．首先提出了Ｂｉ－ＳＣＡＮ磁盘调度算法,并将其应用到ＶＢＲ视频流的Ｉ／Ｏ调度．接着讨论了两种确定性接纳控制算法．确定性接纳控制能提供确保的服务质量,但系统资源的利用率很低．为此提出了一种基于统计复用的统计接纳控制算法,该算法将ＶＢＲ视频数据复杂的统计特性转化为磁盘提交的数据块数量的统计特性,使问题得     

基于磁盘存取受限的视频流组播策略

在宽带环境下，系统的网络通信能力很强，为了提高视频点播的并发点播数和实时响应性能，需要解决视频服务器端磁盘存取速度的瓶颈效应，文章提出的视频组播策略采用了自适应缓存算法，它在综合考虑网络通信能力和磁盘存取速度的基础上，优化了系统的整体性能，提高了传统视频点播批处理算法的效率。     

一种面向视频播放系统的RAID并行预取技术及实现

随着视频数字化技术的广泛应用，视频播放系统中的存在“瓶颈”也日益突出，在分析视频存储系统磁盘阵列的I／O调度算法和在实际应用中视频数据的特点的基础上，提出一种面向视频媒体服务的RAID并行预取实时调度算法，它利用未来数据的可行预测性，预先将其从磁盘取入缓冲区，同时优化任务调度，使主机数据的回送和从磁盘预取数据同步执行，进一步提高了阵列的I／O吞吐率，用I／Ometer测试结果证明，新算法具有很好的性能。     

基于AES算法的磁盘加密设计与实现

设计了一种纯软件的磁盘加密系统,系统利用Windows驱动开发技术,采用AES（高级加密标准：Advanced EncryptionStandard）算法作为磁盘加密算法,在不需要添加额外硬件设备的情况下,实现对磁盘内部数据加密和解密,有效地保护了磁盘的敏感信息。     

Efficient support for interactive operations in multi-resolution video servers

In this paper, we present a placement algorithm that interleaves multi-resolution video streams on a disk array and enables a video server to efficiently support playback of these streams at different resolution levels. We then combine this placement algorithm with a scalable compression technique to efficiently support interactive scan operations (i.e., fast-forward and rewind). We present an analytical model for evaluating the impact of the scan operations on the performance of disk-arr ay-based servers. Our experiments demonstrate that: (1) employing our placement algorithm substantially reduces seek and rotational latency overhead during playback, and (2) exploiting the characteristics of video streams and human perceptual tolerances enables a server to support interactive scan operations without any additional overhead.     

基于并行磁盘阵列的视频数据布局

分析了大规模视频存储服务器的性能指标要求、体系结构、数据布局和准入控制等问题，提出了基于并行磁盘阵列上的、可满足用户多QoS要求的、基于三层可扩展的MPEG2视频编码的多分段视频存储方案，比已有的平衡放置、周期放置等方案能提供更好的灵活性、更高的可扩展性。     

A Design Framework for Multi-Resolution Video Servers

Video can be encoded into multiple-resolution format in nature. A multi-resolution or scalable video stream is a video sequence encoded such that subsets of the full resolution video bit stream can be decoded to recreate lower resolution video streams. Employing scalable video enables a video server to provide multiple resolution services for a variety of clients with different decoding capabilities and network bandwidths connected to the server. The inherent advantages of the multi-resolution video server include: heterogeneous client support, storage efficiency, adaptable service, and interactive operations support.For designing a video server, several issues should be dealt with under a unified framework including data placement/retrieval, buffer management, and admission control schemes for deterministic service guarantee. In this paper, we present a general framework for designing a large-scale multi-resolution video server. First, we propose a general multi-resolution video stream model which can be implemented by various scalable compression techniques. Second, given the proposed stream model, we devise a hybrid data placement scheme to store scalable video data across disks in the server. The scheme exploits both concurrency and parallelism offered by striping data across the disks and achieves the disk load balancing during any resolution video service. Next, the retrieval of multi-resolution video is described. The deterministic access property of the placement scheme permits the retrieval scheduling to be performed on each disk independently and to support interactive operations (e.g. pause, resume, slow playback, fastforward and rewind) simply by reconstructing the input parameters to the scheduler. We also present an efficient admission control algorithm which precisely estimates the actual disk workload for the given resolution services and hence permits the buffer requirement to be much smaller. The proposed schemes are verified through detailed simulation and implementation.     

视频服务器比例服务策略的改进

本文对ＶＯＤ视频服务器中同时为多个点播用户服务的比例服务策略进行了改进,比例服务策略在一个服务循环中,每路视频流所回取的数据块数与该流的播放帧率成正比。当用该算法算出的回取块数不为整数时,利用交替改变读取数据块数的方法,对连续的服务循环中所读出的各条流的数据块数分别进行细调,以获得同时为尽量多点播用户提供服务,同时也使所需的缓冲器大小以及新允许服务的视频流的起动时迟较小。通过增强比例服务算法的动态     

Resource scheduling in a high-performance multimedia server

Supporting continuous media data-such as video and audio-imposes stringent demands on the retrieval performance of a multimedia server. In this paper, we propose and evaluate a set of data placement and retrieval algorithms to exploit the full capacity of the disks in a multimedia server. The data placement algorithm declusters every object over all of the disks in the server-using a time-based declustering unit-with the aim of balancing the disk load. As for runtime retrieval, the quintessence of the algorithm is to give each disk advance notification of the blocks that have to be fetched in the impending time periods, so that the disk can optimize its service schedule accordingly. Moreover, in processing a block request for a replicated object, the server will dynamically channel the retrieval operation to the most lightly loaded disk that holds a copy of the required block. We have implemented a multimedia server based on these algorithms. Performance tests reveal that the server achieves very high disk efficiency. Specifically, each disk is able to support up to 25 MPEG-1 streams. Moreover, experiments suggest that the aggregate retrieval capacity of the server scales almost linearly with the number of disks     

Storage System for Supporting More Video Streams in Video Server

Video server needs a storage system with large bandwidth in order to provide concurrently more users with the real time retrieval requests for video streams. So, the storage system generally has the structure of disk array, which consists of multiple disks. When the storage system serves multiple video stream requests, it's bottlenecks come from the seeking delay caused by the random movement of disk head and from unbalanced disk access due to disk load unbalance among multiple disks.This paper presents a novel placement and retrieval policy. The new policy retrieves the requested data through sequential movement of disk heads and maintaining disk load balance so that it can diminish the bottlenecks on retrieving and can provide the concurrent real time retrieval services for more users simultaneously. In addition, the novel policy reduces the startup latency for the requests. The correctness of the novel placement and retrieval policy is analyzed with theoretical views. Performance analysis of the novel placement and retrieval policy is provided with simulations.     

新的保持边缘的图像放大算法

为了适应视频后处理芯片低成本的需求,提出一种仅需用两行缓存的新的保持边缘的图像放大算法。该方法寻找代表点代替插值点来确定相关方向。找到相关方向后,对应方向上寻找四个邻域点及其对应位置,进行插值。实验结果表明该算法能实现图像的放大,并能消除图像边缘模糊和锯齿效应,可应用于低成本的数字视频后处理芯片中。     

Using rotational mirrored declustering for replica placement in a disk-array-based video server

In a video-on-demand (VOD) environment, disk arrays are often used to support the disk bandwidth requirement. This can pose serious problems on available disk bandwidth upon disk failure. In this paper, we explore the approach of replicating frequently accessed movies to provide high data bandwidth and fault tolerance required in a disk-array-based video server. An isochronous continuous video stream imposes different requirements from a random access pattern on databases or files. Explicitly, we propose a new replica placement method, called rotational mirrored declustering (RMD), to support high data availability for disk arrays in a VOD environment. In essence, RMD is similar to the conventional mirrored declustering in that replicas are stored in different disk arrays. However, it is different from the latter in that the replica placements in different disk arrays under RMD are properly rotated. Combining the merits of prior chained and mirrored declustering methods, RMD is particularly suitable for storing multiple movie copies to support VOD applications. To assess the performance of RMD, we conduct a series of experiments by emulating the storage and delivery of movies in a VOD system. Our results show that RMD consistently outperforms the conventional methods in terms of load-balancing and fault-tolerance capability after disk failure, and is deemed a viable approach to supporting replica placement in a disk-array-based video server.     

Issues in the design of a storage server for video-on-demand

We examine issues related to the design of a storage server for video-on-demand (VOD) applications. The storage medium considered is magnetic disks or arrays of disks. We investigate disk scheduling policies, buffer management policies and I/O bus protocol issues. We derive the number of sessions that can be supported from a single disk or an array of disks and determine the amount of buffering required to support a given number of users. Furthermore, we propose a scheduling mechanism for disk accesses that significantly lowers the buffer-size requirements in the case of disk arrays. The buffer size required under the proposed scheme is independent of the number of disks in the array. This property allows for striping video content over a large number of disks to achieve higher concurrency in access to a particular video object. This enables the server to satisfy hundreds of independent requests to the same video object or to hundreds of different objects while storing only one copy of each video object. The reliability implications of striping content over a large number of disks are addressed and two solutions are proposed. Finally, we examine various policies for dealing with disk thermal calibration and the placement of videos on disks and disk arrays.