The S2 Piggybacking Policy

In video-on-demand systems, users expect to watch a film right after its selection. Nonetheless, such a short response time is feasible only if there is available bandwidth. In line with that, several techniques have been proposed to reduce the huge bandwidth demand on video servers. In this paper, we introduce the Piggybacking policy S², which adds a second level of optimization to the Snapshot policy. Moreover, we introduce a heuristic to reduce the complexity to generate the tree of superimposed video streams.     

Extracting viewer interests for automated bookmarking in video-on-demand services

Video-on-demand (VoD) services have become popular on the Internet in recent years. In VoD, it is challenging to support the VCR functionality, especially the jumps, while maintaining a smooth streaming quality. Previous studies propose to solve this problem by predicting the jump target locations and prefetching the contents. However, through our analysis on traces from a real-world VoD service, we find that it would be fundamentally difficult to improve a viewer’s VCR experience by simply predicting his future jumps, while ignoring the intentions behind these jumps. Instead of the prediction-based approach, in this paper, we seek to support the VCR functionality by bookmarking the videos. There are two key techniques in our proposed methodology. First, we infer and differentiate viewers’ intentions in VCR jumps by decomposing the interseek times, using an expectation-maximization (EM) algorithm, and combine the decomposed inter-seek times with the VCR jumps to compute a numerical interest score for each video segment. Second, based on the interest scores, we propose an automated video bookmarking algorithm. The algorithm employs the time-series change detection techniques of CUSUMandMB-GT, and bookmarks videos by detecting the abrupt changes on their interest score sequences. We evaluate our proposed techniques using real-world VoD traces from dozens of videos. Experimental results suggest that with our methods, viewers’ interests within a video can be precisely extracted, and we can position bookmarks on the video’s highlight events accurately. Our proposed video bookmarking methodology does not require any knowledge on video type, contents, and semantics, and can be applied on various types of videos.     

Interactive Television Trials and Marketplace Experiences

This article provides a review of ITV trials and services from the 1970s through the mid 1990s. It presents an annotated history of ITV and draws a number of lessons about content, pricing, consumer appeal and advertising within an interactive television context. ITV has alternated between peaks of marketing hyperbole and valleys of skepticism. A realistic path of development may now be emerging.     

A Video Server cost/performance Estimator tool

The Video Server Estimator (VSE) is an analytical tool which allows a user to perform a cost/performance analysis of video servers with hierarchical storage. The underlying model comprises multiple systems, main memory, expanded storage, disks and a tape library. The main objective of the tool is to optimally allocate the video files to different storage media based on the system parameters and the video file request probability distribution. The cost and the size of the video server that can accommodate a customer profile are determined. Furthermore, the impact of design parameters on the cost and performance are examined through a parametric analysis.     

Efficient schemes for broadcasting popular videos

We provide a formal framework for studying broadcasting schemes and design a family of schemes for broadcasting popular videos, the greedy disk-conserving broadcasting (GDB) family. We analyze the resource requirements for GDB, i.e., the number of server broadcast channels, the client storage space, and the client I/O bandwidth required by GDB. Our analysis shows that all of our proposed broadcasting schemes are within a small factor of the optimal scheme in terms of the server bandwidth requirement. Furthermore, GDB exhibits a tradeoff between any two of the three resources. We compare our scheme with a recently proposed broadcasting scheme, skyscraper broadcasting (SB). With GDB, we can reduce the client storage space by as much as 50% or the number of server channels by as much as 30% at the cost of a small additional increase in the amount of client I/O bandwidth. If we require the client I/O bandwidth of GDB to be identical to that of SB, GDB needs only 70% of the client storage space required by SB or one less server channel than SB does. In addition, we show that with small client I/O bandwidth, the resource requirements of GDB are close to the minimum achievable by any disk-conserving broadcasting scheme.     

Disk placement for arbitrary-rate playback in an interactive video server

Multimedia data, especially continuous media including video and audio objects, represent a rich and natural stimulus for humans, but require large amount of storage capacity and real-time processing. In this paper, we describe how to organize video data efficiently on multiple disks in order to support arbitrary-rate playback requested by different users independently. Our approach is to segment and decluster video objects and to place the segments in multiple disks using a restricted round-robin scheme, called prime round-robin (PRR). Its placement scheme provides uniform load balance of disks for arbitrary retrieval rate as well as normal playback, since it eliminates hot spots. Moreover, it does not require any additional disk bandwidth to support VCR-like operations such as fast-forward and rewind. We have studied the various effects of placement and retrieval schemes in a storage server by simulation. The results show that PRR offers even disk accesses, and the failure in reading segment by deadline occurs only at the beginning of new operations. In addition, the number of users admitted is not decreased, regardless of arbitrary-rate playback requests.     

一个真实VoD/P2P系统Novasky的设计与实现

近年来,基于对等网络的视频点播系统(VoD/P2P)备受人们关注.这类系统的实现还面临诸多挑战,如存储策略、用户激励、媒体版权等.本文提出一种高效率、低成本、易扩展的VoD/P2P系统设计方案Novasky.与已有系统相比,Novasky的最大不同是引入了编码存储策略与虚拟货币机制.经过三年多的开发与完善,Novasky已发展成为一个跨平台的分布式系统.它是少数几个使用人数较多的研究性VoD/P2P系统之一.自2009年9月在清华大学开放使用以来,已接受1100多用户对346个视频的6288次点播,累计点播数据量2.1TB.     

P2P流媒体中的数据分配算法

最近兴起的P2P技术在充分利用客户资源、提高系统的可伸缩性方面具有巨大的潜力,基于P2P提供视频服务已成为Internet的一项重要应用.在多对单P2P模式下,对多个发送端最优地分配发送速率和数据是一个难题.为此,提出了一种新的分配算法.首先,应用排队论把最优速率分配问题模型化为非线性最优化问题,推导出求解最优化问题的速率分配公式;然后,基于该公式提出最优速率分配算法(ORAA),并对ORAA输出解的最优性给出证明;最后,提出动态速率分配算法(DRAA).DRAA对动态的网络环境具有自适应性,能根据网络条件的变化最优地为多个发送端进行速率和数据分配.仿真实验结果表明,在不同的参数条件下,DRAA算法减少了计算和通信开销,比同类算法有更好的性能.     

基于P2P方式的视频点播模型

提出了一种P2P方式的视频点播模型,兼有网状与树状的特点,具有很高的稳健型与组织性。有效提高了视频点播的利用率。     

IP流媒体技术在电视转播系统中的应用

概述了IP流媒体技术的特点、原理,并与其他技术方案进行了对比,重点论述了利用该技术组建电视转播系统的过程,为在类似案例情况下选择技术方案提供实践依据。