The Split and Merge protocol for interactive video-on-demand

A true video-on-demand (VoD) system lets users view any video program, at any time, and perform any VCR-like user interactions. To reduce the per-user video delivery cost, multiple users may be batched and share the same video stream. Existing sharing schemes do not allow true VoD. A new protocol, called Split and Merge (SAM), does allow true VoD. SAM also provides an innovative way to merge these individuals back into the batching streams when they resume normal play mode     

Wavelength division multiplexing-based video-on-demand systems

Serving video-on-demand (VOD) traffic via isochronous transmission service is highly desirable because of the characteristics of VOD traffic. This paper proposes a mechanism to transfer VOD traffic over wavelength division multiplexing (WDM) networks by employing isochronous transmission service. Based on the proposed mechanism, the problem of scheduling isochronous and asynchronous traffic for single-star WDM networks with multiple receivers and transmitters is investigated. The lower bounds on the total switching duration and the number of switching modes for the isochronous and asynchronous traffic scheduling problem are derived. An optimal scheduling algorithm is presented for the cases where only asynchronous traffic exists; and a heuristic algorithm is also proposed for the cases where both the isochronous and asynchronous traffic coexist in the WDM networks. Simulation results indicate that the average switching duration and the average number of switching modes obtained by the proposed algorithm are close to the lower bounds, which implies that the proposed scheduling algorithm is effective     

Maximizing the number of users in an interactive video-on-demand system

Video prefetching is a technique that has been proposed for the transmission of variable-bit-rate (VBR) videos over packet-switched networks. The objective of these protocols is to prefetch future frames at the customers' set-top box (STB) during light load periods. Experimental results have shown that video prefetching is very effective and it achieves much higher network utilization (and potentially larger number of simultaneous connections) than the traditional video smoothing schemes. The previously proposed prefetching algorithms, however, can only be efficiently implemented when there is one centralized server. In a distributed environment there is a large degradation in their performance. In this paper we introduce a new scheme that utilizes smoothing along with prefetching, to overcome the problem of distributed prefetching. We show that our scheme performs almost as well as the centralized prefetching protocol even though it is implemented in a distributed environment. In addition, we introduce a call admission control algorithm for a fully interactive video-on-demand (VoD) system that utilizes this concept of distributed video prefetching. Using the theory of effective bandwidths, we develop an admission control algorithm for new requests, based on the user's viewing behavior and the required quality of service (QoS).     

Queueing network model of interactive computing systems

A closed queueing network model with state dependent routing probabilities is developed for the study of interactive computing systems which use swapping as a memory managmnent strategy. An algorithm to obtain an approximate solution of the mathematical model is proposed. Based on meamuements of a dual-processor PDP-10 system, the model is found to be better in predicting the system performance than the classical model without state dependent routing probabilities.     

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     

Adaptive batching scheme for multicast video-on-demand systems

In this paper, an adaptive algorithm is developed for providing true video on demand (VoD) services in a multicast environment. In conventional batching schemes, the batching time of the system is fixed and the performance of such static schemes is highly dependent on the selection of the batching time. If the batching time is wrongly estimated, the performance of the system will be greatly degraded. Our algorithm tries to dynamically find the optimal batching time by the newly updated arrival rate so as to minimize the bandwidth requirement. The results show that the system performance of the adaptive approach is always better than the static scheme in terms of total bandwidth requirement and customer reneging probability, especially in using long batching time for the high arrival rate     

Design of multicast delivery for providing VCR functionality ininteractive video-on-demand systems

Multicast delivery is one of the solutions to reduce the cost in a large video-on-demand (VoD) system. However, multicast transmission makes much more difficult the implementation of interactive functions for individual users and introduces start-up delays for the users, which contradicts the idea of on-demand services. In this paper, we first try to explore and evaluate the performance of different multicast VoD systems. A new scheme called single-rate multicast double-rate unicast (SRMDRU) is then developed to minimize the system resources for supporting full VCR functionality in a multicast VoD system. This scheme also allows multicast systems to support true VoD services so customers can be served as soon as the system receives the requests. Computer simulations show that the multicast systems using the SRMDRU scheme perform much better than other multicast systems in terms of system blocking probabilities     

协同认知模型及其在远程交互系统中的应用

阐述了协同工作中协同认知的概念、方式和进程，并给出了一个协同认知的基本参考模型，讨论了这一参考模型在远程交互系统中实际应用的方式和具体的实现途径。     

A low cost optical storage server for near video-on-demand systems

A near video-on-demand system is one of the most economic and practical applications to provide high quality digital video services through a network in terms of cost, storage and network capacity requirements. In this paper, an optical storage server with a novel data placement and retrieval schemes is proposed for a near video-on-demand system. The proposed data placement scheme on the optical discs fully exploits the periodical broadcast characteristic of an NVOD service to optimize the disc bandwidth utilization. By further applying our retrieval schedule strategy, the buffer requirement of a system can be significantly reduced. In that way, the maximal number of supported streams with the minimal buffer requirement can be easily achieved, The storage system can be applied not only to CD-ROMs storing MPEG-1, but also to Digital Video Disks (DVDs) storing MPEG-2 in the near future     

Power-aware operating systems for interactive systems

Many portable systems deploy operating systems (OS) to support versatile functionality and to manage resources, including power. This paper presents a new approach for using OS to reduce the power consumption of I/O devices in interactive systems. Low-power OS observes the relationship between hardware devices and processes. The OS kernel estimates the utilization of a device from each process. If a device is not used by any running process, the OS puts it into a low-power state. This paper also explains how scheduling can facilitate power management. When processes are properly scheduled, power reduction can be achieved without degrading performance. We implemented a prototype on Linux to control two devices; experimental results showed nearly 70% power saving on a network card and a hard disk drive     

Analytic modeling of interactive systems

An overview is presented of queueing theoretic modeling and analysis of interactive computing systems. While the emphasis is on recent advances, an introduction is given which briefly trices the historical development of this area to put current research in perspective. Models, methods of analysis, and applications to real systems are described. An extensive bibliography provides the references for a more in-depth study.     

Performance model of software systems using Petri nets

Recent trends of economization in the development and application of computer software systems have become an important consideration for the design of modern computer systems. This has increased the efforts towards the study, evaluation and testing of computer software. An appropriate measure may further help in overcoming the difficulties encountered during the testing of software.The present paper utilizes the concepts of Petri nets for the evaluation of various software parameters through a measure termed as “software measure”. This measure along with the firing characteristics of the transitions may then be used for obtaining the suitable testing methodology of a software.     

Design patterns for interactive musical systems

The authors propose Musical Design Patterns as an approach to developing interactive, music-oriented systems for use as novel media content. Such development integrates three key aspects: user interface design, modeling media semantics, and application software engineering (content development). They support their claims with examples from WorldBeat, an award-winning interactive music exhibit on display at various technology museums     

Harmonic broadcasting for video-on-demand service

Using conventional broadcasting, if we want to support a 120-minute popular movie every 10 minutes, we need 12 video channels. Assuming the set-top box at the client end can buffer portions of the playing video on a disk, pyramid broadcasting schemes can reduce the bandwidth requirements to 5.7 channels. We present a new scheme which only needs 3.2 channels. For a movie with length D minutes, if we want to reduce the viewer waiting time to D/N minutes, we only need to allocate H(N) video channels to broadcast the movie periodically, where H(N) is the harmonic number of N, H(N)=1+1/2+…+1/N. In order to support video-on-demand service for a popular movie, the new scheme greatly reduces the bandwidth requirements     

Portable video-on-demand in wireless communication

Our present ability to work with video has been confined to a wired environment, requiring both the video encoder and decoder to be physically connected to a power supply and a wired communication link. This paper describes an integrated approach to the design of a portable video-on-demand system capable of delivering high-quality image and video data in a wireless communication environment. The discussion will focus on both the algorithm and circuit design techniques developed for implementing a low-power video compression/decompression system at power levels that are two orders of magnitude below existing solutions. This low-power video compression system not only provides a compression efficiency similar to industry standards, but also maintains a high degree of error tolerance to guard against transmission errors often encountered in wireless communication. The required power reduction can best be attained through reformulating compression algorithms for energy conservation. We developed an intra-frame compression algorithm that requires minimal computation energy in its hardware implementations     

Timeshared video-on-demand: a workable solution

True video-on-demand (T-VOD) lets you browse, select, view, and scan through programs from a large content repository, at any time, without leaving your home. Imagine choosing and watching what you want, when you want it, and not be constrained by what the TV networks have chosen for you to watch. Actually, the dream of T-VOD has been in the public mind for more than a decade now, but in spite of today's technological advances, such a service is not cost-competitive to the combination of cable TV, digital video disk (DVD), and video cassette rental services. In the past, many researchers have suggested service aggregation to make VOD economical. To achieve aggregation requires us to make a number of assumptions about user behavior and content access patterns. In this article, I argue that these assumptions are impractical for VOD scenarios today. Existing proposals lack a strong business case that appeals to consumers and service providers alike. I present a radically different vision called timeshared VOD that can make commercial T-VOD a practical reality     

Communicating expressiveness and affect in multimodal interactive systems

Multisensory integrated expressive environments is a framework for mixed reality applications in the performing arts such as interactive dance, music, or video installations. MIEEs address the expressive aspects of nonverbal human communication. We present the multilayer conceptual framework of MIEEs, algorithms for expressive content analysis and processing, and MIEEs-based art applications.     

Baseband and passband transport systems for interactive videoservices

As essentially none of the existing telecommunication networks are capable of providing interactive video services (IVS), network providers have begun to consider the network architecture that is best to deploy. Two approaches have received most of the consideration. Because of the embedded base of broadcast, coax-based cable TV networks and because of the unconfirmed demand for IVS, much attention has been paid to upgrading these networks to provide IVS transport even though extensive modification would be required. These networks are referred to as passband networks because of the use of modulated subcarriers as the signal transport mechanism. The alternative approach under consideration is the use of fiber-to-the-curb transport systems. Because such networks transport IVS directly as baseband signals without subcarrier modulation, they are known as baseband networks. The paper compares the baseband and passband approaches in several areas including: compatibility with the optical transmission medium; compatibility with IVS source/sink equipment; compatibility with the emerging telecommunications interoffice and feeder networks; and the cost of deployment. The recent history in which passband and baseband approaches competed to become the preferred transport mechanism in LAN applications is reviewed. The fact that in that case baseband emerged as the preferred approach has important implications for the selection of the preferred approach in today's IVS applications. The constituent elements and transport requirements of the end-to-end network for delivering IVS are reviewed     

A temporal model for interactive multimedia scenarios

Many authoring tools let authors create scenarios, but very few let them create an active multimedia scenario that will not only play itself back, but will change course dynamically, depending on user interactions. Our temporal model provides a new way to represent asynchronous and synchronous temporal events, allowing authors to create scenarios that offer viewers seamless, transparent options