VoD Systems Research Articles

Elevating Personalized VOD Systems: Formal Analysis With VCR Actions and Trusted Computing

Elevating Personalized VOD Systems: Formal Analysis With VCR Actions and Trusted Computing

Challenges and opportunities for digital convergence of TV: audience measurement in the digital era

The research on television market and audience has been so far dominated by a telemetric system operating within a determined panel in the longitudinal manner. Nevertheless, the rise of digital era marked by the growing consumption of audiovisual content and TV in the Internet via VOD systems, subscription services, streaming etc. has changed the way the TV audience should be measured and tackled in order to deliver the significant data to advertisers. The digital services and therefore the online ads consumption are forcing the telemetric companies to re-design their methodology and measurement services. This thus requires not only new measurement methods and sample designs or research planning but also demonstrate new challenges and requirements starting from technical aspects and finishing on social and economic ones. Therefore, it is of great interests to find out how digital TV audience era is changing the way telemetric services are designed and conducted globally and at Polish market. The study attempts to find out how the TV audience measurement service is responding to the changes caused by digitalisation, which challenges and requirements have to be met in order to approach the issue of digitalisation of TV market in terms of the research planning and methodology. Finally, the present research pretend to determine and describe how the global market, and the Polish one in particular, perceives the services offered by Nielsen Audience Measurement. The research includes the series of individual semi-structured online individual interviews with managers and board of directors of the company as well as digital ads ratings department in Poland and headquarters in Switzerland. The results demonstrate the key changes, opportunities and challenges resulted from the digitalisation of TV consumption as perceived by management board, the company’s strategy towards digital convergence and the estimation of the needs of new markets and audiences on the course of the digital transformation.

Fuzzy Clustering Algorithms in Combination with Other Segmentation Methods for Videos

Segmentation has crucial applications in computer vision, pattern recognition, and the processing of digital information. Video segmentation is a problem that crops up in lots of different contexts, such VOD, DVR, e-learning, GIS, and other similar systems. Pixels are roughly separated using a membership grading system that relies on a way of expanding the basic area. Motion capture and clustering of video segmentation is a major hurdle to overcome when obtaining and storing video data. Fuzzy c-means clustering is used here to divide up a movie into its constituent parts. Fuzzy theory provides a framework for describing scene changes based on fuzzy judgements. Because the data space is partitioned appropriately by the membership functions. The suggested method achieves a high degree of accuracy at a low rate of error.

A novel POMDP-based server RAM caching algorithm for VoD systems

In contrast to other services on the Internet, streaming media service needs to fetch data from local disks more frequently, since it always lasts long and the bit rate is quite high. In addition, because of the much slower reading/writing speed of disk than random access memory (RAM), adopting advisable RAM caching policy can efficiently reduce disk I/O. In this paper, we study the problem of reducing disk I/O by using a novel approach. We first provide a new popularity estimate algorithm. Then a formal optimization problem about average disk I/O is presented, and a suboptimal caching algorithm for a special case of the problem is given. Furthermore, a partially observable Markov decision process (POMDP) model is constructed for the caching problem. Based on the model, popularity is taken advantage of to predict clients’ randomized behaviors, data replacing decisions are made when the defined observations occur, and the impact of caching actions on disk performance for future infinite steps is assessed. The method of event-based optimization is applied in search of the optimal stochastic policy. Disk I/O, as the long-run average performance measure, is optimized by applying the policy-gradient algorithm. The simulation results illustrate that data required by clients could be better predicted and lower disk I/O could be achieved by using the model proposed in this paper.

Tackling energy and battery issues in mobile P2P VoD systems

As video streaming services dominate the global internet traffic nowadays, several service providers are considering a shift towards peer-to-peer (P2P) architectures in order to lower their costs. However, these architectures tend to use the peers’ network resources aggressively without taking any energy-efficient measures. Ignoring battery constraints in a P2P service that is dominated by mobile users can significantly deteriorate the system’s efficiency and lead to low Quality of Experience (QoE) to all users. In this paper, we examine the effect of battery and energy consumption in the performance of P2P VoD systems and we present a novel distributed system that successfully utilizes peers’ upload bandwidth resources, while taking into account energy and battery resources. Its components that manage the overlay and the data scheduling are tested under extensive simulations that show promising results.

Bandwidth-Availability-Based Replication Strategy for P2P VoD Systems

Bandwidth-Availability-Based Replication Strategy for P2P VoD Systems

Joint Replication Density and Rate Allocation Optimization for VoD Systems Over Wireless Mesh Networks

Due to the limited resources and dynamically varying nature of wireless links, guaranteeing high quality demands for a large number of heterogeneous users is very challenging in video streaming over wireless networks. In this paper, we introduce a layered multiple description coding with an embedded forward error correction scheme (LMDC-FEC). The combination of layered MDC and FEC aims at coping with not only the diverse bandwidth and unreliability of wireless links but also the heterogeneous user devices. We further propose a joint replication density and rate allocation (RD-RA) optimization problem in the context of video on-demand systems (VoDs) over wireless mesh networks (WMNs), and employ a genetic algorithms based approach to solve the optimization problem. Our objective is to elaborately distribute proper replication density for each video segment and allocate optimal bit rate to each layer of each segment in order to gain high user-perceived quality (UPQ) with small consumption of storage resource. By this method, both optimal replication densities and rate allocations are found in accordance with the access rate of segments, the diverse loss characteristics of descriptions in each segment, and the rate-distortion relationship of segments, so as to thoroughly optimize UPQ and storage resource consumption. Simulation results demonstrate that our proposed method significantly enhances the streaming performance of VoDs over WMNs.

Research on P2P-VoD System Based on IPv6 Network

In this paper, for the shortage of network quality of service, multicast support and other deficiencies in VoD systems based on IPv4 network, we built a P2P VoD system architecture based on IPv6 network and data transfer mechanisms were in-depth studied. This paper describes the basic idea of the system and system architecture. According to the characteristics of P2P and multicast, we designed a collaboration data transmission of P2P and IP multicast and did some experiments and analysis on the system. Experimental results show that the system can effectively solve the P2P bandwidth problem and the unreliable of multicast data, and has high efficiency and practical value.

A Study on the Proposal of the Cloud Based Technology for VoD Systems and Analysis of Economic Effects

본 논문에서는 2가지의 시나리오를 가지고 클라우드 기술 기반 VoD 시스템의 구성 방안을 제안하였다. 첫번째 시나리오는 기존 VoD 시스템에서 DMC 및 각 SO의 콘텐츠 스트리지와 스트림 서버를 가상화하여 추가적으로 필요한 저장용량 및 스트림 서버의 사용을 효율적으로 하는 방법이며, 두 번째 시나리오는 VoD 시스템과 더불어 케이블 방송 시스템을 클라우드화 하는 방법으로 가입자 STB은 네트워크에 연결할 수 있는 최소한의 프로그램과 저장 공간만을 가지고 기존 가입자 STB에 있던 운영체제 및 미들웨어는 클라우드 데이터 센터로 이동하는 방법을 제안하였다. <BR> 또한 기존 시스템의 STB 교체비용과 클라우드 VoD 시스템의 구축비용의 비교 등 케이블 방송 환경에 클라우드 기술을 적용하였을 때의 경제성 분석을 통해 클라우드 VoD 시스템의 구축으로 인한 케이블 방송 사업자의 비용절감을 분석하였다.

Architecture for Cooperative Prefetching in P2P Video-on- Demand System

Most P2P VoD schemes focused on service architectures and overlays optimization without considering segments rarity and the performance of prefetching strategies. As a result, they cannot better support VCRoriented service in heterogeneous environment having clients using free VCR controls. Despite the remarkable popularity in VoD systems, there exist no prior work that studies the performance gap between different prefetching strategies. In this paper, we analyze and understand the performance of different prefetching strategies. Our analytical characterization brings us not only a better understanding of several fundamental tradeoffs in prefetching strategies, but also important insights on the design of P2P VoD system. On the basis of this analysis, we finally proposed a cooperative prefetching strategy called "cooching". In this strategy, the requested segments in VCR interactivities are prefetched into session beforehand using the information collected through gossips. We evaluate our strategy through extensive simulations. The results indicate that the proposed strategy outperforms the existing prefetching mechanisms.

A low complexity algorithm of packet scheduling and resource allocation for wireless VoD systems

This paper investigates the problem of multiuser packet scheduling and resource allocation for video transmission in wireless VoD system. A cross-layer optimization problem is formulated with the goal to maximize the received video quality. To satisfy requirement of the real-time application, a suboptimal algorithm with low complexity is proposed. The algorithm is compatible with the emerging wireless standards, such as IEEE 802.16. The simulation results show that the proposed algorithm has the low computational complexity and outperforms the previous resource allocation schemes in terms of received video qualities.

Optimising upload bandwidth for quality of VCR operations in P2P VoD systems

Many P2P VoD systems have been proposed, but only few can support VCR operations. Most of the works require very well provisioned source servers to guarantee the quality. The challenge is to do the same without requiring well provisioned source servers. In this paper, we take the heterogeneity of bandwidth into consideration, and also consider the practical case in which the capacity of the streaming buffer is limited. With these conditions, we formulate the problem as an upload bandwidth optimisation problem. We first prove that this problem is NP-hard and then propose an optimal dynamic programming solution.

An Expanded Patching Technique using Four Types of Streams for True VoD Services

In this paper, we propose an expanded patching technique in order to reduce the server network bandwidth requirements to support true VoD services in VoD Systems. Double Patching, which is a typical multicast technique, ensures that a long patching stream delivers not only essential video data for the current client but also extra video data for future clients. Since the extra data may include useless data, it results in server network bandwidth wastage. In order to prevent a server from transmitting useless data, the proposed patching technique uses a new kind of stream called a linking stream. A linking stream is transmitted to clients that have received short patching streams, and it plays a linking role between a patching stream and a regular stream. The linking stream enables a server to avoid transmitting unnecessary data delivered by a long patching stream in Double Patching, so the server never wastes its network bandwidth. Mathematical analysis shows that the proposed technique requires less server network bandwidth to support true VoD services than Double Patching. Moreover, simulation results show that it has better average service latency and client defection rate compared with Double Patching.

Measurement-based study on the relation between users’ watching behavior and network sharing in P2P VoD systems

P2P-based Video on Demand (P2P VoD) systems can provide higher quality video services than P2P live systems. However, owing to the unavailability of open source codes, the characteristics of P2P VoD systems have not been fully explored. For this purpose, in this paper, we first implemented reverse engineering to the protocols of two most popular VoD systems used in China. Peers' watching behavior and network sharing were then studied through the measured buffer messages. Based on our study, we found that uploading-only peers were more than downloading peers, and smooth-watching peers were more than randomly-seeking peers in the current P2P VoD systems. This finding is significantly different from the existing P2P-based file dissemination systems and the results obtained in the previous work on VoD systems. Furthermore, this study revealed the relations between watching behavior and network sharing. It has been observed that randomly-seeking peers will provide more regular as well as rare chunks than smooth-watching peers. A simple mathematical model was established to analytically demonstrate the relation between the watching index (WI) distribution and network-sharing profile, and this relation was also validated by our measured data.

On the Design of the Peer-Assisted UGC VoD System

User Generated Content (UGC) VoD services such as YouTube are becoming more and more popular, and their maintenance costs are growing as well. Many P2P solutions have been proposed to reduce server load in such systems, but almost all of them focus on the single-video approach, which only has limited effect on the systems serving short videos such as UGC. The purpose of this paper is to investigate the potential of an alternative approach, the multi-video approach, and we use a very simple method called collaborative caching to show that methods using the multi-video approach are generally more suitable for current UGC VoD systems. We also study the influence of the major design factors through simulations and provide guidelines for efficiently building systems with this method.

The design of video segmentation-aided VCR support for P2P VoD systems

VCR functionality is difficult to be implemented in a P2P VoD system, since it may give more server workload and fails some distribution paths. In this paper, we first analyze the user behavior of VCR interaction, and propose a video segmentation-aided P2P VoD System with VCR functionality. Specifically, a scene segmentation method is proposed based on the manifold representation of video visual feature and the Markov chain Monte Carlo (MCMC) method is used. And a novel P2P distribution method for video-segmentation-aided VCR functionality is considered and evaluated. Simulation results demonstrate that our proposed mechanism could reduce the server workload and improve the VCR performance at end hosts I.

Video Locality Based Buffering Mechanism for VoD Systems

Client side buffering and peer-to-peer computing can considerably improve the performance of VoD systems. Earlier, a module called LCBBS was developed for clients on a LAN. A FIFO based buffering mechanism was used in LCBBS, considering the "video locality" concept. In this way, clients first check their own buffers, and then their peers' buffers before requesting segments from remote servers. In this study, a leading segments-based buffering mechanism is integrated to the LCBBS client. The simulation results indicate that the performance of the resulting VoD system is improved further, especially in terms of startup latency. The effect of "video popularity" was also tested, assuming that in a real life environment, some videos are more popular than others. When popularity is considered in buffering decisions, simulation results show that typical video clips are displayed smoothly with small delays even when the display rate is three times faster than the download rate.

A request distribution method for clustered VOD servers considering buffer sharing effects

The clustering of multiple video servers is a popular architecture for huge VOD systems. In a clustered VOD system, user requests are distributed among the video servers by the dispatcher. Each video server consists of independent disks and a local buffer memory. The buffer mechanism is recognized helpful to the improvement of the disk performance. However, its effects have not been effectively utilized so far for the request distribution strategies of the clustered VOD system. In this work, we investigate the effects of buffer sharing on the throughput of the clustered VOD system. And, based on the results, we propose a request distribution method for the clustered VOD system, where the buffer sharing effects are utilized for improving the system's throughput. By experiments, we evaluate the performance of the proposed method compared with the conventional request distribution methods.

Buffer management for heterogeneous resolution display in home VOD services

This paper presents an efficient buffer management scheme to support heterogeneous resolution display in home VOD services. The proposed scheme provides different quality services for various home appliances such as digital TV, home theater, and personal digital assistants (PDAs). Specifically, the proposed scheme exploits the reference popularity of video objects as well as the inter-arrival time between two consecutive requests on the same object. The scheme also considers the different streaming rate of video objects to provide QoS adaptive VOD service for heterogeneous appliances. Experiments with real world VOD traces show that the proposed scheme improves the performance of home VOD systems significantly

Adaptive Channel Management Scheme for Video Broadcasting Services

Traditional unicast VOD systems require huge amounts of the server network's bandwidth, so near-VOD systems using broadcast protocols have been proposed to reduce the bandwidth requirement. Such systems have not been able to allocate channels dynamically to adapt to environments where the popularity distribution of videos changes, because of the essential inflexibility of existing broadcasting protocols. We address dynamic channel allocation for video broadcasting services, and propose a channel management technique that can adapt well to the dynamic environment, using a flexible broadcasting scheme presented in our previous work (2005). Our channel management scheme decides how many channels should be allocated to each video to maximize the system throughput, based on the video's popularity and reneging probability. The proposed scheme has been verified using extensive simulation.