• Journal of Korea Multimedia Society
• /
• v.8 no.12
• /
• pp.1597-1604
• /
• 2005

Recursive Patching is an efficient multicast technique for large-scale video on demand systems and recursively shares existing video streams with asynchronous clients. When Recursive Patching initiates a transition stream, it always makes a transition stream have additional data for the worst future request. In order to share a VOD server's limited network bandwidth efficiently, this paper proposes Practical Patching that removes the unnecessary data included in the transition stream. The proposed Practical Patching dynamically expands ongoing transition streams when a new request actually arrives at the server. As a result, the transition streams never have unnecessary data. Simulation result confirmed that the proposed technique is better than Recursive Patching in terms of service latency and defection rate.

• Journal of Korea Multimedia Society
• /
• v.4 no.3
• /
• pp.205-214
• /
• 2001

As the real time multimedia data service has become available due to the rapid progress of computer and Internet technology, the users can enjoy the newly developed service, which is called Video On-Dem-and(VOD). However, most of service providers have not paid their attention much on the software for various service modes on VOD, but they are only concentrating un the hardware to provide with the high resolution video display. Therefore, the service providers are recently to pay more attention on the software to cope with the various demands of users than hardware. So this paper has designed and implemented the VOD service system for those demands. Since the VOD service system suggested by this paper enable off-line search functions through E-mail, the users can possibly get the necessary information from off-line Search without connecting to the server while the current VOD service can prominently help users to save the time and effort to sea고 and select the Video contents by using periodical current awareness service supported by PUSH technology and user oriented information booking and feedback service supported by SDI service.

• The Transactions of the Korea Information Processing Society
• /
• v.5 no.3
• /
• pp.592-605
• /
• 1998

주문형 비디오(VOD) 서버는 대용량의 비디오 데이터를 저장하고 사용자에게 이를 실시간으로 전송하여야 하는 제약 조건을 만족시켜야 한다. 기존의 VOD 서버 시스템은 실시간 반응 시간을 보장하기 위해 대부분 비디오 데이터의 영구 저장 장치로 하드 디스크를 사용하지만 대용량의 비디오 데이터를 저장하는 데에는 경제성과 신뢰성의 문제점이 대두된다. 본 논문은 이러한 문제점을 보완하기 위해 대용량 저장 장치인 광자기 디스크 쥬크박스를 사용하는 복합 다단계 VOD 서버에서 다양한 비디오 데이터저장 방법들을 제안하고 각 방법의 저장 비용 및 성능을 비교 분석한다. 또한, 복합 다단계 시스템과 하드 디스크를 기반으로 하는 서버의 특성을 고려하여 비디오 데이터를 저장함으로써 비용 효과적인 VOD 서버 구성 방법을 제안한다.

• Proceedings of the Korea Information Processing Society Conference
• /
• 2001.10a
• /
• pp.305-308
• /
• 2001

초고속 통신망 인프라 구축으로 인해 인터넷을 통한 대용량 멀티미디어 데이터 전송이 가능하게 되었고, 이와 관련하여 VOD(Video-On-Demand) 서버에 대한 연구가 활발히 진행중이다. 대용량의 비디오 데이터를 실시간으로 서비스하기 위해서는 단일 VOD 서버로는 그 한계가 있기 때문에 최근 여러개의 PC들을 클러스트링하여 구성된 병렬 VOD 서버들이 개발되고 있다. 본 논문에서는 병렬 VOD 서버로 현재 많이 활용되고 있는 모텔들에 대해 알아보고 각각의 성능을 비교 분석함으로써 보다 나은 모델에 대한 방향을 제시해 보고자 한다.

• Journal of Korea Multimedia Society
• /
• v.8 no.4
• /
• pp.502-508
• /
• 2005

This paper proposes a dynamic hybrid patching technique that can improve the performance of VOD systems by adopting the advantages of both greedy patching and grace patching to use a VOD server's limited network-I/O bandwidth. The proposed technique uses grace patching to the requests for the videos, arrival intervals of which are smaller than the size of patching window, and uses greedy patching to the rest requests. In addition, proposed patching technique expands the latest particular patching multicast into a regular multicast for a new request. In result, the patching multicast data for the new request can be the data from the beginning to the skew point of the video and the holding time of a dispatched channel can exceedingly decrease. Simulation results confirm that the proposed technique is better than grace patching in terms of defection rate and average service latency.

• Journal of Internet Computing and Services
• /
• v.8 no.2
• /
• pp.77-87
• /
• 2007

A typical VOD service allows that a number of remote clients playback a desired video from a large collection of videos stored in one or more video servers. The main bottleneck for a VOD service is the network bandwidth connecting to the VOD server to the client due to the high bandwidth requirements. Many previous researches have shown that VOD server can be greatly improved through the use of multicast, broadcast, or P2P scheme. Broadcast is one of the most efficient techniques because it can transmit a stream to many users without additional network bandwidth. But the broadcast has long latency time. In order to overcome the drawback, in this paper, we propose P2Prefix broadcast scheme that can solve the service latency time, which is the problem of broadcast scheme, by using P2P caching as well as minimizing the client buffer requirement.

• Proceedings of the Korean Information Science Society Conference
• /
• 1998.10a
• /
• pp.130-132
• /
• 1998

기존의 VOD 시스템을 확대하여 원거리에 존재하는 서비스 제공자로부터에서 사용자에세 더 빠른 응답서비스를 제공하고, 장애가 발생하더라도 사용자에게 중단 없이 제공되도록 하기 위하여 프락시 서버를 두었는데, 특히 일정 지역내 존재하는 프락시 서버들간에 틀러스터를 형성하여 단일 프락시 서버로 만족할 수 없는 다수의 클라이언트로부터의 요구를 받아들이고 cache사이즈와 감소와, 더 높은 hit tate를 제공하도록 한다. 또한 이 클러스터내의 프로그램관리를 위해 비디오데이터에 대한 정보를 hint로 저장하여 각 프락시에서 관리함으로써 네트웍을 통해 사용자까지 실시간으로 비디오 데이터를 전송이 가증하고, 직접 데이터를 전달 없이 클러스터를 효율적으로 관리할 수 있도록 한다.

• Proceedings of the Korean Information Science Society Conference
• /
• 1998.10b
• /
• pp.286-288
• /
• 1998

본 논문은 VOD 서버에서 자원 활용 및 서비스 상황에 따라 융통성 있게 버퍼공유 크기를 변경함으로써 버퍼공유 효과를 높이면서 시스템 성능을 향상시켜 다수의 사용자들의 요구를 수용할 수 있는 버퍼공유 기법을 제안하다. 공유쌍이 버퍼를 모두 선점하여 더 이상의 새로운 서비스가 불가능한 경우 여분의 디스크 대역폭이 존재한다면 기존 서비스에 아무런 영향 없이 공유쌍을 분리시켜 새로운 서비스를 제공하도록 한다.

• The Transactions of the Korea Information Processing Society
• /
• v.6 no.5
• /
• pp.1189-1202
• /
• 1999

As compared with VOD data, NOD article data has the following characteristics: it is created at any time, has a short life cycle, is selected as not one article but several articles by a user, and has high access locality in time. Because of these intrinsic features, user access patterns of NOD article data are different from those of VOD. Thus, building NOD system using the existing techniques of VOD system leads to poor performance. In this paper, we analysis the log file of a currently running electronic newspaper, show that the popularity distribution of NOD articles is different from Zipf distribution of VOD data, and suggest a new popularity model of NOD article data MS-Zipf(Multi-Selection Zipf) distribution and its approximate solution. Also we present a life cycle model of NOD article data, which shows changes of popularity over time. Using this life cycle model, we develop LLBF (Largest Life-cycle Based Frequency) prefetching algorithm and analysis he performance by simulation. The developed LLBF algorithm supports the similar level in hit-ratio to the other prefetching algorithms such as LRU(Least Recently Used) etc, while decreasing the number of data replacement in article prefetching and reducing the overhead of the prefetching in system performance. Using the accurate user access patterns of NOD article data, we could analysis correctly the performance of NOD server system and develop the efficient policies in the implementation of NOD server system.

• Journal of the Korea Computer Industry Society
• /
• v.6 no.3
• /
• pp.379-390
• /
• 2005

Intensive studies have been made in the area of VOD server Multimedia files in the VOD sever are characterized with the large volume of data, the requirements of synchronization and real-time playback of streams. The basic goal of the study is to find an efficient mechanism to allow maximum number of users under the limited resources such as Buffer size and disk bandwidth. we propose a efficient $pre\_fetching$ policy for multimedia services with dynamic monitoring and management of VOD sever resources. Simulation results show that the rate of buffer usage and service time of proposed scheme are about $28\%$ performance improved than that of traditional methods. This implies that our method can allow much more users for given resources.