• Proceedings of the IEEK Conference
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• 2000.09a
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• pp.979-982
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• 2000

In this paper we suggest the adaptive QoS-based VOD system design, which can diagnose and reflect the variable network situation. This system is based on the changeable Forward Error Correction(FEC) coding and re-transmission to enhance system quality by using the measured real-time network value such as loss, delay and jitter.

• Journal of KIISE:Computer Systems and Theory
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• v.33 no.10
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• pp.734-745
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• 2006

This paper presents a PC cluster-based distributed VOD server that minimizes the load of an interconnection network by adopting the VIA communication protocol and the interval cache algorithm. Video data is distributed to the disks of the distributed VOD server and each server node receives the data through the interconnection network and sends it to clients. The load of the interconnection network increases because of the large amount of video data transferred. This paper developed a distributed VOD file system, which is based on VIA, to minimize cost using interconnection network when accessing remote disks. VIA is a user-level communication protocol removing the overhead of TCP/IP. This papers also improved the performance of the interconnection network by expanding the maximum transfer size of VIA. In addition, the interval cache reduces traffic on the interconnection network by caching, in main memory, the video data transferred from disks of remote server nodes. Experiments using the distributed VOD server of this paper showed a maximum performance improvement of 21.3% compared with a distributed VOD server without VIA and the interval cache, when used with a four-node PC cluster.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.1052-1059
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• 2016

Video-on-Demand(VoD) is one of the most popular media streaming which attracted many researchers' attention. VMesh is one of the most cited works in the field of the VoD system. VMesh is proposed to solve the problem of random seeking functionality. However, a large number of the DHT(Distributed Hash Table) searches in VMesh is sill the main problem which needs to be solved. In order to reduce the number of the DHT searches, the clustered segment index(CSI) scheme is proposed. In this scheme, the video segments are divided into clusters. The segment information of the video segments, which are clustered into the same cluster, are stored in the same clustered segment index that can be searched by using the hash key. Each peer also can request the required segments by using this clustered segment index. The experiment results show that the number of the DHT searches in the proposed scheme is less than that of VMesh even in case of peers leave and join the network or peers perform the fast forward/backward operations.

• Journal of Broadcast Engineering
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• v.3 no.1
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• pp.100-109
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• 1998

The coding of video sequences has been the focus of research in recent years. High Definition TV(HDTV), video conferencing and video on demand(VOD) are some of the well known applications. In the moving picture compression, motion estimation algorithm plays a very important role, but due to its high computational complexity, there has been many approaches to overcome this difficulty. We propose a new block matching criterion that uses modified cost functions. This new block matching criterion classifies pixels into 2-levels, 4-levels and 8-levels with a suitable thresholding method. We also show that our new proposed algorithms can easily be combined with many other fast motion estimation algorithms with good performance.

• Proceedings of the Korea Information Processing Society Conference
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• 2009.04a
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• pp.1116-1119
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• 2009

최근 그룹 통신 분야에서 전통적으로 대표되는 IP 멀티캐스트의 대안기술로서 호스트기반 멀티캐스트 및 P2P시스템은 기존의 IP 멀티캐스트의 단점을 극복하고자 하는 연구이다. 이러한 호스트기반 멀티캐스트는 사용자 중심의 서비스를 제공함으로써 다양한 네트워크 환경에서 누구나 사용자들이 효율적으로 데이터를 공유하게 해주고 있다. 본 논문에서는 이러한 협동 기반의 호스트 멀티캐스트를 사용하여 미디어 서비스를 제공하는 VOD 시스템 전반에 관한 연구를 수행하고 이러한 VOD의 서비스를 고도화 하고자 한다. 보다 구체적으로는 패칭 기법을 사용하여 사용자간의 전달 지연을 최소화 할 수 있는 효율적인 자료 전송 경로를 설정 방법과 주문형 비디오 서버를 위한 현실적인 호스트 기반 멀티캐스트 트리 구성 모델을 제시하고자 한다.

• Proceedings of the Korea Information Processing Society Conference
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• 2000.04a
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• pp.303-308
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• 2000

VOD(Video-On-Demand) 시스템에서 제한 없는 VCR 서비스는 클라이언트들의 개별 서비스 요청에 대하여 유일한 비디오 스트림을 할당함으로서 제공될 수 있다. 이 방식은 서버 부하의 증가와 부족한 네트워크 자원의 고갈 등과 같은 중대한 문제점을 갖고 있으나 클라이언트의 셋톱박스에 버퍼를 구현함으로서 매우 제한된 VCR 기능을 제공하게 된다. 본 논문에서는 대화형 VOD 시스템에서 제한 없는 VCR 기능을 제공할 수 있는 새로운 MBA(Multicast Buffering Algorithm) 알고리듬을 제안한다. MBA 알고리듬 하에서 VCR 서비스는 버퍼가 동적으로 확장되어 비디오 데이터를 저장하기 때문에 사용자에게 제한 없이 제공되어진다. 또한 MBA 알고리듬은 버퍼의 사용 효율을 증대시키는 방법을 제공하며 모든 클라이언트들의 서비스 요청을 지연 없이 즉시 처리하므로 사용자들에게 진정한 대화형 VOD 서비스를 제공하게 된다. 본 논문에서는 MBA 알고리듬을 이용하여 지연 없는 VCR 기능을 갖춘 VOD 서비스를 구현하였으며 시뮬레이션 결과는 MBA 알고리듬이 다른 버퍼링 방식과 비교하여 매우 우수한 성능을 갖고 있음을 보여주고 있다.

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

• Proceedings of the KAIS Fall Conference
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• 2001.11a
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• pp.215-219
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• 2001

VOD는 사용자가 원하는 Video등의 멀티미디어 데이터들을 선택적으로 제 받을 수 있는 서비스이다. VOD는 여러 가지 응용분야의 요구사항을 만족하기에는 기술적으로 해결하여야 할 문제점이 여러 가지 존재한다. 그래서 본 논문에서는 클러스터링 시스템 구조에서 멀티미디어 데이터의 실시간 디스플레이를 보장하는 병렬/분산 입출력 시스템에 대한 연구를 제시하여 Linux 운영체제를 사용하는 컴퓨터를 단위 노드로 하여 테스트베드 시스템을 구성한다. 이 환경에서 멀티미디어 데이터를 각 I/O노드에 디클러스터링하여 비디오 설시간성과 멀티미디어 데이터의 대역폭 요구를 만족하기 위한 방법을 연구 개발하고 특정 응용 프로그램에 연구개발하고 특정응용 프로그램에 연구 개발된 방법을 적용하여 제시된 방법의 우수성과 클러스터링 환경에서 멀티미디어 데이터처리에 장점을 이 논문에서 입증하고자 한다.

• Proceedings of the IEEK Conference
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• 1998.10a
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• pp.123-126
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• 1998

Generally, in a VOD(video on Demand) system, batching technique is oten used to improve throughput. Since subscribers to VOD servives tend to withdraw their requests as the latency becomes large, an optimal scheduling scheme should consider not only batching size but also withdrawal rae, service latency and fairness between different programs. In this paper, we propose a new scheduling scheme, which shows improvement in fairness and reduction in withdrawal rate and service latency compared with other well known schemes. When there are 2 or more streams are available in the VOD server, proposed scheme apply different program selection policies to each streams. Using this approach effectiveness of stream usage can be improved.

• The Transactions of the Korea Information Processing Society
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• v.7 no.11
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• pp.3519-3533
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• 2000

In a VOD(Video-On-Demand) system, I/O performance and storage requirements are generally more important than computing capability, Due to the development of CPU tecnology, the gap between the performance of processors and desk speed are widening. Therefore, the disk system typically becomes the bohleneck ina VOD system. In order to allevte those effects from physical constramts, disk array system is used. The I/O performance of disk arrays can be improved by the capability of processors, I/O schefuling polcy, the number of member disks in the array, disk block size, block placemet method etc. In this paper, we considered the disk scheduling schemes including EDF( Earliest Deadine First), SCAN, SGAN-EDF, Round-robm. GSS(Grouped Sweeping scheme), and C-SCAN, LOOK, C-LOOK which are variations of SCAN Mamly focusing on those disk scheduling schemes, we performed the simulation in order to compare and eview the perionmance of disk arrays considening seveial related parameters under diverse environments and analyzed the effects of those parameters to the performance.