• Journal of Korea Society of Industrial Information Systems
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• v.13 no.1
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• pp.46-56
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• 2008

Double Patching is a multicasting technique for a VoD system which has been proposed to provide a true VoD service by making clients share a long patching stream as well as a regular stream For subsequent short patching streams, the technique always makes the long patching stream have extra data that will be played back during a double period of a patching window. In this paper, we propose a technique, using the start time of the latest short patching stream, optimizes Double Patching by deleting the useless data included in the long patching stream when the patching window of the long patching stream closes. The mean requirement for the server's bandwidth to provide the true VoD service is used as a performance metric, and the effect of the request inter-arrival time, the size of the client's local buffer and the video length on the mean bandwidth requirement is evaluated. Performance evaluation result shows that the proposed technique optimizes Double Patching in all cases.

• Proceedings of the Korea Multimedia Society Conference
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• 2002.11b
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• pp.569-572
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• 2002

True VOD 시스템은 클라이언트들이 서비스 요청을 할 때마다 통신망을 통하여 즉시 비디오서비스를 제공할 수 있는 대화형 시스템이다. 그러나 멀티미디어 스트리밍 응용은 비디오나 오디오 클립들이 높은 대역과 긴 재생시간을 요구하기 때문에 많은 서버 및 네트워크 자원을 요구한다. 패칭기법은 클라이언트들의 요청에 대해 미디어 스트림을 멀티캐스트 전송함으로써 요구되는 서버 및 네트워크 자원을 줄이는 동적 멀티캐스트 방법이다. 하지만 패칭은 클라이언트의 요청을 즉시 처리하기 위해 많은 량의 버퍼링을 필요로 하며 높은 디스크 대역을 요구한다. 본 논문에서는 비디오 서버의 입출력 요청을 동적으로 감소시키며, 인기 있는 비디오에 대한 요청을 즉시 처리할 수 있도록 정규채널과 패칭 채널을 예약해 두는 True VOD 시스템을 위한 개선된 패칭 알고리즘을 제안한다.

• Journal of KIISE:Computer Systems and Theory
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• v.30 no.10
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• pp.523-532
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• 2003

Video on Demand(VOD) services cause high resource consumption in a video seuer, because multimedia are characterized by continuous playback, a high bandwidth requirement, and long playback duration. Patching has been proposed to save the network I/O bandwidth of a video server. To achieve true VOD, patching uses multicasting to share video streams, thereby providing immediate VOD services to users without any service latency. A communication channel is used to either multicast the entire video as a regular channel or multicast only the leading portion of a video as a Patching channel. This paper Proposes a buffering patching technique that divides regular channels, as used in patching, into sub-regular channels and regular channels to shorten the holding time of the channels. In the proposed technique, the last portion of video data, corresponding to the size of the buffering window, is not transferred by sub-regular channels, but rather downloaded and buffered in the user buffer from the latest regular channel. When simulations were performed to compare the performance of the proposed technique with that of conventional patching, the results indicated that the proposed technique was superior in terms of the defection rate, average service latency, and fairness, although the amount of video data buffered at each user station was higher than that with patching.