This paper presents a P2P VOD system based on RF-IPS algorithm, and this system consists of two parts, server-side and clients. We put emphasis on the piece selection module of server-side, and in this part we cite th...This paper presents a P2P VOD system based on RF-IPS algorithm, and this system consists of two parts, server-side and clients. We put emphasis on the piece selection module of server-side, and in this part we cite the RF-IPS algorithm proposed in the past. In the piece selection module, we also proposed a weighting function except the RF-IPS algorithm. Using this function we will find the best server peers effectively and quickly, it will enhance the performance of this system. We carry on experiments on RF-IPS algorithm, and the results show this algorithm is efficient. Overall, we believe that the RF-IPS algorithm is feasible to further improve system performance and provide a cost-effective P2P VOD service with acceptable user experience.展开更多
Structure and working theory of VOD system on teaching is discussed in this paper. The 50M data stream adapter is effective to debase the needs for video server and to enhance the ratio of performance to price.The flo...Structure and working theory of VOD system on teaching is discussed in this paper. The 50M data stream adapter is effective to debase the needs for video server and to enhance the ratio of performance to price.The flow chart for NVOD/TVOD is displayed and a 64-channel VOD system for teaching was construted.展开更多
In peer-to-peer （P2P） video-on-demand （VoD） streaming systems, each peer contributes a fixed amount of hard disk storage （usually 2 GB） to store viewed videos and then uploads them to other requesting peers. How...In peer-to-peer （P2P） video-on-demand （VoD） streaming systems, each peer contributes a fixed amount of hard disk storage （usually 2 GB） to store viewed videos and then uploads them to other requesting peers. However, the daily hits （namely popularity） of different segments of a video is highly diverse, which means that taking the whole video as the basic storage unit may lead to redundancy of unpopular segment replicas and scarcity of popular segment replicas in the P2P storage network. To address this issue, we propose a video slicing mechanism （VSM） in which the whole video is sliced into small blocks （20 MB, for instance）. Under VSM, peers can moderately remove unpopular blocks from and accordingly add popular ones into their contributed hard disk storage, which increases the usage of peers＇ contributed resource （storage and bandwidth）. To reasonably assign bandwidth among peers with different download capacity, we propose a moderate prefetching strategy （MPS） based on VSM. Under MPS, when the amount of prefetched content reaches the predefined threshold, peers immediately stop prefetching video content and then release occupied bandwidth for others. A stochastic model is established to analyze the performance of the MPS and it is found that perfect playback continuity can be got under MPS. Then the MPS is applied to PPLive VoD system （one of the largest P2P VoD systems in China） and measurement results demonstrate that low server load and perfect user satisfaction can be achieved. Also, the server bandwidth contribution of PPLive VoD system under MPS （namely 5%） is much lower than that of UUSee VoD system （namely 30%）.展开更多
In this paper, we discuss the relationship between the blocking probabilityand the configuration of storage hierarchy in a Video on Demand ( VoD) server using the queueingmodel we propose. With this model, the optimal...In this paper, we discuss the relationship between the blocking probabilityand the configuration of storage hierarchy in a Video on Demand ( VoD) server using the queueingmodel we propose. With this model, the optimal configuration of the storage system can be obtained .展开更多
In peer-to-peer （P2P） video on demand （VoD） system, once the P2P downloading rate cannot satisfy the need of playback, server is quickly referred to for help in providing enough bandwidth. Thus the switch of downl...In peer-to-peer （P2P） video on demand （VoD） system, once the P2P downloading rate cannot satisfy the need of playback, server is quickly referred to for help in providing enough bandwidth. Thus the switch of downloading from other peers （P2P） and server （HTTP） exists. This paper uses the proportion of P2P downloading amount （PPDA） during the video watching process to measure server load. This article is interested in finding a better strategy or switch rule between P2P and HTTP downloading for saving server bandwidth. The authors suggest and model a kind of switch rule based on local buffer amount, using mathematical theory of Brownian motion. It can effectively alleviate the impact of P2P rate fluctuation, reduce the switch times and improve the PPDA by at least 3%-5% on the basis of the former switch rule, which means substantial cost can be saved. Particularly the PPDA is related with the ratio of playback bit rate to the HTTP downloading rate which means the PPDA can be restricted by controlling the ratio in the real-world system. Though the result comes from constant bit rate （CBR） video supposition, it provides perspective and method for variable bit rate （VBR） application, and valuable insights for the future development of P2P VoD system.展开更多
A great number of video clips can be stored in the optical jukebox in VoDSystems. In this paper a scheduling scheme, called Combined MQL/FCFS (CMF), of short video clips inthe jukebox is proposed. Simulation shows tha...A great number of video clips can be stored in the optical jukebox in VoDSystems. In this paper a scheduling scheme, called Combined MQL/FCFS (CMF), of short video clips inthe jukebox is proposed. Simulation shows that the proposed scheme balances the efficiency andfairness, and reduces the defection probability and increases the throughput significantly comparedwith MQL and FCFS schemes.展开更多
以实际工艺流程30 t EAF-VOD-LF-模铸冶炼20Cr13不锈钢为背景,通过热力学计算,对VOD精炼硅脱氧处理后,重新造渣过程中炉渣碱度、合金含量以及钢液温度对钢液中平衡氧含量的影响进行了研究。研究结果表明:钢液中的氧含量随炉渣碱度的增...以实际工艺流程30 t EAF-VOD-LF-模铸冶炼20Cr13不锈钢为背景,通过热力学计算,对VOD精炼硅脱氧处理后,重新造渣过程中炉渣碱度、合金含量以及钢液温度对钢液中平衡氧含量的影响进行了研究。研究结果表明:钢液中的氧含量随炉渣碱度的增加呈现明显的减小趋势,实际生产中炉渣碱度一般应确保在2以上;为了保证添加合金进行脱氧的冶炼效果,应保证钢液中的硅的质量分数在0.3%以上;降低冶炼温度有利于降低钢液平衡氧含量;炉渣碱度对平衡溶解氧含量和实际生产全氧含量的影响规律基本相同,拟合出平衡溶解氧含量与实际全氧含量之间存在线性关系。展开更多
文摘This paper presents a P2P VOD system based on RF-IPS algorithm, and this system consists of two parts, server-side and clients. We put emphasis on the piece selection module of server-side, and in this part we cite the RF-IPS algorithm proposed in the past. In the piece selection module, we also proposed a weighting function except the RF-IPS algorithm. Using this function we will find the best server peers effectively and quickly, it will enhance the performance of this system. We carry on experiments on RF-IPS algorithm, and the results show this algorithm is efficient. Overall, we believe that the RF-IPS algorithm is feasible to further improve system performance and provide a cost-effective P2P VOD service with acceptable user experience.
文摘Structure and working theory of VOD system on teaching is discussed in this paper. The 50M data stream adapter is effective to debase the needs for video server and to enhance the ratio of performance to price.The flow chart for NVOD/TVOD is displayed and a 64-channel VOD system for teaching was construted.
基金supported by the National Basic Research Program of China (2007CB307101)the National Natural Science Foundation of China (60672069,60772043)
文摘In peer-to-peer （P2P） video-on-demand （VoD） streaming systems, each peer contributes a fixed amount of hard disk storage （usually 2 GB） to store viewed videos and then uploads them to other requesting peers. However, the daily hits （namely popularity） of different segments of a video is highly diverse, which means that taking the whole video as the basic storage unit may lead to redundancy of unpopular segment replicas and scarcity of popular segment replicas in the P2P storage network. To address this issue, we propose a video slicing mechanism （VSM） in which the whole video is sliced into small blocks （20 MB, for instance）. Under VSM, peers can moderately remove unpopular blocks from and accordingly add popular ones into their contributed hard disk storage, which increases the usage of peers＇ contributed resource （storage and bandwidth）. To reasonably assign bandwidth among peers with different download capacity, we propose a moderate prefetching strategy （MPS） based on VSM. Under MPS, when the amount of prefetched content reaches the predefined threshold, peers immediately stop prefetching video content and then release occupied bandwidth for others. A stochastic model is established to analyze the performance of the MPS and it is found that perfect playback continuity can be got under MPS. Then the MPS is applied to PPLive VoD system （one of the largest P2P VoD systems in China） and measurement results demonstrate that low server load and perfect user satisfaction can be achieved. Also, the server bandwidth contribution of PPLive VoD system under MPS （namely 5%） is much lower than that of UUSee VoD system （namely 30%）.
文摘In this paper, we discuss the relationship between the blocking probabilityand the configuration of storage hierarchy in a Video on Demand ( VoD) server using the queueingmodel we propose. With this model, the optimal configuration of the storage system can be obtained .
基金supported by PPLive company, and the National Basic Research Program of China (2007CB307101-1)the National Natural Science Foundation of China (60672069, 60772043)
文摘In peer-to-peer （P2P） video on demand （VoD） system, once the P2P downloading rate cannot satisfy the need of playback, server is quickly referred to for help in providing enough bandwidth. Thus the switch of downloading from other peers （P2P） and server （HTTP） exists. This paper uses the proportion of P2P downloading amount （PPDA） during the video watching process to measure server load. This article is interested in finding a better strategy or switch rule between P2P and HTTP downloading for saving server bandwidth. The authors suggest and model a kind of switch rule based on local buffer amount, using mathematical theory of Brownian motion. It can effectively alleviate the impact of P2P rate fluctuation, reduce the switch times and improve the PPDA by at least 3%-5% on the basis of the former switch rule, which means substantial cost can be saved. Particularly the PPDA is related with the ratio of playback bit rate to the HTTP downloading rate which means the PPDA can be restricted by controlling the ratio in the real-world system. Though the result comes from constant bit rate （CBR） video supposition, it provides perspective and method for variable bit rate （VBR） application, and valuable insights for the future development of P2P VoD system.
文摘A great number of video clips can be stored in the optical jukebox in VoDSystems. In this paper a scheduling scheme, called Combined MQL/FCFS (CMF), of short video clips inthe jukebox is proposed. Simulation shows that the proposed scheme balances the efficiency andfairness, and reduces the defection probability and increases the throughput significantly comparedwith MQL and FCFS schemes.
文摘以实际工艺流程30 t EAF-VOD-LF-模铸冶炼20Cr13不锈钢为背景,通过热力学计算,对VOD精炼硅脱氧处理后,重新造渣过程中炉渣碱度、合金含量以及钢液温度对钢液中平衡氧含量的影响进行了研究。研究结果表明:钢液中的氧含量随炉渣碱度的增加呈现明显的减小趋势,实际生产中炉渣碱度一般应确保在2以上;为了保证添加合金进行脱氧的冶炼效果,应保证钢液中的硅的质量分数在0.3%以上;降低冶炼温度有利于降低钢液平衡氧含量;炉渣碱度对平衡溶解氧含量和实际生产全氧含量的影响规律基本相同,拟合出平衡溶解氧含量与实际全氧含量之间存在线性关系。
