Minimizing buffer requirements in video-on-demand servers

There has been an increasing trend in designing the Video-on-Demand systems using parallel server-based architectures to meet the client demands for online streaming of videos. We use a distributed architecture for effective Buffer management which efficiently utilizes various server resources like the disk Bandwidth, memory utilization and provides clients with VCR like functionalities. In this paper we proposed a unique On-line dynamic buffer replacement policy that does not base its results solely on a single parameter such as video popularity but calculates a cumulative popularity based on several other factors and hence chooses the video with the least popularity thus calculated. It is necessary to batch requests to minimize the bandwidth requirement, to reduce I/O demand, improve throughput and increase the number of customers served by using less number of streams. We proposed a Modified Adaptive Batching Policy for batching requests arriving at a server. This is different fr...

Information Sciences, 2001

Interactive multimedia applications require short initial latency. Initial latency increases as the buer size allocated to each user request increases. Hence, the buer size must be minimized. This paper proposes a buer allocation scheme (DyBASe) that dynamically allocates the minimum buer size to user requests based on the number of user requests in service. Through analysis and simulation, we show that DyBASe reduces the average initial latency by 31±65% compared with the existing static one.

Multimedia Systems, 2000

Excessive buffer requirement to handle continuous-media playbacks is an impediment to costeffective provisioning for on-line video retrieval. Given the skewed distribution of video popularity, it is expected that often there are concurrent playbacks of the same video file within a short time interval. This creates an opportunity to batch multiple requests and to service them with a single stream from the disk without violating the on-demand constraint. However, there is a need to keep data in memory between successive uses to do this. This leads to a buffer space trade-off between servicing a request in memory mode vs. servicing it in disk-mode. In this work, we develop a novel algorithm to minimize the buffer requirement to support a set of concurrent playbacks. One of the beauties of the proposed scheme is that it enables the server to dynamically adapt to the changing workload while minimizing the total buffer space requirement. Our algorithm makes a significant contribution in decreasing the total buffer requirement, especially when the user access pattern is biased in favor of a small set of files. The idea of the proposed scheme is modeled in detail using an analytical formulation, and optimality of the algorithm is proved. An analytical framework is developed so that the proposed scheme can be used in combination with various existing disk-scheduling strategies. Our simulation results confirm that under certain circumstances, it is much more resource efficient to support some of the playbacks in memory mode and subsequently the proposed scheme enables the server to minimize the overall buffer space requirement.

Telecommunication Systems, 1998

Toward the direction of supporting an end-to-end video-on-demand (VOD) system with guaranteed quality over ATM networks, this paper introduces our e orts to solve this challenging problem from the source: building VOD servers. One of the performance objectives of building VOD servers is to support the maximum number of concurrent video streams with acceptable quality of services (e.g., guaranteed delay, bandwidth, and jitter). We have designed and implemented a controllable software architecture for a VOD server. With the proposed software architecture, the design issues for the storage, processing and network subsystems have been addressed. We have investigated several disk striping schemes in the storage subsystem. The impact of these disk striping schemes on the utilization of system resources has been measured. For the processing component, we have observed that additional concurrent video streams can be supported by using e cient memory interleaving. Bu ering with a large memory space in the processing subsystem is a common technique to alleviate the latency variance of accessing di erent system components. By employing user-level control and scheduling, the variance can be decreased and therefore the resulting bu er space for each video stream is reduced. For the network subsystem, we have adopted a server-driven approach for investigating the MPEG-2 video delivery over the ATM networks. The VOD server controls the pace of video transmission and reduces the complexity of the clients. Since the client only has limited bu er space because of the cost consideration, we have reduced the bu er requirement by regulating the transmission based on the timing information embedded in MPEG-2 streams. Our research and experimental results are based on a VOD server which is under construction. The current prototype server is based on an SGI shared-memory multiprocessor with a mass storage system which consists of RAID-3 and RAID-5 disk arrays. Using 30 RAID-3 disk arrays, preliminary experimental results show that it can potentially support more than 360 high-quality video streams with careful design and coordination of the di erent system components.

Iet Software/iee Proceedings - Software, 1999

Video-on-demand (VoD) is a service that has received much attention recently and the concept has become popular with computer and communication companies. Basically, VoD consists of a video server, interconnection network and user display equipment (UDE). It provides a similar service to the neighbourhood rental store. Videos or movies are distributed from the video server to users upon request through the network and users can view interactively using their UDE along with VCR-like functions (e.g. forward, rewind, pause and resume). VoD offers a convenient service since users do not have to leave their homes, which also leads to shorter response times than with today's video stores. One important aspect of any VoD is the storage scheme used, which affects the amount and type of storage required, the maximum number of concurrent video streams and the average waiting time experienced by users of the service from the moment they choose a video to the moment video playback starts. The paper reviews some well known storage schemes, such as the phase based method and the phase based with replication method, and then proposes two new schemes that further increase the number of concurrent streams and reduce the waiting time, while reducing the total storage space required. These new schemes rely on two concepts called immediate playback RAM and sustainable playback storage. Using a case study, the new schemes are briefly compared with an existing scheme and their strengths and shortcomings are highlighted. Using some typical values, analyses are carried out that quantify the performance gain resulting from the new storage schemes.

Proceedings. 24th EUROMICRO Conference (Cat. No.98EX204)

In this paper we present a new buffering technique that reduces Video-On-Demand server memo y requirements in more than one order of magnitude. This technique, Per-Storage-Device Buffering (PSDB), is based on the allocation of a,fixed number of buffers per storage device, as opposed to existing solutions based on per-stream bufering allocation. The combination of this technique with disk array servers is studied in detail, as well as the injuence of' Variable Bit Streams. We also present an interleaved data placement strategy, Constant Time Length Declustering, that results in optimal performance in the sewice of VBR streams. PSDB is evaluated by extensive simulation of a dish-array server model that incorporates a simulation-based admission test.

International Conference & Workshop on Emerging Trends in Technology, 2012

As computer and network technology advance, multimedia data can be transferred in real time on the internet. The increasing user demands for various multimedia data make VoD (video on demand) services to be developed. Video on demand (VoD) services are being used in lots of fields such as entertainment, distant learning, home shopping, and interactive news. Video-on-Demand (VoD) has been gaining increasing popularity in recent years. The computational problems arising in such systems are very large and require appropriate mechanisms for distributing the data among the processors. The goal is to decide the rank of the videos, the no. of copies and place them on the proxy servers so that the no. of hits is maximized. In this paper, we focus on various architecture and scheme for video placement, Distributed load balancing and buffer management for video on demand system. We then proposed the Architecture and Mathematical Model for Video placement, Distributed Load Balancing and Buffer Management Scheme for Video-on-demand systems. We then proposed algorithm for calculates the rank of the videos in a novel way. It is very effective as it also calculates the access difference using access rate of 48hr and 24hr. Also the expected bandwidth of a video is changed in every 24 hr. The algorithm also considers size and bandwidth of a video while calculating its rank. This gives optimum solution for short and mostly viewed videos; finally, we proposed the algorithm for Distributed load balancing and Buffer Management.

Computer Networks, 1999

. Video-on-demand VOD servers have a limited amount of bandwidth with which to service client requests. Conventional VOD servers dedicate a unique stream of data for each client, and that strategy can quickly allocate all of the available bandwidth on the server. We describe a system called stream tapping that allows clients to ''tap'' into existing streams on the VOD server. By using existing streams as much as possible, clients can reduce the amount of new bandwidth they require, and that allows more clients to use the server at once, reducing client latency. Stream tapping uses less than 20% of the bandwidth required by a conventional VOD server for popular videos, and it performs better than many other strategies designed to improve VOD servers.

IEEE Transactions on Knowledge and Data Engineering, 2003

Ž. Video-on-demand VOD servers have a limited amount of bandwidth with which to service client requests. Conventional VOD servers dedicate a unique stream of data for each client, and that strategy can quickly allocate all of the available bandwidth on the server. We describe a system called stream tapping that allows clients to ''tap'' into existing streams on the VOD server. By using existing streams as much as possible, clients can reduce the amount of new bandwidth they require, and that allows more clients to use the server at once, reducing client latency. Stream tapping uses less than 20% of the bandwidth required by a conventional VOD server for popular videos, and it performs better than many other strategies designed to improve VOD servers. q