Efficient memory management in video on demand servers

In this article we present, analyse and evaluate a new memory management technique for video-on-demand servers. Our proposal, Memory Reservation Per Storage Device (MRPSD), relies on the allocation of a fixed, small number of memory buffers per storage device. Selecting adequate scheduling algorithms, information storage strategies and admission control mechanisms, we demonstrate that MRPSD is suited for the deterministic service of variable bit rate streams to intolerant clients. MRPSD allows large memory savings compared to traditional memory management techniques, based on the allocation of a certain amount of memory per client served, without a significant performance penaltyPublicad

Efficient memory management in VOD disk array servers usingPer-Storage-Device buffering

We present a buffering technique that reduces video-on-demand server memory 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 buffering allocation. The combination of this technique with disk array servers is studied in detail, as well as the influence of Variable Bit Streams. We also present an interleaved data placement strategy, Constant Time Length Declustering, that results in optimal performance in the service of VBR streams. PSDB is evaluated by extensive simulation of a disk array server model that incorporates a simulation based admission test.This research was supported in part by the National R&D Program of Spain, Project Number TIC97-0438.Publicad

Minimizing buffer requirements in video-on-demand servers

23rd Euromicro Conference EUROMICRO 97: 'New Frontiers of Information Technology', Budapest, Hungary, 1-4 Sept 1997Memory management is a key issue when designing cost effective video on demand servers. State of the art techniques, like double buffering, allocate buffers in a per stream basis and require huge amounts of memory. We propose a buffering policy, namely Single Pair of Buffers, that dramatically reduces server memory requirements by reserving a pair of buffers per storage device. By considering in detail disk and network interaction, we have also identified the particular conditions under which this policy can be successfully applied to engineer video on demand servers. Reduction factors of two orders of magnitude compared to the double buffering approach can be obtained. Current disk and network parameters make this technique feasible.Publicad

An experimental dynamic RAM video cache

As technological advances continue to be made, the demand for more efficient distributed multimedia systems is also affirmed. Current support for end-to-end QoS is still limited; consequently mechanisms are required to provide flexibility in resource loading. One such mechanism, caching, may be introduced both in the end-system and network to facilitate intelligent load balancing and resource management. We introduce new work at Lancaster University investigating the use of transparent network caches for MPEG-2. A novel architecture is proposed, based on router-oriented caching and the employment of large scale dynamic RAM as the sole caching medium. The architecture also proposes the use of the ISO/IEC standardised DSM-CC protocol as a basic control infrastructure and the caching of pre-built transport packets (UDP/IP) in the data plane. Finally, the work discussed is in its infancy and consequently focuses upon the design and implementation of the caching architecture rather than an investigation into performance gains, which we intend to make in a continuation of the work

System sizing and resource allocation for video-on-demand systems.

by Mary Y.Y. Leung.Thesis (M.Phil.)--Chinese University of Hong Kong, 1997.Includes bibliographical references (leaves 64-66).Abstract --- p.iAcknowledgments --- p.iiiChapter 1 --- Introduction --- p.1Chapter 1.1 --- Video-On-Demand Environment --- p.1Chapter 1.2 --- Problem Definition --- p.3Chapter 2 --- Related Work --- p.7Chapter 2.1 --- Data Sharing Techniques --- p.7Chapter 2.1.1 --- Batching --- p.7Chapter 2.1.2 --- Buffering --- p.9Chapter 2.1.3 --- Static Partitioning --- p.10Chapter 2.1.4 --- Adaptive Piggybacking --- p.10Chapter 2.2 --- Providing VCR Functionalities --- p.12Chapter 3 --- System Model --- p.15Chapter 3.1 --- Operations involved in VCR Control --- p.15Chapter 3.2 --- Normal Playback Model --- p.17Chapter 3.3 --- VCR Model --- p.18Chapter 4 --- Resource Allocation for Normal Playback --- p.21Chapter 4.1 --- Mathematical Model --- p.22Chapter 4.1.1 --- Hits occurring within the same partition (hit w) --- p.24Chapter 4.1.2 --- Jump to other partitions (hito) --- p.27Chapter 4.1.3 --- Fast-forwarding to the end of a movie --- p.30Chapter 4.1.4 --- The expected hit probability P(hit) --- p.31Chapter 4.2 --- Model Verification --- p.32Chapter 5 --- Resource Allocation for VCR mode --- p.35Chapter 5.1 --- Scheme 1: No merging --- p.36Chapter 5.2 --- Scheme 2: Merging by adaptive piggybacking and buffering --- p.36Chapter 5.2.1 --- Resuming within the threshold (Δ ≤ k) --- p.38Chapter 5.2.2 --- Resuming beyond the threshold (Δ > k) --- p.39Chapter 5.3 --- Verification --- p.42Chapter 6 --- Applications to System sizing --- p.45Chapter 6.1 --- Cost of Resources for Normal Playback --- p.46Chapter 6.2 --- Cost of Resources for VCR functions --- p.48Chapter 6.3 --- Overall system cost --- p.49Chapter 6.4 --- Comparison --- p.50Chapter 6.4.1 --- Scheme 1 vs. Scheme 2 --- p.51Chapter 6.4.2 --- Scheme 2 vs. pure I/O & pure buffer --- p.54Chapter 6.4.3 --- Different values of k --- p.58Chapter 6.4.4 --- Different values of ψ --- p.60Chapter 7 --- Conclusions --- p.62Bibliography --- p.64Chapter A --- Appendix --- p.67Chapter A.l --- Rewind --- p.67Chapter A.1.1 --- Hits occurring within the same partition (hit w) --- p.67Chapter A.1.2 --- Jump to other partitions (hit0) --- p.68Chapter A.2 --- Pause --- p.7

Design, analysis, and experiment on multiple servers technology for video-on-demand service in distributed networks

Master'sMASTER OF ENGINEERIN

ATOM : a distributed system for video retrieval via ATM networks

The convergence of high speed networks, powerful personal computer processors and improved storage technology has led to the development of video-on-demand services to the desktop that provide interactive controls and deliver Client-selected video information on a Client-specified schedule. This dissertation presents the design of a video-on-demand system for Asynchronous Transfer Mode (ATM) networks, incorporating an optimised topology for the nodes in the system and an architecture for Quality of Service (QoS). The system is called ATOM which stands for Asynchronous Transfer Mode Objects. Real-time video playback over a network consumes large bandwidth and requires strict bounds on delay and error in order to satisfy the visual and auditory needs of the user. Streamed video is a fundamentally different type of traffic to conventional IP (Internet Protocol) data since files are viewed in real-time, not downloaded and then viewed. This streaming data must arrive at the Client decoder when needed or it loses its interactive value. Characteristics of multimedia data are investigated including the use of compression to reduce the excessive bit rates and storage requirements of digital video. The suitability of MPEG-1 for video-on-demand is presented. Having considered the bandwidth, delay and error requirements of real-time video, the next step in designing the system is to evaluate current models of video-on-demand. The distributed nature of four such models is considered, focusing on how Clients discover Servers and locate videos. This evaluation eliminates a centralized approach in which Servers have no logical or physical connection to any other Servers in the network and also introduces the concept of a selection strategy to find alternative Servers when Servers are fully loaded. During this investigation, it becomes clear that another entity (called a Broker) could provide a central repository for Server information. Clients have logical access to all videos on every Server simply by connecting to a Broker. The ATOM Model for distributed video-on-demand is then presented by way of a diagram of the topology showing the interconnection of Servers, Brokers and Clients; a description of each node in the system; a list of the connectivity rules; a description of the protocol; a description of the Server selection strategy and the protocol if a Broker fails. A sample network is provided with an example of video selection and design issues are raised and solved including how nodes discover each other, a justification for using a mesh topology for the Broker connections, how Connection Admission Control (CAC) is achieved, how customer billing is achieved and how information security is maintained. A calculation of the number of Servers and Brokers required to service a particular number of Clients is presented. The advantages of ATOM are described. The underlying distributed connectivity is abstracted away from the Client. Redundant Server/Broker connections are eliminated and the total number of connections in the system are minimized by the rule stating that Clients and Servers may only connect to one Broker at a time. This reduces the total number of Switched Virtual Circuits (SVCs) which are a performance hindrance in ATM. ATOM can be easily scaled by adding more Servers which increases the total system capacity in terms of storage and bandwidth. In order to transport video satisfactorily, a guaranteed end-to-end Quality of Service architecture must be in place. The design methodology for such an architecture is investigated starting with a review of current QoS architectures in the literature which highlights important definitions including a flow, a service contract and flow management. A flow is a single media source which traverses resource modules between Server and Client. The concept of a flow is important because it enables the identification of the areas requiring consideration when designing a QoS architecture. It is shown that ATOM adheres to the principles motivating the design of a QoS architecture, namely the Integration, Separation and Transparency principles. The issue of mapping human requirements to network QoS parameters is investigated and the action of a QoS framework is introduced, including several possible causes of QoS degradation. The design of the ATOM Quality of Service Architecture (AQOSA) is then presented. AQOSA consists of 11 modules which interact to provide end-to-end QoS guarantees for each stream. Several important results arise from the design. It is shown that intelligent choice of stored videos in respect of peak bandwidth can improve overall system capacity. The concept of disk striping over a disk array is introduced and a Data Placement Strategy is designed which eliminates disk hot spots (i.e. Overuse of some disks whilst others lie idle.) A novel parameter (the B-P Ratio) is presented which can be used by the Server to predict future bursts from each video stream. The use of Traffic Shaping to decrease the load on the network from each stream is presented. Having investigated four algorithms for rewind and fast-forward in the literature, a rewind and fast-forward algorithm is presented. The method produces a significant decrease in bandwidth, and the resultant stream is very constant, reducing the chance that the stream will add to network congestion. The C++ classes of the Server, Broker and Client are described emphasizing the interaction between classes. The use of ATOM in the Virtual Private Network and the multimedia teaching laboratory is considered. Conclusions and recommendations for future work are presented. It is concluded that digital video applications require high bandwidth, low error, low delay networks; a video-on-demand system to support large Client volumes must be distributed, not centralized; control and operation (transport) must be separated; the number of ATM Switched Virtual Circuits (SVCs) must be minimized; the increased connections caused by the Broker mesh is justified by the distributed information gain; a Quality of Service solution must address end-to-end issues. It is recommended that a web front-end for Brokers be developed; the system be tested in a wide area A TM network; the Broker protocol be tested by forcing failure of a Broker and that a proprietary file format for disk striping be implemented

An architecture for an ATM network continuous media server exploiting temporal locality of access

With the continuing drop in the price of memory, Video-on-Demand (VoD) solutions that have so far focused on maximising the throughput of disk units with a minimal use of physical memory may now employ significant amounts of cache memory. The subject of this thesis is the study of a technique to best utilise a memory buffer within such a VoD solution. In particular, knowledge of the streams active on the server is used to allocate cache memory. Stream optimised caching exploits reuse of data among streams that are temporally close to each other within the same clip; the data fetched on behalf of the leading stream may be cached and reused by the following streams. Therefore, only the leading stream requires access to the physical disk and the potential level of service provision allowed by the server may be increased. The use of stream optimised caching may consequently be limited to environments where reuse of data is significant. As such, the technique examined within this thesis focuses on a classroom environment where user progress is generally linear and all users progress at approximately the same rate for such an environment, reuse of data is guaranteed. The analysis of stream optimised caching begins with a detailed theoretical discussion of the technique and suggests possible implementations. Later chapters describe both the design and construction of a prototype server that employs the caching technique, and experiments that use of the prototype to assess the effectiveness of the technique for the chosen environment using `emulated' users. The conclusions of these experiments indicate that stream optimised caching may be applicable to larger scale VoD systems than small scale teaching environments. Future development of stream optimised caching is considered

Bookmarking and Seeking Tool for Online Videos

At 2014, 66% of internet traffic was related to video content [1]. This number and everyday experience shows that by improving handheld device capabilities, social networks and internet speed, the video content which has been seen and posted is taking up most internet traffic. As a result, this thesis focuses on improving the user experience with videos in two supplementary features: Bookmarking videos and enhanced seeking. There have been many cases, such as CCTV and medical cases, where making a video summary and video synopsis does not serve the purpose and the whole video must be available. However, the user is only interested in certain moments in the video. Usually in these cases either a video summary is generated along the main video, interesting moments in the video is kept as a note, or the user finds it manually by making seeking forward and backward. Video bookmarking, which means keeping the original video and makes a list of interesting moments in the video, so that the user can seek toward them by selecting them solves this issue. The bookmarks are standardized JSON objects in a JSON array that can be added, deleted or modified. In their simplest form, they have a relative start time, duration and a caption. Having bookmarks available in the cases mentioned above, user behavior can be predicted. The user is highly likely to request a seek for a bookmarked moment. By caching the video content, which has the bookmarked content, the user does not need to wait for buffering to see the video playing from the seek target. Currently, the user must wait for buffering. It has a major impact in cases such as CCTV and medical cases, where different cameras have recorded a scene from different angles and a seek action must seek all the video content, at the same time. In this thesis, an application has been developed as proof of concept which has met both requirements. It has been developed over an existing application, which is used for treatment of epilepsy by using automated seizure detection

Design, analysis, and experimental verification of continuous media retrieval and caching strategies for network-based multimedia services

Ph.DDOCTOR OF PHILOSOPH