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1.
Kelvin K.W. Law John C.S. Lui Leana Golubchik 《The VLDB Journal The International Journal on Very Large Data Bases》1999,8(2):133-153
Advances in high-speed networks and multimedia technologies have made it feasible to provide video-on-demand (VOD) services
to users. However, it is still a challenging task to design a cost-effective VOD system that can support a large number of
clients (who may have different quality of service (QoS) requirements) and, at the same time, provide different types of VCR
functionalities. Although it has been recognized that VCR operations are important functionalities in providing VOD service,
techniques proposed in the past for providing VCR operations may require additional system resources, such as extra disk I/O,
additional buffer space, as well as network bandwidth. In this paper, we consider the design of a VOD storage server that
has the following features: (1) provision of different levels of display resolutions to users who have different QoS requirements,
(2) provision of different types of VCR functionalities, such as fast forward and rewind, without imposing additional demand
on the system buffer space, I/O bandwidth, and network bandwidth, and (3) guarantees of the load-balancing property across
all disks during normal and VCR display periods. The above-mentioned features are especially important because they simplify
the design of the buffer space, I/O, and network resource allocation policies of the VOD storage system. The load-balancing
property also ensures that no single disk will be the bottleneck of the system. In this paper, we propose data block placement,
admission control, and I/O-scheduling algorithms, as well as determine the corresponding buffer space requirements of the
proposed VOD storage system. We show that the proposed VOD system can provide VCR and multi-resolution services to the viewing
clients and at the same time maintain the load-balancing property.
Received June 9, 1998 / Accepted April 26, 1999 相似文献
2.
Multimedia systems store and retrieve large amounts of data which require extremely high disk bandwidth and their performance
critically depends on the efficiency of disk storage. However, existing magnetic disks are designed for small amounts of data
retrievals geared to traditional operations; with speed improvements mainly focused on how to reduce seek time and rotational
latency. When the same mechanism is applied to multimedia systems, overheads in disk I/O can result in dramatic deterioration
in system performance. In this paper, we present a mathematical model to evaluate the performance of constant-density recording
disks, and use this model to analyze quantitatively the performance of multimedia data request streams. We show that high
disk throughput may be achieved by suitably adjusting the relevant parameters. In addition to demonstrating quantitatively
that constant-density recording disks perform significantly better than traditional disks for multimedia data storage, a novel
disk-partitioning scheme which places data according to their bandwidths is presented. 相似文献
3.
In a multimedia server, multiple media streams are generally serviced in a cyclic fashion. Due to non-uniform playback rates
and asynchronous arrivals of queries, there tends to be spare disk bandwidth in each service cycle. In this paper, we study
the issue of dynamically using spare disk bandwidth and buffer to maximize the system throughput of a multimedia server. We
introduce the concept of minimizing buffer consumption as the criterion to select an appropriate media stream to utilize the spare system resources. Buffer consumption measures
not only the amount of buffer but also the amount of time such buffer space is occupied (i.e., the space-time product). Different
alternatives to utilizing spare disk bandwidth are examined, including different rate-adjustable retrievals of an already
activated stream and prefetching the next waiting stream. For rate-adjustable retrievals, we study buffer consumption-based and remaining-time-based criteria for selecting an active stream to increase retrievals. Simulations are conducted to evaluate and compare different
cases. The results show that (1) minimizing buffer consumption is the right criterion for maximizing the system throughput
with spare disk bandwidth; (2) in general, prefetching a waiting stream incurs more buffer consumption, and thus is less effective
than rate-adjustable retrieval of active streams in maximizing the system throughput; and (3) the advantage of rate-adjustable
retrieval over prefetching is especially significant when service cycle time is small. 相似文献
4.
For admission control in real-time multimedia systems, buffer space, disk bandwidth and network bandwidth must be considered.
The CBR-based mechanisms do not use system resources effectively, since media data is usually encoded with VBR compression
techniques. We propose an admission control mechanism based on a VBR data model that has a dynamic period length. In our mechanism,
the period can be adaptively changed to maximize the performance, considering both disk bandwidth and buffer space. To compare
the performance, extensive simulations are conducted on RR, SCAN, and GSS schemes which have the dynamic period length and
the static period length. 相似文献
5.
Aya Soffer Hanan Samet 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(4):253-274
Symbolic images are composed of a finite set of symbols that have a semantic meaning. Examples of symbolic images include
maps (where the semantic meaning of the symbols is given in the legend), engineering drawings, and floor plans. Two approaches
for supporting queries on symbolic-image databases that are based on image content are studied. The classification approach
preprocesses all symbolic images and attaches a semantic classification and an associated certainty factor to each object
that it finds in the image. The abstraction approach describes each object in the symbolic image by using a vector consisting
of the values of some of its features (e.g., shape, genus, etc.). The approaches differ in the way in which responses to queries
are computed. In the classification approach, images are retrieved on the basis of whether or not they contain objects that
have the same classification as the objects in the query. On the other hand, in the abstraction approach, retrieval is on
the basis of similarity of feature vector values of these objects. Methods of integrating these two approaches into a relational
multimedia database management system so that symbolic images can be stored and retrieved based on their content are described.
Schema definitions and indices that support query specifications involving spatial as well as contextual constraints are presented.
Spatial constraints may be based on both locational information (e.g., distance) and relational information (e.g., north of).
Different strategies for image retrieval for a number of typical queries using these approaches are described. Estimated costs
are derived for these strategies. Results are reported of a comparative study of the two approaches in terms of image insertion
time, storage space, retrieval accuracy, and retrieval time.
Received June 12, 1998 / Accepted October 13, 1998 相似文献
6.
The next generation of interactive multimedia documents can contain both static media, e.g., text, graph, image, and continuous
media, e.g., audio and video, and can provide user interactions in distributed environments. However, the temporal information
of multimedia documents cannot be described using traditional document structures, e.g., Open Document Architecture (ODA)
and Standard Generalized Mark-up Language (SGML); the continuous transmission of media units also raises some new synchronization
problems, which have not been met before, for processing user interactions. Thus, developing a distributed interactive multimedia
document system should resolve the issues of document model, presentation control architecture, and control scheme. In this
paper, we (i) propose a new multimedia document model that contains the logical structure, the layout structure, and the temporal
structure to formally describe multimedia documents, and (ii) point out main interaction-based synchronization problems, and
propose a control architecture and a token-based control scheme to solve these interaction-based synchronization problems.
Based on the proposed document model, control architecture, and control scheme, a distributed interactive multimedia document
development mechanism, which is called MING-I, is developed on SUN workstations. 相似文献
7.
Handling a tertiary storage device, such as an optical disk library, in the framework of a disk-based stream service model,
requires a sophisticated streaming model for the server, and it should consider the device-specific performance characteristics
of tertiary storage. This paper discusses the design and implementation of a video server which uses tertiary storage as a
source of media archiving. We have carefully designed the streaming mechanism for a server whose key functionalities include
stream scheduling, disk caching and admission control. The stream scheduling model incorporates the tertiary media staging
into a disk-based scheduling process, and also enhances the utilization of tertiary device bandwidth. The disk caching mechanism
manages the limited capacity of the hard disk efficiently to guarantee the availability of media segments on the hard disk.
The admission controller provides an adequate mechanism which decides upon the admission of a new request based on the current
resource availability of the server. The proposed system has been implemented on a general-purpose operating system and it
is fully operational. The design principles of the server are validated with real experiments, and the performance characteristics
are analyzed. The results guide us on how servers with tertiary storage should be deployed effectively in a real environment.
RID="*"
ID="*" e-mail: hjcha@cs.yonsei.ac.kr 相似文献
8.
Design and analysis of a video-on-demand server 总被引:6,自引:0,他引:6
The availability of high-speed networks, fast computers and improved storage technology is stimulating interest in the development
of video on-demand services that provide facilities similar to a video cassette player (VCP). In this paper, we present a
design of a video-on-demand (VOD) server, capable of supporting a large number of video requests with complete functionality
of a remote control (as used in VCPs), for each request. In the proposed design, we have used an interleaved storage method
with constrained allocation of video and audio blocks on the disk to provide continuous retrieval. Our storage scheme interleaves
a movie with itself (while satisfying the constraints on video and audio block allocation. This approach minimizes the starting delay and the
buffer requirement at the user end, while ensuring a jitter-free display for every request. In order to minimize the starting
delay and to support more non-concurrent requests, we have proposed the use of multiple disks for the same movie. Since a
disk needs to hold only one movie, an array of inexpensive disks can be used, which reduces the overall cost of the proposed
system. A scheme supported by our disk storage method to provide all the functions of a remote control such as “fast-forwarding”,
“rewinding” (with play “on” or “off”), “pause” and “play” has also been discussed. This scheme handles a user request independent
of others and satisfies it without degrading the quality of service to other users. The server design presented in this paper
achieves the multiple goals of high disk utilization, global buffer optimization, cost-effectiveness and high-quality service
to the users. 相似文献
9.
Issues in the design of a storage server for video-on-demand 总被引:2,自引:0,他引:2
Antoine N. Mourad 《Multimedia Systems》1996,4(2):70-86
We examine issues related to the design
of a storage server for video-on-demand (VOD) applications.
The storage medium considered is magnetic disks
or arrays of disks. We investigate disk scheduling policies,
buffer management policies and I/O bus protocol issues.
We derive the number of sessions that can be
supported from a single disk or an array of disks and determine the
amount of buffering required to support a given number of users.
Furthermore,
we propose a scheduling mechanism for disk accesses that significantly
lowers the buffer-size requirements in the case of disk arrays.
The buffer size required under the proposed scheme is independent
of the number of disks in the array. This property allows for striping
video content over a large number of disks to achieve higher
concurrency in access to a particular video object.
This enables the server to satisfy hundreds of independent requests
to the same video object or to hundreds of different objects while
storing only one copy of each video object.
The reliability implications of striping content over a large number of disks
are addressed and two solutions are proposed.
Finally, we examine various policies for dealing with disk thermal calibration
and the placement of videos on disks and disk arrays. 相似文献
10.
Igor D.D. Curcio Antonio Puliafito Salvatore Riccobene Lorenzo Vita 《Multimedia Systems》1998,6(6):367-381
The relative simplicity of access to digital communications nowadays and the simultaneous increase in the available bandwidth
are leading to the definition of new telematic services, mainly oriented towards multimedia applications and interactivity
with the user. In the near future, a decisive role will be played in this scenario by the providers of interactive multimedia
services of the on-demand type, which will guarantee the end user a high degree of flexibility, speed and efficiency. In this
paper, some of the technical aspects regarding these service providers are dealt with, paying particular attention to the
problems of storing information and managing service requests. More specifically, the paper presents and evaluates a new storage
technique based on the use of disk array technology, which can manage both typical multimedia connections and traditional
requests. The proposed architecture is based on the joint use of the partial dynamic declustering and the information dispersal
algorithm, which are employed for the allocation and retrieval of the data stored on the disk array. We also define efficient
strategies for request management in such a way as to meet the time constraints imposed by multimedia sessions and guarantee
good response times for the rest of the traffic. The system proposed is then analyzed using a simulation approach. 相似文献
11.
A video-on-demand (VOD) server needs to store hundreds of movie titles and to support thousands of concurrent accesses.
This, technically and economically, imposes a great challenge on the design of the disk storage subsystem of a VOD server.
Due to different demands for different movie titles, the numbers of concurrent accesses to each movie can differ a lot. We
define access profile as the number of concurrent accesses to each movie title that should be supported by a VOD server.
The access profile is derived based on the popularity of each movie title and thus serves as a major design goal for the
disk storage subsystem. Since some popular (hot) movie titles may be concurrently accessed by hundreds of users and a current
high-end magnetic disk array (disk) can only support tens of concurrent accesses, it is necessary to replicate and/or stripe
the hot movie files over multiple disk arrays. The consequence of replication and striping of hot movie titles is the potential
increase on the required number of disk arrays. Therefore, how to replicate, stripe, and place the movie files over a minimum
number of magnetic disk arrays such that a given access profile can be supported is an important problem. In this paper,
we formulate the problem of the video file allocation over disk arrays, demonstrate that it is a NP-hard problem, and present
some heuristic algorithms to find the near-optimal solutions. The result of this study can be applied to the design of the
storage subsystem of a VOD server to economically minimize the cost or to maximize the utilization of disk arrays. 相似文献
12.
Adaptive piggybacking: a novel technique for data sharing in video-on-demand storage servers 总被引:17,自引:0,他引:17
Recent technology advances have made multimedia on-demand services, such as home entertainment and home-shopping, important
to the consumer market. One of the most challenging aspects of this type of service is providing access either instantaneously
or within a small and reasonable latency upon request. We consider improvements in the performance of multimedia storage servers
through data sharing between requests for popular objects, assuming that the I/O bandwidth is the critical resource in the system. We discuss a novel approach to data sharing,
termed adaptive piggybacking, which can be used to reduce the aggregate I/O demand on the multimedia storage server and thus
reduce latency for servicing new requests. 相似文献
13.
HweeHwa Pang 《Multimedia Systems》1997,5(6):386-399
Multimedia applications that are required to manipulate large collections of objects are becoming increasingly common. Moreover,
the size of multimedia objects, which are already huge, are getting even bigger as the resolution of output devices improve.
As a result, many multimedia storage systems are not likely to be able to keep all of their objects disk-resident. Instead,
a majority of the less popular objects have to be off-loaded to tertiary storage to keep costs down. The speed at which objects
can be accessed from tertiary storage is thus an important consideration. In this paper, we propose an adaptive data retrieval
algorithm that employs a combination of staging and direct access in servicing tertiary storage retrieval requests. At retrieval
time, an object that resides in tertiary storage can either be staged to and then played back from disks, or the object can
be accessed directly from the tertiary drives. We show that a simplistic policy that adheres strictly to staging or direct
access does not exploit the full retrieval capacity of both the tertiary library and the secondary storage. To overcome the
problem, we propose a data retrieval algorithm that dynamically chooses between staging and direct access, based on the relative
load on the tertiary versus secondary devices. A series of simulation experiments confirms that the algorithm achieves good
access times over a wide range of workloads and resource configurations. Moreover, the algorithm is very responsive to changing
load conditions. 相似文献
14.
Thomas A. Mueck Martin L. Polaschek 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(4):312-332
With respect to the specific requirements of advanced OODB applications, index data structures for type hierarchies in OODBMS
have to provide efficient support for multiattribute queries and have to allow index optimization for a particular query profile.
We describe the multikey type index and an efficient implementation of this indexing scheme. It meets both requirements: in addition to its multiattribute query
capabilities it is designed as a mediator between two standard design alternatives, key-grouping and type-grouping. A prerequisite
for the multikey type index is a linearization algorithm which maps type hierarchies to linearly ordered attribute domains
in such a way that each subhierarchy is represented by an interval of this domain. The algorithm extends previous results
with respect to multiple inheritance. The subsequent evaluation of our proposal focuses on storage space overhead as well
as on the number of disk I/O operations needed for query execution. The analytical results for the multikey type index are
compared to previously published figures for well-known single-key search structures. The comparison clearly shows the superiority
of the multikey type index for a large class of query profiles.
Edited by E. Bertino. Received October 7, 1996 / Accepted March 28, 1997 相似文献
15.
As multimedia applications spread widely, it is crucial for programming and design support systems to handle “time” in multimedia
documents effectively and flexibly. This paper presents a set of interactive system support tools for designing and maintaining
the temporal behavior of multimedia documents. The tool set provides mechanisms for anomaly detection, temporal query processing,
and interactive scheduling. It is based on a fast incremental constraint solver we have developed, which can be adapted by
any constraint-based system. The incremental constraint solver provides immediate feedback to the user, supporting a highly
interactive design process. Combined with existing optimal layout generation mechanisms proposed in the literature, our tools
effectively utilize the flexibility provided by constraint-based systems. 相似文献
16.
Changzhou Wang X. Sean Wang 《The VLDB Journal The International Journal on Very Large Data Bases》2001,9(4):344-361
Similarity queries on complex objects are usually translated into searches among their feature vectors. This paper studies
indexing techniques for very high-dimensional (e.g., in hundreds) vectors that are sparse or quasi-sparse, i.e., vectors each having only a small number (e.g., ten) of non-zero or significant values. Based on the R-tree, the paper introduces the xS-tree
that uses lossy compression of bounding regions to guarantee a reasonable minimum fan-out within the allocated storage space
for each node. In addition, the paper studies the performance and scalability of the xS-tree via experiments.
Received: 3 May 1999 / Accepted: 23 October 2000 Published online: 27 April 2001 相似文献
17.
Video services are likely to dominate the traffic in future broadband networks. Most of these services will be provided by
large- scale public-access video servers. Research to date has shown that disk arrays are a promising technology for providing
the storage and throughput required to serve many independent video streams to a large customer population. Large disk arrays,
however, are susceptible to disk failures which can greatly affect their reliability. In this paper, we discuss suitable redundancy
mechanisms to increase the reliability of disk arrays and compare the performance of the RAID-3 and RAID-5 redundancy schemes.
We use cost and performability analyses to rigorously compare the two schemes over a variety of conditions. Accurate cost
models are developed and Markov reward models (with time-dependent reward structures) are developed and used to give insight
into the tradeoffs between system cost and revenue earning potential. The paper concludes that for large-scale video servers,
coarse-grained striping in a RAID-5 style of disk array is most cost effective. 相似文献
18.
R. Braumandl M. Keidl A. Kemper D. Kossmann A. Kreutz S. Seltzsam K. Stocker 《The VLDB Journal The International Journal on Very Large Data Bases》2001,10(1):48-71
We present the design of ObjectGlobe, a distributed and open query processor for Internet data sources. Today, data is published
on the Internet via Web servers which have, if at all, very localized query processing capabilities. The goal of the ObjectGlobe
project is to establish an open marketplace in which data and query processing capabilities can be distributed and used by any kind of Internet application. Furthermore, ObjectGlobe integrates cycle providers (i.e., machines) which carry out query processing operators. The overall picture is to make it possible to execute a query
with – in principle – unrelated query operators, cycle providers, and data sources. Such an infrastructure can serve as enabling
technology for scalable e-commerce applications, e.g., B2B and B2C market places, to be able to integrate data and data processing
operations of a large number of participants. One of the main challenges in the design of such an open system is to ensure
privacy and security. We discuss the ObjectGlobe security requirements, show how basic components such as the optimizer and
runtime system need to be extended, and present the results of performance experiments that assess the additional cost for
secure distributed query processing. Another challenge is quality of service management so that users can constrain the costs
and running times of their queries.
Received: 30 October 2000 / Accepted: 14 March 2001 Published online: 7 June 2001 相似文献
19.
Multimedia databases 总被引:2,自引:0,他引:2
A.Desai Narasimhalu 《Multimedia Systems》1996,4(5):226-249
The rapidly growing interest in building multimedia tools and applications has created a need for the development of multimedia
database management systems (MMDBMSs) as a tool for efficient organization, storage and retrieval of multimedia objects. We
begin with a word about traditional database management systems (DBMSs). Then we present an overview of the MMDBMS research
issues, challenges, methods, models, and architectures. We review the state of the art and research contributions from related
disciplines. Finally, we consider possibilities and probabilities for MMDBMS research in the future. 相似文献