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1.
In this paper, we propose and study a dynamic approach to schedule real-time requests in a video-on-demand (VOD) server.
Providing quality of service in such servers requires uninterrupted and on-time retrieval of motion video data. VOD services
and multimedia applications further require access to the storage devices to be shared among multiple concurrent streams.
Most of the previous VOD scheduling approaches use limited run-time,0 information and thus cannot exploit the potential capacity
of the system fully. Our approach improves throughput by making use of run-time information to relax admission control. It
maintains excellent quality of service under varying playout rates by observing deadlines and by reallocating resources to
guarantee continuous service. It also reduces start-up latency by beginning service as soon as it is detected that deadlines
of all real-time requests will be met. We establish safe conditions for greedy admission, dynamic control of disk read sizes,
fast initial service, and sporadic services. We conduct thorough simulations over a wide range of buffer capacities, load
settings, and over varying playout rates to demonstrate the significant improvements in quality of service, throughput and
start-up latency of our approach relative to a static approach. 相似文献
2.
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
3.
Providing QOS guarantees for disk I/O 总被引:1,自引:0,他引:1
In this paper, we address the problem of providing different levels of performance guarantees or quality of service for disk
I/O. We classify disk requests into three categories based on the provided level of service. We propose an integrated scheme
that provides different levels of performance guarantees in a single system. We propose and evaluate a mechanism for providing
deterministic service for variable-bit-rate streams at the disk. We will show that, through proper admission control and bandwidth
allocation, requests in different categories can be ensured of performance guarantees without getting impacted by requests
in other categories. We evaluate the impact of scheduling policy decisions on the provided service. We also quantify the improvements
in stream throughput possible by using statistical guarantees instead of deterministic guarantees in the context of the proposed
approach. 相似文献
4.
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
5.
Efficient admission control algorithms for multimedia servers 总被引:3,自引:0,他引:3
In this paper, we have proposed efficient admission control algorithms for multimedia storage servers that are providers
of variable-bit-rate media streams. The proposed schemes are based on a slicing technique and use aggressive methods for admission
control. We have developed two types of admission control schemes: Future-Max (FM) and Interval Estimation (IE). The FM algorithm uses the maximum bandwidth requirement of the future to estimate the bandwidth requirement. The IE
algorithm defines a class of admission control schemes that use a combination of the maximum and average bandwidths within
each interval to estimate the bandwidth requirement of the interval. The performance evaluations done through simulations
show that the server utilization is improved by using the FM and IE algorithms. Furthermore, the quality of service is also
improved by using the FM and IE algorithms. Several results depicting the trade-off between the implementation complexity,
the desired accuracy, the number of accepted requests, and the quality of service are presented. 相似文献
6.
G. Maria Kalavathy N. Edison Rathinam P. Seethalakshmi 《Multimedia Tools and Applications》2012,57(3):633-650
The main objective of this paper is to design and develop a Self-Adaptable Media Service Architecture (SAMSA) for providing
reliable dynamic composite multimedia service through policy-based actions. The multimedia services such as media retrieval,
transcoding, scaling and display services are combined based on the preferences of the user to create a dynamic composite
multimedia service called as Video-on-Demand service. Such distributed multimedia services deployed using Service Oriented
Architecture (SOA) can be accessed in heterogeneous environments that are prone to changes during run-time. To provide reliable
and adaptive multimedia services, a powerful self-adaptable architecture with dynamic compositions of multimedia services
is necessary to adapt during run-time and react to the environment. The adaptability in this proposed architecture is achieved
by enabling the service providers to Monitor, Analyze and Act on the defined policies that support customization of compositions
of multimedia services and guarantee the Quality of Service (QoS) provisioning. The Media Service Monitor (MSM) observes the
business and quality metrics associated with the multimedia services during run-time. The monitored results are analyzed by
Monitored Results Analyzer (MRA) which identifies the type and location of the fault. The Adaptive Media Service Manager (AMSM)
takes corrective actions based on the monitored results, through the policies defined as an extension of WS-Policy (Web Service—Policy
framework). The effectiveness of the proposed Self-Adaptable Media Service Architecture (SAMSA) has been evaluated on Dynamic
Composite Real-time Video-on-Demand Web Service (DCRVoDWS) for a maximum of 200 simultaneous client’s requests. The analysis
of results shows that the proposed architecture provides better improvement on reliability, response time and user satisfaction. 相似文献
7.
A large-scale, distributed video-on-demand (VOD) system allows geographically dispersed residential and business users to
access video services, such as movies and other multimedia programs or documents on demand from video servers on a high-speed
network. In this paper, we first demonstrate through analysis and simulation the need for a hierarchical architecture for
the VOD distribution network.We then assume a hierarchical architecture, which fits the existing tree topology used in today's
cable TV (CATV) hybrid fiber/coaxial (HFC) distribution networks. We develop a model for the video program placement, configuration,
and performance evaluation of such systems. Our approach takes into account the user behavior, the fact that the user requests
are transmitted over a shared channel before reaching the video server containing the requested program, the fact that the
input/output (I/O) capacity of the video servers is the costlier resource, and finally the communication cost. In addition,
our model employs batching of user requests at the video servers. We study the effect of batching on the performance of the
video servers and on the quality of service (QoS) delivered to the user, and we contribute dynamic batching policies which
improve server utilization, user QoS, and lower the servers' cost. The evaluation is based on an extensive analytical and
simulation study. 相似文献
8.
Without user interactions, multimedia presentations are just fancy slide shows with sound and video supports. User interactions
by themselves do not change the temporal relationships among multimedia objects, such as texts, graphics, images, audio, and
video, but affect the playback schedules. In this paper, we propose a synchronization mechanism to guarantee the quality of
multimedia presentation with user interactions. In our protocol, each presentation site requests media transmission from the
required media servers at certain time intervals prior to the playback deadlines, where these time intervals are the response
times to cover possible experienced end-to-end delays and packet losses, and waits for an initial setup time to ensure intermedia
synchronization before starting the presentation. Users may interact with the presentation. This synchronization mechanism
solves the problems incurred by user interactions by determining the new presentation scenario produced by the interactive
operation, calculating the corresponding setup time, and then rendering the new playback and retrieval schedules. 相似文献
9.
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
10.
Recent advances in computer technologies have made it feasible to provide multimedia services, such as news distribution
and entertainment, via high-bandwidth networks. The storage and retrieval of large multimedia objects (e.g., video) becomes
a major design issue of the multimedia information system. While most other works on multimedia storage servers assume an
on-line disk storage system, we consider a two-tier storage architecture with a robotic tape library as the vast near-line
storage and an on-line disk system as the front-line storage. Magnetic tapes are cheaper, more robust, and have a larger
capacity; hence, they are more cost effective for large scale storage systems (e.g., video-on-demand (VOD) systems may
store tens of thousands of videos). We study in detail the design issues of the tape subsystem and propose some novel tape-scheduling
algorithms which give faster response and require less disk buffer space. We also study the disk-striping policy and the
data layout on the tape cartridge in order to fully utilize the throughput of the robotic tape system and to minimize the
on-line disk storage space. 相似文献
11.
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
12.
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
13.
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
14.
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
15.
Domenico Ferrari 《Multimedia Systems》1996,4(6):299-304
Protocols for multimedia communication are needed to integrate into a single network services intended to satisfy the different
requirements of multiple types of traffic. An essential prerequisite for designing these protocols is that the services to
be offered by the network must be selected and specified in detail. We present the service models proposed, or being developed,
by the Internet community, by the ATM community, and by the Tenet Group. We compare their common characteristics, which reveal
the characteristics of the first integrated services networks are likely to offer. The services referred to in this paper
are those at the network and transport layers, which support the services to be offered to the system's end users. 相似文献
16.
We describe a system which supports dynamic user interaction with multimedia information using content-based hypermedia navigation
techniques, specialising in a technique for navigation of musical content. The model combines the principles of open hypermedia, whereby hypermedia link information is maintained by a link service, with content-based retrieval techniques in which a database is queried based on a feature of the multimedia content; our approach could be described as
‘content-based retrieval of hypermedia links’. The experimental system focuses on temporal media and consists of a set of
component-based navigational hypermedia tools. We propose the use of melodic pitch contours in this context and we present
techniques for storing and querying contours, together with experimental results. Techniques for integrating the contour database
with open hypermedia systems are also discussed. 相似文献
17.
Francesco Garibaldo 《AI & Society》2002,16(4):305-331
This article, first of all, supports the idea that the undeniable process of ICT-based technological convergence implies
the social, cultural and business unification of the world of media and culture. The poor performance of the megamerger is
a clear indicator of the unstable ground of the convergence hypothesis. Secondly, it argues in favour of cooperation between
different expertise, skills and cultures to make multimedia products or to supply multimedia services, instead of creating
from scratch a brand new class of hybrid skills and professions. Thirdly, a variety of new possible and realistically achievable
professional profiles in cultural industries and institutions are illustrated. Eventually a set of public policies, in the
light of a new role for cities and regions, is developed.
Correspondence and offprint requests to: Francesco Garibaldo, Fondazione ‘Istituto Per il Lavoro (IPL)’, via Marconi 8, 40122 Bologna, Italy. Email: f.garibaldo@ipielle.emr.it 相似文献
18.
Stephan Greene Egemen Tanin Catherine Plaisant Ben Shneiderman Lola Olsen Gene Major Steve Johns 《International Journal on Digital Libraries》1999,2(2-3):79-90
The Human-Computer Interaction Laboratory (HCIL) of the University of Maryland and NASA have collaborated over three years
to refine and apply user interface research concepts developed at HCIL in order to improve the usability of NASA data services.
The research focused on dynamic query user interfaces, visualization, and overview + preview designs. An operational prototype,
using query previews, was implemented with NASA’s Global Change Master Directory (GCMD), a directory service for earth science
datasets. Users can see the histogram of the data distribution over several attributes and choose among attribute values.
A result bar shows the cardinality of the result set, thereby preventing users from submitting queries that would have zero
hits. Our experience confirmed the importance of metadata accuracy and completeness. The query preview interfaces make visible
the problems or gaps in the metadata that are undetectable with classic form fill-in interfaces. This could be seen as a problem,
but we think that it will have a long-term beneficial effect on the quality of the metadata as data providers will be compelled
to produce more complete and accurate metadata. The adaptation of the research prototype to the NASA data required revised
data structures and algorithms.
Received: 12 December 1997 / Revised: June 1999 相似文献
19.
A buffer-inventory-based dynamic scheduling algorithm for multimedia-on-demand servers 总被引:2,自引:0,他引:2
We present a producer-consumer model of multimedia-on-demand (MOD) servers. The producer retrieves media data from a disk
and places it into a set of buffers, while the consumer sends out the data in the buffers to the users. We develop for the
producer a buffer-inventory-based dynamic scheduling (BIDS) algorithm that guarantees non-zero inventory and non-overflow
of data in the buffers to meet the continuity requirement and no-loss of data for each media stream. The algorithm can deal
with heterogeneous me dia streams as well as the transient circumstances upon service completions and arrivals of new requests.
To smooth out the impact of bursty data of variable-bit-rate media streams and therefore increase the maximum admissible load
of requests, we also introduce into the scheduling scheme a time-scale-dependent peak consumption rate and a virtual cycle
time. Based on BIDS, an effective admission control mechanism can be easily established by checking two simple conditions
respectively on the overall system load and buffer size. Our algorithm is very easy to implement. Experiments carried out
with an actual disk system and real video stream data verify that it is more robust compared to static scheduling algorithms
previously proposed in the literature, especially when handling variable-bit-rate media streams. 相似文献
20.
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