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1.
Automatic text segmentation and text recognition for video indexing 总被引:13,自引:0,他引:13
Efficient indexing and retrieval of digital video is an important function of video databases. One powerful index for retrieval
is the text appearing in them. It enables content-based browsing. We present our new methods for automatic segmentation of
text in digital videos. The algorithms we propose make use of typical characteristics of text in videos in order to enable
and enhance segmentation performance. The unique features of our approach are the tracking of characters and words over their
complete duration of occurrence in a video and the integration of the multiple bitmaps of a character over time into a single
bitmap. The output of the text segmentation step is then directly passed to a standard OCR software package in order to translate
the segmented text into ASCII. Also, a straightforward indexing and retrieval scheme is introduced. It is used in the experiments
to demonstrate that the proposed text segmentation algorithms together with existing text recognition algorithms are suitable
for indexing and retrieval of relevant video sequences in and from a video database. Our experimental results are very encouraging
and suggest that these algorithms can be used in video retrieval applications as well as to recognize higher level semantics
in videos. 相似文献
2.
Much work on video servers has concentrated on movies on demand, in which a relatively small number of titles are viewed
and users are given basic VCR-style controls. This paper concentrates on analyzing video server performance for non-linear
access applications. In particular, we study two non-linear video applications: video libraries, in which users select from
a large collection of videos and may be interested in viewing only a small part of the title; and video walk-throughs, in
which users can move through an image-mapped representation of a space. We present a characterization of the workloads of
these applications. Our simulation studies show that video server architectures developed for movies on demand can be adapted
to video library usage, though caching is less effective and the server can support a smaller user population for non-linear
video applications. We also show that video walk-throughs require extremely large amounts of RAM buffering to provide adequate
performance for even a small number of users. 相似文献
3.
In this paper, we present a novel approach for multimedia data indexing and retrieval that is machine independent and highly
flexible for sharing multimedia data across applications. Traditional multimedia data indexing and retrieval problems have
been attacked using the central data server as the main focus, and most of the indexing and query-processing for retrieval
are highly application dependent. This precludes the use of created indices and query processing mechanisms for multimedia
data which, in general, have a wide variety of uses across applications. The approach proposed in this paper addresses three
issues: 1. multimedia data indexing; 2. inference or query processing; and 3. combining indices and inference or query mechanism
with the data to facilitate machine independence in retrieval and query processing. We emphasize the third issue, as typically
multimedia data are huge in size and requires intra-data indexing. We describe how the proposed approach addresses various
problems faced by the application developers in indexing and retrieval of multimedia data. Finally, we present two applications
developed based on the proposed approach: video indexing; and video content authorization for presentation. 相似文献
4.
Multimedia data, especially continuous media including video and audio objects, represent a rich and natural stimulus for
humans, but require large amount of storage capacity and real-time processing. In this paper, we describe how to organize
video data efficiently on multiple disks in order to support arbitrary-rate playback requested by different users independently.
Our approach is to segment and decluster video objects and to place the segments in multiple disks using a restricted round-robin
scheme, called prime round-robin (PRR). Its placement scheme provides uniform load balance of disks for arbitrary retrieval rate as well as normal playback,
since it eliminates hot spots. Moreover, it does not require any additional disk bandwidth to support VCR-like operations
such as fast-forward and rewind. We have studied the various effects of placement and retrieval schemes in a storage server
by simulation. The results show that PRR offers even disk accesses, and the failure in reading segment by deadline occurs
only at the beginning of new operations. In addition, the number of users admitted is not decreased, regardless of arbitrary-rate
playback requests. 相似文献
5.
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
6.
Analyzing scenery images by monotonic tree 总被引:3,自引:0,他引:3
Content-based image retrieval (CBIR) has been an active research area in the last ten years, and a variety of techniques
have been developed. However, retrieving images on the basis of low-level features has proven unsatisfactory, and new techniques
are needed to support high-level queries. Research efforts are needed to bridge the gap between high-level semantics and low-level
features. In this paper, we present a novel approach to support semantics-based image retrieval. Our approach is based on
the monotonic tree, a derivation of the contour tree for use with discrete data. The structural elements of an image are modeled
as branches (or subtrees) of the monotonic tree. These structural elements are classified and clustered on the basis of such
properties as color, spatial location, harshness and shape. Each cluster corresponds to some semantic feature. This scheme
is applied to the analysis and retrieval of scenery images. Comparisons of experimental results of this approach with conventional
techniques using low-level features demonstrate the effectiveness of our approach. 相似文献
7.
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
8.
We present efficient schemes for scheduling the delivery of variable-bit-rate MPEG-compressed video with stringent quality-of-service
(QoS) requirements. Video scheduling is being used to improve bandwidth allocation at a video server that uses statistical
multiplexing to aggregate video streams prior to transporting them over a network. A video stream is modeled using a traffic
envelope that provides a deterministic time-varying bound on the bit rate. Because of the periodicity in which frame types
in an MPEG stream are typically generated, a simple traffic envelope can be constructed using only five parameters. Using
the traffic-envelope model, we show that video sources can be statistically multiplexed with an effective bandwidth that is often less than the source peak rate. Bandwidth gain is achieved without sacrificing the stringency of the requested
QoS. The effective bandwidth depends on the arrangement of the multiplexed streams, which is a measure of the lag between the GOP periods of various streams. For homogeneous streams,
we give an optimal scheduling scheme for video sources at a video-on-demand server that results in the minimum effective bandwidth.
For heterogeneous sources, a sub-optimal scheduling scheme is given, which achieves acceptable bandwidth gain. Numerical examples
based on traces of MPEG-coded movies are used to demonstrate the effectiveness of our schemes. 相似文献
9.
E. Panagos A. Biliris 《The VLDB Journal The International Journal on Very Large Data Bases》1997,6(3):209-223
Client-server object-oriented database management systems differ significantly from traditional centralized systems in terms
of their architecture and the applications they target. In this paper, we present the client-server architecture of the EOS
storage manager and we describe the concurrency control and recovery mechanisms it employs. EOS offers a semi-optimistic locking
scheme based on the multi-granularity two-version two-phase locking protocol. Under this scheme, multiple concurrent readers
are allowed to access a data item while it is being updated by a single writer. Recovery is based on write-ahead redo-only
logging. Log records are generated at the clients and they are shipped to the server during normal execution and at transaction
commit. Transaction rollback is fast because there are no updates that have to be undone, and recovery from system crashes
requires only one scan of the log for installing the changes made by transactions that committed before the crash. We also
present a preliminary performance evaluation of the implementation of the above mechanisms.
Edited by R. King. Received July 1993 / Accepted May 1996 相似文献
10.
Multimedia streams such as audio and video impose tight temporal constraints for their presentation. Often, related multimedia
streams, such as audio and video, must be presented in a synchronized way. We introduce a novel scheme to ensure the continuous
and synchronous delivery of distributed stored multimedia streams across a communications network. We propose a new protocol for synchronized playback and compute the buffer
required to achieve both, the continuity within a single substream and the synchronization between related substreams. The
scheme is very general and does not require synchronized clocks. Using a resynchronization protocol based on buffer level
control, the scheme is able to cope with server drop-outs and clock drift. The synchronization scheme has been implemented
and the paper concludes with our experimental results. 相似文献
11.
Excessive buffer requirement to handle continuous-media playbacks is an impediment to cost- effective 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. 相似文献
12.
As the number of video streams to be supported by a digital video delivery system (DVDS) increases, an improved understanding
of the necessity for reliable and cost-efficient support for a considerable number of video streams (in the magnitude of tens
of thousands), and the dependency largely on software capabilities emerges. Even in the presence of an optimal hardware configuration,
or model, and associated costs, using software to exploit the underlying hardware capabilities is of paramount importance.
Although a number of DVDSs have become operational, their ability to deliver the required services mainly depends on the small
number of streams supported and the hardware trade-offs. It is imperative that current software developments account for
the eventual scalability of the number of video streams without commensurate increase in hardware. In this paper, we present
strategies for the management of video streams in order to maintain and satisfy their space and time requirements. We use
a DVDS architectural model with functionally dichotomized nodes: a single-node partition is responsible for data retrieval,
while the remaining partition of nodes accepts user requests, determines object locations, and routes requests through the
network that connects both partitions. We present a detailed analysis of the issues related to queuing I/O requests and data
buffering. The discussion includes the requirements for arranging and scheduling I/O requests and data buffers, with the objective
of guaranteeing the required data availability rates for continuous media display. 相似文献
13.
Byzantine quorum systems 总被引:12,自引:0,他引:12
Summary. Quorum systems are well-known tools for ensuring the consistency and availability of replicated data despite the benign failure
of data repositories. In this paper we consider the arbitrary (Byzantine) failure of data repositories and present the first
study of quorum system requirements and constructions that ensure data availability and consistency despite these failures.
We also consider the load associated with our quorum systems, i.e., the minimal access probability of the busiest server.
For services subject to arbitrary failures, we demonstrate quorum systems over servers with a load of , thus meeting the lower bound on load for benignly fault-tolerant quorum systems. We explore several variations of our quorum
systems and extend our constructions to cope with arbitrary client failures.
Received: October 1996 / Accepted June 1998 相似文献
14.
In this paper, we present a placement algorithm that interleaves multi-resolution video streams on a disk array and enables
a video server to efficiently support playback of these streams at different resolution levels. We then combine this placement
algorithm with a scalable compression technique to efficiently support interactive scan operations (i.e., fast-forward and
rewind). We present an analytical model for evaluating the impact of the scan operations on the performance of disk-arr ay-based
servers. Our experiments demonstrate that: (1) employing our placement algorithm substantially reduces seek and rotational
latency overhead during playback, and (2) exploiting the characteristics of video streams and human perceptual tolerances
enables a server to support interactive scan operations without any additional overhead. 相似文献
15.
The major drawback of the existing cluster placement scheme is the long response time caused by admission control if the
number of clusters and the number of users are large. A circular skip-cluster placement scheme is proposed to reduce the size
of the data buffer as well as the system response time. Furthermore, the popularity of each video is different in the real
world. We propose a new popularity-based data allocation scheme to allocate data units within a cluster such that the corresponding
data units of these popular videos are stored in those cylinders at one end of each cluster. Due to a higher spatial locality
within these hot cylinders, some data units requested by the users are stored in the same cylinder such that one seek operation,
one rotation, and one transfer operation are required to retrieve these data units. Therefore, the time required to retrieve
data for these requests can be reduced, thus also reducing the system response time. Based on our results, the buffer size
and the system response time can be reduced by half or more. These findings are essential for constructing video-on-demand
systems that provide satisfactory performance. 相似文献
16.
Recent advances in storage technology, coupled with the
dramatic increase in the bandwidth of networks,
now make it possible to provide "video-on-demand" service to
viewers. A video-on-demand server is a
computer system that stores videos in compressed digital form
and provides support for
various portions of compressed video data to
be accessed and transmitted concurrently.
We present a low-cost storage architecture
for a video-on-demand server that relies principally on disks.
The high bandwidths of disks in conjunction with a
clever strategy for striping videos
on them enables
simultaneous
access and transmission of portions of a video,
separated by fixed time intervals.
We also present schemes for implementing
VCR-like functions including fast forward, rewind, and pause,
and extend our schemes to the case in which videos have
different rate requirements. 相似文献
17.
Yueh-Min Huang Jen-Wen Ding Shiao-Li Tsao 《The VLDB Journal The International Journal on Very Large Data Bases》1999,8(1):44-54
To provide high accessibility of continuous-media (CM) data, CM servers generally stripe data across multiple disks. Currently,
the most widely used striping scheme for CM data is round-robin permutation (RRP). Unfortunately, when RRP is applied to variable-bit-rate
(VBR) CM data, load imbalance across multiple disks occurs, thereby reducing overall system performance. In this paper, the
performance of a VBR CM server with RRP is analyzed. In addition, we propose an efficient striping scheme called constant
time permutation (CTP), which takes the VBR characteristic into account and obtains a more balanced load than RRP. Analytic
models of both RRP and CTP are presented, and the models are verified via trace-driven simulations. Analysis and simulation
results show that CTP can substantially increase the number of clients supported, though it might introduce a few seconds/minutes
of initial delay.
Received June 9, 1998 / Accepted January 21, 1999 相似文献
18.
Fast image retrieval using color-spatial information 总被引:1,自引:0,他引:1
Beng Chin Ooi Kian-Lee Tan Tat Seng Chua Wynne Hsu 《The VLDB Journal The International Journal on Very Large Data Bases》1998,7(2):115-128
In this paper, we present an image retrieval system that employs both the color and spatial information of images to facilitate
the retrieval process. The basic unit used in our technique is a single-colored cluster, which bounds a homogeneous region of that color in an image. Two clusters from two images are similar if they are of the
same color and overlap in the image space. The number of clusters that can be extracted from an image can be very large, and
it affects the accuracy of retrieval. We study the effect of the number of clusters on retrieval effectiveness to determine
an appropriate value for “optimal' performance. To facilitate efficient retrieval, we also propose a multi-tier indexing
mechanism called the Sequenced Multi-Attribute Tree (SMAT). We implemented a two-tier SMAT, where the first layer is used to prune away clusters that are of different colors,
while the second layer discriminates clusters of different spatial locality. We conducted an experimental study on an image
database consisting of 12,000 images. Our results show the effectiveness of the proposed color-spatial approach, and the efficiency
of the proposed indexing mechanism.
Received August 1, 1997 / Accepted December 9, 1997 相似文献
19.
In this paper, we present an efficient approach for supporting fast-scanning (FS) operations in MPEG-based video-on-demand
(VOD) systems. This approach is based on storing multiple, differently encoded versions of the same movie at the server. A
normal version is used for normal playback, while several scan versions are used for FS. Each scan version supports forward and backward FS at a given speedup. The server responds to an FS request
by switching from the normal version to an appropriate scan version. Scanning versions are produced by encoding a sample of
the raw frames using the same GOP pattern of the normal version. When a scanning version is decoded and played back at the
normal frame rate, it gives a perceptual motion speedup. By being able to control the traffic envelopes of the scan versions,
our approach can be integrated into a previously proposed framework for distributing archived, MPEG-coded video streams. FS
operations are supported using no or little extra network bandwidth beyond what is already allocated for normal playback.
Mechanisms for controlling the traffic envelopes of the scan versions are presented. The actions taken by the server and the
client's decoder in response to various types of interactive requests are described in detail. The latency incurred in implementing
various interactive requests is shown to be within an acceptable range. Striping and disk-scheduling strategies for storing
various versions at the server are presented. Issues related to the implementation of our approach are discussed. 相似文献
20.
This paper presents a new data placement scheme for continuous-media playback via a scalable storage system. Multimedia contents
are segmented into data blocks for the purpose of being stored, retrieved, and manipulated. If these data blocks belong to
some continuous media, then they must be handled in a timely manner, for example, being retrieved before some deadline. One
of the main challenges in implementing the above system is the simultaneous retrieval of a great number of different media
streams from a very large storage system. The proposed scheme efficiently reduces the seeking delay by a very simple placement
method and a retrieval scheduler. Thus, both the storage capacity and the number of concurrent accesses to the storage are
scalable. The performance of the proposed scheme is evaluated through a simple analytical model and a practical prototype
implementation. 相似文献