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1.
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
2.
The peer-to-peer (P2P) network structure is widely employed for video streaming applications because of its high stability, flexible extensibility, and ability to distribute data stream loading among different peer nodes. Numerous P2P schemes have been proposed for video on demand (VoD) applications. High video source searching cost and long response latency are always issues in dealing with VCR functionality, such as jump and fast-forward/rewind, because of asynchronous interactive and random join/leave behaviors of end users. To overcome this bottleneck, an interleaved video frame distribution (IVFD) scheme is proposed to support full VCR functionality in a P2P environment without searching for new sources. Instead of acquiring video stream data from a single parent peer in the published schemes, each child peer in the IVFD scheme can simultaneously acquire interleaved video data from multiple parent peers. When a client peer carries out arbitrary VCR operations, such as jump or fast-forward/rewind, its parent peers are still able to provide intermittent video stream data for the client peer; thus, no video source search is necessary. Simulation results reveal excellent load distribution performance and response latency for VCR operations in the proposed IVFD scheme. 相似文献
3.
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
4.
Easy-to-use audio/video authoring tools play a crucial role in moving multimedia software from research curiosity to mainstream
applications. However, research in multimedia authoring systems has rarely been documented in the literature. This paper describes
the design and implementation of an interactive video authoring system called Zodiac, which employs an innovative edit history abstraction to support several unique editing features not found in existing commercial
and research video editing systems. Zodiac provides users a conceptually clean and semantically powerful branching history model of edit operations to organize the authoring process, and to navigate among versions of authored documents. In addition,
by analyzing the edit history, Zodiac is able to reliably detect a composed video stream's shot and scene boundaries, which facilitates interactive video browsing.
Zodiac also features a video object annotation capability that allows users to associate annotations to moving objects in a video sequence. The annotations themselves could
be text, image, audio, or video. Zodiac is built on top of MMFS, a file system specifically designed for interactive multimedia development environments, and implements an internal buffer
manager that supports transparent lossless compression/decompression. Shot/scene detection, video object annotation, and buffer
management all exploit the edit history information for performance optimization. 相似文献
5.
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
6.
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
7.
Fast techniques for the optimal smoothing of stored video 总被引:3,自引:0,他引:3
Work-ahead smoothing is a technique whereby a server, transmitting stored compressed video to a client, utilizes client buffer
space to reduce the rate variability of the transmitted stream. The technique requires the server to compute a schedule of
transfer under the constraints that the client buffer neither overflows nor underflows. Recent work established an optimal
off-line algorithm (which minimizes peak, variance and rate variability of the transmitted stream) under the assumptions of
fixed client buffer size, known worst case network jitter, and strict playback of the client video. In this paper, we examine
the practical considerations of heterogeneous and dynamically variable client buffer sizes, variable worst case network jitter
estimates, and client interactivity. These conditions require on-line computation of the optimal transfer schedule. We focus on techniques for reducing on-line computation time. Specifically,
(i) we present an algorithm for precomputing and storing the optimal schedules for all possible client buffer sizes in a compact
manner; (ii) we show that it is theoretically possible to precompute and store compactly the optimal schedules for all possible
estimates of worst case network jitter; (iii) in the context of playback resumption after client interactivity, we show convergence
of the recomputed schedule with the original schedule, implying greatly reduced on-line computation time; and (iv) we propose
and empirically evaluate an “approximation scheme” that produces a schedule close to optimal but takes much less computation
time. 相似文献
8.
On fast microscopic browsing of MPEG-compressed video 总被引:1,自引:0,他引:1
Boon-Lock Yeo 《Multimedia Systems》1999,7(4):269-281
MPEG has been established as a compression standard for efficient storage and transmission of digital video. However, users
are limited to VCR-like (and tedious) functionalities when viewing MPEG video. The usefulness of MPEG video is presently limited
by the lack of tools available for fast browsing, manipulation and processing of MPEG video.
In this paper, we first address the problem of rapid access to individual shots and frames in MPEG video. We build upon the
compressed-video-processing framework proposed in [1, 8], and propose new and fast algorithms based on an adaptive mixture
of approximation techniques for extracting spatially reduced image sequence of uniform quality from MPEG video across different frame types and also under different motion activities in the scenes. The algorithms
execute faster than real time on a Pentium personal computer. We demonstrate how the reduced images facilitate fast and convenient
shot- and frame-level video browsing and access, shot-level editing and annotation, without the need for frequent decompression
of MPEG video. We further propose methods for reducing the auxiliary data size associated with the reduced images through
exploitation of spatial and temporal redundancy. We also address how the reduced images lead to computationally efficient algorithms for video analysis based
on intra- and inter-shot processing for video database and browsing applications. The algorithms, tools for browsing and techniques
for video processing presented in this paper have been used by many in IBM Research on more than 30 h of MPEG-1 video for
video browsing and analysis. 相似文献
9.
10.
In this paper, we present two novel disk failure recovery methods that utilize the inherent characteristics of video streams
for efficient recovery. Whereas the first method exploits the inherent redundancy in video streams (rather than error-correcting
codes) to approximately reconstruct data stored on failed disks, the second method exploits the sequentiality of video playback
to reduce the overhead of online failure recovery in conventional RAID arrays. For the former approach, we present loss-resilient
versions of JPEG and MPEG compression algorithms. We present an inherently redundant array of disks (IRAD) architecture that combines these loss-resilient compression algorithms with techniques for efficient placement of video streams
on disk arrays to ensure that on-the-fly recovery does not impose any additional load on the array. Together, they enhance
the scalability of multimedia servers by (1) integrating the recovery process with the decompression of video streams, and
thereby distributing the reconstruction process across the clients; and (2) supporting graceful degradation in the quality
of recovered images with increase in the number of disk failures. We present analytical and experimental results to show that
both schemes significantly reduce the failure recovery overhead in a multimedia server. 相似文献
11.
Query by video clip 总被引:15,自引:0,他引:15
Typical digital video search is based on queries involving a single shot. We generalize this problem by allowing queries
that involve a video clip (say, a 10-s video segment). We propose two schemes: (i) retrieval based on key frames follows the traditional approach of identifying shots, computing key frames from a video, and then extracting image features
around the key frames. For each key frame in the query, a similarity value (using color, texture, and motion) is obtained
with respect to the key frames in the database video. Consecutive key frames in the database video that are highly similar
to the query key frames are then used to generate the set of retrieved video clips. (ii) In retrieval using sub-sampled frames, we uniformly sub-sample the query clip as well as the database video. Retrieval is based on matching color and texture features
of the sub-sampled frames. Initial experiments on two video databases (basketball video with approximately 16,000 frames and
a CNN news video with approximately 20,000 frames) show promising results. Additional experiments using segments from one
basketball video as query and a different basketball video as the database show the effectiveness of feature representation
and matching schemes. 相似文献
12.
In video processing, a common first step is to segment the videos into physical units, generally called shots. A shot is a video segment that consists of one continuous action. In general, these physical units need to be clustered
to form more semantically significant units, such as scenes, sequences, programs, etc. This is the so-called story-based video
structuring. Automatic video structuring is of great importance for video browsing and retrieval. The shots or scenes are
usually described by one or several representative frames, called key-frames. Viewed from a higher level, key frames of some shots might be redundant in terms of semantics. In this paper, we propose
automatic solutions to the problems of: (i) video partitioning, (ii) key frame computing, (iii) key frame pruning. For the
first problem, an algorithm called “net comparison” is devised. It is accurate and fast because it uses both statistical and
spatial information in an image and does not have to process the entire image. For the last two problems, we develop an original
image similarity criterion, which considers both spatial layout and detail content in an image. For this purpose, coefficients
of wavelet decomposition are used to derive parameter vectors accounting for the above two aspects. The parameters exhibit
(quasi-) invariant properties, thus making the algorithm robust for many types of object/camera motions and scaling variances.
The novel “seek and spread” strategy used in key frame computing allows us to obtain a large representative range for the
key frames. Inter-shot redundancy of the key-frames is suppressed using the same image similarity measure. Experimental results
demonstrate the effectiveness and efficiency of our techniques. 相似文献
13.
In a video-on-demand (VOD) environment, disk arrays are often used to support the disk bandwidth requirement. This can pose
serious problems on available disk bandwidth upon disk failure. In this paper, we explore the approach of replicating frequently
accessed movies to provide high data bandwidth and fault tolerance required in a disk-array-based video server. An isochronous
continuous video stream imposes different requirements from a random access pattern on databases or files. Explicitly, we
propose a new replica placement method, called rotational mirrored declustering (RMD), to support high data availability for disk arrays in a VOD environment. In essence, RMD is similar to the conventional
mirrored declustering in that replicas are stored in different disk arrays. However, it is different from the latter in that
the replica placements in different disk arrays under RMD are properly rotated. Combining the merits of prior chained and
mirrored declustering methods, RMD is particularly suitable for storing multiple movie copies to support VOD applications.
To assess the performance of RMD, we conduct a series of experiments by emulating the storage and delivery of movies in a
VOD system. Our results show that RMD consistently outperforms the conventional methods in terms of load-balancing and fault-tolerance
capability after disk failure, and is deemed a viable approach to supporting replica placement in a disk-array-based video
server. 相似文献
14.
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
15.
Sibel Adalı K. Selçuk Candan Su-Shing Chen Kutluhan Erol V.S. Subrahmanian 《Multimedia Systems》1996,4(4):172-186
We describe how video data can be organized and structured so as to facilitate efficient querying. We develop a formal model
for video data and show how spatial data structures, suitably modified, provide an elegant way of storing such data. We develop
algorithms to process various kinds of video queries and show that, in most cases, the complexity of these algorithms is linear.
A prototype system, called the Advanced Video Information System (AVIS), based on these concepts, has been designed at the
University of Maryland. 相似文献
16.
Xiaodong Wen Theodore D. Huffmire Helen H. Hu Adam Finkelstein 《Multimedia Systems》1999,7(5):350-358
We present several algorithms suitable for analysis of broadcast video. First, we show how wavelet analysis of frames of
video can be used to detect transitions between shots in a video stream, thereby dividing the stream into segments. Next we
describe how each segment can be inserted into a video database using an indexing scheme that involves a wavelet-based “signature.”
Finally, we show that during a subsequent broadcast of a similar or identical video clip, the segment can be found in the
database by quickly searching for the relevant signature. The method is robust against noise and typical variations in the
video stream, even global changes in brightness that can fool histogram-based techniques. In the paper, we compare experimentally
our shot transition mechanism to a color histogram implementation, and also evaluate the effectiveness of our database-searching
scheme. Our algorithms are very efficient and run in realtime on a desktop computer. We describe how this technology could
be employed to construct a “smart VCR” that was capable of alerting the viewer to the beginning of a specific program or identifying 相似文献
17.
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
18.
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
19.
I/O scheduling for digital continuous media 总被引:4,自引:0,他引:4
A growing set of applications require access to digital video and audio. In order to provide playback of such continuous
media (CM), scheduling strategies for CM data servers (CMS) are necessary. In some domains, particularly defense and industrial process control, the timing requirements of these applications
are strict and essential to their correct operation. In this paper we develop a scheduling strategy for multiple access to
a CMS such that the timing guarantees are maintained at all times. First, we develop a scheduling strategy for the steady state,
i.e., when there are no changes in playback rate or operation. We derive an optimal Batched SCAN (BSCAN) algorithm that requires minimum buffer space to schedule concurrent accesses. The scheduling strategy incorporates two key
constraints: (1) data fetches from the storage system are assumed to be in integral multiples of the block size, and (2) playback
guarantees are ensured for frame-oriented streams when each frame can span multiple blocks. We discuss modifications to the
scheduling strategy to handle compressed data like motion-JPEG and MPEG.
Second, we develop techniques to handle dynamic changes brought about by VCR-like operations executed by applications. We define a suite of primitive VCR-like operations that can be executed. We show that an unregulated change in the BSCAN schedule, in response to VCR-like operations, will affect playback guarantees. We develop two general techniques to ensure playback guarantees while responding
to VCR-like operations: passive and active accumulation. Using user response time as a metric we show that active accumulation algorithms
outperform passive accumulation algorithms. An optimal response-time algorithm in a class of active accumulation strategies
is derived. The results presented here are validated by extensive simulation studies. 相似文献
20.
David Crandall Sameer Antani Rangachar Kasturi 《International Journal on Document Analysis and Recognition》2003,5(2-3):138-157
Abstract. The popularity of digital video is increasing rapidly. To help users navigate libraries of video, algorithms that automatically
index video based on content are needed. One approach is to extract text appearing in video, which often reflects a scene's
semantic content. This is a difficult problem due to the unconstrained nature of general-purpose video. Text can have arbitrary
color, size, and orientation. Backgrounds may be complex and changing. Most work so far has made restrictive assumptions about
the nature of text occurring in video. Such work is therefore not directly applicable to unconstrained, general-purpose video.
In addition, most work so far has focused only on detecting the spatial extent of text in individual video frames. However,
text occurring in video usually persists for several seconds. This constitutes a text event that should be entered only once
in the video index. Therefore it is also necessary to determine the temporal extent of text events. This is a non-trivial
problem because text may move, rotate, grow, shrink, or otherwise change over time. Such text effects are common in television
programs and commercials but so far have received little attention in the literature. This paper discusses detecting, binarizing,
and tracking caption text in general-purpose MPEG-1 video. Solutions are proposed for each of these problems and compared
with existing work found in the literature.
Received: January 29, 2002 / Accepted: September 13, 2002
D. Crandall is now with Eastman Kodak Company, 1700 Dewey Avenue, Rochester, NY 14650-1816, USA; e-mail: david.crandall@kodak.com
S. Antani is now with the National Library of Medicine, 8600 Rockville Pike, Bethesda, MD 20894, USA; e-mail: antani@nlm.nih.gov
Correspondence to: David Crandall 相似文献