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1.
Transporting QoS adaptive flows 总被引:4,自引:0,他引:4
Distributed audio and video applications need to adapt to fluctuations in delivered quality of service (QoS). By trading
off temporal and spatial quality to available bandwidth, or manipulating the playout time of continuous media in response
to variation in delay, audio and video flows can be made to adapt to fluctuating QoS with minimal perceptual distortion. In
this paper, we extend our previous work on a QoS Architecture (QoS-A) by populating the QoS management planes of our architecture
with a framework for the control and management of multilayer coded flows operating in heterogeneous multimedia networking
environments. Two key techniques are proposed: i) an end-to-end rate-shaping scheme which adapts the rate of MPEG-coded flows
to the available network resources while minimizing the distortion observed at the receiver; and ii) an adaptive network service,
which offers “hard” guarantees to the base layer of multilayer coded flows and “fairness” guarantees to the enhancement layers
based on a bandwidth allocation technique called Weighted Fair Sharing. 相似文献
2.
E. Francesconi M. Gori S. Marinai G. Soda 《International Journal on Document Analysis and Recognition》2001,3(3):160-168
In this paper we describe the connectionist-based classification engine of an OCR system. The classification engine is based
on a new modular connectionist architecture, where a multilayer perceptron (MLP) acting as a classifier is properly combined
with a set of autoassociators – one for each class – trained to copy the input to the output layer. The MLP-based classifier
selects a small group of classes with high score, that are afterwards verified by the corresponding autoassociators. The learning
samples used to train the classifiers are constructed by means of a synthetic noise generator starting from few grey level
characters labeled by the user. We report experimental results for comparing three neural architectures: an MLP-based classifier,
an autoassociator-based classifier, and the proposed combined architecture. The experiments show that the proposed architecture
exhibits the best performance, without increasing significantly the computational burden.
Received March 6, 2000 / Revised July 12, 2000 相似文献
3.
Surface approximation to scanned data 总被引:6,自引:0,他引:6
A method to approximate scanned data points with a B-spline surface is presented. The data are assumed to be organized in
the form of Q
i,j, i=0,…,n; j=0,…,m
i, i.e., in a row-wise fashion. The method produces a C
(p-1, q-1) continuous surface (p and q are the required degrees) that does not deviate from the data by more than a user-specified tolerance. The parametrization
of the surface is not affected negatively by the distribution of the points in each row, and it can be influenced by a user-supplied
knot vector. 相似文献
4.
We propose a novel method, based on the two-pass Z-buffer algorithm, to calculate shadows with sufficient precision and efficiency for rendering a daytime landscape with solar
penumbrae. The special feature of the proposed method is that the shadows can be preserved with a precision superior to that
of any visible surface. We use the optimal number of plural shadow buffers to do this; it gives a fairly satisfying trade–off
between computation time and quality of shadows. 相似文献
5.
In this paper, we present a correlation scheme that incorporates a color ring-projection representation for the automatic
inspection of defects in textured surfaces. The proposed color ring projection transforms a 2-D color image into a 1-D color
pattern as a function of radius. For a search window of width W, data dimensionality is reduced from in the 2-D image to O(W) in the 1-D ring-projection space. The complexity of computing a correlation function is significantly reduced accordingly.
Since the color ring-projection representation is invariant to rotation, the proposed method can be applied for both isotropic
and oriented textures at arbitrary orientations. Experiments on regular textured surfaces have shown the efficacy of the proposed
method.
Received: 30 March 2000 / Accepted: 24 July 2001
Correspondence to: D.-M. Tsai (e-mail: iedmtsai@saturn.yzu.edu.tw) 相似文献
6.
I. Alexander 《Requirements Engineering》2002,6(4):252-255
Scenarios are ways of representing knowledge. They may take many forms, from films of real events through acted scenes to
documented procedures. These forms differ in many ways, including how vivid or abstract they are, how accessible they are
as specifications, and how effective they are in helping to elicit requirements. Scenarios, especially as Use Cases, are in
use or proposed for many aspects of systems engineering. Understanding of the different forms scenarios may take, and then
of the costs and benefits of applying these forms in practice, may be valuable. 相似文献
7.
Motion picture films are susceptible to local degradations such as dust spots. Other deteriorations are global such as intensity
and spatial jitter. It is obvious that motion needs to be compensated for before the detection/correction of such local and
dynamic defects. Therefore, we propose a hierarchical motion estimation method ideally suited for high resolution film sequences.
This recursive block-based motion estimator relies on an adaptive search strategy and Radon projections to improve processing
speed. The localization of dust particles then becomes straightforward. Thus, it is achieved by simple inter-frame differences
between the current image and motion compensated successive and preceding frames. However, the detection of spatial and intensity
jitter requires a specific process taking advantage of the high temporal correlation in the image sequence. In this paper,
we present our motion compensation-based algorithms for removing dust spots, spatial and intensity jitter in degraded motion
pictures. Experimental results are presented showing the usefulness of our motion estimator for film restoration at reasonable
computational costs.
Received: 9 July 2000 / Accepted: 13 January 2002
Correspondence to:S. Boukir 相似文献
8.
This paper describes a method for recognizing partially occluded objects under different levels of illumination brightness
by using the eigenspace analysis. In our previous work, we developed the “eigenwindow” method to recognize the partially occluded
objects in an assembly task, and demonstrated with sufficient high performance for the industrial use that the method works
successfully for multiple objects with specularity under constant illumination. In this paper, we modify the eigenwindow method
for recognizing objects under different illumination conditions, as is sometimes the case in manufacturing environments, by
using additional color information. In the proposed method, a measured color in the RGB color space is transformed into one
in the HSV color space. Then, the hue of the measured color, which is invariant to change in illumination brightness and direction,
is used for recognizing multiple objects under different illumination conditions. The proposed method was applied to real
images of multiple objects under various illumination conditions, and the objects were recognized and localized successfully. 相似文献
9.
We present an efficient and accurate method for retrieving images based on color similarity with a given query image or histogram.
The method matches the query against parts of the image using histogram intersection. Efficient searching for the best matching
subimage is done by pruning the set of subimages using upper bound estimates. The method is fast, has high precision and recall
and also allows queries based on the positions of one or more objects in the database image. Experimental results showing
the efficiency of the proposed search method, and high precision and recall of retrieval are presented.
Received: 20 January 1997 / Accepted: 5 January 1998 相似文献
10.
Using vanishing points for camera calibration and coarse 3D reconstruction from a single image 总被引:5,自引:0,他引:5
In this paper, we show how to calibrate a camera and to recover the geometry and the photometry (textures) of objects from
a single image. The aim of this work is to make it possible walkthrough and augment reality in a 3D model reconstructed from
a single image. The calibration step does not need any calibration target and makes only four assumptions: (1) the single
image contains at least two vanishing points, (2) the length (in 3D space) of one line segment (for determining the translation
vector) in the image is known, (3) the principle point is the center of the image, and (4) the aspect ratio is fixed by the
user. Each vanishing point is determined from a set of parallel lines. These vanishing points help determine a 3D world coordinate
system R
o. After having computed the focal length, the rotation matrix and the translation vector are evaluated in turn for describing
the rigid motion between R
o and the camera coordinate system R
c. Next, the reconstruction step consists in placing, rotating, scaling, and translating a rectangular 3D box that must fit
at best with the potential objects within the scene as seen through the single image. With each face of a rectangular box,
a texture that may contain holes due to invisible parts of certain objects is assigned. We show how the textures are extracted
and how these holes are located and filled. Our method has been applied to various real images (pictures scanned from books,
photographs) and synthetic images. 相似文献
11.
As feedback from Three Mile Island No. 2, a large amount of human–machine interface (HMI) design has been proposed to support
operators during accidents by presenting information on plant status, some of which is implemented in commercial nuclear power
plants (NPPs). However, it has not yet been discussed what role HMI should play under conditions where operators must take
action as instructed under emergency operating procedure. Regarding this principal issue, an HMI design is proposed together
with specific screen images. The advantage of this design is based on the involvement of an ex-operator in NPP in this paper.
The participation of users in the design of HMI has been rare. Accordingly the proposed HMI is comprehensive for average operators
and is expected to be acceptable for future implementation in commercial NPPs. The effectiveness of the proposed HMI has been
examined in a small experiment. 相似文献
12.
This paper presents an efficient method for creating the animation of flexible objects. The mass-spring model was used to
represent flexible objects. The easiest approach to creating animation with the mass-spring model is the explicit Euler method,
but the method has a serious weakness in that it suffers from an instability problem. The implicit integration method is a possible
solution, but a critical flaw of the implicit method is that it involves a large linear system. This paper presents an approximate
implicit method for the mass-spring model. The proposed technique updates with stability the state of n mass points in O(n) time when the number of total springs is O(n). In order to increase the efficiency of simulation or reduce the numerical errors of the proposed approximate implicit method,
the number of mass points must be as small as possible. However, coarse discretization with a small number of mass points
generates an unrealistic appearance for a cloth model. By introducing a wrinkled cubic spline curve, we propose a new technique
that generates realistic details of the cloth model, even though a small number of mass points are used for simulation. 相似文献
13.
Sonia Garcia-Salicetti Bernadette Dorizzi Patrick Gallinari Zsolt Wimmer 《International Journal on Document Analysis and Recognition》2001,4(1):56-68
In this paper, we present a hybrid online handwriting recognition system based on hidden Markov models (HMMs). It is devoted
to word recognition using large vocabularies. An adaptive segmentation of words into letters is integrated with recognition,
and is at the heart of the training phase. A word-model is a left-right HMM in which each state is a predictive multilayer
perceptron that performs local regression on the drawing (i.e., the written word) relying on a context of observations. A
discriminative training paradigm related to maximum mutual information is used, and its potential is shown on a database of
9,781 words.
Received June 19, 2000 / Revised October 16, 2000 相似文献
14.
Sérgio Vale Aguiar Campos Edmund Clarke 《International Journal on Software Tools for Technology Transfer (STTT)》1999,2(3):260-269
The task of checking if a computer system satisfies its timing specifications is extremely important. These systems are often
used in critical applications where failure to meet a deadline can have serious or even fatal consequences. This paper presents
an efficient method for performing this verification task. In the proposed method a real-time system is modeled by a state-transition
graph represented by binary decision diagrams. Efficient symbolic algorithms exhaustively explore the state space to determine
whether the system satisfies a given specification. In addition, our approach computes quantitative timing information such
as minimum and maximum time delays between given events. These results provide insight into the behavior of the system and
assist in the determination of its temporal correctness. The technique evaluates how well the system works or how seriously
it fails, as opposed to only whether it works or not. Based on these techniques a verification tool called Verus has been constructed. It has been used in the verification of several industrial real-time systems such as the robotics system
described below. This demonstrates that the method proposed is efficient enough to be used in real-world designs. The examples
verified show how the information produced can assist in designing more efficient and reliable real-time systems. 相似文献
15.
An alternative, hybrid approach for disparity estimation, based on the phase difference technique, is presented. The proposed
technique combines the robustness of the matching method with the sub-pixel accuracy of the phase difference approach. A matching
between the phases of the left and right signals is introduced in order to allow the phase difference method to work in a
reduced disparity range. In this framework, a new criterion to detect signal singularities is proposed. The presented test
cases show that the performance of the proposed technique in terms of accuracy and density of the disparity estimates has
greatly improved.
Received: 24 June 1997 / Accepted: 15 September 1998 相似文献
16.
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
17.
Abstract. We propose a new adaptive strategy for text recognition that attempts to derive knowledge about the dominant font on a given
page. The strategy uses a linguistic observation that over half of all words in a typical English passage are contained in
a small set of less than 150 stop words. A small dictionary of such words is compiled from the Brown corpus. An arbitrary
text page first goes through layout analysis that produces word segmentation. A fast procedure is then applied to locate the
most likely candidates for those words, using only widths of the word images. The identity of each word is determined using
a word shape classifier. Using the word images together with their identities, character prototypes can be extracted using
a previously proposed method. We describe experiments using simulated and real images. In an experiment using 400 real page
images, we show that on average, eight distinct characters can be learned from each page, and the method is successful on
90% of all the pages. These can serve as useful seeds to bootstrap font learning.
Received October 8, 1999 / Revised March 29, 2000 相似文献
18.
Delay-jitter control in multimedia applications 总被引:1,自引:0,他引:1
The growing needs of multimedia communications are leading to
new developments in providing real-time communication with guarantees.
Several extensions
have been proposed for different layers of the
Open Systems Interconnection Reference
Model to accomodate these
needs. In this paper, we study methods for guaranteeing delay jitter
bounds for high-speed networks in the network and application layers of
this model. The method proposed for the network layer
provides distributed jitter control. The method proposed
for the application layer allows the destination application to control
delay jitter. We use a simulation to compare the effects on delay
jitter in each
method for various scenarios, such as constant bit rate,
cross traffic, and bursty data. In addition, the buffer space
requirements for accommodating real-time channels are monitored at
each node in the network. 相似文献
19.
Abstract. The purpose of this study is to discuss existing fractal-based algorithms and propose novel improvements of these algorithms
to identify tumors in brain magnetic-response (MR) images. Considerable research has been pursued on fractal geometry in various
aspects of image analysis and pattern recognition. Magnetic-resonance images typically have a degree of noise and randomness
associated with the natural random nature of structure. Thus, fractal analysis is appropriate for MR image analysis. For tumor
detection, we describe existing fractal-based techniques and propose three modified algorithms using fractal analysis models.
For each new method, the brain MR images are divided into a number of pieces. The first method involves thresholding the pixel
intensity values; hence, we call the technique piecewise-threshold-box-counting (PTBC) method. For the subsequent methods,
the intensity is treated as the third dimension. We implement the improved piecewise-modified-box-counting (PMBC) and piecewise-triangular-prism-surface-area
(PTPSA) methods, respectively. With the PTBC method, we find the differences in intensity histogram and fractal dimension
between normal and tumor images. Using the PMBC and PTPSA methods, we may detect and locate the tumor in the brain MR images
more accurately. Thus, the novel techniques proposed herein offer satisfactory tumor identification.
Received: 13 October 2001 / Accepted: 28 May 2002
Correspondence to: K.M. Iftekharuddin 相似文献
20.
Making Workflow Change Acceptable 总被引:1,自引:0,他引:1
Virtual professional communities are supported by network information systems composed from standard Internet tools. To satisfy
the interests of all community members, a user-driven approach to requirements engineering is proposed that produces not only
meaningful but also acceptable specifications. This approach is especially suited for workflow systems that support partially structured, evolving work
processes. To ensure the acceptability, social norms must guide the specification process. The RENISYS specification method
is introduced, which facilitates this process using composition norms as formal representations of social norms. Conceptual
graph theory is used to represent four categories of knowledge definitions: type definitions, state definitions, action norms
and composition norms. It is shown how the composition norms guide the legitimate user-driven specification process by analysing
a case on the development of an electronic law journal. 相似文献