Showing papers in "IEEE Signal Processing Magazine in 1999"
TL;DR: The article provides arguments in favor of an alternative approach that uses splines, which is equally justifiable on a theoretical basis, and which offers many practical advantages, and brings out the connection with the multiresolution theory of the wavelet transform.
Abstract: The article provides arguments in favor of an alternative approach that uses splines, which is equally justifiable on a theoretical basis, and which offers many practical advantages. To reassure the reader who may be afraid to enter new territory, it is emphasized that one is not losing anything because the traditional theory is retained as a particular case (i.e., a spline of infinite degree). The basic computational tools are also familiar to a signal processing audience (filters and recursive algorithms), even though their use in the present context is less conventional. The article also brings out the connection with the multiresolution theory of the wavelet transform. This article attempts to fulfil three goals. The first is to provide a tutorial on splines that is geared to a signal processing audience. The second is to gather all their important properties and provide an overview of the mathematical and computational tools available; i.e., a road map for the practitioner with references to the appropriate literature. The third goal is to give a review of the primary applications of splines in signal and image processing.
1,732 citations
TL;DR: This article introduces the so-called model-based (or parametric) time-frequency analysis method, and introduces the basic concepts and well-tested algorithms for joint time- frequencies analysis.
Abstract: It has been well understood that a given signal can be represented in an infinite number of different ways. Different signal representations can be used for different applications. For example, signals obtained from most engineering applications are usually functions of time. But when studying or designing the system, we often like to study signals and systems in the frequency domain. Although the frequency content of the majority of signals in the real world evolves over time, the classical power spectrum does not reveal such important information. In order to overcome this problem, many alternatives, such as the Gabor (1946) expansion, wavelets, and time-dependent spectra, have been developed and widely studied. In contrast to the classical time and frequency analysis, we name these new techniques joint time-frequency analysis. We introduce the basic concepts and well-tested algorithms for joint time-frequency analysis. Analogous to the classical Fourier analysis, we roughly partition this article into two parts: the linear (e.g., short-time Fourier transform, Gabor expansion) and the quadratic transforms (e.g., Wigner-Ville (1932, 1948) distribution). Finally, we introduce the so-called model-based (or parametric) time-frequency analysis method.
699 citations
TL;DR: The application of high-order adaptive filters to the problem of acoustical echo cancellation with particular application to hands free telephone systems is discussed and a means to achieve robust performance is described.
Abstract: We have discussed the application of high-order adaptive filters to the problem of acoustical echo cancellation with particular application to hands free telephone systems. We described a means to achieve robust performance. We further presented methods for reducing computational complexity that allow implementation in low-cost, fixed-point digital signal processors. Progress in technology will allow the use of more sophisticated algorithms at lower cost in the near future.
428 citations
TL;DR: The estimation of 2D motion from time-varying images is reviewed, showing that even ideal constraints may not provide a well-defined estimation criterion and presenting several fast search strategies for the optimization of an estimation criterion.
Abstract: We have reviewed the estimation of 2D motion from time-varying images, paying particular attention to the underlying models, estimation criteria, and optimization strategies. Several parametric and nonparametric models for the representation of motion vector fields and motion trajectory fields have been discussed. For a given region of support, these models determine the dimensionality of the estimation problem as well as the amount of data that has to be interpreted or transmitted thereafter. Also, the interdependence of motion and image data has been addressed. We have shown that even ideal constraints may not provide a well-defined estimation criterion. Therefore, the data term of an estimation criterion is usually supplemented with a smoothness term that can be expressed explicitly or implicitly via a constraining motion model. We have paid particular attention to the statistical criteria based on Markov random fields. Because the optimization of an estimation criterion typically involves a large number of unknowns, we have presented several fast search strategies.
395 citations
TL;DR: This article motivates the structure from motion (SfM) approaches by describing some current practical applications and the reliability and flexibility of the approach in those settings, and concludes with results from an independent evaluation study conducted by industry where the proposed SfM algorithm compared favorably to alternative approaches.
Abstract: This article motivates the structure from motion (SfM) approaches by describing some current practical applications. This is followed by a brief discussion of the background of the field. Then, several techniques are outlined that show various important approaches and paradigms to the SfM problem. Critical issues, advantages and disadvantages are pointed out. Subsequently, we present our SfM approach for recursive estimation of motion, structure, and camera geometry in a nonlinear dynamic system framework. Results are given for synthetic and real images. These are used to assess the accuracy and stability of the technique. We then discuss some practical and real-time applications we have encountered and the reliability and flexibility of the approach in those settings. Finally, we conclude with results from an independent evaluation study conducted by industry where the proposed SfM algorithm compared favorably to alternative approaches.
236 citations
TL;DR: A unified view of algorithms for adaptive transversal FIR filtering and system identification has been presented, and the LMS algorithm and its offspring have been presented and interpreted as stochastic approximations of iterative deterministic steepest descent optimization schemes.
Abstract: A unified view of algorithms for adaptive transversal FIR filtering and system identification has been presented. Wiener filtering and stochastic approximation are the origins from which all the algorithms have been derived, via a suitable choice of iterative optimization schemes and appropriate design parameters. Following this philosophy, the LMS algorithm and its offspring have been presented and interpreted as stochastic approximations of iterative deterministic steepest descent optimization schemes. On the other hand, the RLS and the quasi-RLS algorithms, like the quasi-Newton, the FNTN, and the affine projection algorithm, have been derived as stochastic approximations of iterative deterministic Newton and quasi-Newton methods. Fast implementations of these methods have been discussed. Block-adaptive, and block-exact adaptive filtering have also been considered. The performance of the adaptive algorithms has been demonstrated by computer simulations.
232 citations
TL;DR: A unifying view of the dynamic programming approach to the search problem from the statistical point-of-view is given and how the search space results from the acoustic and language models required by the statistical approach are shown.
Abstract: The authors gives a unifying view of the dynamic programming approach to the search problem. They review the search problem from the statistical point-of-view and show how the search space results from the acoustic and language models required by the statistical approach. Starting from the baseline one-pass algorithm using a linear organization of the pronunciation lexicon, they have extended the baseline algorithm toward various dimensions. To handle a large vocabulary, they have shown how the search space can be structured in combination with a lexical prefix tree organization of the pronunciation lexicon. In addition, they have shown how this structure of the search space can be combined with a time-synchronous beam search concept and how the search space can be constructed dynamically during the recognition process. In particular, to increase the efficiency of the beam search concept, they have integrated the language model look-ahead into the pruning operation. To produce sentence alternatives rather than only the single best sentence, they have extended the search strategy to generate a word graph. Finally, they have reported experimental results on a 64 k-word task that demonstrate the efficiency of the various search concepts presented.
194 citations
TL;DR: The first generation of 3D television will be a two-image system comprising a pair of images directed to the appropriate viewers' eyes by means of steering optics controlled by a head-position tracker.
Abstract: In this article, the requirements for 3D television are outlined, and the suitability of different display types are considered. A brief description of our own approach is offered, which suggests that the first generation of 3D television will be a two-image system comprising a pair of images directed to the appropriate viewers' eyes. This will be achieved by means of steering optics controlled by a head-position tracker.
158 citations
TL;DR: This article showed that JTF analysis is a useful tool for improving radar signal and image processing for time- and frequency-varying cases and applied it to radar backscattering and feature extraction.
Abstract: The Fourier transform has been widely used in radar signal and image processing. When the radar signals exhibit time- or frequency-varying behavior, an analysis that can represent the intensity or energy distribution of signals in the joint time-frequency (JTF) domain is most desirable. In this article, we showed that JTF analysis is a useful tool for improving radar signal and image processing for time- and frequency-varying cases. We applied JTF analysis to radar backscattering and feature extraction; we also examined its application to radar imaging of moving targets. Most methods of JTF analysis are non-parametric. However, parametric or model-based methods of time-frequency analysis, such as adaptive Gaussian and chirplets, are more suitable for radar signals and images.
147 citations
TL;DR: This article provides an overview of current techniques for dense geometric correspondence estimation and focuses on the Bayesian approach, which is very well suited for this task, and for which several promising algorithms have previously been developed.
Abstract: This article provides an overview of current techniques for dense geometric correspondence estimation. We first formally define geometric correspondence and investigate the different types of image pairs. Then, we briefly look at the classic approaches to correspondence estimation, at their feasibility and flaws for simultaneous dense estimation. We focus on the Bayesian approach, which is very well suited for this task, and for which several promising algorithms have previously been developed.
84 citations
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TL;DR: The authors discuss immersive audio systems and the signal processing issues that pertain to the acquisition and subsequent rendering of 3D sound fields over loudspeakers and the commercial implications of audio DSP.
Abstract: The authors discuss immersive audio systems and the signal processing issues that pertain to the acquisition and subsequent rendering of 3D sound fields over loudspeakers. On the acquisition side, recent advances in statistical methods for achieving acoustical arrays in audio applications are reviewed. Classical array signal processing addresses two major aspects of spatial filtering, namely localization of a signal of interest, and adaptation of the spatial response of an array of sensors to achieve steering in a given direction. The achieved spatial focusing in the direction of interest makes array signal processing a necessary component in immersive sound acquisition systems. On the rendering side, 3D audio signal processing methods are described that allow rendering of virtual sources around the listener using only two loudspeakers. Finally, the authors discuss the commercial implications of audio DSP.
TL;DR: Different techniques for object-based stereoscopic image sequence coding are reviewed and the various models used for representing motion and structure are reviewed.
Abstract: The author begins by discussing what object based coding is and goes on to consider the structure of object based stereoscopic coders. Different techniques for object-based stereoscopic image sequence coding are reviewed. These techniques basically differ in the way they define models and estimate model parameters. We review the various models used for representing motion and structure. Then we review segmentation techniques, and discuss coding of object parameters and image synthesis.
TL;DR: The article introduces the search problem, discusses in detail a typical implementation of a search engine, and demonstrates the efficacy of this approach on a range of problems, which is scalable across a wide range of applications.
Abstract: Large vocabulary continuous speech recognition (LVCSR) systems have advanced significantly due to the ability to handle extremely large problem spaces in fairly small amounts of memory. The article introduces the search problem, discusses in detail a typical implementation of a search engine, and demonstrates the efficacy of this approach on a range of problems. The approach presented is scalable across a wide range of applications. It is designed to address research needs, where a premium is placed on the flexibility of the system architecture, and the needs of application prototypes, which require near-real-time speed without a great sacrifice in word error rate (WER). One major area of focus for researchers is the development of real-time systems. With only minor degradations in performance (typically, no more than a 25% increase in WER), the systems described in this article can be transformed into systems that operate at 10/spl times/RT or less. There are four active areas of research related to this problem. First, more intelligent pruning algorithms that prune the search space more heavily are required. Look-ahead and N-best strategies at all levels of the system are key to achieving such large reductions in the search space. Second, multi-pass systems that perform a quick search using a simple system, and then rescore only the N-best resulting hypotheses using better models are very popular for real-time implementation. Third, since much of the computation in these systems is devoted to acoustic model processing, fast-matching strategies within the acoustic model are important. Finally, since Gaussian evaluation at each state in the system is a major consumer of CPU time, vector quantization-like approaches that enable one to compute only a small number of Gaussians per frame are proven to be successful. In some sense, the Viterbi (1967) based system presented represents only one path through this continuum of recognition search strategies.
TL;DR: It is shown that using the Gabor expansion is a way to achieve a good echo cancellation algorithm that has a fast convergence rate, small steady-state residual echo, and less implementation cost.
Abstract: A good echo cancellation algorithm should have a fast convergence rate, small steady-state residual echo, and less implementation cost. The normalized least mean square (NLMS) adaptive filtering algorithm may not achieve this goal. We show that using the Gabor expansion is a way to achieve this goal. For direct digital signal processing compatibility the Gabor expansion introduced in this paper is for discrete-time signals, although the Gabor expansion also can be used for continuous-time signals. The Gabor expansion can be defined as a discrete-time signal representation in the joint time-frequency domain of a weighted sum of the collection of functions (known as the synthesis functions). There are several design issues in the echo canceller based on the Gabor expansion: the design of the analysis functions for the far-end speech, the design of the analysis functions for the near-end signal containing the echo plus the near-end speech, the design of the adaptive filters in the subsignal path, and the design of the synthesis functions. All the adaptive filters are designed using identical NLMS adaptive filtering algorithms.
Journal Article•
TL;DR: As the early history of music is one of the most interesting as well as one the most obscure topics connected with the art, an authoritative new investigation like that before us is of real value.
Abstract: MUSIC is now being cultivated in a much more earnest and thorough manner than heretofore, not only as a practical art, but as a matter of theoretical and historical interest, as is evidenced by the late formation of a “Society for the study of the Art and Science of Music,” the object of which is to encourage musical studies of a higher character than those comprised in ordinary musical training. Hence, as the early history of music is one of the most interesting as well as one of the most obscure topics connected with the art, an authoritative new investigation like that before us is of real value.The History of Music. Vol. 1. From the Earliest Records to the Fall of the Roman Empire. By William Chappell. (London: Chappell and Co., 1874.)
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TL;DR: A method is proposed, to make the calibration technique adaptive through the analysis of natural scene features, allowing the camera parameters to hold accurate throughout the acquisition session in the presence of parameter drift.
Abstract: In this article, we present some simple and effective techniques for accurately calibrating a multi-camera acquisition system. The proposed methods were proven to be capable of accurate results even when using very simple calibration target sets and low-cost imaging devices, such as standard TV-resolution cameras connected to commercial frame-grabbers. In fact, the performance of our calibration approach yielded results that were about the same as that of other traditional calibration methods based on large 3D target sets. The proposed calibration strategy is based on a multi-view multi-camera approach. This was based on the analysis of a number of views of a simple calibration target-set placed in different (unknown) positions. Furthermore, the method is based on a self-calibration approach, which can refine the a priori knowledge of the world coordinates of the targets (even when such information is very poor) while estimating the parameters of the camera model. Finally we proposed a method, to make the calibration technique adaptive through the analysis of natural scene features, allowing the camera parameters to hold accurate throughout the acquisition session in the presence of parameter drift.
TL;DR: This past year marked the genesis of the Signal Processing for Communications (SPCOM) Technical Committee (TC), which was formed during ICASSPPS in Seattle, WA and carries the responsibilities of running andsponsor-ing workshops; recommending editors, papers, and society awards; and reviewing submissions to ICasSP-and SPCOM-related meetings.
Abstract: article celebrates and highlights 50 years of signal processing technology as it has been ,ip-plied to communications systems. It also looks forward to some of the numerous opportunities t h s exciting area opens up for signal processing research and development. This comes at a time when we witness a dramatic upswing in modern telecommunications worldwide. Over the past 50 years, the SP community has contributed to the communications evolution a plethora of analytical tools (for compres-of computing and communicating devices, the widespread internet access through the World Wide Web, proliferation of wireless links, and an increasing demand for mobile cellular services at the consumer-end, habe all prompted the IEEE Signal Processing Society (SPS) to join focused efforts and contribute enthusiastically to re-Georjios B. Gzannakis is with the University of Minnesota alizing the dream of \" communicating with anyone, anywhere, anytime. \" In addition to celebrating our society's 50th anniversary , this past year marked the genesis of the Signal Processing for Communications (SPCOM) Technical Committee (TC). This comes in response to our mem-bers' increasing interest in SPCOM subjects, evidenced by the growing number of SPCOM-related publications in our transactions, international conferences, and workshops. Such an interest reflects a corresponding need to disseminate information, and streamline, review, facilitate , and support SP research and development in telecommunications a view also shared by educational institutions , government, and industrial agencies. With these long-term objectives, the SPCOM TC was formed during ICASSPPS in Seattle, WA. On par with other TCs of our society, the SPCOM TC carries the responsibilities of running and (co-)sponsor-ing workshops; recommending editors, papers, and society awards; and reviewing submissions to ICASSP-and SPCOM-related meetings. SPCOM TC sponsors the workshop on Signal Processing Advances in Wireless
TL;DR: The authors discuss how disparity-based processing can be used both for compression of multiview video data, and generation of arbitrary viewpoints from the available information of multiple cameras in the context of the MPEG-4 multimedia standard.
Abstract: The authors discuss how disparity-based processing can be used both for compression of multiview video data, and generation of arbitrary viewpoints from the available information of multiple cameras in the context of the MPEG-4 multimedia standard. The examples and results presented here show that viewpoint adaptation toward video objects can be accomplished with low-complexity schemes such as disparity-compensated projection, while high-quality results are presented. The ability to process multiview video is another example of the high flexibility of the MPEG-4 standard, which we expect to be applicable to various new challenging services in the multimedia market.
TL;DR: The Media Immersion Environment will serve well as a national testbed for the future work of integrated media systems, as the integrated media system develops new, interrelated ways for humans to gather and manipulate information.
Abstract: As multimedia technologies have progressed, it has become evident that a unifying vehicle would serve to give needed direction to research in the related disciplines. The Media Immersion Environment fills that role as an overarching, unifying framework. The engine within the MIE framework has evolved to become the integrated media system, a computer-based facility powering the convergence of multimedia technologies. As the integrated media system develops new, interrelated ways for humans to gather and manipulate information, these new ways fall under the abstract, centering vision of cooperative immersipresence: a controlled, customized multimedia universe. MIE will serve well as a national testbed for the future work of integrated media systems.
TL;DR: The Department of Electrical and Computer Engineering at the University of Illinois recently adopted new undergraduate curricula, and the introduction of ECE 210, Analog Signal Processing, in place of both the sophomore-level circuit analysis course and the junior-level signals and systems course is introduced.
Abstract: The Department of Electrical and Computer Engineering at the University of Illinois recently adopted new undergraduate curricula. The most radical change was the introduction of ECE 210, Analog Signal Processing, in place of both the sophomore-level circuit analysis course and the junior-level signals and systems course. The new course combines core material from these traditional courses, along with applications such as AM radio and a modest laboratory component, in a way that improves both the students’ understanding and their motivation. The new course still serves well as the base of the required curriculum and as a prerequisite for subsequent courses, while realizing savings in the early curriculum and allowing more time for advanced signal processing and systems courses in future semesters .
TL;DR: It is commonly believed that the time-varying frequency characteristics are important for the inelastic response of structures, but much more in-depth research is necessary before any meaningful engineering design conclusions can be reached.
Abstract: It is commonly believed that the time-varying frequency characteristics are important for the inelastic response of structures. Design code modification means structural cost changes; therefore any change must be based on solid evidence. Although the significance of time-varying frequency characteristics to ground motion has been recognized for a while, much more in-depth research is necessary before any meaningful engineering design conclusions can be reached. We apply joint time-frequency analysis techniques to a fully non-stationary ground motion model, with both intensity and frequency being non-stationary. The chirplet-based signal approximation is used to extract the time-varying frequencies from seismic ground-motion data samples. Based on that information, we compute the frequency-dependent modulating function in the stochastic model of the evolutionary random process. We generate and compare the artificial waves based on stochastic models of a uniform modulating random process and an evolutionary random process, separately. We also investigate the importance of the time-varying frequency characteristics of earthquake ground motion through an oscillator, with a single degree of freedom and elastic-plastic material behavior.
TL;DR: Recent breakthroughs in signal processing fundamentals that have happened in the last two decades include various advances and extensions from old techniques to new techniques, which have resulted in new tools that find applications in various domains.
Abstract: In this article members of the Digital Signal Processing (DSP) Technical Committee (TC) report recent breakthroughs in signal processing fundamentals that have happened in the last two decades. These breakthroughs include various advances and extensions from old techniques to new techniques. For example, signal processing techniques have moved from single-rate to multirate processing, from time-invariant to adaptive processing, from frequency-domain (the traditional Fourier transform, as we know it) to time-frequency analysis, and from linear to non-linear signal processing. Recent developments in these areas have not only renovated the theory of digital signal processing, they have also resulted in new tools that find applications in various domains. For instance, multirate signal processing has triggered recent advances in modem technology and speech/audio coding; adaptive filtering has made echo cancellation and noise suppression possible; time-frequency analysis has found its way into various applications in radar and medical signal processing; and non-linear processing has made engineers rethink various problems in speech recognition and image analysis. This article provides an extensive list of highlights from these recent developments.
TL;DR: An attempt is made to provide a historical overview of signal processing through the present, followed by a highly personal speculation for the future.
Abstract: Multimedia, as an application, has at its very core the field of signal processing technology. In this article, an attempt is made to provide a historical overview of signal processing through the present, followed by a highly personal speculation for the future. As important as the multimedia technology is today, its further dramatic growth is predictable. Technological constraints, such as communication bandwidth, processing components, availability of open standards, and display technologies are being successfully addressed by industry. Signal processing technologies have made important contributions to all areas of multimedia and will continue to do so. Signal processing has been particularly important in all areas of compression, modeling, and the entire field of digital representation of complex signals.
TL;DR: In this article, a top-down course sequence that uses as its underlying principle the transmission and manipulation of information has been developed, with the goals of helping students appreciate electrical and computer engineering and framing a context for advanced courses.
Abstract: Traditional introductory courses in electrical engineering are typically circuit theory courses, which may include both analog and digital hardware and possibly software. The alternatives have focused on how to teach (using discrete-time signals rather than analog) than on what to teach. We developed a top-down course sequence that uses as its underlying principle the transmission and manipulation of information. Students are given a broad perspective of both analog and digital approaches, with the goals of helping students appreciate electrical and computer engineering and framing a context for advanced courses. Laboratories stress construction of analog systems and analysis with signal processing tools.
TL;DR: The paper reviews the developments in DSP education by dividing them into two categories, and describes curriculum changes, ranging from reorganisation to radical reformation, which provide a more central role for signal processing in electrical and computer engineering training.
Abstract: The paper reviews the developments in DSP education by dividing them into two categories. The first describes curriculum changes, most of which have been classroom tested in their early forms. These proposals, ranging from reorganisation to radical reformation, all provide a more central role for signal processing in electrical and computer engineering training. The second category examines the future learning environment for DSP.
TL;DR: A wide range of graduate and undergraduate degree programs related to integrated media systems on behalf of the Integrated Media Systems Center (IMSC), for the School of Engineering at the University of Southern California, are described.
Abstract: For four years, we have been developing a wide range of graduate and undergraduate degree programs related to integrated media systems on behalf of the Integrated Media Systems Center (IMSC), for the School of Engineering at the University of Southern California (USC). The IMSC is a National Science Foundation Engineering Research Center (ERC) that became operational in 1996. It is not an academic department; however, one of its important missions is education. Most of the developed degree programs have been for engineering students, but one is available to all students. These degree programs are administered either by an academic department (e.g., computer science) or by an assistant dean of the School of Engineering. The purpose of this article is to not only describe these degree programs, but to also provide some lessons that have been learned along the way, lessons that may help expedite the development of similar programs at other universities.
TL;DR: Systems is already in place, rccogiiizing that iiiost uiiticrgraduate proglaiiis i n HE include an introciuciory co~irsc 011 signals n n c i systcnis that is Iiccdcd is tlic vision and willpower to make it happen.
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TL;DR: In the 20th Ccnttuy, serials hecaiiie associated with pulp ami sci-ciicc fiction and, as " The Shadow Knows, " with ~ c c l d p radio shows.
Abstract: pnblishcd in instull-nlcnts-llcas a lllotlcy history. I t startcd as a scan1 whcn, tdlow-iiig the Stamp Act of 171 2, iicwspa-per publishers in lhgland pacldcd the news with reprints of portions of novels to create a clocumcnt long cnough to C O l l l l t as a palllphlct (Llll-caxcd) rathcr tllall 3s a ncwspapcr (taxed). Serials came into tlicir owii with l>icltcns's I'iclzii~ick l'apm, the first major novel to sec first light as a serial, followed I)p such illustrious novels as Eliot's Middlemarch, 1 lardy's 7bc IlehLm of the 1\\lntive, Eve11 p c try-nll ~ nyson's Idylls of the Kipg-appcarcd as a serial. In the 20th Ccnttuy, serials hecaiiie associated with pulp ami sci-ciicc fiction and, as \" The Shadow Knows, \" with ~ c c l d p radio shows.