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15
Determining Optical Flow
 ARTIFICIAL INTELLIGENCE
, 1981
"... Optical flow cannot be computed locally, since only one independent measurement is available from the image sequence at a point, while the flow velocity has two components. A second constraint is needed. A method for finding the optical flow pattern is presented which assumes that the apparent veloc ..."
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Cited by 1747 (7 self)
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Optical flow cannot be computed locally, since only one independent measurement is available from the image sequence at a point, while the flow velocity has two components. A second constraint is needed. A method for finding the optical flow pattern is presented which assumes that the apparent velocity of the brightness pattern varies smoothly almost everywhere in the image. An iterative implementation is shown which successfully computes the optical flow for a number of synthetic image sequences. The algorithm is robust in that it can handle image sequences that are quantized rather coarsely in space and time. It is also insensitive to quantization of brightness levels and additive noise. Examples are included where the assumption of smoothness is violated at singular points or along lines in the image.
Manipulation and Compositing of MCDCT Compressed Video
, 1994
"... Many advanced video applications require manipulations of compressed video signals. Popular video manipulation functions include overlap (opaque or semitransparent), translation, scaling, linear filtering, rotation, and pixel multiplication. In this paper, we propose algorithms to manipulate compre ..."
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Cited by 94 (16 self)
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Many advanced video applications require manipulations of compressed video signals. Popular video manipulation functions include overlap (opaque or semitransparent), translation, scaling, linear filtering, rotation, and pixel multiplication. In this paper, we propose algorithms to manipulate compressed video in the compressed domain. Specifically, we focus on compression algorithms using the Discrete Cosine Transform (DCT) with or without Motion Compensation (MC). Compression systems of such kind include JPEG, Motion JPEG, MPEG, and H.261. We derive a complete set of algorithms for all aforementioned manipulation functions in the transform domain, in which video signals are represented by quantized transform coefficients. Due to a much lower data rate and the elimination of decompression/compression conversion, the transformdomain approach has great potential in reducing the computational complexity. The actual computational speedup depends on the specific manipulation functions and ...
Dynamic Estimation in Computational Vision
, 1992
"... Spatial coherence constraints are commonly used to regularize the problems of reconstructing dense visual fields like depth, shape, and motion. Recent developments in theory and practice show that the local nature of spatial coherence constraints allows us to solve singleframe reconstruction proble ..."
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Cited by 19 (4 self)
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Spatial coherence constraints are commonly used to regularize the problems of reconstructing dense visual fields like depth, shape, and motion. Recent developments in theory and practice show that the local nature of spatial coherence constraints allows us to solve singleframe reconstruction problems efficiently with, for example, multiresolution approaches. While it is reasonable to impose temporal as well as spatial coherence on the unknown for a more robust estimation through data fusion over both space and time, such temporal, multiframe extensions of the problems have not been as widely considered, perhaps due to the different and severe computational demands imposed by the sequential arrival of the image data. We present here an efficient filtering algorithm for sequential estimation of dense visual fields, using stochastic descriptor dynamic system models to capture temporal smoothness and dynamics of the fields. Theoretically, standard Kalman filtering techniques (generalized...
Realtime 23 pulldown elimination applying motion estimation/compensation in a programmable device
 IEEE Transaction on Consumer Electronics, Volume 44, Number
, 1988
"... A software package realizes realtime video processing on a commercially available programmable device 1. The software implements a motion estimator and a picture rate convertor to provide judderfree display of movie material broadcast in 2–3 pulldown mode. A new objectbased truemotion estimatio ..."
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Cited by 8 (3 self)
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A software package realizes realtime video processing on a commercially available programmable device 1. The software implements a motion estimator and a picture rate convertor to provide judderfree display of movie material broadcast in 2–3 pulldown mode. A new objectbased truemotion estimation algorithm efficiently uses the VLIW core of the processor. It permits quasisimultaneous motion estimation/segmentation for a fixed maximum number of objects. 1
Number of Solutions for Motion and Structure from Multiple Frame Correspondence
, 1997
"... Much of the dynamic computer vision literature deals with the determination of motion and structure by observing two frames captured at two instants of time. Motion prediction and understanding can be improved significantly, particularly in the presence of noise, by analyzing an image sequence conta ..."
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Cited by 5 (3 self)
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Much of the dynamic computer vision literature deals with the determination of motion and structure by observing two frames captured at two instants of time. Motion prediction and understanding can be improved significantly, particularly in the presence of noise, by analyzing an image sequence containing more than two frames. In this paper, we assume knowledge of correspondence of points on the surface of an object which is moving with constant motion, i.e. constant translation and constant rotation around an unknown center. We give a new formulation of the problem and prove that the following results hold in general for the number of solutions to motion and structure values (i.e. values of translation, rotation, and depth): (a) For three point correspondences over three views, there are at most two solutions, only one of which has all positive depth values; (b) For two point correspondences over four views, there is a unique solution; (c) For one point correspondence over five views, there can be up to ten solutions; (d) For one point correspondence over six view, there is a unique solution. The method of solution for each of the above formulations requires the solving of a system of multivariate polynomials, whose coefficients are functions of the observed data. In order to determine the number of solutions to these systems, we use theorems from algebraic geometry which imply that under a few mild conditions, the number of solutions at one set of data points provides an upper bound on the number of solutions for almost all sets of data points. Thus a bound on the number of solutions is obtained when a single system is solved by a method such as homotopy continuation, which we use here.
New Motion Estimation Algorithm Using Adaptively Quantized Low BitResolution Image and Its VLSI Architecture for MPEG2 Video Encoding
 IEEE Transactions on Circuits and Systems for Video Technology
, 1998
"... This paper describes a new motion estimation algorithm that is suitable for hardware implementation and substantially reduces the hardware cost by using a low bitresolution image in the block matching. In the low bitresolution image generation, adaptive quantization is employed to reduce the bit r ..."
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Cited by 4 (0 self)
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This paper describes a new motion estimation algorithm that is suitable for hardware implementation and substantially reduces the hardware cost by using a low bitresolution image in the block matching. In the low bitresolution image generation, adaptive quantization is employed to reduce the bit resolution of the pixel values, which is better than simple truncation of the least significant bits in preserving the dynamic range of the pixel values. The proposed algorithm consists of two search steps: in the lowresolution search, a set of candidate motion vectors is determined, and in the fullresolution search, the motion vector is found from these candidate motion vectors. The hardware cost of the proposed algorithm is 1/17 times of the full search algorithm, while its peak signaltonoise ratio is better than that of the 4 : 1 alternate subsampling for the search range of 632 2632: A VLSI architecture of the proposed algorithm is also described, which can concurrently perform two prediction modes of the MPEG2 video standard with the search range of (032.0,032.0)(+31.5,+31.5). We fabricated a MPEG2 motion estimator with a 0.5m triplemetal CMOS technology. The VLSI chip includes 110 K gates of random logic and 90 K bits of SRAM in a die size of 11.5 mm 2 12.5 mm. The full functionality of the fabricated chip was confirmed with an MPEG2 encoder chip.
Simplified Block Matching Algorithm for Fast Motion Estimation in Video Compression
"... Abstract: Block matching motion estimation was one of the most important modules in the design of any video encoder. It consumed more than 85 % of video encoding time due to searching of a candidate block in the search window of the reference frame. To minimize the search time on block matching, a s ..."
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Cited by 4 (0 self)
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Abstract: Block matching motion estimation was one of the most important modules in the design of any video encoder. It consumed more than 85 % of video encoding time due to searching of a candidate block in the search window of the reference frame. To minimize the search time on block matching, a simplified and efficient Block Matching Algorithm for Fast Motion Estimation was proposed. It had two steps such as prediction and refinement. The temporal correlation among successive frames and the direction of the previously processed frame for predicting the motion vector of the candidate block was considered during prediction step. Different combination of search points was considered in the refinement step of the algorithm which subsequently minimize the search time. Experiments were conducted on various SIF and CIF video sequences. The performance of the algorithm was compared with existing fast block matching motion estimation algorithms which were used in recent video coding standards. The experimental results were shown that the algorithm provided a faster search with minimum distortion when compared to the optimal fast block matching motion estimation algorithms. Key words: Block matching algorithm, motion estimation, video compression
Image and video compression: a survey
 International Journal of Imaging Systems and Technology
, 1999
"... ABSTRACT: At the present time, we stand upon the threshold of a revolution in the means available to us for the widespread dissemination of information in visual form through the rapidly increasing use of international standards for image and video compression. Yet, such standards, as observed by th ..."
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Cited by 3 (0 self)
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ABSTRACT: At the present time, we stand upon the threshold of a revolution in the means available to us for the widespread dissemination of information in visual form through the rapidly increasing use of international standards for image and video compression. Yet, such standards, as observed by the casual user, are only the tip of the coding iceberg. Something like half a century of scientific and technological development has contributed to a vast body of knowledge concerning techniques for coding still and moving pictures, and the present article presents a survey of developments which have taken place since the first (predictive) coding algorithms were implemented in the 1950s. Initially, we briefly review the characteristics of the human eye which influence how we approach the design of coding algorithms; then we examine the still picture techniques of major interest—predictive and transform coding, vector quantization, and subband and wavelet multiresolution approaches. Recognizing that other forms of algorithm have also been of interest during this period, we next consider such techniques as quadtree decomposition and segmentation before looking at the problems arising from the presence of motion and its compensation in the coding of video signals. In the next section, various approaches to the coding of image sequences are reviewed, and we concentrate upon the now universally used hybrid motion compensated transform algorithm before examining more advanced techniques such as model and objectbased coding. Of course, the key to widespread acceptance of any technological development is the establishment of standards, and all major proposals—JPEG, MPEGI,II, andIV, H.261, and H.263, are considered with emphasis on the way in which the coding algorithm is implemented rather than on protocol and syntax considerations. Finally, comments are offered in respect of the future viability of coding standards, of less wellresearched algorithms, and the overall position of image and video compression techniques in the rapidly developing field of visual information provision. © 1999 John Wiley &
Hierarchical Motion Compensated Deinterlacing
 In Proc.ofthe SPIE
, 1991
"... This paper introduces a new method of converting interlaced video to a progressively scanned video. The missing pixel values of the interlaced sequence are interpolated from past fields according to motion vectors found between the present and past. Hierarchical blockmatching motion estimation is u ..."
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Cited by 2 (0 self)
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This paper introduces a new method of converting interlaced video to a progressively scanned video. The missing pixel values of the interlaced sequence are interpolated from past fields according to motion vectors found between the present and past. Hierarchical blockmatching motion estimation is used in finding these motion vectors. This approach gives improved results over conventional deinterlacing methods such as median filtering and linear spatial interpolation. 1. INTRODUCTION Interlaced video is widely used in transmitting a sequence of images. Most television systems incorporate interlace for its many advantages, including the reduction of bandwith. However, some image processing tasks require that interlaced video be converted to progressively scanned video. Conversion of frame rates between different interlaced television standards is a good example. For television systems implementing progressively scanned display, deinterlacing is certainly a necessity. Motion estimatio...
Contentbased and perceptual bit allocation using Matching Pursuits
, 2001
"... When commu nicating at a verylow bitrate, video coders areu nable to preserve high visu al qu ality for all images. A selection of key regions according to hu man viewing anduSV rstanding may therefore beuN fu : it allows extracting essential featu res and to code them with a high qu ality, while ..."
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Cited by 1 (0 self)
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When commu nicating at a verylow bitrate, video coders areu nable to preserve high visu al qu ality for all images. A selection of key regions according to hu man viewing anduSV rstanding may therefore beuN fu : it allows extracting essential featu res and to code them with a high qu ality, while the remainder of the image is coarsely transmitted.Su ch an approach requ ires a signal decomposition allowing an adaptive spatial variant bit allocation. Matching Pu rsu its (MP) is an iterative proceduV leading tosu h a signal representation. Incorporated within a motion compensated video codec, MP allows for adaptive representation of the Displaced Frame Di#erence. Bit allocation procedu res for Matching Pu rsu its di#er from the onesu sed for DCT or other transform based signal representations. For transformbased methods, the signal is first projected on a complete set of orthogonal base fu nctions. Coe#cients are then qu antized. Thequ antization selects which information is transmitted. So, the selection is constrained by the chosen transform. On the contrary, MP explicitly select the information to be transmitted among a large and overcomplete set of fu nctions and qu antize it according to a fixed and constant step. For MP, bit allocation isequ ivalent to fu nction selection. This makes Matching Pu rsu its wellsu ited for spatial variant bit allocation, since fu nctions matched to important objects can be chosen. In this paper, we first show the abilities of Matching Pu3R2 ts to allocate an available bitbu2 et according to a semanticu3V rstanding of the scene. This semantic information can be provided eitherau tomatically or interactively. Second, the possibility to incorporate perceptive criteria within the MP coding algorithm is investigated. Key words: content...