References of "Van Droogenbroeck, Marc"
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See detailRecognition of emotions in facial images
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

Report (2012)

This document reports about some work done in the field of emotions classification in facial images.

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See detailEstimation of human orientation based on silhouettes and machine learning principles
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International conference on pattern recognition applications and methods (ICPRAM) (2012, February)

Estimating the orientation of the observed person is a crucial task for home entertainment, man-machine interaction, intelligent vehicles, etc. This is possible but complex with a single camera because it ... [more ▼]

Estimating the orientation of the observed person is a crucial task for home entertainment, man-machine interaction, intelligent vehicles, etc. This is possible but complex with a single camera because it only provides one side view. To decrease the sensitivity to color and texture, we use the silhouette to infer the orientation. Under these conditions, we show that the only intrinsic limitation is to confuse the orientation q with the supplementary angle (that is 180°-theta), and that the shape descriptor must distinguish between mirrored images. In this paper, the orientation estimation is expressed and solved in the terms of a regression problem and supervised learning. In our experiments, we have tested and compared 18 shape descriptors; the best one achieves a mean error of 5:24°. However, because of the intrinsic limitation mentioned above, the range of orientations is limited to 180°. Our method is easy to implement and outperforms existing techniques. [less ▲]

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See detailDéveloppement d'un prototype exploitant les brevets ViBe et le chiffrement d'images
Schadeck, Damien ULg; Van Droogenbroeck, Marc ULg

Report (2012)

This report develops many software enhancements proposed to speed up ViBe, a patented technology designed to detect backgrounds and motion in video sequences. It also elaborates on a technology for the ... [more ▼]

This report develops many software enhancements proposed to speed up ViBe, a patented technology designed to detect backgrounds and motion in video sequences. It also elaborates on a technology for the partial encryption of images. [less ▲]

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See detailOn the human pose recovery based on a single view
Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in International conference on pattern recognition applications and methods (ICPRAM) (2012, February)

Estimating the pose of the observed person is crucial for a large variety of applications including home entertainment, man-machine interaction, video surveillance, etc. Often, only a single side view is ... [more ▼]

Estimating the pose of the observed person is crucial for a large variety of applications including home entertainment, man-machine interaction, video surveillance, etc. Often, only a single side view is available, but authors claim that it is possible to derive the pose despite that humans evolve in a 3D environment. In addition, to decrease the sensitivity to color and texture, it is preferable to rely only on the silhouette to recover the pose. Under these conditions, we show that there is an intrinsic limitation: at least two poses correspond to the observed silhouette. We discuss this intrinsic limitation in details in this short paper. To our knowledge, this issue has been overlooked by authors in the past. We observe that this limitation has an impact on the way previous reported results should be interpreted, and it has clearly to be taken into account for designing new methods. [less ▲]

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See detailMultimodal evaluation of gait and stride dynamics in relapsing and progressive forms of multiple sclerosis
Belachew, Shibeshih ULg; Pierard, Sébastien ULg; PHAN BA, Remy ULg et al

in Proceedings of the Belgian Royal Academies of Medicine (2012), 1

Ambulation measures are being increasingly recognized as highly relevant to the quantification of multiple sclerosis (MS) severity and response to treatment. Feet paths are highly informative for gait ... [more ▼]

Ambulation measures are being increasingly recognized as highly relevant to the quantification of multiple sclerosis (MS) severity and response to treatment. Feet paths are highly informative for gait analysis and we have recently designed a new system, which captures the position of the feet in real time. We use several range laser scanners (RLS) to analyze a horizontal slice of the scene in which each foot is considered as a point, and the vertical movements are ignored. Neat ambulation measures may be easily extracted such as walking speed, distance between feet over time, swing phase duration, and gait asymmetry in specific settings of walking recommendations. Our RLS platform is much cheaper than existing sensor-based and motion capture systems and may be more convenient for the development of multicentric clinical trials settings since patients can be easily and rapidly assessed without tags or sensors in the hallway of an outpatient clinic. We use 4 BEA LZR-i100 RLS arranged in a corridor of at least 10m long and 4m width, devoid of obstacle. The scanned plane is chosen to be located at 15 cm above the floor, which is right above the tibio-tarsal joint of the ankle in a barefoot configuration for adult individuals in stance phase. We expect further studies to validate and empower the meaning of non-intrusive RLS-derived gait measures that should pave the ground for major improvements in the way we will assess the efficacy of disease-modifying treatments (DMTs), physical therapy and symptomatic interventions on walking impairment, ataxia and fatigability in MS. RLS-derived gait measures may also reveal to be crucial in the near future for the development of treatments that would specifically target progressive forms of MS. [less ▲]

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See detailThe secrets of the Kinect ... in depth!
Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg; Verly, Jacques ULg

Conference (2011, December 08)

The slides present the Kinect in depth. The major technological ideas are explained. In addition, the presentation gives an overview of all the libraries available to interface to the Kinect.

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See detailA new jump edge detection method for 3D cameras
Lejeune, Antoine ULg; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg et al

in International Conference on 3D Imaging (IC3D) (2011, December)

Edges is a fundamental clue for analyzing, interpreting, and understanding 3D scenes: they describe objects boundaries. Available edge detection methods are not suited for 3D cameras such as the Microsoft ... [more ▼]

Edges is a fundamental clue for analyzing, interpreting, and understanding 3D scenes: they describe objects boundaries. Available edge detection methods are not suited for 3D cameras such as the Microsoft Kinect or a time-of-flight camera: they are slow and do not take into consideration the characteristics of the cameras. In this paper, we present a fast jump edge detection technique for 3D cameras based on the principles of Canny’s edge detector. We first analyze the characteristics of the range signal for two different kinds of cameras: a time-of-flight camera (the PMD[vision] CamCube) and the Microsoft Kinect. From this analysis, we define appropriate operators and thresholds to perform the edge detection. Then, we present some results of the developed algorithms for both cameras. [less ▲]

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See detailA new low-cost and non-intrusive feet tracker
Pierard, Sébastien ULg; PHAN BA, Remy ULg; Van Droogenbroeck, Marc ULg et al

in Workshop on Circuits, Systems and Signal Processing (ProRISC) (2011, November)

Capturing gait is useful for many applications, including video-surveillance and medical purposes. The most common sensors used to capture gait suffer from significant drawbacks. We have therefore ... [more ▼]

Capturing gait is useful for many applications, including video-surveillance and medical purposes. The most common sensors used to capture gait suffer from significant drawbacks. We have therefore designed a new low-cost and nonintrusive system to capture gait. Our system is able to track the feet on the horizontal plane in both the stance and the swing phases by combining measures of several range laser scanners. The number of sensors can be adjusted according to the target application specifications. The first issue addressed in this work is the calibration: we have to know the precise location of the sensors in a plane, and their orientations. The second issue addressed is how to calculate feet coordinates from the distance profiles given by the sensors. Our method has proven to be robust and precise to measure gait abnormalities in various medical conditions, especially neurological diseases (with a focus on multiple sclerosis). [less ▲]

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See detail3D Vision
Van Droogenbroeck, Marc ULg

Learning material (2011)

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See detailVisual Background Extractor
Van Droogenbroeck, Marc ULg; Barnich, Olivier

Patent (2011)

The present invention relates to a Visual Background Extractor (VIBE) consisting in a method for detecting a background in an image selected from a plurality of related images. Each one of said set of ... [more ▼]

The present invention relates to a Visual Background Extractor (VIBE) consisting in a method for detecting a background in an image selected from a plurality of related images. Each one of said set of images is formed by a set of pixels, and captured by an imaging device. This background detection method comprising the steps of: establishing, for a determined pixel position in said plurality of images, a background history comprising a plurality of addresses, in such a manner as to have a sample pixel value stored in each address; comparing the pixel value corresponding to said determined pixel position in the selected image with said background history, and, if said pixel value from the selected image substantially matches at least a predetermined number of said sample pixel values: classifying said determined pixel position as belonging to the image background; and—updating said background history by replacing the sample pixel values in one randomly chosen address of said background history with said pixel value from the selected image. The method of the invention is applicable a.o. for video surveillance purposes, videogame interaction and imaging devices with embedded data processors. [less ▲]

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See detailAnalysis of a robot positioning system based on a rotating receiver, beacons, and coded signals
Pierlot, Vincent ULg; Van Droogenbroeck, Marc ULg

in Proceedings of the European Signal Processing Conference (EUSIPCO) (2011, August)

Positioning is a fundamental issue in mobile robot applications that can be achieved in multiple ways. Among these methods, triangulation with active beacons is widely used, robust, accurate, and flexible ... [more ▼]

Positioning is a fundamental issue in mobile robot applications that can be achieved in multiple ways. Among these methods, triangulation with active beacons is widely used, robust, accurate, and flexible. In this paper, we analyze the performance of an original system, introduced in a one of our previous papers, that comprises a rotating receiver and beacons that send an On-Off Keying modulated infrared signal. The probability density function of the measured angles is established and discussed. In particular, it is shown that the proposed estimator is a non biased estimator of the beacon angular position. We also evaluate the theoretical results by means of both a simulator and measurements. [less ▲]

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See detailEstimation of human orientation in images captured with a range camera
Pierard, Sébastien ULg; Leroy, Damien; Hansen, Jean-Frédéric et al

in Advanced Concepts for Intelligent Vision Systems (ACIVS) (2011, August)

Estimating the orientation of the observed person is a crucial task for some application fields like home entertainment, man-machine interaction, or intelligent vehicles. In this paper, we discuss the ... [more ▼]

Estimating the orientation of the observed person is a crucial task for some application fields like home entertainment, man-machine interaction, or intelligent vehicles. In this paper, we discuss the usefulness of conventional cameras for estimating the orientation, present some limitations, and show that 3D information improves the estimation performance. Technically, the orientation estimation is solved in the terms of a regression problem and supervised learning. This approach, combined to a slicing method of the 3D volume, provides mean errors as low as 9.2° or 4.3° depending on the set of considered poses. These results are consistent with those reported in the literature. However, our technique is faster and easier to implement than existing ones. [less ▲]

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See detailObject descriptors based on a list of rectangles: method and algorithm
Van Droogenbroeck, Marc ULg; Pierard, Sébastien ULg

in Soille (Ed.) International Symposium on Mathematical Morhology (ISMM) (2011, July)

Most morphological operators use a unique structuring element, possibly at different scales, to describe an object. In addition, morphological algorithms are often restricted to 1D structuring elements ... [more ▼]

Most morphological operators use a unique structuring element, possibly at different scales, to describe an object. In addition, morphological algorithms are often restricted to 1D structuring elements, combinations of 1D elements, or isotropic structuring elements (like circles), because of the lack of methods directly applicable to 2D structuring elements. While these descriptors have proved useful in the past, we propose an alternative that uses the list of maximal rectangles contained in a set X. In particular, we focus on an opening that preserves large rectangles contained in a set X and on its companion 2D algorithm that builds a list of all the maximal rectangles that fit inside an arbitrary set X. This list is the base of new descriptors that have been used successfully for machine learning tasks. [less ▲]

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See detailVisual background extractor
Van Droogenbroeck, Marc ULg; Barnich, Olivier

Patent (2011)

The present invention relates to a VIsual Background Extractor ( VIBE ) consisting in a method for detecting a background in an image selected from a plurality of related images. Each one of said set of ... [more ▼]

The present invention relates to a VIsual Background Extractor ( VIBE ) consisting in a method for detecting a background in an image selected from a plurality of related images. Each one of said set of images is formed by a set of pixels, and captured by an imaging device. This background detection method comprising the steps of: - establishing, for a determined pixel position in said plurality of images, a background history comprising a plurality of addresses, in such a manner as to have a sample pixel value stored in each address; - comparing the pixel value corresponding to said determined pixel position in the selected image with said background history, and, if said pixel value from the selected image substantially matches at least a predetermined number of said sample pixel values: - classifying said determined pixel position as belonging to the image background; ; and - updating said background history by replacing the sample pixel values in one randomly chosen address of said background history with said pixel value from the selected image. The method of the invention is applicable a.o. for video surveillance purposes, videogame interaction and imaging devices with embedded data processors. [less ▲]

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See detailViBe: A universal background subtraction algorithm for video sequences
Barnich, Olivier; Van Droogenbroeck, Marc ULg

in IEEE Transactions on Image Processing (2011), 20(6), 1709-1724

This paper presents a technique for motion detection that incorporates several innovative mechanisms. For example, our proposed technique stores, for each pixel, a set of values taken in the past at the ... [more ▼]

This paper presents a technique for motion detection that incorporates several innovative mechanisms. For example, our proposed technique stores, for each pixel, a set of values taken in the past at the same location or in the neighborhood. It then compares this set to the current pixel value in order to determine whether that pixel belongs to the background, and adapts the model by choosing randomly which values to substitute from the background model. This approach differs from those based on the classical belief that the oldest values should be replaced first. Finally, when the pixel is found to be part of the background, its value is propagated into the background model of a neighboring pixel. We describe our method in full details (including pseudocode and the parameter values used) and compare it to other background subtraction techniques. Efficiency figures show that our method outperforms recent and proven state-of-the-art methods in terms of both computation speed and detection rate. We also analyze the performance of a downscaled version of our algorithm to the absolute minimum of one comparison and one byte of memory per pixel. It appears that even such a simplified version of our algorithm performs better than mainstream techniques. There is a dedicated web page for ViBe at http://www.motiondetection.org [less ▲]

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See detailA new three object triangulation algorithm based on the power center of three circles
Pierlot, Vincent ULg; Van Droogenbroeck, Marc ULg; Urbin-Choffray, Maxime

in Research and Education in Robotics (EUROBOT) (2011, June)

Positioning is a fundamental issue in mobile robot applications that can be achieved in multiple ways. Among these methods, triangulation is a proven technique. As it exists for a long time, many variants ... [more ▼]

Positioning is a fundamental issue in mobile robot applications that can be achieved in multiple ways. Among these methods, triangulation is a proven technique. As it exists for a long time, many variants of triangulation have been proposed. Which variant is most appropriate depends on the application because some methods ignore the beacon ordering while other have blind spots. Some methods are reliable but at a price of increasing complexity or special cases study. In this paper, we present a simple and new three object triangulation algorithm. Our algorithm works in the whole plane (except when the beacons and the robot are concyclic or colinear), and for any beacon ordering. Moreover, it does not need special cases study and has a strong geometrical meaning. Benchmarks show that our algorithm is faster than existing and comparable algorithms. Finally, a quality measure is intrinsically derived for the triangulation result in the whole plane, which can be used to identify the pathological cases, or as a validation gate in Kalman filters. [less ▲]

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See detailA probabilistic pixel-based approach to detect humans in video streams
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

in International Conference on Acoustics, Speech, and Signal Processing (ICASSP 2011) (2011, May)

Human detection in video streams is an important task in many applications including video surveillance. Surprisingly, only few papers have been devoted to this topic. This paper presents a new approach ... [more ▼]

Human detection in video streams is an important task in many applications including video surveillance. Surprisingly, only few papers have been devoted to this topic. This paper presents a new approach to detect humans in video streams. Our approach is based on the temporal information present in videos. A background subtraction algorithm is first used to segment the silhouettes of the users and the moving objects. Then a classification process in two steps determines for each connected component if it corresponds to the silhouette of a human or not. During the first step, a probabilistic information is computed for each pixel independently. The information from a subset of pixels is then gathered to predict the class of the observed silhouette. This paper presents the principles and some results obtained on real silhouettes. It is shown that our approach is efficient for the detection of humans in video streams. [less ▲]

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See detailA virtual curtain for the detection of humans and access control
Barnich, Olivier; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg

in Advanced Concepts for Intelligent Vision Systems (ACIVS) (2010, December)

Biometrics has become a popular field for the development of techniques that aim at recognizing humans based upon one or more intrinsic physical or behavioral traits. In particular, many solutions ... [more ▼]

Biometrics has become a popular field for the development of techniques that aim at recognizing humans based upon one or more intrinsic physical or behavioral traits. In particular, many solutions dedicated to access control integrate biometric features like fingerprinting or face recognition. This paper describes a new method designed to interpret what happens when crossing an invisible vertical plane, called virtual curtain hereafter, at the footstep of a door frame. It relies on the use of two laser scanners located in the upper corners of the frame, and on the classification of the time series of the information provided by the scanners after registration. The technique is trained and tested on a set of sequences representative for multiple scenarios of normal crossings by a single person and for tentatives to fool the system. We present the details of the technique and discuss classification results. It appears that the technique is capable to recognize many scenarios which may lead to the development of new commercial applications. [less ▲]

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See detail3D information is valuable for the detection of humans in video streams
Pierard, Sébastien ULg; Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg

in 3D Stereo Media (2010, December)

In this paper, we propose a technique based on 3D information (also called depth or range) for the detection of humans. First, a background subtraction technique operates to detect the silhouettes of ... [more ▼]

In this paper, we propose a technique based on 3D information (also called depth or range) for the detection of humans. First, a background subtraction technique operates to detect the silhouettes of humans and objects moving in the scene. Then, a machine learning algorithm is used to predict if a silhouette annotated with depth matches a human silhouette or not. The complete method is designed to cope with defects introduced during the segmentation step. Results, obtained on computer generated data, show that 3D depth data is a valuable information for detecting humans in that it improves over techniques based on binary silhouettes. In our experiments, we have reached an accuracy of 99.9% thanks to the depth information. [less ▲]

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