References of "Van Droogenbroeck, Marc"
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See detailSatellite Communications
Van Droogenbroeck, Marc ULg

Learning material (2012)

Introduction to satellite communications.

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See detailDetection and Quantification of Efficiency and Quality of Gait Impairment in Multiple Sclerosis through Foot Path Analysis
PHAN BA, Remy ULg; Pierard, Sébastien ULg; MOONEN, Gustave ULg et al

Poster (2012, October 11)

Introduction: Walking speed is generally considered as the best outcome measure in trials for people with multiple sclerosis (pMS). We recently designed a device based on range laser scanner capable to ... [more ▼]

Introduction: Walking speed is generally considered as the best outcome measure in trials for people with multiple sclerosis (pMS). We recently designed a device based on range laser scanner capable to track feet paths of walking subjects. Our purpose was to explore gait descriptors of pMS and compare them with those of healthy volunteers (HV). Methods: Fourty-four pMS (considered as moderatly or highly disabled according to a cut-off EDSS value of 3.0) and 28 HV performed 4 walking tasks along 2 trajectories in 3 walking modes. Twenty-six gait descriptors crudely dichotomized in « efficiency» and « quality » of gait were compared in the 2 populations using unpaired t-tests. Results: (i) apart from an older age in pMS, the two populations were comparable, (ii) efficiency of gait descriptors including walking speed distinguished HV from pMS, and pMS with moderate from pMS with high disability, (iii) quality of gait descriptors were also significantly altered in pMS, including in walking tasks where their walking speed was comparable to that of HV. Conclusions: RLS technology can distinguish pMS from HV according to (i) more efficiency of gait descriptors than the sole walking speed and (ii) quality of gait descriptors, including in subjects with a « normal » walking speed. [less ▲]

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See detailAdaptive bilateral filtering for range images
Lejeune, Antoine ULg; Van Droogenbroeck, Marc ULg; Verly, Jacques ULg

in URSI Benelux Forum 2012 (2012, September 14)

We propose an improvement for range images of the standard bilateral filter consisting in adapting it locally to the distribution of the range noise at each pixel.

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See detailUtilisation de la Kinect
Lejeune, Antoine ULg; Pierard, Sébastien ULg; Van Droogenbroeck, Marc ULg et al

in Linux Magazine France (2012), 151

Fin 2010, Microsoft lançait la Kinect pour Xbox 360, la première caméra 3D destinée au grand public. Une semaine plus tard sortait la première librairie permettant d'utiliser l'appareil sur un ordinateur ... [more ▼]

Fin 2010, Microsoft lançait la Kinect pour Xbox 360, la première caméra 3D destinée au grand public. Une semaine plus tard sortait la première librairie permettant d'utiliser l'appareil sur un ordinateur personnel. Depuis lors, des centaines d'applications ont vu le jour utilisant l'information de profondeur capturée par la Kinect pour analyser le mouvement humain ou guider des robots. Dans cette article, nous allons voir comment développer une application utilisant la Kinect sous GNU/Linux. [less ▲]

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See detailBackground Subtraction: Experiments and Improvements for ViBe
Van Droogenbroeck, Marc ULg; Paquot, Olivier

in Change Detection Workshop (2012, June)

Motion detection plays an important role in most video based applications. One of the many possible ways to detect motion consists in background subtraction. This paper discusses experiments led for a ... [more ▼]

Motion detection plays an important role in most video based applications. One of the many possible ways to detect motion consists in background subtraction. This paper discusses experiments led for a particular background subtraction technique called ViBe. This technique models the background with a set of samples for each pixel and compares new frames, pixel by pixel, to determine if a pixel belongs to the background or to the foreground. In its original version, the scope of ViBe is limited to background modeling. In this paper, we introduce a series of modifications that alter the working of ViBe, like the inhibition of propagation around internal borders or the distinction between the updating and segmentation masks, or process the output, for example by some operations on the connected components. Experimental results obtained for video sequences provided on the workshop site validate the improvements of the proposed modifications. [less ▲]

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See detailLa détection de mouvement dans une vidéo: histoire d'une technologie et d'un brevet
Van Droogenbroeck, Marc ULg

Conference given outside the academic context (2012)

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See detailNeural networks for musical chords recognition
Osmalsky, Julien ULg; Embrechts, Jean-Jacques ULg; Van Droogenbroeck, Marc ULg et al

in Journées d'informatique musicale (2012, May)

In this paper, we consider the challenging problem of music recognition and present an effective machine learning based method using a feed-forward neural network for chord recognition. The method uses ... [more ▼]

In this paper, we consider the challenging problem of music recognition and present an effective machine learning based method using a feed-forward neural network for chord recognition. The method uses the known feature vector for automatic chord recognition called the Pitch Class Profile (PCP). Although the PCP vector only provides attributes corresponding to 12 semi-tone values, we show that it is adequate for chord recognition. Part of our work also relates to the design of a database of chords. Our database is primarily designed for chords typical of Western Europe music. In particular, we have built a large dataset filled with recorded guitar chords under different acquisition conditions (instruments, microphones, etc), but also with samples obtained with other instruments. Our experiments establish a twofold result: (1) the PCP is well suited for describing chords in a machine learning context, and (2) the algorithm is also capable to recognize chords played with other instruments, even unknown from the training phase. [less ▲]

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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 ▲]

Detailed reference viewed: 127 (18 ULg)