Pierre Vandergheynst

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We study the effect of a violation of the strong equivalence principle (SEP) on the cosmic microwave background (CMB). Such a violation would modify the weight of baryons in the primordial gravitational potentials and hence their impact in the establishment of the photon-baryon plasma acoustic oscillations before recombination. This cosmological Nordtvedt effect alters the odd peaks height of the CMB temperature anisotropy power spectrum. A gravitational baryonic mass density of the universe may already be

Hybrid video coding combines together two stages: first, motion estimation and compensation predict each frame from the neighboring frames, then the prediction error is coded, reducing the correlation in the spatial domain. In this work, we focus on the latter stage, presenting a scheme that profits from some of the features introduced by the standard H.264/AVC for motion estimation and replaces the transform in the spatial domain. The prediction error is so coded using the matching pursuit algorithm which

This paper explores a novel approach for ventricular and atrial activities estimation in electrocardiogram (ECG) signals, based on sparse source separation. Sparse decompositions of ECG over signal-adapted multi-component dictionaries can lead to natural separation of its components. In this work, dictionaries of functions adapted to ventricular and atrial activities are respectively defined. Then, the weighted orthogonal matching pursuit algorithm is used to unmix the two components of ECG signals. Despite

This paper studies quantization error in the context of Matching Pursuit coded streams and proposes a new coefficient quantization scheme taking benefit of the Matching Pursuit properties. The coefficients energy in Matching Pursuit indeed decreases with the iteration number, and the decay rate can be upper-bounded with an exponential curve driven by the redundancy of the dictionary. The redundancy factor is therefore used to design an optimal a posteriori quantization scheme for multi-resolution Matching P

This paper presents a novel local motion estimation algorithm for omnidirectional images. The algorithm captures correlation between two spherical images of a scene, taken from arbitrary viewpoints, with the objective to reduce the encoding rate of these images. It first performs a multiresolution decomposition of the spherical images, in order to improve the consistency of the motion estimation, with a limited computational complexity. Then, it determines pairs of similar solid angles and matches blocks of

In this talk, we discuss the issue of source separation in a signal on the sphere or on the plane, relying on the sparsity of one signal component in a scale-discretized steerable wavelet basis. The steerability of wavelets allows to probe in detail the local morphology of a signal at each analysis scale. It gives access to local measures of signed-intensity, orientation, elongation, etc. The scale discretization of the wavelets allows the reconstruction of the signal analyzed. In this context, local direct

In this work we present a method to jointly separate active audio and visual structures on a given mixture. Blind Audiovisual Source Separation is achieved exploiting the coherence between a video signal and a one-microphone audio track. The efficient repr ...

We propose a new content-aware image resizing scheme, "Stream Carving", which is based on the well-known seam carving method. Our algorithm may introduce larger seams in the retargeted image, i.e. seams with a width larger than one pixel, that we call "str ...

In this work, we present a method that jointly separates active audio and visual structures on a given mixture. This new concept, the Blind Audiovisual Source Separation (BAVSS), is achieved by exploiting the coherence existing between the recorded signal of a video camera and only one microphone. An efficient representation of audio and video sequences allows to build robust audiovisual relationships between temporally correlated structures of both modalities or, what turns to be the same, two parts of the

Local Binary Descriptors are becoming more and more popular for image matching tasks, especially when going mobile. While they are extensively studied in this context, their ability to carry enough information in order to infer the original image is seldom ...

Matching pursuit decomposes a signal into a linear expansion of functions selected from a redundant dictionary, isolating the signal structures that are coherent with respect to a given dictionary. In this paper we focus on the Matching Pursuit representation of the displaced frame difference (dfd). In particular, we introduce a new dictionary for matching pursuit that efficiently exploits the signal structures of the dfd. We also propose a fast strategy to find the atoms exploiting the maximum of the absol

A method to extract patterns of activity from time series of data structured as a network of objects, the method comprising the steps of creating a base graph of similar or related items from a given corpus by comparing intrinsic features of the items, com ...

In this paper we propose a novel method which is able to detect and separate audio-visual sources present in a scene. Our method exploits the correlation between the video signal captured with a camera and a synchronously recorded one-microphone audio trac ...

The performance of audio source separation from underde- termined convolutive mixture assuming known mixing filters can be significantly improved by using an analysis sparse prior optimized by a reweighting l1 scheme and a wideband data- fidelity term, as ...

We continue the analysis of the continuous wavelet transform on the 2-sphere, introduced in a previous paper. After a brief review of the transform, we define and discuss the notion of directional spherical wavelet, i.e., wavelets on the sphere that are sensitive to directions. Then we present a calculation method for data given on a regular spherical grid . This technique, which uses the FFT, is based on the invariance of under discrete rotations around the z axis preserving the sampling. Next, a numerical

A new biologically-inspired vision sensor made of one hundred "eyes" is presented, which is suitable for real-time acquisition and processing of 3-D image sequences. This device, named the Panoptic camera, consists of a layered arrangement of approximately ...

We address the problem of depth and ego-motion estimation from omnidirectional images. We propose a correspondence-free structure from motion problem for images mapped on the 2-sphere. A novel graph-based variational framework is proposed for depth estimation. The problem is cast into a TV-L1 optimization problem that is solved by fast graph-based optimization techniques. The ego-motion is then estimated directly from the depth information without computation of the optical flow. Both problems are addressed

The purpose of this paper is to extend results by Villemoes about exponential convergence of Matching Pursuit with some structured dictionaries for simple functions in finite or infinite dimension. Our results are based on an extension of Tropp s results about Orthogonal Matching Pursuit in finite dimension, with the observation that it does not only work for OMP but also for MP. Our main contribution is a detailed analysis of the approximation and stability properties of MP with quasi-incoherent dictiona

We address the problem of coding video signals in the presence of correlated video side information. The correlated video signals may originate from cameras that monitor the same scene from different view points. We utilize motion-compensated temporal wavelet transforms to decorrelate the video signals in temporal direction. One camera signal will provide the side information to improve the coding of the second camera signal. The side information is utilized in the transform domain after disparity compensat

Pierre Vandergheynst

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Cosmic microwave background constraints on the strong equivalence principle

Hybrid Video Coding based on Bidimensional Matching Pursuit

Ventricular and Atrial Activity Estimation Through Sparse ECG Signal Decompositions

A Posteriori Quantized Matching Pursuit

Multiresolution Motion Estimation for Omnidirectional Images

Sparsity-based Source Separation with Scale-Discretized Steerable Wavelets

Blind Audiovisual Source Separation Using Sparse Representations

Stream Carving: an Adaptive Seam Carving Algorithm

Blind Audiovisual Source Separation Using Sparse Redundant Representations

From Bits to Images: Inversion of Local Binary Descriptors

A Variational Framework for Structure from Motion in Omnidirectional Image Sequences

New Dictionary and Fast Atom Searching Methods for Matching Pursuit Representation of Displaced Frame Difference

System, device, and method for contextual knowledge retrieval and display

Blind Audio-Visual Source Separation based on Sparse Redundant Representations

Reverberant Audio Source Separation via Sparse and Low-Rank Modeling

Wavelets on the sphere : Implementation and approximations

The PANOPTIC Camera: A Plenoptic Sensor with Real-Time Omnidirectional Capability

A Variational Framework for Structure from Motion in Omnidirectional Image Sequences

On the exponential convergence of matching pursuits in quasi-incoherent dictionaries

Video Coding with Motion-Compensated Temporal Transforms and Side Information