Publications de Martin Vetterli

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Proposes some simple algorithms for decoding BCH codes. The authors show that the pruned FFT is an effective method for evaluating syndromes and for finding the roots of error-locator polynomials. They show that a simple variation of the basic Gaussian elimination procedure can be adapted to compute the error-locator polynomial efficiently for codes with small designed distance. Finally, they give a procedure for computing the error values that has half the complexity of the Forney algorithm.

We study an acoustic tomography problem and propose a new inversion technique based on sparsity. Acoustic tomography observes the parameters of the medium that influence the speed of sound propagation. In the human body, the parameters that mostly influenc ...

We study the calibration process in circular ultrasound tomography devices where the sensor positions deviate from the circumference of a perfect circle. This problem arises in a variety of applications in signal processing ranging from breast imaging to s ...

In real-word applications, signal processing is often used to measure and control a physical field by means of sensors and sources, respectively. An aspect that has been often neglected is the optimization of the sources' locations. In this work, we discuss the source placement problem as the dual of the sensor placement problem and propose two polynomial-time algorithms, for scenarios with or without noise. Both algorithms are near-optimal and indicate the possibility to make the control of such physical f

The paper studies wavelet transform extrema and zero-crossings representations within the framework of convex representations in L(Z). Wavelet zero-crossings representation of two-dimensional signals is introduced as a convex multiscale edge representation as well. One appealing property of convex representations is that the reconstruction problem can be solved, at least theoretically, using the method of alternating projections onto convex sets. It turns out that in the case of the wavelet extrema and wave

We show a rate-distortion optimal way to threshold or drop the DCT coefficients of the JPEG and MPEG compression standards. Our optimal algorithm uses a fast dynamic programming recursive structure. The primary advantage of our approach lies in its complete compatibility with standard JPEG and MPEG decoders.

Consider the problem of sampling signals which are not bandlimited, but still have a finite number of degrees of freedom per unit of time, such as, for example, nonuniform splines or piecewise polynomials, and call the number of degrees of freedom per unit ...

Classical sampling theory for sampling and reconstructing bandlimited fields in

\Re^d

addresses the problem of sampling on lattice points. We consider a generalization of this problem, in which one samples the field along

1

-dimensional spatial trajectories in

\Re^d

rather than at points. The process of sampling records the value of the field at all points on the sampling trajectories. Such a sampling setup is relevant in the problem of spatial sampling using mobile sensors. We study various possible d

We consider three-dimensional cubic barcodes, consisting of smaller cubes, each built from one of two possible materials and carry one bit of information. To retrieve the information stored in the barcode, we measure a 2-D projection of the barcode using a ...

What makes a source–channel communication system optimal? It is shown that in order to achieve an optimal cost–distortion tradeoff, the source and the channel have to be matched in a probabilistic sense. The match (or lack of it) involves the source distribution, the distortion measure, the channel conditional distribution, and the channel input cost func- tion. Closed-form necessary and sufficient expressions relating the above entities are given. This generalizes both the separa- tion-based approach as we

The literature on gradient and differential microphone arrays makes a distinction between the two types, and nevertheless shows how both types can be used to obtain the same directional responses. A more theoretically sound rationale for using delays in differential microphone arrays has not yet been given. This paper presents a gradient analysis of the sound field viewed as a spatio-temporal phenomenon, and gives a theoretical interpretation of the working principles of gradient and differential microphone

Aliasing artifacts in images are visually very disturbing. Therefore, most imaging devices apply a low-pass filter before sampling. This removes all aliasing from the image, but it also creates a blurred image. Actually, all the image information above hal ...

Accuracy of simple analog-to-digital conversion depends on both resolution of discretization in amplitude and resolution of discretization in time. For implementation convenience, high conversion accuracy is attained by refining the discretization in time using oversampling. It is commonly believed that oversampling adversely impacts rate-distortion properties of the conversion, since the bit rate, B, increases linearly with oversampling, resulting in a slow error decay in the bit rate, on the order of O(1/

Over the last decade or so, wavelets have had a growing impact on signal processing theory and practice, both because of the unifying role and their successes in applications. Filter banks, which lie at the heart of wavelet-based algorithms, have become standard signal processing operators, used routinely in applications ranging from compression to modems. The contributions of wavelets have often been in the subtle interplay between discrete-time and continuous-time signal processing. The purpose of this ar

This toolkit has everything you need to perform imaging with a lensless camera. We make use of a low-cost implementation of DiffuserCam, namely replacing the lens with a piece of tape and using the Raspberry Pi HQ camera sensor. Similar principles and meth ...

Massive Open Online Courses (MOOCs) have become an emergent paradigm of large-scale knowledge distribution, have generated wide interest in the higher education community and are anticipated by many to bring impact to the future of higher education. In this research project, we study the learning analytics and learner dynamics of a pilot MOOC, the Digital Signal Processing (DSP) MOOC on Coursera. In the first part, we study the learning analytics using scheduling theories and ranking algorithms; in the seco

We address the problem of integrating directional analysis of sound into the filterbank of a spatial audio coder, with the purpose of processing and coding with some degree of inde- pendence the plane waves traveling in different directions. A plane wave r ...

The information content of binaural signals can be beneficial to many algorithms deployed in current digital hearing aids. However, the exchange of such signals over a wireless communication link requires transmission schemes that must fulfill demanding te ...

We study the design of sampling trajectories for stable sampling and the reconstruction of bandlimited spatial fields using mobile sensors. The spectrum is assumed to be a symmetric convex set. As a performance metric we use the path density of the set of ...

This paper deals with multiwavelets and the different properties of approximation and smoothness that are associated with them. In particular, we focus on the important issue of the preservation of discrete time polynomial signals by multiwavelet based filter banks. We give here a precise definition of balancing for higher degree discrete time polynomial signals and link it to a very natural factorization of the lowpass refinement mask that is the counterpart of the well-known 'zeros at pi' condition on the

Martin Vetterli

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Simple algorithms for BCH decoding

Efficient and Stable Acoustic Tomography Using Sparse Reconstruction Methods

Calibration Using Matrix Completion with Application to Ultrasound Tomography

Near-Optimal Source Placement for Linear Physical Fields

Discrete-Time Wavelet Extrema Representation - Design and Consistent Reconstruction

Rate-distortion optimal fast thresholding with complete JPEG/MPEG decoder compatibility

Sampling Moments and Reconstructing Signals of Finite Rate of Innovation: Shannon Meets Strang-Fix

Sampling Trajectories for Mobile Sensing

Three-Dimensional Cubic Barcodes

To code or not to code: lossy source-channel communication revisited

Spatio-Temporal Gradient Analysis of Differential Microphone Arrays

Super-Resolution from Highly Undersampled Images

Error-rate characteristics of oversampled analog-to-digital conversion

Wavelets, approximation, and compression

LenslessPiCam: A Hardware and Software Platform for Lensless Computational Imaging with a Raspberry Pi

Analysis and Design of Large-scale Online Classes

Coding of spatio-temporal audio spectra using tree-structured directional filterbanks

Distributed Spatial Audio Coding in Wireless Hearing Aids

On Minimal Trajectories for Mobile Sampling of Bandlimited Fields

High Order Balanced MultiWavelets: Theory, Factorization and Design