News & Events

80 Events and Talks were found.


  •  TALK   Sparse projections onto convex sets
    Date: Tuesday, July 3, 2012
    Speaker: Prof. Volkan Cevher, EPFL
    MERL Host: Petros Boufounos
    Research Area: Multimedia
    Brief
    • Many natural and man-made signals exhibit a few degrees of freedom relative to their dimension due to natural parameterizations or constraints. The inherent low-dimensional structure of such signals are mathematically modeled via combinatorial and geometric concepts, such as sparsity, unions-of-subspaces, or spectral sets, and are now revolutionizing the way we address linear inverse problems from incomplete data.

      In this talk, we describe a set of structured sparse models for constrained linear inverse problems that feature exact and epsilon-approximate projections in polynomial time. We pay particular attention to the sparsity models based on matroids, multi-knapsack, and clustering as well as spectrally constrained models. We then study sparse projections onto convex sets, such as the (general) simplex, and ell-1,2,inf balls. Finally, we describe a hybrid optimization framework which explicitly leverages these non-convex models along with additional convex constraints to obtain better recovery performance in compressive sensing, learn interpretable sparse densities from finite samples, and improved sparse Markowitzs portfolios with better return/cost performance.
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  •  EVENT   ICASSP 2012 - Special Session on Signal-Processing Challenges and Opportunities in Depth Cameras
    Date & Time: Friday, March 30, 2012; 2:00 PM - 4:00 PM
    MERL Contact: Anthony Vetro
    Location: Kyoto, Japan
    Research Area: Multimedia
    Brief
    • Anthony Vetro co-organized a Special Session of ICASSP 2012 on Signal-Processing Challenges and Opportunities in Depth Cameras. ICASSP 2012 will be held in Kyoto, Japan, in March 2012.
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  •  TALK   Learning Intermediate-Level Representations of Form and Motion from Natural Movies
    Date & Time: Wednesday, February 22, 2012; 11:00 AM
    Speaker: Dr. Charles Cadieu, McGovern Institute for Brain Research, MIT
    MERL Host: Jonathan Le Roux
    Research Areas: Multimedia, Speech & Audio
    Brief
    • The human visual system processes complex patterns of light into a rich visual representation where the objects and motions of our world are made explicit. This remarkable feat is performed through a hierarchically arranged series of cortical areas. Little is known about the details of the representations in the intermediate visual areas. Therefore, we ask the question: can we predict the detailed structure of the representations we might find in intermediate visual areas?

      In pursuit of this question, I will present a model of intermediate-level visual representation that is based on learning invariances from movies of the natural environment and produces predictions about intermediate visual areas. The model is composed of two stages of processing: an early feature representation layer, and a second layer in which invariances are explicitly represented. Invariances are learned as the result of factoring apart the temporally stable and dynamic components embedded in the early feature representation. The structure contained in these components is made explicit in the activities of second-layer units that capture invariances in both form and motion. When trained on natural movies, the first-layer produces a factorization, or separation, of image content into a temporally persistent part representing local edge structure and a dynamic part representing local motion structure. The second-layer units are split into two populations according to the factorization in the first-layer. The form-selective units receive their input from the temporally persistent part (local edge structure) and after training result in a diverse set of higher-order shape features consisting of extended contours, multi-scale edges, textures, and texture boundaries. The motion-selective units receive their input from the dynamic part (local motion structure) and after training result in a representation of image translation over different spatial scales and directions, in addition to more complex deformations. These representations provide a rich description of dynamic natural images, provide testable hypotheses regarding intermediate-level representation in visual cortex, and may be useful representations for artificial visual systems.
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  •  TALK   User-guided 2D-to-3D Conversion
    Date & Time: Tuesday, February 21, 2012; 12:00 PM
    Speaker: Dimitri Androutsos, Richard Rzeszutek, Ryerson University
    MERL Host: Anthony Vetro
    Research Area: Multimedia
    Brief
    • The problem of converting monoscopic footage into stereoscopic or multi-view content is inherently difficult and ill-posed. On the surface, this does not appear to be the case as the problem may be summed up as, "Given single-view image or video, create one or more views as if they were taken from a different camera view." However, capturing a three-dimensional scene as a two-dimensional image is a lossy process and any information regarding the distance of objects to the camera is lost. Methods exist for extracting depth information from a monoscopic view and it is possible to obtain metrically-correct depth estimates under certain conditions. But since conversion is primarily used as a post-processing stage in film production, the user requires a degree of control over the results. This, in turn, makes it ill-posed as there is no way to know ahead of time what the user wants from the conversion. In this talk we will present the work being done at Ryerson University on user-guided 2D-to-3D conversion. In particular, we will focus on how existing image segmentation techniques may be combined to produce reasonable depth maps for conversion while still providing complete control to the user. We will also discuss how our research can be applied to both images and video without any significant alterations to our methods.
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  •  EVENT   99th MPEG meeting
    Date: Monday, February 6, 2012 - Friday, February 10, 2012
    MERL Contact: Anthony Vetro
    Location: San Jose, CA
    Research Area: Multimedia
    Brief
    • MERL is a sponsor for the 99th MPEG meeting to be held in San Jose, CA, in February 2012. MERL researcher Anthony Vetro serves as Head of the US Delegation to MPEG.
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  •  TALK   Secure Computation and Interference in Networks: Performance Limits and Efficient Protocols
    Date & Time: Wednesday, January 4, 2012; 12:00 PM
    Speaker: Dr. Ye Wang, AgaMatrix, Inc.
    Research Area: Multimedia
    Brief
    • In the field of Secure Multi-party Computation, the general objective is to design protocols that allow a group of parties to securely compute functions of their collective private data, while maintaining privacy (in that no parties reveal any more information about their personal data than necessary) and ensuring correctness (in that no parties can disrupt or influence the computation beyond the affect of changing their input data). Information theoretic approaches toward this broad problem, that provide provable (unconditional) security guarantees (even against adversaries that have unbounded computational power), have established that general computation is possible in a variety of scenarios. However, these general solutions are not always the most efficient or finely tuned to the requirements of specific problems and applications.

      In this talk, we will overview our work toward the development of efficient information theoretic approaches for secure multi-party computation applications within the common theme of secure computation and inference over a distributed data network. These applications include:

      1) private information retrieval, where the objective is to privately obtain data without revealing what was selected;
      2) secure statistical analysis, the problem of extracting statistics without revealing anything else about the underlying distributed data;
      3) secure sampling, which is the secure distributed generation of new data with a given joint distribution; and
      4) secure authentication, where the identity of a party needs to authenticated via inference on his credentials and stored registration data.

      Our contributions toward these applications include the following. We proposed a novel oblivious transfer protocol, applicable to private information retrieval, that trades off a small amount privacy for a drastic increase in efficiency. We leveraged a dimensionality reduction that exploits functional structure to simultaneously achieve arbitrarily high accuracy and efficiency in protocols that perform secure statistical analysis of distributed databases. Toward characterizing the region of distributions that can be securely sampled from scratch, we fully characterized the two-party scenario and provided inner and outer bounds on the multi-party scenario. Toward enabling secure distributed authentication, we proposed a two-factor secure biometric authentication system that is robust against the compromise of registered biometric data, allowing for revocability and providing resistance against cross-enrollment attacks.
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  •  TALK   Scheduling and Medium Access in Wireless Networks
    Date & Time: Friday, November 18, 2011; 12:00 PM
    Speaker: Shreeshankar Bodas, MIT
    Research Area: Multimedia
    Brief
    • We look at the problem of designing "efficient" resource allocation algorithms for wireless networks. The volume of data transferred over the wireless network has been ever-growing, but the resources (time, frequency) are not growing at the same rate. We therefore need to design good resource allocation schemes to guarantee a good quality of service to the users.

      In the first part of the talk, we look at the wireless access network, such as Wi-Fi. We have three objectives: ensure high resource utilization, low user-perceived latency, while keeping the computational burden on the devices to a minimum. An interesting recent result by Shah et al says that these three objectives are incompatible with other, unless P=NP. We design a physical layer-aware medium access algorithm that simultaneously achieves the three objectives, and thereby show that the hardness result by Shah et al is an artifact of a simplistic view of the physical layer.

      The second part of the talk focuses on designing scheduling algorithms for wireless downlink networks, such as a cellular network. Our objectives (again) are high resource utilization, low per-user delay, and a "simple" algorithm. We outline the drawbacks of the classic MaxWeight-type algorithms, and design iterative resource allocation schemes that perform well on all the three fronts.
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  •  EVENT   Audio and Music Signal Processing Mini-Symposium
    Date & Time: Thursday, October 20, 2011; 2:00 PM -5:00 PM
    MERL Contact: Jonathan Le Roux
    Location: MERL
    Research Areas: Multimedia, Speech & Audio
    Brief
    • MERL is hosting a mini-symposium on audio and music signal processing, with three talks by eminent researchers in the field: Prof. Mark Plumbley, Dr. Cedric Fevotte and Prof. Nobutaka Ono.
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  •  TALK   Itakura-Saito nonnegative matrix factorization and friends for music signal decomposition
    Date & Time: Thursday, October 20, 2011; 3:00 PM
    Speaker: Dr. Cedric Fevotte, CNRS - Telecom ParisTech, Paris
    MERL Host: Jonathan Le Roux
    Research Areas: Multimedia, Speech & Audio
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  •  TALK   Analysing Digital Music
    Date & Time: Thursday, October 20, 2011; 2:20 PM
    Speaker: Prof. Mark Plumbley, Queen Mary, London
    MERL Host: Jonathan Le Roux
    Research Areas: Multimedia, Speech & Audio
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  •  TALK   Auxiliary Function Approach to Source Localization and Separation
    Date & Time: Thursday, October 20, 2011; 3:40 PM
    Speaker: Prof. Nobutaka Ono, National Institute of Informatics, Tokyo
    MERL Host: Jonathan Le Roux
    Research Areas: Multimedia, Speech & Audio
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  •  EVENT   MMSP 2011 - IEEE Multimedia Signal Processing Workshop
    Date: Monday, October 17, 2011 - Wednesday, October 19, 2011
    MERL Contact: Anthony Vetro
    Location: Hangzhou, China
    Research Area: Multimedia
    Brief
    • MERL is a sponsor for the 2011 edition of the IEEE Multimedia Signal Processing Workshop.
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  •  EVENT   MMSP 2011 - IEEE Multimedia Signal Processing Workshop
    Date: Monday, October 17, 2011 - Wednesday, October 19, 2011
    MERL Contact: Anthony Vetro
    Location: Hangzhou, China
    Research Area: Multimedia
    Brief
    • Anthony Vetro is the General Co-chair of MMSP 2011, the IEEE Multimedia Signal Processing Workshop, to be held in Hangzhou, China, in October 2011.
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  •  TALK   Image and Sensor-based Navigation in Fluorescence Endoscopy
    Date & Time: Thursday, September 1, 2011; 12:00 PM
    Speaker: Alexander Behrens, RWTH Aachen University
    MERL Host: Anthony Vetro
    Research Area: Multimedia
    Brief
    • Today, photodynamic diagnostics is commonly used for cancer detection in endoscopic interventions of the urinary bladder. Although the visual contrast between benign and malignant tissue is significantly enhanced using fluorescence markers, the field of view (FOV) of the endoscope becomes very limited. This impedes the navigation and the re-identifying of multi-focal tumors for the physician. Thus, new image mosaicking algorithms and visualization methods, which provide larger FOVs in real-time from free-hand bladder scans are developed and will be presented. Furthermore a novel method for an automatic control of seamless inspections using graphs are addressed. Going beyond image processing, a first low-cost inertial 3-D navigation system will be introduced, and a guided navigation tool for tumor re-identification and its application to virtual endoscopy will be discussed.
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  •  TALK   Gigapixel Binary Sensing: Image Acquisition Using Oversampled One-Bit Poisson Statistics
    Date & Time: Wednesday, June 15, 2011; 12:00 PM
    Speaker: Dr. Yue M. Lu, Harvard School of Engineering and Applied Sciences
    MERL Host: Petros Boufounos
    Research Area: Multimedia
    Brief
    • Before the advent of digital image sensors, photography, for the most part of its history, used film to record light information. In this talk, I will present a new digital image sensor that is reminiscent of photographic film. Each pixel in the sensor has a binary response, giving only a one-bit quantized measurement of the local light intensity.

      To analyze its performance, we formulate the binary sensing scheme as a parameter estimation problem based on quantized Poisson statistics. We show that, with a single-photon quantization threshold and large oversampling factors, the Cramer-Rao lower bound of the estimation variance approaches that of an ideal unquantized sensor, that is, as if there were no quantization in the sensor measurements. Furthermore, this theoretical performance bound is shown to be asymptotically achievable by practical image reconstruction algorithms based on maximum likelihood estimators.

      Numerical results on both synthetic data and images taken by a prototype sensor verify the theoretical analysis and the effectiveness of the proposed image reconstruction algorithm. They also demonstrate the benefit of using the new binary sensor in applications involving high dynamic range imaging.

      Joint work with Feng Yang, Luciano Sbaiz and Martin Vetterli.
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  •  TALK   Recursive Sparse Recovery and Applications in Dynamic Imaging
    Date & Time: Friday, June 3, 2011; 11:00 AM
    Speaker: Prof. Namrata Vaswani, Iowa State University
    MERL Host: Petros Boufounos
    Research Area: Multimedia
    Brief
    • In this talk, I will discuss our recent work on Recursive Sparse Recovery (RecSparsRec) and show how it provides novel solutions to two very different problems in dynamic imaging. RecSparsRec refers to recursive approaches to causally recover a time sequence of signals/images from a greatly reduced number of measurements (compared to existing approaches), by utilizing their sparsity.

      The motivating application for RecSparsRec is fast recursive dynamic magnetic resonance imaging (MRI) for real-time applications like MRI-guided surgery. MRI is a technique for cross-sectional imaging that acquires Fourier projections of the cross-section to be reconstructed, one-at-a-time. Thus, the ability to accurately reconstruct using fewer measurements directly translates into reduced scan times. This, along with online (causal) and fast (recursive) reconstruction algorithms, can enable real-time imaging of fast changing physiological phenomena, and thus make real-time MRI feasible. Cross-sectional images of the brain, heart, or other organs are known to be wavelet sparse. Our recent work was the first to observe that, in a time sequence, their sparsity pattern changes quite slowly. Using this fact, we were able to reformulate the RecSparsRec problem as one of sparse reconstruction with partially known support. We introduced a simple, but very powerful, approach called!
      Modified-CS that achieves provably exact reconstruction (in the noise-free case) and whose error is provably stable over time (in the noisy case), with using much fewer measurements than existing work. Our preliminary experiments indicate that Modified-CS needs roughly 5-times fewer measurements than existing MR scanner technology and 1.5-times fewer than existing research literature.

      I will briefly also discuss our ongoing work on the difficult video analysis problem of separating foreground moving objects from a background scene that is itself is changing and dong this in real-time. This can be posed as a recursive robust principal components analysis (PCA) problem in the presence of correlated sparse outliers or equivalently, as a problem of recursive sparse recovery in the presence of very large, but ``low rank" noise (noise with a low rank covariance matrix).
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  •  EVENT   IEEE Signal Processing Magazine, Special Issue on Distributed Image Processing and Communications
    Date: Sunday, May 1, 2011
    MERL Contact: Anthony Vetro
    Research Area: Multimedia
    Brief
    • Anthony Vetro is Guest Editor for the Special Issue on Distributed Image Processing and Communications of the IEEE Signal Processing Magazine.
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  •  EVENT   Proceedings of the IEEE, Special Issue on 3D Media & Displays
    Date: Friday, April 1, 2011
    MERL Contact: Anthony Vetro
    Research Area: Multimedia
    Brief
    • Anthony Vetro is Guest Editor for the Special Issue on 3D Media & Displays of the Proceedings of the IEEE.
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  •  EVENT   MMSP 2010 - IEEE Multimedia Signal Processing Workshop
    Date: Monday, October 4, 2010 - Wednesday, October 6, 2010
    MERL Contact: Anthony Vetro
    Location: St Malo, France
    Research Area: Multimedia
    Brief
    • MERL is a sponsor for the 2010 edition of the IEEE Multimedia Signal Processing Workshop.
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  •  EVENT   VCIP 2005 - Visual Communications and Image Processing
    Date: Tuesday, July 12, 2005 - Friday, July 15, 2005
    MERL Contact: Anthony Vetro
    Location: Beijing, China
    Research Area: Multimedia
    Brief
    • Anthony Vetro is the Special Session Co-Chair of VCIP 2005, the IEEE Visual Communications and Image Processing Conference.
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