Institut de Mathématiques de Marseille, UMR 7373




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30 juin 2017: 2 événements

Séminaire

  • Agenda ERC IChaos

    Du 27 au 30 juin - Pierre LAZAG

    Scientific collaboration with Nizar DEMNI (IRMAR)

    Résumé : Poly-analytical determinant process in the hyperbolic disc

    Lieu : Institut de Recherche Mathématique de Rennes - Campus de Beaulieu
    Bâtiment 22

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En savoir plus : Agenda ERC IChaos

  • Séminaire Signal et Apprentissage

    Vendredi 30 juin 14:00-15:00 - Matthieu KOWALSKI - L2S, Université Paris-Sud

    Low-rank time-frequency synthesis

    Résumé : Many single-channel signal decomposition techniques rely on a low-rank factorization of a time-frequency transform. In particular, nonnegative matrix factorization (NMF) of the spectrogram – the (power) magnitude of the short-time Fourier transform (STFT) – has been considered in many audio applications. In this setting, NMF with the Itakura-Saito divergence was shown to underly a generative Gaussian composite model (GCM) of the STFT, a step forward from more empirical approaches based on ad-hoc transform and divergence specifications. Still, the GCM is not yet a generative model of the raw signal itself, but only of its STFT. The work presented in this paper fills in this ultimate gap by proposing a novel signal synthesis model with low-rank time-frequency structure. In particular, our new approach opens doors to multi-resolution representations, that were not possible in the traditional NMF setting. We describe expectation-maximization algorithms for estimation in the new model and report audio signal processing results with music decomposition and new approach to the compressive sampling inverse problem, that exploits latent low-rank time-frequency structure instead of sparsity, with superior results for the considered data.

    JPEG - 5.2 ko
    Mathieu KOWALSKI

    Lieu : CMI, salle de séminaire R164 - I2M - Château-Gombert
    39 rue Frédéric Joliot-Curie
    13453 Marseille cedex 13

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    En savoir plus : Séminaire Signal et Apprentissage