An entropy based method for local time-adaptation of the spectrogram

Authors:
Marco Liuni;Axel Röbel;Marco Romito;Xavier Rodet
Affiliations:
Universitá di Firenze, Dip. di Matematica "U. Dini", Florence, Italy and IRCAM, CNRS, STMS, Paris, France;IRCAM, CNRS, STMS, Paris, France;Universitá di Firenze, Dip. di Matematica "U. Dini", Florence, Italy;IRCAM, CNRS, STMS, Paris, France
Venue:
CMMR'10 Proceedings of the 7th international conference on Exploring music contents
Year:
2010

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Abstract

We propose a method for automatic local time-adaptation of the spectrogram of audio signals: it is based on the decomposition of a signal within a Gabor multi-frame through the STFT operator. The sparsity of the analysis in every individual frame of the multi-frame is evaluated through the Rényi entropy measures: the best local resolution is determined minimizing the entropy values. The overall spectrogram of the signal we obtain thus provides local optimal resolution adaptively evolving over time. We give examples of the performance of our algorithm with an instrumental sound and a synthetic one, showing the improvement in spectrogram displaying obtained with an automatic adaptation of the resolution. The analysis operator is invertible, thus leading to a perfect reconstruction of the original signal through the analysis coefficients.