Filter banks, both uniform and non-uniform, are widely used for signal analysis and processing. However, the application of a timefrequency localized filter inevitably causes some amount of spectral and temporal leakage that, simultaneously, cannot be arbitrarily reduced. Reassignment is a classical procedure to eliminate this leakage in short-time Fourier spectrograms, thereby providing a sharper, more exact time-frequency domain signal representation. The reassignment technique was recently generalized to general filter banks, opening new possibilities for its application in signal analysis and processing. We present here the very first implementation of filter bank reassignment in a real-time analysis setting, more specifically as visualization in a basic audio player application. The visualization provides a low delay moving spectrogram with respect to virtually any time-frequency filter bank by interfacing the C backend of the LTFAT open-source toolbox for time-frequency processing. Low delay is achieved by blockwise processing, implemented with the JUCE C++ Library.

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The knowledge of the phase of STFT is a prerequisite for a successful signal reconstruction. However, the phase might be lost or no longer applicable depending on the kind of processing involved. We propose a real-time spectrogram inversion algorithm based on the relationship of the gradients of the phase and the logarithm of the magnitude and on the gradient integration theorem. We present a detailed comparison with the state-of-the-art phase reconstruction algorithms.

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