Cross product enhanced subband block based harmonic transposition

Abstract

The invention is directed to a system configured to generate a time stretched and / or frequency transposed signal from an input signal. The system comprises an analysis filter bank (101) configured to derive a number Ye1 of analysis subband signals from the input signal, wherein each analysis subband signal comprises a plurality of complex-valued analysis sample, each having a phase and a magnitude; a subband processing unit (102) configured to generate a synthesis subband signal from the Y analysis subband signal using a subband transposition factor Q and a subband stretch factor S, at least one of Q and S being greater than one, the subband processing unit comprises a block extractor configured to i) form Y frames of L input samples, each frame being extracted from said plurality of complex-valued analysis samples in an analysis subband signal and the frame length being L > 1; and ii) apply a block hop size of h samples to said plurality of analysis samples, prior to forming a subsequent frame of L input samples, thereby generating a sequence of frames of input samples; a nonlinear frame processing unit configured to generate, on the basis of Y corresponding frames of input samples formed by the block extractor, a frames of processes sample by determining a phase and magnitude for each processed sample of the frames, wherein, for at least one processed sample: i) the phase of processed sample is based on the respective phases of the corresponding input sample in each of the Y frames of input samples; and ii) the magnitude of the processed sample is determined as a mean value of the magnitude of the corresponding input sample in a first frame of the Y frames of input samples and the magnitude of the corresponding input sample in a second frame of the Y frames of input samples; and an overlap and add unit configured to determine the synthesis subband signal by overlapping and adding the samples of a sequences of frames of processed samples. The system further comprises a synthesis filter bank configured to generate the time stretched and / or frequency transposed signal from the synthesis subband signal, wherein the system is operable at least for Y=2

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