FILTERBANKSYNCHROSQUEEZE - Synchrosqueeze filterbank spectrogram

Usage

cr = filterbanksynchrosqueeze(c,tgrad,cfreq);
cr = filterbanksynchrosqueeze(c,tgrad,g);
[cr,repos,Lc] = filterbanksynchrosqueeze(...);

Input parameters

Output parameters

Description

filterbanksynchrosqueeze(c,tgrad,cfreq) will reassign the values of the filterbank coefficients c according to instantaneous frequency tgrad. The frequency center frequencies of filters are given by cfreq. The filterbank coefficients c are assumed to be obtained from a non-subsampled filterbank (a=1).

filterbanksynchrosqueeze(s,tgrad,g) will do the same thing except the center frequencies are estimated from a set of filters g.

[sr,repos,Lc]=filterbanksynchrosqueeze(...) does the same thing, but in addition returns a vector of subband lengths Lc (Lc = cellfun(@numel,s)) and cell array repos with sum(Lc) elements. Each element corresponds to a single coefficient obtained by cell2mat(sr) and it is a vector of indices identifying coefficients from cell2mat(s) assigned to the particular time-frequency position.

The arguments s, tgrad must be cell-arrays of vectors of the same lengths. Arguments cfreq or g must have the same number of elements as the cell arrays with coefficients.

Examples:

This example shows how to synchrosqueeze a ERB filterbank spectrogram:

% Genrate 3 chirps half a second long
L = 22050; fs = 44100; l = 0:L-1;

f = sin(2*pi*(l/35+(l/300).^2)) + ...
    sin(2*pi*(l/10+(l/300).^2)) + ...
    sin(2*pi*(l/5-(l/450).^2));
f = 0.7*f';

% Create ERB filterbank
[g,~,fc]=erbfilters(fs,L,'uniform','spacing',1/12,'warped');

% Compute phase gradient
[tgrad,~,~,c]=filterbankphasegrad(f,g,1);
% Do the reassignment
sr=filterbanksynchrosqueeze(c,tgrad,cent_freqs(fs,fc));
figure(1); subplot(211);
plotfilterbank(c,1,fc,fs,60);
title('ERBlet spectrogram of 3 chirps');
subplot(212);
plotfilterbank(sr,1,fc,fs,60);
title('Synchrosqueezed ERBlet spectrogram of 3 chirps');