FILTERBANKSYNCHROSQUEEZE Synchrosqueeze filterbank spectrogram
Usage: cr = filterbanksynchrosqueeze(c,tgrad,cfreq);
cr = filterbanksynchrosqueeze(c,tgrad,g);
[cr,repos,Lc] = filterbanksynchrosqueeze(...);
Input parameters:
c : Coefficients to be synchrosqueezed.
tgrad : Instantaneous frequency relative to original position.
cfreq : Vector of relative center frequencies in ]-1,1].
g : Set of filters.
Output parameters:
cr : Synchrosqueezed filterbank coefficients.
repos : Reassigned positions.
Lc : Subband lengths.
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');
References:
N. Holighaus, Z. Průša, and P. L. Soendergaard. Reassignment and
synchrosqueezing for general time-frequency filter banks, subsampling
and processing. Signal Processing, 125:1--8, 2016. [1]http ]
References
1. http://www.sciencedirect.com/science/article/pii/S0165168416000141
Url: http://ltfat.github.io/doc/filterbank/filterbanksynchrosqueeze.html
See also: filterbankphasegrad, gabreassign.
Package: ltfat