GABREASSIGNADJUST Adjustable reassignment of a time-frequency distribution
Usage: sr = gabreassignadjust(s,pderivs,a,mu);
GABREASSIGNADJUST(s,pderivs,a,mu) reassigns the values of the positive
time-frequency distribution s using first and second order phase
derivatives given by pderivs and parameter mu*>0.
The lattice is determined by the time shift a and the number of
channels deduced from the size of s.
pderivs is a cell array of phase derivatives which can be obtained
as follows:
pderivs = gabphasederiv({'t','f','tt','ff','tf'},...,'relative');
Please see help of GABPHASEDERIV for description of the missing
parameters.
gabreassign(s,pderivs,a,mu,despeckle) works as above, but some
coeficients are removed prior to the reassignment process. More
precisely a mixed phase derivative pderivs{5} is used to determine
which coefficients m,n belong to sinusoidal components (such that
abs(1+pderivs{5}(m,n)) is close to zero) and to impulsive
components (such that abs(pderivs{5}(m,n)) is close to zero).
Parameter despeckle determines a threshold on the previous quantities
such that coefficients with higher associated values are set to zeros.
Algorithm
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The routine uses the adjustable reassignment presented in the
references.
Examples:
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The following example demonstrates how to manually create a
reassigned spectrogram.:
% Compute the phase derivatives
a=4; M=100;
[pderivs, c] = gabphasederiv({'t','f','tt','ff','tf'},'dgt',bat,'gauss',a,M,'relative');
% Reassignemt parameter
mu = 0.1;
% Perform the actual reassignment
sr = gabreassignadjust(abs(c).^2,pderivs,a,mu);
% Display it using plotdgt
plotdgt(sr,a,143000,50);
References:
F. Auger, E. Chassande-Mottin, and P. Flandrin. On phase-magnitude
relationships in the short-time fourier transform. Signal Processing
Letters, IEEE, 19(5):267--270, May 2012.
F. Auger, E. Chassande-Mottin, and P. Flandrin. Making reassignment
adjustable: The Levenberg-Marquardt approach. In Acoustics, Speech and
Signal Processing (ICASSP), 2012 IEEE International Conference on,
pages 3889--3892, March 2012.
Z. Průša. STFT and DGT phase conventions and phase derivatives
interpretation. Technical report, Acoustics Research Institute,
Austrian Academy of Sciences, 2015.
Url: http://ltfat.github.io/doc/gabor/gabreassignadjust.html
See also: gabphasederiv, gabreassign.
Package: ltfat