ERBFILTERS ERB-spaced filters
Usage: [g,a,fc,L]=erbfilters(fs,Ls);
[g,a,fc,L]=erbfilters(fs,Ls,...);
Input parameters:
fs : Sampling rate (in Hz).
Ls : Signal length.
Output parameters:
g : Cell array of filters.
a : Downsampling rate for each channel.
fc : Center frequency of each channel.
L : Next admissible length suitable for the generated filters.
[g,a,fc]=ERBFILTERS(fs,Ls) constructs a set of filters g that are
equidistantly spaced on the ERB-scale (see FREQTOERB) with bandwidths
that are proportional to the width of the auditory filters
AUDFILTBW. The filters are intended to work with signals with a
sampling rate of fs.
Note that this function just forwards the arguments to AUDFILTERS.
Please see the help of AUDFILTERS for more details.
Examples:
---------
In the first example, we construct a highly redudant uniform
filterbank and visualize the result:
[f,fs]=greasy; % Get the test signal
[g,a,fc]=erbfilters(fs,length(f),'uniform','M',100);
c=filterbank(f,g,a);
plotfilterbank(c,a,fc,fs,90,'audtick');
In the second example, we construct a non-uniform filterbank with
fractional sampling that works for this particular signal length, and
test the reconstruction. The plot displays the response of the
filterbank to verify that the filters are well-behaved both on a
normal and an ERB-scale. The second plot shows frequency responses of
filters used for analysis (top) and synthesis (bottom). :
[f,fs]=greasy; % Get the test signal
L=length(f);
[g,a,fc]=erbfilters(fs,L,'fractional');
c=filterbank(f,{'realdual',g},a);
r=2*real(ifilterbank(c,g,a));
norm(f-r)
% Plot the response
figure(1);
subplot(2,1,1);
R=filterbankresponse(g,a,L,fs,'real','plot');
subplot(2,1,2);
semiaudplot(linspace(0,fs/2,L/2+1),R(1:L/2+1));
ylabel('Magnitude');
% Plot frequency responses of individual filters
gd=filterbankrealdual(g,a,L);
figure(2);
subplot(2,1,1);
filterbankfreqz(gd,a,L,fs,'plot','linabs','posfreq');
subplot(2,1,2);
filterbankfreqz(g,a,L,fs,'plot','linabs','posfreq');
References:
T. Necciari, P. Balazs, N. Holighaus, and P. L. Soendergaard. The ERBlet
transform: An auditory-based time-frequency representation with perfect
reconstruction. In Proceedings of the 38th International Conference on
Acoustics, Speech, and Signal Processing (ICASSP 2013), pages 498--502,
Vancouver, Canada, May 2013. IEEE.
Url: http://ltfat.github.io/doc/filterbank/erbfilters.html
See also: audfilters, filterbank, ufilterbank, ifilterbank, ceil23.
Package: ltfat