filterbank/erbfilters.m

function [g,a,fc,L]=erbfilters(fs,Ls,varargin)
%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');
%
%
%   See also: audfilters, filterbank, ufilterbank, ifilterbank, ceil23
%
%   References: ltfatnote027

% Authors: Peter L. Søndergaard, Zdenek Prusa, Nicki Holighaus

[g,a,fc,L]=audfilters(fs,Ls,varargin{:},'erb');