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function gout=freqfilter(winname,bw,varargin)
%-*- texinfo -*-
%@deftypefn {Function} freqfilter
%@verbatim
%FREQFILTER Construct filter in frequency domain
% Usage: g=freqfilter(winname,bw);
% g=freqfilter(winname,bw,fc);
%
% Input parameters:
% winname : Name of prototype
% bw : Effective support length of the prototype
% fc : Center frequency
%
% FREQFILTER(winname,bw) creates a full-length frequency response
% filter. The parameter winname specifies the shape of the frequency
% response. For accepted shape please see FREQWIN. bw defines a
% -6dB bandwidth of the filter in normalized frequencies.
%
% FREQFILTER(winname,bw,fc) constructs a filter with a centre
% frequency of fc measured in normalized frequencies.
%
% If one of the inputs is a vector, the output will be a cell array
% with one entry in the cell array for each element in the vector. If
% more input are vectors, they must have the same size and shape and the
% the filters will be generated by stepping through the vectors. This
% is a quick way to create filters for FILTERBANK and UFILTERBANK.
%
% FREQFILTER accepts the following optional parameters:
%
% 'fs',fs If the sampling frequency fs is specified then the
% bandwidth bw and the centre frequency fc are
% specified in Hz.
%
% 'complex' Make the filter complex valued if the centre frequency
% is non-zero. This is the default.
%
% 'real' Make the filter real-valued if the centre frequency
% is non-zero.
%
% 'delay',d Set the delay of the filter. Default value is zero.
%
% 'scal',s Scale the filter by the constant s. This can be
% useful to equalize channels in a filter bank.
%
% 'pedantic' Force window frequency offset (g.foff) to a subsample
% precision by a subsample shift of the window.
%
%@end verbatim
%@strong{Url}: @url{http://ltfat.github.io/doc/sigproc/freqfilter.html}
%@end deftypefn
% Copyright (C) 2005-2016 Peter L. Soendergaard <peter@sonderport.dk>.
% This file is part of LTFAT version 2.3.1
%
% This program is free software: you can redistribute it and/or modify
% it under the terms of the GNU General Public License as published by
% the Free Software Foundation, either version 3 of the License, or
% (at your option) any later version.
%
% This program is distributed in the hope that it will be useful,
% but WITHOUT ANY WARRANTY; without even the implied warranty of
% MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
% GNU General Public License for more details.
%
% You should have received a copy of the GNU General Public License
% along with this program. If not, see <http://www.gnu.org/licenses/>.
% Authors: Nicki Holighaus & Zdenek Prusa
% Date: September 15, 2016
if ~iscell(winname), winname = {winname}; end
% Define initial value for flags and key/value pairs.
definput.import={'normalize'};
definput.importdefaults={'energy'};
definput.keyvals.delay=0;
definput.keyvals.fc=0;
definput.keyvals.fs=2;
%definput.keyvals.order=4;
definput.keyvals.scal=1;
definput.keyvals.min_win=1;
%definput.keyvals.trunc_at=10^(-5);
definput.keyvals.bwtruncmul = 4;
definput.flags.pedantic = {'pedantic','nopedantic'};
definput.flags.real={'complex','real'};
[flags,kv]=ltfatarghelper({'fc'},definput,varargin);
[bw,kv.fc,kv.delay,kv.scal]=scalardistribute(bw,kv.fc,kv.delay,kv.scal);
% Sanitize
kv.fc=modcent(2*kv.fc/kv.fs,2);
Lw = @(L,bw) min(ceil(bw*kv.bwtruncmul*L/kv.fs),L);
fsRestricted = @(L,bw) kv.fs/L*Lw(L,bw);
if flags.pedantic
fc_offset = @(L,fc) L/2*fc-round(L/2*fc);
else
fc_offset = @(L,fc) 0;
end
Nfilt = numel(bw);
gout = cell(Nfilt,1);
for ii=1:Nfilt
g=struct();
g.foff=@(L) round(L/2*kv.fc(ii)) - floor(Lw(L,bw(ii))/2);
if flags.do_1 || flags.do_area
g.H=@(L) fftshift(...
freqwin(winname,Lw(L,bw(ii)),bw(ii),fsRestricted(L,bw(ii)),...
'shift',fc_offset(L,kv.fc(ii)))...
)*kv.scal(ii)*L;
end
if flags.do_2 || flags.do_energy
g.H=@(L) fftshift(...
freqwin(winname,Lw(L,bw(ii)),bw(ii),fsRestricted(L,bw(ii)),...
'shift',fc_offset(L,kv.fc(ii)))...
)*kv.scal(ii)*sqrt(L);
end
if flags.do_inf || flags.do_peak
g.H=@(L) fftshift(...
freqwin(winname,Lw(L,bw(ii)),bw(ii),fsRestricted(L,bw(ii)),...
'shift',fc_offset(L,kv.fc(ii)))...
)*kv.scal(ii);
end
g.realonly=flags.do_real;
g.delay=kv.delay(ii);
g.fs=kv.fs;
gout{ii}=g;
end
if Nfilt==1
gout=g;
end;
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