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function gout=warpedblfilter(winname,fsupp,fc,fs,freqtoscale,scaletofreq,varargin)
%-*- texinfo -*-
%@deftypefn {Function} warpedblfilter
%@verbatim
%WARPEDBLFILTER Construct a warped band-limited filter
% Usage: g=warpedblfilter(winname,fsupp,fc,fs,freqtoscale,scaletofreq);
%
% Input parameters:
% winname : Name of prototype.
% fsupp : Support length of the prototype (in scale units).
% fc : Centre frequency (in Hz).
% fs : Sampling rate
% freqtoscale : Function handle to convert Hz to scale units
% scaletofreq : Function to convert scale units into Hz.
%
% Output parameters:
% g : Filter definition, see BLFILTER.
%
% WARPEDBLFILTER(winname,fsupp,fc,fs,freqtoscale,scaletofreq) constructs
% a band-limited filter that is warped on a given frequency scale. The
% parameter winname specifies the basic shape of the frequency response.
% The name must be one of the shapes accepted by FIRWIN. The support of
% the frequency response measured on the selected frequency scale is
% specified by fsupp, the centre frequency by fc and the scale by the
% function handle freqtoscale of a function that converts Hz into the
% choosen scale and scaletofreq doing the inverse.
%
% 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.
%
% WARPEDBLFILTER accepts the following optional parameters:
%
% '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.
%
% 'symmetric' The filters with fc<0 (or fc>fs/2) will be created
% on the positive frequencies and mirrored. This allows
% using freqtoscale defined only for the positive
% numbers.
%
% '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 filterbank.
%
% It is possible to normalize the transfer function of the filter by
% passing any of the flags from the NORMALIZE function. The default
% normalization is 'energy'.
%
% The filter can be used in the PFILT routine to filter a signal, or
% in can be placed in a cell-array for use with FILTERBANK or
% UFILTERBANK.
%
% The output format is the same as that of BLFILTER.
%
%@end verbatim
%@strong{Url}: @url{http://ltfat.github.io/doc/sigproc/warpedblfilter.html}
%@seealso{blfilter, firwin, pfilt, filterbank}
%@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/>.
capmname = upper(mfilename);
complainif_notenoughargs(nargin,6,capmname);
complainif_notposint(fs,'fs',capmname);
if isempty(freqtoscale) || ~isa(freqtoscale,'function_handle')
error('%s: freqtoscale must be a function handle',capmname);
end
if isempty(scaletofreq) || ~isa(scaletofreq,'function_handle')
error('%s: scaletofreq must be a function handle',capmname);
end
if isempty(fc) || ~isnumeric(fc)
error('%s: fc must be numeric',capmname);
end
if isempty(fsupp) || ~isnumeric(fsupp)
error('%s: fc must be numeric',capmname);
end
% Define initial value for flags and key/value pairs.
definput.import={'normalize'};
definput.importdefaults={'energy'};
definput.keyvals.delay=0;
definput.keyvals.scal=1;
definput.flags.real={'complex','real'};
definput.flags.symmetry = {'nonsymmetric','symmetric'};
[flags,kv]=ltfatarghelper({},definput,varargin);
if ~isscalar(kv.scal)
error('%s: scal must be a scalar',capmname);
end
if ~isscalar(kv.delay)
error('%s: delay must be a scalar',capmname);
end
[fsupp,fc,kv.delay,kv.scal]=scalardistribute(fsupp,fc,kv.delay,kv.scal);
Nfilt=numel(fsupp);
gout=cell(1,Nfilt);
if ischar(winname)
wn = {winname};
elseif iscell(winname)
wn = winname;
else
error('%s: Incorrect format of winname.',upper(mfilename));
end
for ii=1:Nfilt
g=struct();
if flags.do_1 || flags.do_area
g.H=@(L) comp_warpedfreqresponse( wn{1},fc(ii), ...
fsupp(ii),fs,L,freqtoscale, ...
scaletofreq, flags.norm,...
flags.symmetry)*kv.scal(ii)*L;
end;
if flags.do_2 || flags.do_energy
g.H=@(L) comp_warpedfreqresponse(wn{1},fc(ii), ...
fsupp(ii),fs,L,freqtoscale,scaletofreq, ...
flags.norm,flags.symmetry)*kv.scal(ii)*sqrt(L);
end;
if flags.do_inf || flags.do_peak
g.H=@(L) comp_warpedfreqresponse(wn{1},fc(ii), ...
fsupp(ii),fs,L,freqtoscale,scaletofreq, ...
flags.norm,flags.symmetry)*kv.scal(ii);
end;
g.foff=@(L) comp_warpedfoff(fc(ii),fsupp(ii),fs,L,freqtoscale,...
scaletofreq,flags.do_symmetric);
g.realonly=flags.do_real;
if kv.delay~=0
g.delay=kv.delay(ii);
end
g.fs=fs;
gout{ii}=g;
end;
if Nfilt==1
gout=g;
end;
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