function varargout=audspecgram(insig,fs,varargin)
%AUDSPECGRAM  Auditory spectrogram
%   Usage: audspecgram(insig,fs,op1,op2, ... );
%          C=audspecgram(insig,fs, ... );
%
%   AUDSPECGRAM(insig,fs) plots an auditory spectrogram of the signal insig,
%   which has been sampled at a sampling rate of fs Hz. The output is
%   low-pass modulation filtered before presentation.
%
%   The frequency axis is diplayed on a erb-scale, but labelled in
%   Hz. Using the mouse to get plot coordinates will reveal the real
%   value in erb's. Use erbtofreq to convert to Hz.
%
%   C=AUDSPECGRAM(insig,fs, ... ) returns the image to be displayed as a
%   matrix. Use this in conjunction with imwrite etc. Do *not* use this as a
%   method to compute an auditory representation. Use some of the model
%   preprocessing functions for this.
%
%   Additional arguments can be supplied like this:
%
%     audspecgram(insig,fs,'dynrange',30);
%
%   The arguments must be character strings possibly followed by an argument:
%
%     'adapt'       Model adaptation. This is the default. This options also
%                   sets the output to be displayed on a linear scale.
%    
%     'noadapt'     Do not model adaptation. This option also sets a dB scale to
%                   display the output.
%    
%     'ihc',modelname
%                   Pass modelname to IHCENVELOPE to determine the inner
%                   hair cell envelope extraction process to use. Default is to
%                   use the 'dau' model.
%    
%     'classic'     Display a classic spectrogram. This option is equal to
%                   {'ihc','hilbert', 'noadapt', 'nomf'}
%    
%     'mlp',f       Modulation low-pass filter to frequency f. Default is to
%                   low-pass filter to 50 Hz.
%    
%     'mf',f        Modulation filter with specified center frequency.
%    
%     'nomf'        No modulation filtering of any kind.
%    
%     'image'       Use imagesc to display the spectrogram. This is the default.
%    
%     'clim',clim   Use a colormap ranging from clim(1) to clim(2). These              
%                   values are passed to imagesc. See the help on imagesc.
%    
%     'dynrange',r  Limit the displayed dynamic range to r. This option
%                   is especially usefull when displaying on a dB scale (no adaptation).
%    
%     'fullrange'   Use the full dynamic range. This is the default.
%    
%     'ytick'       A vector containing the frequency in Hz of the yticks.
%    
%     'thr',r       Keep only the largest fraction r of the coefficients, and
%                   set the rest to zero.
%    
%     'frange',frange
%                   Choose a frequency scale ranging from frange(1) to
%                   frange(2), values are entered in Hz. Default is to display from
%                   0 to 8000 Hz.
%    
%     'xres',xres   Approximate number of pixels along x-axis / time.
%    
%     'yres',yres   Approximate number of pixels along y-axis / frequency If
%                   only one of 'xres' and 'yres' is specified, the default
%                   aspect ratio will be used.
%    
%     'displayratio',r  Set the default aspect ratio.
%    
%     'contour'     Do a contour plot to display the spectrogram.
%           
%     'surf'        Do a surf plot to display the spectrogram.
%    
%     'mesh'        Do a mesh plot to display the spectrogram.
%
%     'colorbar'    Display the colorbar. This is the default.
%
%     'nocolorbar'  Do not display the colorbar.
%
%   Examples:
%   ---------
%
%   The following figure shows a classic spectrogram on an Erb scale of a
%   spoken word:
%
%     audspecgram(greasy,16000,'classic','dynrange',50);
%
%   The next example shows a Dau-style spectrogram (including adaptation
%   and modulation low-pass filtering) of the same word:
%
%     audspecgram(greasy,16000);
%
%   See also:   dau1997_preproc
%
%   Url: http://amtoolbox.sourceforge.net/data/amt-test/htdocs/amt-0.10.0/doc/general/audspecgram.php

% Copyright (C) 2009-2020 Piotr Majdak and the AMT team.
% This file is part of Auditory Modeling Toolbox (AMT) version 0.10.0
%
% 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/>.
  
%   AUTHOR : Peter Søndergaard.
  
if nargin<2
  error('Too few input arguments.');
end;

if ~isnumeric(insig) || ~isvector(insig)
  error('%s: Input must be a vector.',upper(mfilename));
end;

definput.import={'plotfilterbank','ltfattranslate','tfplot'};
definput.importdefaults={'lin','audtick'};

% Define initial value for flags and key/value pairs.
definput.flags.adapt={'adapt','noadapt'};
definput.flags.thr={'nothr','thr'};
definput.flags.mlp={'mlp','mf','nomf'};
definput.flags.delay={'gammatonedelay','zerodelay'};

definput.keyvals.ihc='ihc_dau';
definput.keyvals.thr=0;
%definput.keyvals.ytick=[0,100,250,500,1000,2000,4000,8000];
definput.keyvals.mlp=50;
definput.keyvals.mf=[0 5 10 16.6 27.7];
definput.keyvals.frange=[0,8000];
definput.keyvals.xres=800;
definput.keyvals.yres=600;

definput.flags.colorbar={'colorbar','nocolorbar'};

definput.groups.classic={'ihc','hilbert', 'noadapt', 'nomf'};


[flags,kv]=ltfatarghelper({},definput,varargin);

siglen=length(insig);

fhigh=kv.frange(2);
flow =kv.frange(1);

audlimits=freqtoerb(kv.frange);

% fhigh can at most be the Nyquest frequency
fhigh=min(fhigh,fs/2);

% Downsample this signal if it is sampled at a much higher rate than
% 2*fhigh. This reduces memory consumption etc. 1.5 and 1.2 are choosen as a
% safeguard to not loose information.
if fs>2*1.5*fhigh
  
  fsnew=round(fhigh*2*1.2);

  % Determine new signal length
  siglen=round(siglen/fs*fsnew);
  
  % Do the resampling using an FFT based method, as this is more flexible
  % than the 'resample' method included in Matlab
  insig=fftresample(insig,siglen);

  % Switch to new value
  fs=fsnew;  
end;

% Determine the hopsize
% Using a hopsize different from 1 is currently not possible because all
% the subsequent filters fail because of a to low subband sampling rate.
%hopsize=max(1,floor(siglen/xres));

hopsize=1;

% find the center frequencies used in the filterbank
fc = erbspace(flow,fhigh,kv.yres);

if 1
  % Calculate filter coefficients for the gammatone filter bank.
  [gt_b, gt_a, delay]=gammatone(fc, fs, 'complex');
  
  % Apply the Gammatone filterbank
  outsig = 2*real(ufilterbankz(gt_b,gt_a,insig,hopsize));
  
else
  L=siglen;
  bw_gauss=audfiltbw(fc)/fs*L/0.79;

  fc_gauss=round(fc/fs*L);
  g=cell(1,kv.yres);

  for m=1:kv.yres
    g{m}=real(pgauss(L,'bw',bw_gauss(m),'cf',fc_gauss(m)));
  end;
  
  outsig=filterbank(insig,g,hopsize);
end;


  
% The subband are now (possibly) sampled at a lower frequency than the
% original signal.
fssubband=round(fs/hopsize);

outsig = ihcenvelope(outsig,fssubband,kv.ihc);

if flags.do_adapt
  % non-linear adaptation loops
  outsig = adaptloop(outsig, fssubband);
end;

if flags.do_nomf
  modfilt_outsig=outsig;
end;
  
if flags.do_mlp
  % Calculate filter coefficients for the 50 Hz modulation lowpass
  % filter. Just use a 2nd order Butterworth for this.
  
  % FIXME: This filter places a pole /very/ close to the unit circle.
  %mlp_a = exp(-(1/0.02)/fs);
  mlp_a = exp(-kv.mlp/fs);
  mlp_b = 1 - mlp_a;
  mlp_a = [1, -mlp_a];

  % Apply the low-pass modulation filter.
  modfilt_outsig = filter(mlp_b,mlp_a,outsig);
end;

if flags.do_mf
  nreps=length(kv.mf)-1;
else
  nreps=1;    
end;

% Loop over the number of modulation frequency channels
for jj=1:nreps

  if flags.do_mf
    % Calculate filter coefficients for the 50 Hz modulation lowpass
    % filter. Just use a 2nd order Butterworth for this.
    [mf_b,mf_a] = butter(2,[kv.mf(jj),kv.mf(jj+1)]/(subbandfs/2));
    
    % Apply the modulation filter.
    modfilt_outsig = filter(mf_b,mf_a,outsig);
    
    if mfc(nmfc) <= 10
      modfilt_outsig = 1*real(modfilt_outsig);
    else
      modfilt_outsig = 1/sqrt(2)*abs(modfilt_outsig);
    end

  end;

  
  if flags.do_thr
    % keep only the largest coefficients.
    modfilt_outsig=largestr(modfilt_outsig,kv.thr);
  end
  
  % Apply transformation to coefficients.
  if flags.do_noadapt
    % This is a safety measure to avoid log of negative numbers.
    modfilt_outsig(:)=max(modfilt_outsig(:),eps);
    
    modfilt_outsig=20*log10(modfilt_outsig);
  end;
  
  plotfilterbank(modfilt_outsig,1,fc,fs,'argimport',flags,kv,'fc',fc,'fs',fs);

  if nargout>0
    varargout={modfilt_outsig,fc};
  end;
  
end
  
% complex frequency shifted first order lowpass
function [b,a] = efilt(w0,bw);

e0 = exp(-bw/2);

b = 1 - e0;
a = [1, -e0*exp(1i*w0)];