function varargout=sgram(f,varargin)
%SGRAM Spectrogram
% Usage: sgram(f,op1,op2, ... );
% sgram(f,fs,op1,op2, ... );
% C=sgram(f, ... );
%
% SGRAM(f) plots a spectrogram of f using a Discrete Gabor Transform (DGT).
%
% SGRAM(f,fs) does the same for a signal with sampling rate fs (sampled
% with fs samples per second);
%
% SGRAM(f,fs,dynrange) additionally limits the dynamic range of the
% plot. See the description of the 'dynrange' parameter below.
%
% C=SGRAM(f, ... ) returns the image to be displayed as a matrix. Use this
% in conjunction with imwrite etc. These coefficients are *only* intended to
% be used by post-processing image tools. Numerical Gabor signal analysis
% and synthesis should *always* be done using the DGT, IDGT, DGTREAL and
% IDGTREAL functions.
%
% Additional arguments can be supplied like this:
%
% sgram(f,fs,'dynrange',50)
%
% The arguments must be character strings possibly followed by an
% argument:
%
% 'dynrange',r Limit the dynamical range to r by using a colormap in
% the interval [chigh-r,chigh], where chigh is the highest
% value in the plot. The default value of [] means to not
% limit the dynamical range.
%
% 'db' Apply 20*log10 to the coefficients. This makes it possible to
% see very weak phenomena, but it might show too much noise. A
% logarithmic scale is more adapted to perception of sound.
% This is the default.
%
% 'lin' Show the energy of the coefficients on a linear scale.
%
% 'tfr',v Set the ratio of frequency resolution to time resolution.
% A value v=1 is the default. Setting v>1 will give better
% frequency resolution at the expense of a worse time
% resolution. A value of 0<v<1 will do the opposite.
%
% 'wlen',s Window length. Specifies the length of the window
% measured in samples. See help of PGAUSS on the exact
% details of the window length.
%
% 'posfreq' Display only the positive frequencies. This is the
% default for real-valued signals.
%
% 'nf' Display negative frequencies, with the zero-frequency
% centered in the middle. For real signals, this will just
% mirror the upper half plane. This is standard for complex
% signals.
%
% 'tc' Time centering. Move the beginning of the signal to the
% middle of the plot. This is useful for visualizing the
% window functions of the toolbox.
%
% '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.
%
% 'thr',r Keep only the largest fraction r of the coefficients, and
% set the rest to zero.
%
% 'fmax',y Display y as the highest frequency. Default value of []
% means to use the Nyquist frequency.
%
% 'xres',xres Approximate number of pixels along x-axis / time.
% The default value is 800
%
% 'yres',yres Approximate number of pixels along y-axis / frequency
% The Default value is 600
%
% 'contour' Do a contour plot to display the spectrogram.
%
% 'surf' Do a surf plot to display the spectrogram.
%
% 'colorbar' Display the colorbar. This is the default.
%
% 'nocolorbar' Do not display the colorbar.
%
% In addition to these parameters, SGRAM accepts any of the flags from
% SETNORM. The window used to calculate the spectrogram will be
% normalized as specified.
%
% Examples:
% ---------
%
% The GREASY signal is sampled using a sampling rate of 16 kHz. To
% display a spectrogram of GREASY with a dynamic range of 90 dB, use:
%
% sgram(greasy,16000,90);
%
% To create a spectrogram with a window length of 20ms (which is
% typically used in speech analysis) use :
%
% fs=16000;
% sgram(greasy,fs,90,'wlen',round(20/1000*fs));
%
% See also: dgt, dgtreal
%
% Url: http://ltfat.github.io/doc/gabor/sgram.html
% Copyright (C) 2005-2023 Peter L. Soendergaard <peter@sonderport.dk> and others.
% This file is part of LTFAT version 2.6.0
%
% 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 L. Søndergaard.
% TESTING: NA
% REFERENCE: NA
if nargin<1
error('Too few input arguments.');
end;
if sum(size(f)>1)>1
error('Input must be a vector.');
end;
definput.import={'ltfattranslate','setnorm','tfplot'};
% Override the setting from tfplot, because SGRAM does not support the
% 'dbsq' setting (it does not make sense).
definput.flags.log={'db','lin'};
% Define initial value for flags and key/value pairs.
definput.flags.wlen={'nowlen','wlen'};
definput.flags.thr={'nothr','thr'};
if isreal(f)
definput.flags.posfreq={'posfreq','nf'};
else
definput.flags.posfreq={'nf','posfreq'};
end;
definput.keyvals.tfr=1;
definput.keyvals.wlen=0;
definput.keyvals.thr=0;
definput.keyvals.fmax=[];
definput.keyvals.xres=800;
definput.keyvals.yres=600;
[flags,kv,fs]=ltfatarghelper({'fs','dynrange'},definput,varargin);
% Downsample
if ~isempty(kv.fmax)
if ~isempty(fs)
resamp=kv.fmax*2/fs;
else
resamp=kv.fmax*2/length(f);
end;
f=fftresample(f,round(length(f)*resamp));
kv.fs=2*kv.fmax;
end;
Ls=length(f);
if flags.do_posfreq
kv.yres=2*kv.yres;
end;
try
[a,M,L,N,Ndisp]=gabimagepars(Ls,kv.xres,kv.yres);
catch
err=lasterror;
if strcmp(err.identifier,'LTFAT:noframe')
error(sprintf(['The signal is too long. SGRAM cannot visualize all the details.\n' ...
'Try a shorter signal or increase the image resolution by calling:\n\n' ...
' sgram(...,''xres'',xres,''yres'',yres);\n\n' ...
'for larger values of xres and yres.\n'...
'The current values are:\n xres=%i\n yres=%i'],kv.xres,kv.yres));
else
rethrow(err);
end;
end;
% Set an explicit window length, if this was specified.
if flags.do_wlen
kv.tfr=kv.wlen^2/L;
end;
g={'gauss',kv.tfr,flags.norm};
if flags.do_nf
coef=abs(dgt(f,g,a,M));
else
coef=abs(dgtreal(f,g,a,M));
end;
% Cut away zero-extension.
coef=coef(:,1:Ndisp);
if flags.do_thr
% keep only the largest coefficients.
coef=largestr(coef,kv.thr);
end
if flags.do_nf
coef=plotdgt(coef,a,'argimport',flags,kv);
else
coef=plotdgtreal(coef,a,M,'argimport',flags,kv);
end;
if nargout>0
varargout={coef};
end;