comparison toolboxes/MIRtoolbox1.3.2/AuditoryToolbox/spectrogram.m @ 0:e9a9cd732c1e tip

first hg version after svn

+function [array,raw] = spectrogram(wave,segsize,nlap,ntrans);
+%function array = spectrogram(wave,segsize,nlap,ntrans);
+% defaults spectrogram(wave,128,8,4)
+% nlap is number of hamming windows overlapping a point;
+% ntrans is factor by which transform is bigger than segment;
+% returns a spectrogram 'array' with fourth root of power,
+% filter smoothed and formatted for display.
+
+% Added option to return raw spectrogram.... Malcolm 5/26/95
+% Added code so that input could be any direction ... Malcolm 5/26/95
+% (c) 1998 Interval Research Corporation  
+
+if nargin < 4; ntrans=4; end
+if nargin < 3; nlap=8; end
+if nargin < 2; segsize=128; end
+
+[r c] = size(wave);
+if (r < c)
+	wave = filter([1 -0.95],[1],wave');
+else
+	wave = filter([1 -0.95],[1],wave);
+end
+
+s = length(wave);
+nsegs = floor(s/(segsize/nlap))-nlap+1;
+array = zeros(ntrans/2*segsize,nsegs);
+window = 0.54-0.46*cos(2*pi/(segsize+1)*(1:segsize)');
+for i = 1:nsegs
+ seg = zeros(ntrans*segsize,1); % leave half full of zeroes
+ seg(1:segsize) = ...
+	 window.*wave(((i-1)*segsize/nlap+1):((i+nlap-1)*segsize/nlap));
+ seg = abs(fft(seg));
+						% reverse for image display
+ array(:,i) = seg(((ntrans/2*segsize)+1):(ntrans*segsize));
+end
+
+if nargout > 1
+	raw = array;
+end
+
+array = array .* array;			% back into power domain for smoothing
+
+for i=1:nsegs    % smooth the spectral slices
+ array(:,i) = filter([.2 1 .2],[1],array(:,i));
+end
+
+for i=1:ntrans/2*segsize    % smooth the channels
+ array(i,:) = filter([.2 1 .2],[1],array(i,:));
+end
+
+% compress with square root of amplitude (fourth root of power)
+off = 0.0001*max(max(array));      	% low end stabilization offset,
+array = (off+array).^0.25-off^0.25; 	% better than a threshold hack!
+array = 255/max(max(array))*array;
+
+
+