spectrogram plotting in matlab
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Hello, I am trying to plot a spectrogram of audio directly from microphone. i did it and the plot looks like this: http://i56.tinypic.com/avg93a.jpg, but i would like something like this, certain range of frequency have a certain colour as the background and in there when i get a signal depended on the intensity of it, it should be light or darker. like this: http://i55.tinypic.com/28holg5.jpg. I am not so sure how to do it, please help and thank you
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Bjorn Gustavsson
2011-7-14
Ok, for this I guess you could do something like this:
t=0:0.001:2; % 2 secs @ 1kHz sample rate
x=chirp(t,0,1,150); % Start @ DC, cross 150Hz at t=1sec
F = 0:.1:100;
[y,f,t,p] = spectrogram(x,256,250,F,1E3,'yaxis');
pcolor(t,f,10*log10(abs(p)));shading flat
% That should be your spectrogram.
% But you wanted the colour to represent frequency
% so make an HSV image with the frequency linearly scaled
% between 0-1 into the hue chanel:
for i2 = 1:size(t,2),
hsv(:,i2,1) = f/max(f);
end
% Then you have to map your amplitude/power to the
% Saturation and value/intensity chanels (and keep the
% values between 0-1):
hsv(:,:,3) = ((p-min(p(:)))/(max(p(:)-min(p(:))))).^0.2;
hsv(:,:,2) = (p-min(p(:)))/(max(p(:)-min(p(:))));
[min(min(hsv(:,:,2))), max(max(hsv(:,:,2)))]
hsv(:,:,2) = log10(1+10*hsv(:,:,2));
[min(min(hsv(:,:,2))), max(max(hsv(:,:,2)))]
hsv(:,:,2) = hsv(:,:,2)/max(max(hsv(:,:,2)));
% Change these after taste...
% Then convert from HSV to RGB:
rgb = hsv2rgb(hsv);
% And display:
imagesc(rgb)
For more advanced displaying of rgb-images I like: http://www.mathworks.com/matlabcentral/fileexchange/3777-tcolor-a-fast-pcolor-that-likes-rgb-images
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