I'm trying to find the fundamental frequencies present in a piano recording using MATLAB. These are the steps I've followed;
Find the envelop of the signal
Find the note onsets
perform FFT between each onset
Harmonic product spectrum.
It's when I try to implement the HPS algorithm that I face a "dimensions don't agree" error. This is the whole code that implements the HPS algorithm .
**% In harmonic prodcut spectrum, you downsample the fft data several times and multiply all those with the original fft data to get the maximum peak. %HPS seg_fft = seg_fft(1 : size(seg_fft,1)/2 ); seg_fft = abs(seg_fft); %HPS: downsampling for i = 1:length(seg_fft) seg_fft2(i,1) = 1; seg_fft3(i,1) = 1; seg_fft4(i,1) = 1; % seg_fft5(i,1) = 1; end for i = 1:floor((length(seg_fft)-1)/2) seg_fft2(i,1) = (seg_fft(2*i,1) + seg_fft((2*i)+1,1))/2; end for i = 1:floor((length(seg_fft)-2)/3) seg_fft3(i,1) = (seg_fft(3*i,1) + seg_fft((3*i)+1,1) + seg_fft((3*i)+2,1))/3; end for i = 1:floor((length(seg_fft)-3)/4) seg_fft4(i,1) = (seg_fft(4*i,1) + seg_fft((4*i)+1,1) + seg_fft((4*i)+2,1) + seg_fft((4*i)+3,1))/4; end %HPS, PartII: calculate product p1 = (seg_fft3) .* (seg_fft4); p2 = p1.* (seg_fft2); p3 = p2.* (seg_fft); HPS, PartIII: find max [f_y1,I] = max(p3) for c = 1 : length(p3) if(p3(c,1) == f_y1) index = c; end end % Convert that to a frequency f_y(h) = (index / NFFT) * FS; h = 1; h=h+1; f_y = abs(f_y)'; end**
p3 = p2.* (seg_fft); the sizes of seg_fft, seg_fft2, seg_fft3, seg_fft4 all have the same dimensions of 16384 1. Then when I DO implement
p3 = p2.* (seg_fft); the size of
seg_fft changes to 8192 1 while the sizes of rest remain at 16384 1 thus causing an error in multiplication as the dimensions aren't the same.
I'm really confused as to why this keeps happening and nothing I try seems to work out. Would really REALLY appreciate some help here... If someone could fix this code it'd be a GREAT help... Thanx in advance.. I'm real desperate here......