Does anyone explain me how pitch modification working?

Hi!

Please somebody explain me how pitch modification working. I don't understand exactly what does it do. I got an error message about the function line. Anyone know why? I would like to pitch modify some wave files, but firstly want to know what exactly do.

Thx in advance

Here is the code:

%%Pitch modification

[x Fs nBits] = wavread(filename);

x = x(:);

sent_L = length(x);

semitone = round(semitone);   

if semitone>12|semitone<-12

      semitone = 0;

      fprintf('semitone has to be in [-12 12], where\n ')

end

scale = 2^(semitone/12);   

Le       = 160; 

S       = Le/4; 

overlap = Le - S;   

Nframe  = floor((sent_L-overlap)/S); %lefelé kerekít

Lq      = round(Le*scale);

a       = 0.50;

b       = -0.50;

n       = 1:Le;

win     = sqrt(S)/sqrt((4*a^2+2*b^2)*Le)*(a+b*cos(2*pi*n/Le));

win     = win(:);

n       = 1:Lq;

winq    = sqrt(S)/sqrt((4*a^2+2*b^2)*Lq)*(a+b*cos(2*pi*n/Lq));

winq    = winq(:);

Nit     = 4;

xfinal  = zeros(sent_L,1);

U = sum(win)/(S);

k = 1;

kk = 1;

h = waitbar(0,'Please wait...');

for n = 1:Nframe

      if k:k+Lq-1<=sent_L

          frm = winq.*x(k:k+Lq-1)/U;

      else

          frm = winq.*[x(k:sent_L);zeros(Lq - (sent_L-k+1),1)]/U;

      end

      frm_resamp = resample(frm, Le, Lq);

      xSTFTM = abs(fft(frm_resamp));

      if k+Le-1<=sent_L

          res = xfinal(k:k+e-1);

      else

          res = [xfinal(k:sent_L);zeros(Le - (sent_L-k+1),1)];

      end

      x_recon = iterated_recon(xSTFTM, res, Nit, win);

      if (k+Le-1<=sent_L)

          xfinal(k:k+Le-1) = xfinal(k:k+Le-1) + x_recon;

      else

          xfinal(k:sent_L) = xfinal(k:sent_L) + x_recon(1:sent_L-k+1);

      end

      k = k + S;

      waitbar(n/Nframe, h)

end

close(h)

outfile = [filename(1:end-4),'_pitch_recon.wav'];

wavwrite(xfinal, Fs, outfile);

function x_recon = iterated_recon(xSTFTM, x_res, Nit, win)

j = sqrt(-1);

for i = 1:Nit

      phi = phase(fft(win.*x_res)) + randn(size(x_res))*0.01*pi;

      % random phase purturbation will reduce some resonance.

      x = xSTFTM.*exp(j*phi); %M-constraint

      x_recon = ifft(x);

      x_res = real(x_recon);

end

x_recon = x_res;

Answer 1

[Walter Roberson]

The part of your file before the "function" line is known in MATLAB terms as a "script". It is not allowed in MATLAB to store a "script" and a "function" in the same file. You will need to move the function into the file iterated_recon.m