Question

Make a simple code of matlab, of autotune or a vocoder

Answer 1

We consider a code of building an LPC vocoder.

function [A,G,a,r]=autolpc(x,p)

%

% function to computer the autocorrelation method solution

%

% Inputs:

% x is the signal frame (usually speech weighted by a window)

% p is the lpc model order

%

% Outputs:

% A is the denominator vector for the lpc solution, i.e.,

% A=1-a1z^{-1}-a2z^{-2}-...-apz^{-p}

% G is the lpc model gain (rms prediction error)

% a is the lpc polynomial (without the 1 term)

% r is the vector of autocorrelation coefficients

% see also ATOK, KTOA, RTOA

% solve for the lpc polynomial using a simple matrix inversion method

L=length(x);

r=[];

for i=0:p

r=[r; sum(x(1:L-i).*x(1+i:L))];

end

R=toeplitz(r(1:p));

a=inv(R)*r(2:p+1);

A=[1; -a];

G=sqrt(sum(A.*r));

end