encoding.m

clear all
clear variables

% A basic codec

musicFile = dir('musique.wav');

[y,Fs] = audioread('musique.wav');

bitsLength = musicFile.bytes * 8;

fprintf("Sampling frequency : %f\n", Fs);
fprintf("Length in bits : %f\n", bitsLength);

sound(y, Fs);

musicEncodedFile = "musicEncoded.wav";

[npt, scale] = coder(y, Fs, bitsLength, 2000, 2500, musicEncodedFile);

fprintf("Scale : %f\n", scale);
fprintf("Number of Points : %f\n", npt);

function [npt, scale] = coder(y, fs, bits, fmin, fmax, file)

    % tfd computation, then ensures column vector
    tfy = fft(y);
    tfy = tfy(:);
    
    % From frequency mask to matlab index
    npt = length(y);
    kmin = round(npt * fmin / fs) + 1;
    kmax = round(npt * fmax / fs) + 1;
    
    % Mask
    tfymasq = tfy(kmin:kmax);
    
    % Real and imaginary part are stored
    % as both channels of a stereo signal
    tfymasq = [real(tfymasq) imag(tfymasq)];
    
    % Ensures maximum value lower than 1
    scale = max(max(abs(tfymasq))) * 1.01;
    tfymasq = tfymasq / scale;
    
    % Stores with same quantization
    audiowrite(file, tfymasq, fs)
    %, bits)

end

function [y, fs, bits] = decoder(file, fmin, fmax, npt, scale)

% reads the windowed Fourier transform stored in file fichier (wavread);
[tfy, Fs] = audioread('musicEncoded.wav');

% rebuild the original Fourier transform with the assumption that the missing values are null, and rescale it
% properly;
tfy = tfy * scale;



tfy = tfy(:);


% computes the inverse Fourier transform;
y = ifft(tfy);

%returns the decoded signal y, and the same output arguments than function wavread.

end

function [f, tfx] = transffourier(y, Nf, fs)
    
    k = 0:Nf-1;
    f = k*fs/Nf;
    tfx = 1/fs*fft(y, Nf);
  
end