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src/SAR1Q5.m

+%Q1_5
+% Chargement du son
+fichier = fullfile('wav', 'single_tone_piano1');
+[signal, Fs] = audioread(fichier);
+% Mono si besoin
+if size(signal,2) == 2
+    signal = mean(signal, 2);
+end
+
+% Extraire 1 seconde de son
+duration = 1;
+N = min(length(signal), round(duration*Fs));
+signal = signal(1:N);
+
+% FFT
+Nfft = length(signal);
+Y = fft(signal);
+f = (0:Nfft-1)*(Fs/Nfft);
+
+% Spectre moitié 
+Y_half = Y(1:floor(Nfft/2));
+f_half = f(1:floor(Nfft/2));
+
+% Détection du fondamentale
+[~, idx_fundamental] = max(abs(Y_half));
+f0 = f_half(idx_fundamental);
+
+% Récupérer les indices des 8 premières harmoniques
+harmonics_freqs = f0 * (1:8);
+harmonic_indices = zeros(1,8);
+
+for k = 1:8
+    [~, idx] = min(abs(f - harmonics_freqs(k)));
+    harmonic_indices(k) = idx;
+end
+
+% Construire un nouveau spectre : garder seulement les harmoniques
+Y_harmonics = zeros(size(Y));
+for idx = harmonic_indices
+    Y_harmonics(idx) = Y(idx);                  % Fréquence positive
+    if idx ~= 1  % éviter de doubler le DC
+        Y_harmonics(end - idx + 2) = conj(Y(idx));  % Fréquence négative conjuguée
+    end
+end
+
+% Reconstruction via IFFT
+synth_ifft = real(ifft(Y_harmonics));
+
+% Normalisation
+synth_ifft = synth_ifft / max(abs(synth_ifft));
+
+% Appliquer enveloppe ADSR
+t = (0:length(synth_ifft)-1)' / Fs;
+
+% ADSR paramètres
+T_attack = 0.05;
+T_decay = 0.1;
+T_sustain = 0.7;
+T_release = 0.2;
+
+n_attack = round(T_attack * Fs);
+n_decay = round(T_decay * Fs);
+n_release = round(T_release * Fs);
+n_sustain = length(t) - (n_attack + n_decay + n_release);
+
+if n_sustain < 0
+    error('Durée insuffisante pour l’ADSR définie.');
+end
+
+env_attack = linspace(0,1,n_attack)';
+env_decay = linspace(1,T_sustain,n_decay)';
+env_sustain = T_sustain * ones(n_sustain,1);
+env_release = linspace(T_sustain,0,n_release)';
+
+envelope = [env_attack; env_decay; env_sustain; env_release];
+
+% Appliquer l’enveloppe
+synth_ifft = synth_ifft .* envelope;
+
+% Écoute
+sound(synth_ifft, Fs);
+
+% Sauvegarde si besoin
+audiowrite('synth_ifft_ADSR.wav', synth_ifft, Fs);
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