Adding the Vocoder part

chanvocoder.m

@@ -0,0 +1,66 @@
+function y = chanvocoder(carrier, modul, chan, numband, overlap)
+% y = chanvocoder(carrier, modul, chan, numband, overlap)
+% The Channel Vocoder modulates the carrier signal with the modulation signal
+% chan = number of channels         (e.g., 512)
+% numband = number of bands (<chan) (e.g., 32)
+% overlap = window overlap          (e.g., 1/4)
+
+if numband>chan
+	error('# bands must be < # channels')
+end
+
+[rc, cc]   = size(carrier);
+if cc>rc
+	carrier = carrier';
+end
+
+[rm, cm]   = size(modul);
+if cm>rm
+	modul = modul';
+end
+
+st         = min(rc,cc);                         % stereo or mono?
+if st~= min(rm,cm)
+	error('carrier and modulator must have same number of tracks');
+end
+
+len        = min(length(carrier),length(modul)); % find shortest length
+carrier    = carrier(1:len,1:st);                % shorten carrier if needed
+modul      = modul(1:len,1:st);                  % shorten modulator if needed
+L          = 2*chan;                             % window length/FFT length
+w          = hanning(L); 
+if st==2
+	w=[w w];
+end  % window/ stereo window
+
+bands      = 1:round(chan/numband):chan;         % indices for frequency bands     
+bands(end) = chan;
+y          = zeros(len,st);                      % output vector
+
+ii         = 0;
+while ii*L*overlap+L <= len
+    ind    = round([1+ii*L*overlap:ii*L*overlap+L]);
+    FFTmod = fft( modul(ind,:) .* w );    % window & take FFT of modulator
+    FFTcar = fft( carrier(ind,:) .* w );  % window & take FFT of carrier  
+    syn    = zeros(chan,st);              % place for synthesized output
+    for jj = 1:numband-1                  % for each frequency band
+        b        = [bands(jj):bands(jj+1)-1]; % current band
+        syn(b,:) = FFTcar(b,:)*diag(mean(abs(FFTmod(b,:))));
+    end                                   % take product of spectra
+    midval   = FFTmod(1+L/2,:).*FFTcar(1+L/2,:); % midpoint is special
+    synfull  = [syn; midval; flipud( conj( syn(2:end,:) ) );]; % + and - frequencies
+    timsig   = real( ifft(synfull) );     % invert back to time
+    y(ind,:) = y(ind,:) + timsig;         % add back into time waveform   
+    ii       = ii+1;
+end
+y = 0.8*y/max(max(abs(y)));               % normalize output
+
+figure;
+set(gcf, 'name','a vs b');
+title('a vs b');
+plot(t_downsample,y_downsampled,'b');
+hold on;
+plot(t_decimate,y_decimated,'g');
+xlabel('time(s)');
+ylabel('amplitude(n.u)');
+legend('o','i',"location","southeastoutside");

chanvocoder2.m

@@ -0,0 +1,83 @@
+
+function [y, modul, carrier, output] = chanvocoder(carrier, modul, chan, numband, overlap)
+% y = chanvocoder(carrier, modul, chan, numband, overlap)
+% The Channel Vocoder modulates the carrier signal with the modulation signal
+% chan = number of channels         (e.g., 512)
+% numband = number of bands (<chan) (e.g., 32)
+% overlap = window overlap          (e.g., 1/4)
+
+if numband>chan
+    error('# bands must be < # channels')
+end
+
+[rc, cc]   = size(carrier);
+if cc>rc
+    carrier = carrier';
+end
+
+[rm, cm]   = size(modul);
+if cm>rm
+    modul = modul';
+end
+
+st         = min(rc,cc);                         % stereo or mono?
+if st~= min(rm,cm)
+    error('carrier and modulator must have the same number of tracks');
+end
+
+len        = min(length(carrier),length(modul)); % find shortest length
+carrier    = carrier(1:len,1:st);                % shorten carrier if needed
+modul      = modul(1:len,1:st);                  % shorten modulator if needed
+L          = 2*chan;                             % window length/FFT length
+w          = hanning(L); 
+if st==2
+    w=[w w];
+end  % window/ stereo window
+
+bands      = 1:round(chan/numband):chan;         % indices for frequency bands     
+bands(end) = chan;
+y          = zeros(len,st);                      % output vector
+modul_out  = zeros(len,st);                      % modulator signal for output
+carrier_out= zeros(len,st);                      % carrier signal for output
+
+ii         = 0;
+while ii*L*overlap+L <= len
+    ind    = round([1+ii*L*overlap:ii*L*overlap+L]);
+    FFTmod = fft( modul(ind,:) .* w );    % window & take FFT of modulator
+    FFTcar = fft( carrier(ind,:) .* w );  % window & take FFT of carrier  
+    syn    = zeros(chan,st);              % place for synthesized output
+    for jj = 1:numband-1                  % for each frequency band
+        b        = [bands(jj):bands(jj+1)-1]; % current band
+        syn(b,:) = FFTcar(b,:)*diag(mean(abs(FFTmod(b,:))));
+    end                                   % take product of spectra
+    midval   = FFTmod(1+L/2,:).*FFTcar(1+L/2,:); % midpoint is special
+    synfull  = [syn; midval; flipud( conj( syn(2:end,:) ) );]; % + and - frequencies
+    timsig   = real( ifft(synfull) );     % invert back to time
+    y(ind,:) = y(ind,:) + timsig;         % add back into time waveform   
+    modul_out(ind,:) = modul(ind,:);      % save modulator signal for output
+    carrier_out(ind,:) = carrier(ind,:);  % save carrier signal for output
+    ii       = ii+1;
+end
+y = 0.8*y/max(max(abs(y)));               % normalize output
+
+% Plotting
+t = (0:len-1) / st;  % time vector
+
+% Plot modulator, carrier, and output signals
+subplot(3,1,1);
+plot(t, modul_out);
+title('Modulator Signal');
+xlabel('Time (s)');
+ylabel('Amplitude');
+
+subplot(3,1,2);
+plot(t, carrier_out);
+title('Carrier Signal');
+xlabel('Time (s)');
+ylabel('Amplitude');
+
+subplot(3,1,3);
+plot(t, y);
+title('Output Signal');
+xlabel('Time (s)');
+ylabel('Amplitude');

main.m

@@ -0,0 +1 @@
+modfile='./data/modulator22.wav';
carfile='./data/carrier22.wav';
outfile='./data/vocodedsound.wav';

[modul, sr1]=audioread(modfile);
[carrier, sr2]=audioread(carfile);

if sr1~=sr2, disp('your sampling rates dont match'); end
y= chanvocoder2(carrier, modul, 512, 16, .2)
srl=sr1;

audiowrite('./data/modulator22_chanvocoder.wav', y , sr1);
spectrogram(y,srl,5,30);
spectrogram(y,srl,5,5);

speech_analysis.m

@@ -35,8 +35,8 @@ t_speedown=0:1/fs_speedown:length(y_speedown)/fs_speedown-1/fs_speedown;
 %frequencySpectrum(y_speedown, fs_speedown, true);
 
 %Illustrate the spectogram of the speed down version at 2 windows values (1 for a precise frequency read and 1 for a precise time domain)
-%spectrogram(y_speedown, fs_speedown, 5, 30);
+spectrogram(y_speedown, fs_speedown, 5, 30);
-%spectrogram(y_speedown, fs_speedown, 5, 5);
+spectrogram(y_speedown, fs_speedown, 5, 5);
 
 %Lowering the sampling frequency using the downsample() function
 ##y_downsampled = downsample(y, 2);