git status -u, learn something new every day.

libs/libcodec2/octave/cbphase.m

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+% cbphase.m
+% David Rowe Aug 2012
+% Used to experiment with critical band phase perception and smoothing
+
+function cbphase
+
+  Wo = 100.0*pi/4000;
+  L = floor(pi/Wo);
+
+  A = zeros(1,L);
+  phi = zeros(1,L);
+
+  % three harmonics in this band
+
+  b = 4; a = b-1; c = b+1;
+
+  % set up phases and mags for 2nd order system (see phasesecord.m)
+   
+  wres = b*Wo;
+  phi(a) = 3*pi/4 + wres;
+  phi(b) = pi/2 + wres;
+  phi(c) = pi/4 + wres;
+
+  A(a) = 0.707;
+  A(b) = 1;
+  A(c) = 0.707;
+
+  % add linear component
+
+  phi(1) = pi;
+  phi(2:L) = phi(2:L) + (2:L)*phi(1);
+  phi = phi - 2*pi*(floor(phi/(2*pi)) + 0.5);
+
+  N = 16000;
+  Nplot = 250;
+  s = zeros(1,N);
+
+  for m=a:c
+    s_m = A(m)*cos(m*Wo*(0:(N-1)) + phi(m));
+    s = s + s_m;
+  endfor
+
+  figure(2);
+  clf;
+  subplot(211)
+  plot((1:L)*Wo*4000/pi, A,'+');
+  subplot(212)
+  plot((1:L)*Wo*4000/pi, phi,'+');
+
+  %v = A(a)*exp(j*phi(a)) + A(b)*exp(j*phi(b)) + A(c)*exp(j*phi(c));
+  %compass(v,"r")
+  %hold off;
+  
+  % est phi1
+
+  diff = phi(b) - phi(a)
+  sumi = sin(diff);
+  sumr = cos(diff);
+  diff = phi(c) - phi(b)
+  sumi += sin(diff);
+  sumr += cos(diff);
+  phi1_ = atan2(sumi, sumr)
+  s_v = cos(Wo*(0:(N-1)) + phi1_);
+
+  figure(1);
+  clf;
+  subplot(211)
+  plot(s(1:Nplot));
+  hold on;
+  plot(s_v(1:Nplot),"r");
+  hold off;
+
+  % build (hopefully) perceptually similar phase
+
+  phi_(a) = a*phi1_;
+  phi_(b) = b*phi1_;
+  phi_(c) = c*phi1_;
+
+  s_ = zeros(1,N);
+
+  for m=a:c
+    s_m = A(m)*cos(m*Wo*(0:(N-1)) + phi_(m));
+    s_ = s_ + s_m;
+  endfor
+ 
+  subplot(212)
+  plot(s_(1:Nplot));
+  
+  gain = 8000;
+  fs=fopen("orig_ph.raw","wb");
+  fwrite(fs,gain*s,"short");
+  fclose(fs);
+  fs=fopen("mod_ph.raw","wb");
+  fwrite(fs,gain*s_,"short");
+  fclose(fs);
+
+endfunction
+