""

svn path=/trunk/; revision=325

1 files changed, 55 insertions, 0 deletions

diff --git a/externals/grill/fftease/src/convert.c b/externals/grill/fftease/src/convert.c
new file mode 100644
index 00000000..8eb238f0
--- /dev/null
+++ b/externals/grill/fftease/src/convert.c
@@ -0,0 +1,55 @@
+#include "pv.h"
+
+/* S is a spectrum in rfft format, i.e., it contains N real values
+   arranged as real followed by imaginary values, except for first
+   two values, which are real parts of 0 and Nyquist frequencies;
+   convert first changes these into N/2+1 PAIRS of magnitude and
+   phase values to be stored in output array C; the phases are then
+   unwrapped and successive phase differences are used to compute
+   estimates of the instantaneous frequencies for each phase vocoder
+   analysis channel; decimation rate D and sampling rate R are used
+   to render these frequency values directly in Hz. */
+
+void convert(float *S, float *C, int N2, float *lastphase,  float fundamental, float factor )
+{
+  float 	phase,
+		phasediff;
+  int 		real,
+		imag,
+		amp,
+		freq;
+  float 	a,
+		b;
+  int 		i;
+
+  float myTWOPI, myPI;
+
+  myTWOPI = 8.*atan(1.);
+  myPI = 4.*atan(1.);
+
+
+    for ( i = 0; i <= N2; i++ ) {
+      imag = freq = ( real = amp = i<<1 ) + 1;
+      a = ( i == N2 ? S[1] : S[real] );
+      b = ( i == 0 || i == N2 ? 0. : S[imag] );
+
+      C[amp] = hypot( a, b );
+      if ( C[amp] == 0. )
+	phasediff = 0.;
+      else {
+	phasediff = ( phase = -atan2( b, a ) ) - lastphase[i];
+	lastphase[i] = phase;
+	
+	while ( phasediff > myPI )
+	  phasediff -= myTWOPI;
+	while ( phasediff < -myPI )
+	  phasediff += myTWOPI;
+      }
+      C[freq] = phasediff*factor + i*fundamental;
+      /*
+      if( i > 8 && i < 12 ) {
+	fprintf(stderr,"convert freq %d: %f\n",i, C[freq]);
+      }
+      */
+    }
+}