1 files changed, 36 insertions, 12 deletions
diff --git a/externals/grill/fftease/src/leanconvert.c b/externals/grill/fftease/src/leanconvert.c
index 36b1452a..ecb6bc54 100644
--- a/externals/grill/fftease/src/leanconvert.c
+++ b/externals/grill/fftease/src/leanconvert.c
@@ -2,18 +2,42 @@
 
 void leanconvert( float *S, float *C, int N2 )
 {
+	register int i;
 
- int		real, imag,
-		amp, phase;
- float		a, b;
-  int		i;
-	
- for ( i = 0; i <= N2; i++ ) {
-   imag = phase = ( 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 );
-   C[phase] = -atan2( b, a );
- }
+	float a = S[0];  // real value at f=0
+	float b = S[1];  // real value at f=Nyquist
+
+	C[0] = fabs(a);
+	C[1] = 0;
+	S += 2,C += 2;
+
+	for ( i = 1; i < N2; i++,S += 2,C += 2 ) {
+		C[0] = hypot( S[0], S[1] );
+		C[1] = -atan2( S[1], S[0] );
+	}
+
+	C[0] = fabs(b);
+	C[1] = 0;
+}
+
+
+/* unconvert essentially undoes what convert does, i.e., it
+  turns N2+1 PAIRS of amplitude and frequency values in
+  C into N2 PAIR of complex spectrum data (in rfft format)
+  in output array S; sampling rate R and interpolation factor
+  I are used to recompute phase values from frequencies */
+
+void leanunconvert( float *C, float *S, int N2 )
+{
+	register int i;
+
+	S[0] = fabs(C[0]);
+	S[1] = fabs(C[N2*2]);
+	S += 2,C += 2;
+
+	for (i = 1; i < N2; i++,S += 2,C += 2 ) {
+		S[0] = C[0] * cos( C[1] );
+		S[1] = -C[0] * sin( C[1] );
+	}
 }