2 files changed, 40 insertions, 0 deletions
diff --git a/common/alcomplex.c b/common/alcomplex.c
index d68277e3..d4045aeb 100644
--- a/common/alcomplex.c
+++ b/common/alcomplex.c
@@ -59,3 +59,34 @@ void complex_fft(ALcomplex *FFTBuffer, ALsizei FFTSize, ALdouble Sign)
         }
     }
 }
+
+void complex_hilbert(ALcomplex *Buffer, ALsizei size)
+{
+    const ALdouble inverse_size = 1.0/(ALdouble)size;
+    ALsizei todo, i;
+
+    for(i = 0;i < size;i++)
+        Buffer[i].Imag = 0.0;
+
+    complex_fft(Buffer, size, 1.0);
+
+    todo = size >> 1;
+    Buffer[0].Real *= inverse_size;
+    Buffer[0].Imag *= inverse_size;
+    for(i = 1;i < todo;i++)
+    {
+        Buffer[i].Real *= 2.0*inverse_size;
+        Buffer[i].Imag *= 2.0*inverse_size;
+    }
+    Buffer[i].Real *= inverse_size;
+    Buffer[i].Imag *= inverse_size;
+    i++;
+
+    for(;i < size;i++)
+    {
+        Buffer[i].Real = 0.0;
+        Buffer[i].Imag = 0.0;
+    }
+
+    complex_fft(Buffer, size, -1.0);
+}
diff --git a/common/alcomplex.h b/common/alcomplex.h
index cf4683fa..2418ce78 100644
--- a/common/alcomplex.h
+++ b/common/alcomplex.h
@@ -55,6 +55,15 @@ inline ALcomplex complex_mult(ALcomplex a, ALcomplex b)
  */
 void complex_fft(ALcomplex *FFTBuffer, ALsizei FFTSize, ALdouble Sign);
 
+/**
+ * Calculate the complex helical sequence (discrete-time analytical signal) of
+ * the given input using the discrete Hilbert transform (In-place algorithm).
+ * Fills Buffer[0...size-1] with the discrete-time analytical signal stored in
+ * Buffer[0...size-1]. Buffer is an array of complex numbers, size MUST BE
+ * power of two.
+ */
+void complex_hilbert(ALcomplex *Buffer, ALsizei size);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif