diff options
| -rw-r--r-- | common/alcomplex.c | 35 | ||||
| -rw-r--r-- | common/alcomplex.h | 9 |
2 files changed, 44 insertions, 0 deletions
diff --git a/common/alcomplex.c b/common/alcomplex.c index d68277e3..8a0786e9 100644 --- a/common/alcomplex.c +++ b/common/alcomplex.c @@ -59,3 +59,38 @@ void complex_fft(ALcomplex *FFTBuffer, ALsizei FFTSize, ALdouble Sign) } } } + +/*Discrete Hilbert Transform (analytic signal form)*/ +void hilbert(ALsizei size, ALcomplex *InOutBuffer )
+{
+ ALsizei k;
+ const ALdouble inverse_size = 1.0/(ALfloat)size;
+
+ for ( k = 0; k < size;k++ )
+ InOutBuffer[k].Imag = 0.0;
+
+ complex_fft( InOutBuffer, size, 1.0 );
+
+ for( k = 0; k < size; k++ )
+ {
+ if( k == 0 || k == size/2 )
+ {
+ InOutBuffer[k].Real *= inverse_size;
+ InOutBuffer[k].Imag *= inverse_size;
+ }
+
+ else if ( k >=1 && k < size/2 )
+ {
+ InOutBuffer[k].Real *= 2.0*inverse_size;
+ InOutBuffer[k].Imag *= 2.0*inverse_size;
+ }
+
+ else
+ {
+ InOutBuffer[k].Real = 0.0;
+ InOutBuffer[k].Imag = 0.0;
+ }
+ }
+
+ complex_fft( InOutBuffer, size,-1.0 );
+} diff --git a/common/alcomplex.h b/common/alcomplex.h index cf4683fa..cfd164b6 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 (or discrete-time analytical signal) + *of the given input using the discrete Hilbert transform (In-place algorithm). + *Fills InOutBuffer[0...size-1] with the discrete-time analytical signal stored + *in InOutBuffer[0...size-1]. InOutBuffer is an array of complex numbers, + *size MUST BE power of two. + */ +void hilbert(ALsizei size, ALcomplex *InOutBuffer ); + #ifdef __cplusplus } // extern "C" #endif |