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Common: Implement discrete Hilbert transform

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Raulshc 2018-05-20 17:21:50 +02:00 committed by GitHub
parent cd2fd126c4
commit dd51ba396b
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2 changed files with 44 additions and 0 deletions
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35
common/alcomplex.c
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@ -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 );
}

9
common/alcomplex.h
View File

@ -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