/// <summary>
/// Result = A (*) B
/// By using DFT for calculations
/// </summary>
/// <param name="A"></param>
/// <param name="B"></param>
/// <param name="Result"></param>
public static void Convolution_DFT_F( FxVectorF A, FxVectorF B, out FxVectorF Result )
{
FxVectorF A_dftReal,A_dftImag,B_dftReal,B_dftImag;
TimeStatistics.ClockLap( "Enter" );
// get the max size from A,B
int maxSize = ( A.Size > B.Size ) ? A.Size : B.Size;
// check for padding
if ( A.Size == maxSize && B.Size != maxSize ) {
// increase the size of B
B.Padding( maxSize - B.Size, true, 0 );
} else if ( B.Size == maxSize && A.Size != maxSize ) {
A.Padding( maxSize - A.Size, true, 0 );
}
TimeStatistics.ClockLap( "AfterPadding" );
// calc the DFT of the signal
SignalTools.DFT_F( A, true, out A_dftReal, out A_dftImag );
TimeStatistics.ClockLap( "After DFT A" );
// calc the DFT of the signal
SignalTools.DFT_F( B, true, out B_dftReal, out B_dftImag );
TimeStatistics.ClockLap( "After DFT B" );
// allocate result vector
Result = new FxVectorF( maxSize );
float real,imag;
// do the multiplication
for ( int i=0; i < maxSize; i++ ) {
// complex multiplication
real = A_dftReal[i] * B_dftReal[i] - A_dftImag[i] * B_dftImag[i];
imag = A_dftReal[i] * B_dftImag[i] + A_dftImag[i] * B_dftReal[i];
// set the new values
A_dftReal[i] = real;
A_dftImag[i] = imag;
}
TimeStatistics.ClockLap( "After multiplication" );
// calc the DFT of the signal
SignalTools.DFT_F( A_dftReal, A_dftImag, false, out Result, out B_dftImag );
TimeStatistics.ClockLap( "After iDFT" );
}
/// <summary>
/// Create a new filter base on existing data
/// </summary>
/// <param name="filter"></param>
public FIR_GenericFilter( FxVectorF filter )
{
p_Impulse = filter.GetCopy() as FxVectorF;
// normalize the filter
p_Impulse.Divide( (float)p_Impulse.Norms( NormVectorType.Manhattan ) );
// check that is power of 2 ( we do that for speed )
if ( Math.Pow( 2, Math.Log( p_Impulse.Size, 2 ) ) != p_Impulse.Size ) {
// calc the size of log2 extence
int sizeLog2 = (int)Math.Floor( Math.Log( p_Impulse.Size, 2 ) ) + 1;
// calc the new maxSize
int newSize = (int)Math.Pow( 2, sizeLog2 );
// increase the size of Impulse
p_Impulse.Padding( newSize - p_Impulse.Size, true, 0 );
}
// calc the fft of impulse
TransformImpulseToFFT();
}
