diff options
Diffstat (limited to 'libs/qm-dsp/dsp/transforms/FFT.cpp')
-rw-r--r-- | libs/qm-dsp/dsp/transforms/FFT.cpp | 181 |
1 files changed, 181 insertions, 0 deletions
diff --git a/libs/qm-dsp/dsp/transforms/FFT.cpp b/libs/qm-dsp/dsp/transforms/FFT.cpp new file mode 100644 index 0000000000..454cfb1422 --- /dev/null +++ b/libs/qm-dsp/dsp/transforms/FFT.cpp @@ -0,0 +1,181 @@ +/* -*- c-basic-offset: 4 indent-tabs-mode: nil -*- vi:set ts=8 sts=4 sw=4: */ + +/* + QM DSP Library + + Centre for Digital Music, Queen Mary, University of London. + This file is based on Don Cross's public domain FFT implementation. +*/ + +#include "FFT.h" + +#include "maths/MathUtilities.h" + +#include <cmath> + +#include <iostream> + +FFT::FFT(unsigned int n) : + m_n(n), + m_private(0) +{ + if( !MathUtilities::isPowerOfTwo(m_n) ) + { + std::cerr << "ERROR: FFT: Non-power-of-two FFT size " + << m_n << " not supported in this implementation" + << std::endl; + return; + } +} + +FFT::~FFT() +{ + +} + +FFTReal::FFTReal(unsigned int n) : + m_n(n), + m_private_real(0) +{ + m_private_real = new FFT(m_n); +} + +FFTReal::~FFTReal() +{ + delete (FFT *)m_private_real; +} + +void +FFTReal::process(bool inverse, + const double *realIn, + double *realOut, double *imagOut) +{ + ((FFT *)m_private_real)->process(inverse, realIn, 0, realOut, imagOut); +} + +static unsigned int numberOfBitsNeeded(unsigned int p_nSamples) +{ + int i; + + if( p_nSamples < 2 ) + { + return 0; + } + + for ( i=0; ; i++ ) + { + if( p_nSamples & (1 << i) ) return i; + } +} + +static unsigned int reverseBits(unsigned int p_nIndex, unsigned int p_nBits) +{ + unsigned int i, rev; + + for(i=rev=0; i < p_nBits; i++) + { + rev = (rev << 1) | (p_nIndex & 1); + p_nIndex >>= 1; + } + + return rev; +} + +void +FFT::process(bool p_bInverseTransform, + const double *p_lpRealIn, const double *p_lpImagIn, + double *p_lpRealOut, double *p_lpImagOut) +{ + if (!p_lpRealIn || !p_lpRealOut || !p_lpImagOut) return; + +// std::cerr << "FFT::process(" << m_n << "," << p_bInverseTransform << ")" << std::endl; + + unsigned int NumBits; + unsigned int i, j, k, n; + unsigned int BlockSize, BlockEnd; + + double angle_numerator = 2.0 * M_PI; + double tr, ti; + + if( !MathUtilities::isPowerOfTwo(m_n) ) + { + std::cerr << "ERROR: FFT::process: Non-power-of-two FFT size " + << m_n << " not supported in this implementation" + << std::endl; + return; + } + + if( p_bInverseTransform ) angle_numerator = -angle_numerator; + + NumBits = numberOfBitsNeeded ( m_n ); + + + for( i=0; i < m_n; i++ ) + { + j = reverseBits ( i, NumBits ); + p_lpRealOut[j] = p_lpRealIn[i]; + p_lpImagOut[j] = (p_lpImagIn == 0) ? 0.0 : p_lpImagIn[i]; + } + + + BlockEnd = 1; + for( BlockSize = 2; BlockSize <= m_n; BlockSize <<= 1 ) + { + double delta_angle = angle_numerator / (double)BlockSize; + double sm2 = -sin ( -2 * delta_angle ); + double sm1 = -sin ( -delta_angle ); + double cm2 = cos ( -2 * delta_angle ); + double cm1 = cos ( -delta_angle ); + double w = 2 * cm1; + double ar[3], ai[3]; + + for( i=0; i < m_n; i += BlockSize ) + { + + ar[2] = cm2; + ar[1] = cm1; + + ai[2] = sm2; + ai[1] = sm1; + + for ( j=i, n=0; n < BlockEnd; j++, n++ ) + { + + ar[0] = w*ar[1] - ar[2]; + ar[2] = ar[1]; + ar[1] = ar[0]; + + ai[0] = w*ai[1] - ai[2]; + ai[2] = ai[1]; + ai[1] = ai[0]; + + k = j + BlockEnd; + tr = ar[0]*p_lpRealOut[k] - ai[0]*p_lpImagOut[k]; + ti = ar[0]*p_lpImagOut[k] + ai[0]*p_lpRealOut[k]; + + p_lpRealOut[k] = p_lpRealOut[j] - tr; + p_lpImagOut[k] = p_lpImagOut[j] - ti; + + p_lpRealOut[j] += tr; + p_lpImagOut[j] += ti; + + } + } + + BlockEnd = BlockSize; + + } + + + if( p_bInverseTransform ) + { + double denom = (double)m_n; + + for ( i=0; i < m_n; i++ ) + { + p_lpRealOut[i] /= denom; + p_lpImagOut[i] /= denom; + } + } +} + |