c@380: /* -*- c-basic-offset: 4 indent-tabs-mode: nil -*-  vi:set ts=8 sts=4 sw=4: */
c@380: 
c@380: /*
c@380:     QM DSP Library
c@380: 
c@380:     Centre for Digital Music, Queen Mary, University of London.
c@380: 
c@380:     This program is free software; you can redistribute it and/or
c@380:     modify it under the terms of the GNU General Public License as
c@380:     published by the Free Software Foundation; either version 2 of the
c@380:     License, or (at your option) any later version.  See the file
c@380:     COPYING included with this distribution for more information.
c@380: */
c@380: 
c@380: #include "DecimatorB.h"
c@380: 
c@380: #include "maths/MathUtilities.h"
c@380: 
c@380: #include <iostream>
c@380: 
c@380: using std::vector;
c@380: 
c@380: DecimatorB::DecimatorB(int inLength, int decFactor)
c@380: {
c@380:     m_inputLength = 0;
c@380:     m_outputLength = 0;
c@380:     m_decFactor = 1;
c@380:     m_aaBuffer = 0;
c@380:     m_tmpBuffer = 0;
c@380: 
c@380:     initialise(inLength, decFactor);
c@380: }
c@380: 
c@380: DecimatorB::~DecimatorB()
c@380: {
c@380:     deInitialise();
c@380: }
c@380: 
c@380: void DecimatorB::initialise(int inLength, int decFactor)
c@380: {
c@380:     m_inputLength = inLength;
c@380:     m_decFactor = decFactor;
c@380:     m_outputLength = m_inputLength / m_decFactor;
c@380: 
c@380:     if (m_decFactor < 2 || !MathUtilities::isPowerOfTwo(m_decFactor)) {
c@380:         std::cerr << "ERROR: DecimatorB::initialise: Decimation factor must be a power of 2 and at least 2 (was: " << m_decFactor << ")" << std::endl;
c@380:         m_decFactor = 0;
c@380:         return;
c@380:     }
c@380: 
c@380:     if (m_inputLength % m_decFactor != 0) {
c@380:         std::cerr << "ERROR: DecimatorB::initialise: inLength must be a multiple of decimation factor (was: " << m_inputLength << ", factor is " << m_decFactor << ")" << std::endl;
c@380:         m_decFactor = 0;
c@380:         return;
c@380:     }        
c@380: 
c@380:     m_aaBuffer = new double[m_inputLength];
c@380:     m_tmpBuffer = new double[m_inputLength];
c@380: 
c@380:     // Order 6 Butterworth lowpass filter
c@380:     // Calculated using e.g. MATLAB butter(6, 0.5, 'low')
c@380: 
c@380:     m_b[0] = 0.029588223638661;
c@380:     m_b[1] = 0.177529341831965;
c@380:     m_b[2] = 0.443823354579912;
c@380:     m_b[3] = 0.591764472773216;
c@380:     m_b[4] = 0.443823354579912;
c@380:     m_b[5] = 0.177529341831965;
c@380:     m_b[6] = 0.029588223638661;
c@380: 
c@380:     m_a[0] = 1.000000000000000;
c@380:     m_a[1] = 0.000000000000000;
c@380:     m_a[2] = 0.777695961855673;
c@380:     m_a[3] = 0.000000000000000;
c@380:     m_a[4] = 0.114199425062434;
c@380:     m_a[5] = 0.000000000000000;
c@380:     m_a[6] = 0.001750925956183;
c@380: 
c@380:     for (int factor = m_decFactor; factor > 1; factor /= 2) {
c@380:         m_o.push_back(vector<double>(6, 0.0));
c@380:     }
c@380: }
c@380: 
c@380: void DecimatorB::deInitialise()
c@380: {
c@380:     delete [] m_aaBuffer;
c@380:     delete [] m_tmpBuffer;
c@380: }
c@380: 
c@380: void DecimatorB::doAntiAlias(const double *src, double *dst, int length,
c@380:                              int filteridx)
c@380: {
c@380:     vector<double> &o = m_o[filteridx];
c@380: 
c@380:     for (int i = 0; i < length; i++) {
c@380: 
cannam@483:         double input = src[i];
cannam@483:         double output = input * m_b[0] + o[0];
c@380: 
cannam@483:         o[0] = input * m_b[1] - output * m_a[1] + o[1];
cannam@483:         o[1] = input * m_b[2] - output * m_a[2] + o[2];
cannam@483:         o[2] = input * m_b[3] - output * m_a[3] + o[3];
cannam@483:         o[3] = input * m_b[4] - output * m_a[4] + o[4];
cannam@483:         o[4] = input * m_b[5] - output * m_a[5] + o[5];
cannam@483:         o[5] = input * m_b[6] - output * m_a[6];
c@380: 
cannam@483:         dst[i] = output;
c@380:     }
c@380: }
c@380: 
c@380: void DecimatorB::doProcess()
c@380: {
c@380:     int filteridx = 0;
c@380:     int factorDone = 1;
c@380: 
c@380:     while (factorDone < m_decFactor) {
c@380: 
c@380:         doAntiAlias(m_tmpBuffer, m_aaBuffer,
c@380:                     m_inputLength / factorDone,
c@380:                     filteridx);
c@380: 
c@380:         filteridx ++;
c@380:         factorDone *= 2;
c@380: 
c@380:         for (int i = 0; i < m_inputLength / factorDone; ++i) {
c@380:             m_tmpBuffer[i] = m_aaBuffer[i * 2];
c@380:         }
c@380:     }
c@380: }
c@380: 
c@380: void DecimatorB::process(const double *src, double *dst)
c@380: {
c@380:     if (m_decFactor == 0) return;
c@380: 
c@380:     for (int i = 0; i < m_inputLength; ++i) {
c@380:         m_tmpBuffer[i] = src[i];
c@380:     }
c@380: 
c@380:     doProcess();
c@380:     
c@380:     for (int i = 0; i < m_outputLength; ++i) {
c@380:         dst[i] = m_tmpBuffer[i];
c@380:     }
c@380: }
c@380: 
c@380: void DecimatorB::process(const float *src, float *dst)
c@380: {
c@380:     if (m_decFactor == 0) return;
c@380: 
c@380:     for (int i = 0; i < m_inputLength; ++i) {
c@380:         m_tmpBuffer[i] = src[i];
c@380:     }
c@380: 
c@380:     doProcess();
c@380:     
c@380:     for (int i = 0; i < m_outputLength; ++i) {
c@380:         dst[i] = m_tmpBuffer[i];
c@380:     }
c@380: }