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