BogaudioModules

BogaudioModules for VCV Rack
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resample.cpp (2462B)

      1 
      2 #include <assert.h>
      3 #include <math.h>
      4 #include <algorithm>
      5 
      6 #include "filters/resample.hpp"
      7 
      8 using namespace bogaudio::dsp;
      9 
     10 void LPFDecimator::setParams(float sampleRate, int factor) {
     11 	_factor = factor;
     12 	_filter.setParams(
     13 		MultipoleFilter::LP_TYPE,
     14 		4,
     15 		factor * sampleRate,
     16 		0.45f * sampleRate,
     17 		0
     18 	);
     19 }
     20 
     21 float LPFDecimator::next(const float* buf) {
     22 	float s = 0.0f;
     23 	for (int i = 0; i < _factor; ++i) {
     24 		s = _filter.next(buf[i]);
     25 	}
     26 	return s;
     27 }
     28 
     29 
     30 // cascaded integrator–comb decimator: https://en.wikipedia.org/wiki/Cascaded_integrator%E2%80%93comb_filter
     31 CICDecimator::CICDecimator(int stages, int factor) {
     32 	assert(stages > 0);
     33 	_stages = stages;
     34 	_integrators = new T[_stages + 1] {};
     35 	_combs = new T[_stages] {};
     36 	setParams(0.0f, factor);
     37 }
     38 
     39 CICDecimator::~CICDecimator() {
     40 	delete[] _integrators;
     41 	delete[] _combs;
     42 }
     43 
     44 void CICDecimator::setParams(float _sampleRate, int factor) {
     45 	assert(factor > 0);
     46 	if (_factor != factor) {
     47 		_factor = factor;
     48 		_gainCorrection = 1.0f / (float)(pow(_factor, _stages));
     49 	}
     50 }
     51 
     52 float CICDecimator::next(const float* buf) {
     53 	for (int i = 0; i < _factor; ++i) {
     54 		_integrators[0] = buf[i] * scale;
     55 		for (int j = 1; j <= _stages; ++j) {
     56 			_integrators[j] += _integrators[j - 1];
     57 		}
     58 	}
     59 	T s = _integrators[_stages];
     60 	for (int i = 0; i < _stages; ++i) {
     61 		T t = s;
     62 		s -= _combs[i];
     63 		_combs[i] = t;
     64 	}
     65 	return _gainCorrection * (s / (float)scale);
     66 }
     67 
     68 
     69 CICInterpolator::CICInterpolator(int stages, int factor) {
     70 	assert(stages > 0);
     71 	_stages = stages;
     72 	_integrators = new T[_stages + 1] {};
     73 	_combs = new T[_stages] {};
     74 	_buffer = NULL;
     75 	setParams(0.0f, factor);
     76 }
     77 
     78 CICInterpolator::~CICInterpolator() {
     79 	delete[] _integrators;
     80 	delete[] _combs;
     81 	delete[] _buffer;
     82 }
     83 
     84 void CICInterpolator::setParams(float _sampleRate, int factor) {
     85 	assert(factor > 0);
     86 	if (_factor != factor) {
     87 		_factor = factor;
     88 		_gainCorrection = 1.0f / 512.0f; // (float)(pow(_factor, _stages / 2));
     89 		if (_buffer) {
     90 			delete[] _buffer;
     91 		}
     92 		_buffer = new T[_factor] {};
     93 	}
     94 }
     95 
     96 void CICInterpolator::next(float sample, float* buf) {
     97 	T s = sample * scale;
     98 	for (int i = 0; i < _stages; ++i) {
     99 		T t = s;
    100 		s -= _combs[i];
    101 		_combs[i] = t;
    102 	}
    103 
    104 	std::fill(_buffer, _buffer + _factor, (T)0);
    105 	_buffer[0] = s;
    106 	for (int i = 0; i < _factor; ++i) {
    107 		_integrators[0] = _buffer[i];
    108 		for (int j = 1; j <= _stages; ++j) {
    109 			_integrators[j] += _integrators[j - 1];
    110 		}
    111 		buf[i] = _gainCorrection * (_integrators[_stages] / (float)scale);
    112 	}
    113 }