145 lines
4.5 KiB
C++
145 lines
4.5 KiB
C++
/* Ported from Audio Library for Teensy, Ladder Filter
|
|
* Copyright (c) 2021, Richard van Hoesel
|
|
* Copyright (c) 2024, Infrasonic Audio LLC
|
|
*
|
|
* Permission is hereby granted, free of charge, to any person obtaining a copy
|
|
* of this software and associated documentation files (the "Software"), to deal
|
|
* in the Software without restriction, including without limitation the rights
|
|
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
|
|
* copies of the Software, and to permit persons to whom the Software is
|
|
* furnished to do so, subject to the following conditions:
|
|
*
|
|
* The above copyright notice, development funding notice, and this permission
|
|
* notice shall be included in all copies or substantial portions of the Software.
|
|
*
|
|
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
|
|
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
|
|
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
|
|
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
|
|
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
|
|
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
|
|
* THE SOFTWARE.
|
|
*/
|
|
|
|
//-----------------------------------------------------------
|
|
// Huovilainen New Moog (HNM) model as per CMJ jun 2006
|
|
// Richard van Hoesel, v. 1.03, Feb. 14 2021
|
|
// v1.7 (Infrasonic/Daisy) add configurable filter mode
|
|
// v1.6 (Infrasonic/Daisy) removes polyphase FIR, uses 4x linear
|
|
// oversampling for performance reasons
|
|
// v1.5 adds polyphase FIR or Linear interpolation
|
|
// v1.4 FC extended to 18.7kHz, max res to 1.8, 4x oversampling,
|
|
// and a minor Q-tuning adjustment
|
|
// v.1.03 adds oversampling, extended resonance,
|
|
// and exposes parameters input_drive and passband_gain
|
|
// v.1.02 now includes both cutoff and resonance "CV" modulation inputs
|
|
// please retain this header if you use this code.
|
|
//-----------------------------------------------------------
|
|
|
|
#pragma once
|
|
#ifndef DSY_LADDER_H
|
|
#define DSY_LADDER_H
|
|
|
|
#include <stdlib.h>
|
|
#include <stdint.h>
|
|
#include <array>
|
|
#ifdef __cplusplus
|
|
|
|
namespace daisysp
|
|
{
|
|
/**
|
|
* 4-pole ladder filter model with selectable filter type (LP/BP/HP 12 or 24 dB/oct),
|
|
* drive, passband gain compensation, and stable self-oscillation.
|
|
*
|
|
*
|
|
*/
|
|
class LadderFilter
|
|
{
|
|
public:
|
|
enum class FilterMode
|
|
{
|
|
LP24,
|
|
LP12,
|
|
BP24,
|
|
BP12,
|
|
HP24,
|
|
HP12
|
|
};
|
|
|
|
LadderFilter() = default;
|
|
~LadderFilter() = default;
|
|
|
|
/** Initializes the ladder filter module.
|
|
*/
|
|
void Init(float sample_rate);
|
|
|
|
/** Process single sample */
|
|
float Process(float in);
|
|
|
|
/** Process mono buffer/block of samples in place */
|
|
void ProcessBlock(float* buf, size_t size);
|
|
|
|
/**
|
|
Sets the cutoff frequency of the filter.
|
|
Units of hz, valid in range 5 - ~nyquist (samp_rate / 2)
|
|
Internally clamped to this range.
|
|
*/
|
|
void SetFreq(float freq);
|
|
|
|
/**
|
|
Sets the resonance of the filter.
|
|
Filter will stably self oscillate at higher values.
|
|
Valid in range 0 - 1.8
|
|
Internally clamped to this range.
|
|
*/
|
|
void SetRes(float res);
|
|
|
|
/**
|
|
Set "passband gain" compensation factor to mitigate
|
|
loss of energy in passband at higher resonance values.
|
|
Drive and passband gain have a dependent relationship.
|
|
Valid in range 0 - 0.5
|
|
Internally clamped to this range.
|
|
*/
|
|
void SetPassbandGain(float pbg);
|
|
|
|
/**
|
|
Sets drive of the input stage into the tanh clipper
|
|
Valid in range 0 - 4.0
|
|
*/
|
|
void SetInputDrive(float drv);
|
|
|
|
/**
|
|
Sets the filter mode/response
|
|
Defaults to classic lowpass 24dB/oct
|
|
*/
|
|
inline void SetFilterMode(FilterMode mode) { mode_ = mode; }
|
|
|
|
private:
|
|
static constexpr uint8_t kInterpolation = 4;
|
|
static constexpr float kInterpolationRecip = 1.0f / kInterpolation;
|
|
static constexpr float kMaxResonance = 1.8f;
|
|
|
|
float sample_rate_, sr_int_recip_;
|
|
float alpha_;
|
|
float beta_[4] = {0.0, 0.0, 0.0, 0.0};
|
|
float z0_[4] = {0.0, 0.0, 0.0, 0.0};
|
|
float z1_[4] = {0.0, 0.0, 0.0, 0.0};
|
|
float K_;
|
|
float Fbase_;
|
|
float Qadjust_;
|
|
float pbg_;
|
|
float drive_, drive_scaled_;
|
|
float oldinput_;
|
|
FilterMode mode_;
|
|
|
|
float LPF(float s, int i);
|
|
void compute_coeffs(float fc);
|
|
float weightedSumForCurrentMode(const std::array<float, 5>& stage_outs);
|
|
};
|
|
|
|
|
|
} // namespace daisysp
|
|
#endif
|
|
#endif
|