Added DaisySP
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/* Ported from Audio Library for Teensy, Ladder Filter
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* Copyright (c) 2021, Richard van Hoesel
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* Copyright (c) 2024, Infrasonic Audio LLC
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice, development funding notice, and this permission
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* notice shall be included in all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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//-----------------------------------------------------------
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// Huovilainen New Moog (HNM) model as per CMJ jun 2006
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// Richard van Hoesel, v. 1.03, Feb. 14 2021
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// v1.7 (Infrasonic/Daisy) add configurable filter mode
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// v1.6 (Infrasonic/Daisy) removes polyphase FIR, uses 4x linear
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// oversampling for performance reasons
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// v1.5 adds polyphase FIR or Linear interpolation
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// v1.4 FC extended to 18.7kHz, max res to 1.8, 4x oversampling,
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// and a minor Q-tuning adjustment
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// v.1.03 adds oversampling, extended resonance,
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// and exposes parameters input_drive and passband_gain
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// v.1.02 now includes both cutoff and resonance "CV" modulation inputs
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// please retain this header if you use this code.
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//-----------------------------------------------------------
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#include "ladder.h"
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#include "Utility/dsp.h"
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using namespace daisysp;
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static inline float fast_tanh(float x)
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{
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if(x > 3.0f)
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return 1.0f;
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if(x < -3.0f)
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return -1.0f;
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float x2 = x * x;
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return x * (27.0f + x2) / (27.0f + 9.0f * x2);
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}
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void LadderFilter::Init(float sample_rate)
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{
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sample_rate_ = sample_rate;
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sr_int_recip_ = 1.0f / (sample_rate * kInterpolation);
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alpha_ = 1.0f;
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K_ = 1.0f;
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Fbase_ = 1000.0f;
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Qadjust_ = 1.0f;
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oldinput_ = 0.f;
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mode_ = FilterMode::LP24;
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SetPassbandGain(0.5f);
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SetInputDrive(0.5f);
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SetFreq(5000.f);
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SetRes(0.2f);
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}
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float LadderFilter::Process(float in)
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{
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float input = in * drive_scaled_;
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float total = 0.0f;
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float interp = 0.0f;
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for(size_t os = 0; os < kInterpolation; os++)
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{
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float in_interp = (interp * oldinput_ + (1.0f - interp) * input);
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float u = in_interp - (z1_[3] - pbg_ * in_interp) * K_ * Qadjust_;
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u = fast_tanh(u);
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float stage1 = LPF(u, 0);
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float stage2 = LPF(stage1, 1);
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float stage3 = LPF(stage2, 2);
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float stage4 = LPF(stage3, 3);
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total += weightedSumForCurrentMode({u, stage1, stage2, stage3, stage4})
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* kInterpolationRecip;
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interp += kInterpolationRecip;
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}
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oldinput_ = input;
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return total;
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}
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__attribute__((optimize("unroll-loops"))) void
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LadderFilter::ProcessBlock(float* buf, size_t size)
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{
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for(size_t i = 0; i < size; i++)
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{
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buf[i] = Process(buf[i]);
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}
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}
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void LadderFilter::SetFreq(float freq)
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{
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Fbase_ = freq;
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compute_coeffs(freq);
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}
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void LadderFilter::SetRes(float res)
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{
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// maps resonance = 0->1 to K = 0 -> 4
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res = daisysp::fclamp(res, 0.0f, kMaxResonance);
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K_ = 4.0f * res;
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}
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void LadderFilter::SetPassbandGain(float pbg)
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{
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pbg_ = daisysp::fclamp(pbg, 0.0f, 0.5f);
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SetInputDrive(drive_);
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}
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void LadderFilter::SetInputDrive(float odrv)
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{
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drive_ = daisysp::fmax(odrv, 0.0f);
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if(drive_ > 1.0f)
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{
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drive_ = fmin(drive_, 4.0f);
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// max is 4 when pbg = 0, and 2.5 when pbg is 0.5
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drive_scaled_ = 1.0f + (drive_ - 1.0f) * (1.0f - pbg_);
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}
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else
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{
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drive_scaled_ = drive_;
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}
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}
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float LadderFilter::LPF(float s, int i)
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{
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// (1.0 / 1.3) (0.3 / 1.3)
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float ft = s * 0.76923077f + 0.23076923f * z0_[i] - z1_[i];
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ft = ft * alpha_ + z1_[i];
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z1_[i] = ft;
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z0_[i] = s;
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return ft;
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}
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void LadderFilter::compute_coeffs(float freq)
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{
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freq = daisysp::fclamp(freq, 5.0f, sample_rate_ * 0.425f);
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float wc = freq * 2.0f * PI_F * sr_int_recip_;
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float wc2 = wc * wc;
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alpha_ = 0.9892f * wc - 0.4324f * wc2 + 0.1381f * wc * wc2
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- 0.0202f * wc2 * wc2;
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//Qadjust = 1.0029f + 0.0526f * wc - 0.0926 * wc2 + 0.0218* wc * wc2;
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Qadjust_ = 1.006f + 0.0536f * wc - 0.095f * wc2 - 0.05f * wc2 * wc2;
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// revised hfQ (rvh - feb 14 2021)
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}
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float LadderFilter::weightedSumForCurrentMode(
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const std::array<float, 5>& stage_outs)
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{
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// Weighted filter stage mixing to achieve selected response
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// as described in "Oscillator and Filter Algorithms for Virtual Analog Synthesis"
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// Välimäki and Huovilainen, Computer Music Journal, vol 60, 2006
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switch(mode_)
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{
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case FilterMode::LP24: return stage_outs[4];
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case FilterMode::LP12: return stage_outs[2];
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case FilterMode::BP24:
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return (stage_outs[2] + stage_outs[4]) * 4.0f
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- stage_outs[3] * 8.0f;
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case FilterMode::BP12: return (stage_outs[1] - stage_outs[2]) * 2.0f;
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case FilterMode::HP24:
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return stage_outs[0] + stage_outs[4]
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- ((stage_outs[1] + stage_outs[3]) * 4.0f)
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+ stage_outs[2] * 6.0f;
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case FilterMode::HP12:
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return stage_outs[0] + stage_outs[2] - stage_outs[1] * 2.0f;
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default: return 0.0f;
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}
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}
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