portapack-mayhem/firmware/common/dsp_iir.hpp
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/*
* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
*
* This file is part of PortaPack.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifndef __DSP_IIR_H__
#define __DSP_IIR_H__
#include <array>
#include "dsp_types.hpp"
struct iir_biquad_config_t {
std::array<float, 3> b;
std::array<float, 3> a;
};
// 0..2 - b, 3..5 - a
typedef std::array<float, 6> iir_biquad_df2_config_t;
constexpr iir_biquad_config_t iir_config_passthrough{
{{1.0f, 0.0f, 0.0f}},
{{0.0f, 0.0f, 0.0f}},
};
constexpr iir_biquad_config_t iir_config_no_pass{
{{0.0f, 0.0f, 0.0f}},
{{0.0f, 0.0f, 0.0f}},
};
class IIRBiquadFilter {
public:
// http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
constexpr IIRBiquadFilter()
: IIRBiquadFilter(iir_config_no_pass) {
}
// Assume all coefficients are normalized so that a0=1.0
constexpr IIRBiquadFilter(
const iir_biquad_config_t& config)
: config(config) {
}
void configure(const iir_biquad_config_t& new_config);
void execute(const buffer_f32_t& buffer_in, const buffer_f32_t& buffer_out);
void execute_in_place(const buffer_f32_t& buffer);
private:
iir_biquad_config_t config;
std::array<float, 3> x{{0.0f, 0.0f, 0.0f}};
std::array<float, 3> y{{0.0f, 0.0f, 0.0f}};
};
class IIRBiquadDF2Filter {
public:
void configure(const iir_biquad_df2_config_t& config);
float execute(float z);
private:
float b0 = 0;
float b1 = 0;
float b2 = 0;
float a1 = 0;
float a2 = 0;
float z0 = 0;
float z1 = 0;
};
#endif /*__DSP_IIR_H__*/