mirror of
https://github.com/eried/portapack-mayhem.git
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74 lines
1.9 KiB
C++
74 lines
1.9 KiB
C++
/*
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* Copyright (C) 2015 Jared Boone, ShareBrained Technology, Inc.
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*
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* This file is part of PortaPack.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2, or (at your option)
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* any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; see the file COPYING. If not, write to
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* the Free Software Foundation, Inc., 51 Franklin Street,
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* Boston, MA 02110-1301, USA.
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*/
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#ifndef __DSP_IIR_H__
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#define __DSP_IIR_H__
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#include <array>
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#include "dsp_types.hpp"
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class IIRBiquadFilter {
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public:
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// http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
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// Assume all coefficients are normalized so that a0=1.0
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constexpr IIRBiquadFilter(
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std::array<float, 3> b,
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std::array<float, 3> a
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) : b(b),
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a(a)
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{
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}
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void execute(buffer_s16_t buffer_in, buffer_s16_t buffer_out) {
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// TODO: Assert that buffer_out.count == buffer_in.count.
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for(size_t i=0; i<buffer_out.count; i++) {
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buffer_out.p[i] = execute_sample(buffer_in.p[i]);
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}
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}
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void execute_in_place(buffer_s16_t buffer) {
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execute(buffer, buffer);
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}
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private:
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const std::array<float, 3> b;
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const std::array<float, 3> a;
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std::array<float, 3> x { { 0.0f, 0.0f, 0.0f } };
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std::array<float, 3> y { { 0.0f, 0.0f, 0.0f } };
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float execute_sample(const float in) {
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x[0] = x[1];
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x[1] = x[2];
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x[2] = in;
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y[0] = y[1];
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y[1] = y[2];
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y[2] = b[0] * x[2] + b[1] * x[1] + b[2] * x[0]
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- a[1] * y[1] - a[2] * y[0];
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return y[2];
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}
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};
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#endif/*__DSP_IIR_H__*/
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