impulse_response_processor.h

/*
 * Copyright © 2015-2023 Synthstrom Audible Limited
 *
 * This file is part of The Synthstrom Audible Deluge Firmware.
 *
 * The Synthstrom Audible Deluge Firmware 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 3 of the License, 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.
 * If not, see <https://www.gnu.org/licenses/>.
 */
 
#pragma once
 
#include "dsp/stereo_sample.h"
#include "util/fixedpoint.h"
#include <cstdint>
 
class [[gnu::hot]] ImpulseResponseProcessor {
    constexpr static size_t IR_SIZE = 26;
    constexpr static size_t IR_BUFFER_SIZE = (IR_SIZE - 1);
 
    constexpr static std::array<int32_t, IR_SIZE> ir = {
        -3203916,   8857848,   24813136,  41537808, 35217472,  15195632,  -27538592, -61984128, 1944654848,
        1813580928, 438462784, 101125088, 6042048,  -22429488, -46218864, -56638560, -64785312, -52108528,
        -37256992,  -11863856, 1390352,   14663296, 12784464,  14254800,  5690912,   4490736,
    };
 
public:
    ImpulseResponseProcessor() = default;
 
    inline void process(const StereoSample input, StereoSample& output) {
        output.l = buffer_[0].l + multiply_32x32_rshift32_rounded(input.l, ir[0]);
        output.r = buffer_[0].r + multiply_32x32_rshift32_rounded(input.r, ir[0]);
 
        for (int32_t i = 1; i < IR_BUFFER_SIZE; i++) {
            buffer_[i - 1].l = buffer_[i].l + multiply_32x32_rshift32_rounded(input.l, ir[i]);
            buffer_[i - 1].r = buffer_[i].r + multiply_32x32_rshift32_rounded(input.r, ir[i]);
        }
 
        buffer_[IR_BUFFER_SIZE - 1].l = multiply_32x32_rshift32_rounded(input.l, ir[IR_BUFFER_SIZE]);
        buffer_[IR_BUFFER_SIZE - 1].r = multiply_32x32_rshift32_rounded(input.r, ir[IR_BUFFER_SIZE]);
    }
 
private:
    std::array<StereoSample, IR_BUFFER_SIZE> buffer_;
};