53 lines
2.0 KiB
C++
53 lines
2.0 KiB
C++
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/*
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* Copyright (C) 2016 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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#include "audio_compressor.hpp"
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float GainComputer::operator()(const float x) const {
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const auto abs_x = std::abs(x);
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const auto db = (abs_x < lin_floor) ? db_floor : log2_db_k * fast_log2(abs_x);
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const auto overshoot_db = db - threshold_db;
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if( knee_width_db > 0.0f ) {
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const auto w2 = knee_width_db / 2.0f;
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const auto a = w2 / (knee_width_db * knee_width_db);
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const auto in_transition = (overshoot_db > -w2) && (overshoot_db < w2);
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const auto rectified_overshoot = in_transition ? (a * std::pow(overshoot_db + w2, 2.0f)) : std::max(overshoot_db, 0.0f);
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return rectified_overshoot * slope;
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} else {
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const auto rectified_overshoot = std::max(overshoot_db, 0.0f);
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return rectified_overshoot * slope;
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}
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}
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void FeedForwardCompressor::execute_in_place(const buffer_f32_t& buffer) {
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constexpr float makeup_gain = std::pow(10.0f, (threshold - (threshold / ratio)) / -20.0f);
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for(size_t i=0; i<buffer.count; i++) {
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buffer.p[i] = execute_once(buffer.p[i]) * makeup_gain;
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}
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}
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float FeedForwardCompressor::execute_once(const float x) {
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const auto gain_db = gain_computer(x);
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const auto peak_db = -peak_detector(-gain_db);
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const auto gain = fast_pow2(peak_db * (3.321928094887362f / 20.0f));
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return x * gain;
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}
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