mirror of
https://github.com/eried/portapack-mayhem.git
synced 2024-10-01 01:26:06 -04:00
103 lines
2.6 KiB
C++
103 lines
2.6 KiB
C++
/*
|
||
* Copyright (C) 2016 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 __AUDIO_COMPRESSOR_H__
|
||
#define __AUDIO_COMPRESSOR_H__
|
||
|
||
#include "dsp_types.hpp"
|
||
#include "utility.hpp"
|
||
|
||
#include <cmath>
|
||
|
||
/* Code based on article in Journal of the Audio Engineering Society
|
||
* Vol. 60, No. 6, 2012 June, by Dimitrios Giannoulis, Michael Massberg,
|
||
* Joshua D. Reiss "Digital Dynamic Range Compressor Design – A Tutorial
|
||
* and Analysis"
|
||
*/
|
||
|
||
class GainComputer {
|
||
public:
|
||
constexpr GainComputer(
|
||
float ratio,
|
||
float threshold
|
||
) : ratio { ratio },
|
||
slope { 1.0f / ratio - 1.0f },
|
||
threshold_db { threshold }
|
||
{
|
||
}
|
||
|
||
float operator()(const float x) const;
|
||
|
||
private:
|
||
const float ratio;
|
||
const float slope;
|
||
const float threshold_db;
|
||
|
||
static constexpr float knee_width_db = 0.0f;
|
||
|
||
static constexpr float db_floor = -120.0f;
|
||
static constexpr float lin_floor = std::pow(10.0f, db_floor / 20.0f);
|
||
static constexpr float log2_db_k = 20.0f * std::log10(2.0f);
|
||
};
|
||
|
||
class PeakDetectorBranchingSmooth {
|
||
public:
|
||
constexpr PeakDetectorBranchingSmooth(
|
||
float att_a,
|
||
float rel_a
|
||
) : att_a { att_a },
|
||
rel_a { rel_a }
|
||
{
|
||
}
|
||
|
||
float operator()(const float db) {
|
||
const auto a = (db > state) ? att_a : rel_a;
|
||
state = db + a * (state - db);
|
||
return state;
|
||
}
|
||
|
||
private:
|
||
float state { 0.0f };
|
||
const float att_a;
|
||
const float rel_a;
|
||
};
|
||
|
||
class FeedForwardCompressor {
|
||
public:
|
||
void execute_in_place(const buffer_f32_t& buffer);
|
||
|
||
private:
|
||
static constexpr float fs = 12000.0f;
|
||
static constexpr float ratio = 10.0f;
|
||
static constexpr float threshold = -30.0f;
|
||
|
||
GainComputer gain_computer { ratio, threshold };
|
||
PeakDetectorBranchingSmooth peak_detector { tau_alpha(0.010f, fs), tau_alpha(0.300f, fs) };
|
||
|
||
float execute_once(const float x);
|
||
|
||
static constexpr float tau_alpha(const float tau, const float fs) {
|
||
return std::exp(-1.0f / (tau * fs));
|
||
}
|
||
};
|
||
|
||
#endif/*__AUDIO_COMPRESSOR_H__*/
|