dB.h

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/*
 * Copyright (C) 2007-2011 Paul Davis <paul@linuxaudiosystems.com>
 * Copyright (C) 2009-2014 David Robillard <d@drobilla.net>
 * Copyright (C) 2013-2015 Robin Gareus <robin@gareus.org>
 *
 * 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 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, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */
 
#ifndef __ardour_dB_h__
#define __ardour_dB_h__
 
#include <limits>
#include "pbd/fastlog.h"
 
#define GAIN_COEFF_ZERO 0.f
#define GAIN_COEFF_SMALL 0.0000001f  //-140dB
#define GAIN_COEFF_UNITY 1.f
 
static inline float dB_to_coefficient (float dB) {
        return dB > -318.8f ? pow (10.0f, dB * 0.05f) : 0.0f;
}
 
static inline float fast_coefficient_to_dB (float coeff) {
        return 20.0f * fast_log10 (coeff);
}
 
static inline float accurate_coefficient_to_dB (float coeff) {
        if (coeff < 1e-15) return  -std::numeric_limits<float>::infinity();
        return 20.0f * log10f (coeff);
}
 
static inline double dB_coeff_step(double max_coeff) {
        const double max_db = lrint(accurate_coefficient_to_dB(max_coeff));
        return 0.1 * (max_coeff / max_db);
}
 
extern double zero_db_as_fraction;
 
#endif /* __ardour_dB_h__ */