1 /* 2 * Copyright (C) 2007-2011 Paul Davis <paul@linuxaudiosystems.com> 3 * Copyright (C) 2009-2014 David Robillard <d@drobilla.net> 4 * Copyright (C) 2013-2015 Robin Gareus <robin@gareus.org> 5 * 6 * This program is free software; you can redistribute it and/or modify 7 * it under the terms of the GNU General Public License as published by 8 * the Free Software Foundation; either version 2 of the License, or 9 * (at your option) any later version. 10 * 11 * This program is distributed in the hope that it will be useful, 12 * but WITHOUT ANY WARRANTY; without even the implied warranty of 13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 14 * GNU General Public License for more details. 15 * 16 * You should have received a copy of the GNU General Public License along 17 * with this program; if not, write to the Free Software Foundation, Inc., 18 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. 19 */ 20 21 #ifndef __ardour_dB_h__ 22 #define __ardour_dB_h__ 23 24 #include <limits> 25 #include "pbd/fastlog.h" 26 27 #define GAIN_COEFF_ZERO 0.f 28 #define GAIN_COEFF_SMALL 0.0000001f //-140dB 29 #define GAIN_COEFF_UNITY 1.f 30 dB_to_coefficient(float dB)31static inline float dB_to_coefficient (float dB) { 32 return dB > -318.8f ? pow (10.0f, dB * 0.05f) : 0.0f; 33 } 34 fast_coefficient_to_dB(float coeff)35static inline float fast_coefficient_to_dB (float coeff) { 36 return 20.0f * fast_log10 (coeff); 37 } 38 accurate_coefficient_to_dB(float coeff)39static inline float accurate_coefficient_to_dB (float coeff) { 40 if (coeff < 1e-15) return -std::numeric_limits<float>::infinity(); 41 return 20.0f * log10f (coeff); 42 } 43 dB_coeff_step(double max_coeff)44static inline double dB_coeff_step(double max_coeff) { 45 const double max_db = lrint(accurate_coefficient_to_dB(max_coeff)); 46 return 0.1 * (max_coeff / max_db); 47 } 48 49 extern double zero_db_as_fraction; 50 51 #endif /* __ardour_dB_h__ */ 52