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106 lines
3.1 KiB
C
106 lines
3.1 KiB
C
/*
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* Copyright (C) 2017 Robin Gareus <robin@gareus.org>
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* Copyright (C) 1999 Paul Davis
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) 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; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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*/
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#ifndef __pbd_control_math_h__
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#define __pbd_control_math_h__
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#include <assert.h>
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#include <math.h>
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#include <stdint.h>
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/* map gain-coeff [0..2] to position [0..1] */
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static inline double
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gain_to_position (double g)
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{
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if (g == 0) {
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return 0;
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}
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return pow ((6.0 * log (g) / log (2.0) + 192.0) / 198.0, 8.0);
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}
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/* map position [0..1] to gain-coeff [0..2] */
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static inline double
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position_to_gain (double pos)
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{
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if (pos == 0.0) {
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return 0.0;
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}
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return exp (((pow (pos, 1.0 / 8.0) * 198.0) - 192.0) / 6.0 * log (2.0));
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}
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/* map position [0..1] to parameter [lower..upper] on a logarithmic scale */
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static inline double
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position_to_logscale (double pos, double lower, double upper)
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{
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assert (upper > lower && lower * upper > 0);
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assert (pos >= 0.0 && pos <= 1.0);
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return lower * pow (upper / lower, pos);
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}
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/* map parameter [lower..upper] to position [0..1] on a logarithmic scale*/
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static inline double
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logscale_to_position (double val, double lower, double upper)
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{
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assert (upper > lower && lower * upper > 0);
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assert (val >= lower && val <= upper);
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return log (val / lower) / log (upper / lower);
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}
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static inline double
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logscale_to_position_with_steps (double val, double lower, double upper, uint32_t steps)
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{
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assert (steps > 1);
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double v = logscale_to_position (val, lower, upper) * (steps - 1.0);
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return round (v) / (steps - 1.0);
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}
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static inline double
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position_to_logscale_with_steps (double pos, double lower, double upper, uint32_t steps)
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{
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assert (steps > 1);
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double p = round (pos * (steps - 1.0)) / (steps - 1.0);
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return position_to_logscale (p, lower, upper);
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}
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static inline double
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interpolate_linear (double from, double to, double fraction)
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{
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return from + (fraction * (to - from));
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}
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static inline double
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interpolate_logarithmic (double from, double to, double fraction, double lower, double upper)
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{
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// this is expensive -- optimize
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double l0 = logscale_to_position (from, lower, upper);
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double l1 = logscale_to_position (to, lower, upper);
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return position_to_logscale (l0 + fraction * (l1 - l0), lower, upper);
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}
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static inline double
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interpolate_gain (double from, double to, double fraction, double upper)
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{
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// this is expensive -- optimize
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double g0 = gain_to_position (from * 2. / upper);
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double g1 = gain_to_position (to * 2. / upper);
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return position_to_gain (g0 + fraction * (g1 - g0)) * upper / 2.;
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}
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#endif
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