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/*
* Copyright (C) 2017 Robin Gareus <robin@gareus.org>
* Copyright (C) 1999 Paul Davis
*
* 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 __pbd_control_math_h__
#define __pbd_control_math_h__
#include <assert.h>
#include <math.h>
#include <stdint.h>
/* map gain-coeff [0..2] to position [0..1] */
static inline double
gain_to_position (double g)
{
if (g == 0) {
return 0;
}
return pow ((6.0 * log (g) / log (2.0) + 192.0) / 198.0, 8.0);
}
/* map position [0..1] to gain-coeff [0..2] */
static inline double
position_to_gain (double pos)
{
if (pos == 0.0) {
return 0.0;
}
return exp (((pow (pos, 1.0 / 8.0) * 198.0) - 192.0) / 6.0 * log (2.0));
}
/* map position [0..1] to parameter [lower..upper] on a logarithmic scale */
static inline double
position_to_logscale (double pos, double lower, double upper)
{
assert (upper > lower && lower * upper > 0);
assert (pos >= 0.0 && pos <= 1.0);
return lower * pow (upper / lower, pos);
}
/* map parameter [lower..upper] to position [0..1] on a logarithmic scale*/
static inline double
logscale_to_position (double val, double lower, double upper)
{
assert (upper > lower && lower * upper > 0);
assert (val >= lower && val <= upper);
return log (val / lower) / log (upper / lower);
}
static inline double
logscale_to_position_with_steps (double val, double lower, double upper, uint32_t steps)
{
assert (steps > 1);
double v = logscale_to_position (val, lower, upper) * (steps - 1.0);
return round (v) / (steps - 1.0);
}
static inline double
position_to_logscale_with_steps (double pos, double lower, double upper, uint32_t steps)
{
assert (steps > 1);
double p = round (pos * (steps - 1.0)) / (steps - 1.0);
return position_to_logscale (p, lower, upper);
}
static inline double
interpolate_linear (double from, double to, double fraction)
{
return from + (fraction * (to - from));
}
static inline double
interpolate_logarithmic (double from, double to, double fraction, double lower, double upper)
{
// this is expensive -- optimize
double l0 = logscale_to_position (from, lower, upper);
double l1 = logscale_to_position (to, lower, upper);
return position_to_logscale (l0 + fraction * (l1 - l0), lower, upper);
}
static inline double
interpolate_gain (double from, double to, double fraction, double upper)
{
// this is expensive -- optimize
double g0 = gain_to_position (from * 2. / upper);
double g1 = gain_to_position (to * 2. / upper);
return position_to_gain (g0 + fraction * (g1 - g0)) * upper / 2.;
}
#endif
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