ref: 9228e6c128882dcb8bbd5a855eb7fb8a1a22d2a3
dir: /src/compandt.h/
/*
* This library is free software; you can redistribute it and/or modify it
* under the terms of the GNU Lesser General Public License as published by
* the Free Software Foundation; either version 2 of the License, or (at
* your option) any later version.
*
* This library 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 Lesser
* General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public License
* along with this library. If not, write to the Free Software Foundation,
* Fifth Floor, 51 Franklin Street, Boston, MA 02111-1301, USA.
*
* Compander Transfer Function: (c) 2007 robs@users.sourceforge.net
*/
#include "sox_i.h"
#include <math.h>
typedef struct {
struct sox_compandt_segment {
double x, y; /* 1st point in segment */
double a, b; /* Quadratic coeffecients for rest of segment */
} * segments;
double in_min_lin;
double out_min_lin;
double outgain_dB; /* Post processor gain */
double curve_dB;
} sox_compandt_t;
sox_bool sox_compandt_parse(sox_compandt_t * t, char * points, char * gain);
sox_bool sox_compandt_show(sox_compandt_t * t, sox_plot_t plot);
void sox_compandt_kill(sox_compandt_t * p);
/* Place in header to allow in-lining */
static double sox_compandt(sox_compandt_t * t, double in_lin)
{
struct sox_compandt_segment * s;
double in_log, out_log;
if (in_lin <= t->in_min_lin)
return t->out_min_lin;
in_log = log(in_lin);
for (s = t->segments + 1; in_log > s[1].x; ++s);
in_log -= s->x;
out_log = s->y + in_log * (s->a * in_log + s->b);
return exp(out_log);
}