/* libSoX Compander Transfer Function  (c) 2007 robs@users.sourceforge.net * * 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 2.1 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, * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA */ #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 lsx_compandt_parse(sox_compandt_t * t, char * points, char * gain);sox_bool lsx_compandt_show(sox_compandt_t * t, sox_plot_t plot);void    lsx_compandt_kill(sox_compandt_t * p); /* Place in header to allow in-lining */static double lsx_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);}