ref: 0141f233364b96bee00bee7463c494a981f50e55
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 <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); }