/* libSoX effect: Overdrive            (c) 2008 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 "sox_i.h" typedef struct {  double gain, colour, last_in, last_out, b0, b1, a1;} priv_t; static int soxcreate(sox_effect_t * effp, int argc, char * * argv){  priv_t * p = (priv_t *)effp->priv;  --argc, ++argv;  p->gain = p->colour = 20;  do {    NUMERIC_PARAMETER(gain, 0, 100)    NUMERIC_PARAMETER(colour, 0, 100)    USED(argv);  } while (0);  p->gain = dB_to_linear(p->gain);  p->colour /= 200;  return argc? lsx_usage(effp) : SOX_SUCCESS;} static int start(sox_effect_t * effp){  priv_t * p = (priv_t *)effp->priv;   if (p->gain == 1)    return SOX_EFF_NULL;   return SOX_SUCCESS;} static int flow(sox_effect_t * effp, const sox_sample_t * ibuf,    sox_sample_t * obuf, size_t * isamp, size_t * osamp){  priv_t * p = (priv_t *)effp->priv;  size_t dummy = 0, len = *isamp = *osamp = min(*isamp, *osamp);  while (len--) {    SOX_SAMPLE_LOCALS;    double d = SOX_SAMPLE_TO_FLOAT_64BIT(*ibuf++, dummy), d0 = d;    d *= p->gain;    d += p->colour;    d = d < -1? -2./3 : d > 1? 2./3 : d - d * d * d * (1./3);    p->last_out = d - p->last_in + .995 * p->last_out;    p->last_in = d;    *obuf++ = SOX_FLOAT_64BIT_TO_SAMPLE(d0 * .5 + p->last_out * .75, dummy);  }  return SOX_SUCCESS;} sox_effect_handler_t const * lsx_overdrive_effect_fn(void){  static sox_effect_handler_t handler = {"overdrive", "[gain [colour]]",    SOX_EFF_GAIN, soxcreate, start, flow, NULL, NULL, NULL, sizeof(priv_t)};  return &handler;}