src/speed.c

   1 /* libSoX Effect: Adjust the audio speed (pitch and tempo together)
   2  * (c) 2006,8 robs@users.sourceforge.net
   3  *
   4  * This library is free software; you can redistribute it and/or modify it
   5  * under the terms of the GNU Lesser General Public License as published by
   6  * the Free Software Foundation; either version 2.1 of the License, or (at
   7  * your option) any later version.
   8  *
   9  * This library is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this library; if not, write to the Free Software Foundation,
  16  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  17  *
  18  *
  19  * Adjustment is given as the ratio of the new speed to the old speed, or as
  20  * a number of cents (100ths of a semitone) to change.  Speed change is
  21  * actually performed by whichever resampling effect is in effect.
  22  */
  23
  24 #include "sox_i.h"
  25 #include <string.h>
  26
  27 typedef struct {
  28   double factor;
  29 } priv_t;
  30
  31 static int getopts(sox_effect_t * effp, int argc, char * * argv)
  32 {
  33   priv_t * p = (priv_t *) effp->priv;
  34   sox_bool is_cents = sox_false;
  35
  36   --argc, ++argv;
  37   if (argc == 1) {
  38     char c, dummy;
  39     int scanned = sscanf(*argv, "%lf%c %c", &p->factor, &c, &dummy);
  40     if (scanned == 1 || (scanned == 2 && c == 'c')) {
  41       is_cents |= scanned == 2;
  42       if (is_cents || p->factor > 0) {
  43         p->factor = is_cents? pow(2., p->factor / 1200) : p->factor;
  44         return SOX_SUCCESS;
  45       }
  46     }
  47   }
  48   return lsx_usage(effp);
  49 }
  50
  51 static int start(sox_effect_t * effp)
  52 {
  53   priv_t * p = (priv_t *) effp->priv;
  54
  55   if (p->factor == 1)
  56     return SOX_EFF_NULL;
  57
  58   effp->out_signal.rate = effp->in_signal.rate * p->factor;
  59
  60   effp->out_signal.length = effp->in_signal.length;
  61     /* audio length if measured in samples doesn't change */
  62
  63   return SOX_SUCCESS;
  64 }
  65
  66 sox_effect_handler_t const * lsx_speed_effect_fn(void)
  67 {
  68   static sox_effect_handler_t handler = {
  69     "speed", "factor[c]",
  70     SOX_EFF_MCHAN | SOX_EFF_RATE | SOX_EFF_LENGTH | SOX_EFF_MODIFY,
  71     getopts, start, lsx_flow_copy, 0, 0, 0, sizeof(priv_t)};
  72   return &handler;
  73 }