src/tremolo.c

   1 /* libSoX effect: tremolo  (c) 2007 robs@users.sourceforge.net
   2  *
   3  * This library is free software; you can redistribute it and/or modify it
   4  * under the terms of the GNU Lesser General Public License as published by
   5  * the Free Software Foundation; either version 2.1 of the License, or (at
   6  * your option) any later version.
   7  *
   8  * This library is distributed in the hope that it will be useful, but
   9  * WITHOUT ANY WARRANTY; without even the implied warranty of
  10  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
  11  * General Public License for more details.
  12  *
  13  * You should have received a copy of the GNU Lesser General Public License
  14  * along with this library; if not, write to the Free Software Foundation,
  15  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  16  */
  17
  18 #include "sox_i.h"
  19
  20 static int getopts(sox_effect_t * effp, int argc, char * * argv)
  21 {
  22   double speed, depth = 40;
  23   char dummy;     /* To check for extraneous chars. */
  24   char offset[100];
  25   char * args[] = {0, "sine", "fmod", 0, 0, "25"};
  26
  27   if (argc < 2 || argc > 3 ||
  28       sscanf(argv[1], "%lf %c", &speed, &dummy) != 1 || speed < 0 ||
  29       (argc > 2 && sscanf(argv[2], "%lf %c", &depth, &dummy) != 1) ||
  30       depth <= 0 || depth > 100)
  31     return lsx_usage(effp);
  32   args[0] = argv[0];
  33   args[3] = argv[1];
  34   sprintf(offset, "%g", 100 - depth / 2);
  35   args[4] = offset;
  36   return lsx_synth_effect_fn()->getopts(effp, (int)array_length(args), args);
  37 }
  38
  39 sox_effect_handler_t const * lsx_tremolo_effect_fn(void)
  40 {
  41   static sox_effect_handler_t handler;
  42   handler = *lsx_synth_effect_fn();
  43   handler.name = "tremolo";
  44   handler.usage = "speed_Hz [depth_percent]";
  45   handler.getopts = getopts;
  46   return &handler;
  47 }