src/upsample.c

   1 /* libSoX effect: Upsample (zero stuff)    (c) 2011 robs@users.sourceforge.net
   2  *
   3  * Sometimes filters perform better at higher sampling rates, so e.g.
   4  *   sox -r 48k input output upsample 4 filter rate 48k vol 4
   5  *
   6  * This library is free software; you can redistribute it and/or modify it
   7  * under the terms of the GNU Lesser General Public License as published by
   8  * the Free Software Foundation; either version 2.1 of the License, or (at
   9  * your option) any later version.
  10  *
  11  * This library is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser
  14  * General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU Lesser General Public License
  17  * along with this library; if not, write to the Free Software Foundation,
  18  * Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA
  19  */
  20
  21 #include "sox_i.h"
  22
  23 typedef struct {unsigned factor, pos;} priv_t;
  24
  25 static int create(sox_effect_t * effp, int argc, char * * argv)
  26 {
  27   priv_t * p = (priv_t *)effp->priv;
  28   p->factor = 2;
  29   --argc, ++argv;
  30   do {NUMERIC_PARAMETER(factor, 1, 256)} while (0);
  31   return argc? lsx_usage(effp) : SOX_SUCCESS;
  32 }
  33
  34 static int start(sox_effect_t * effp)
  35 {
  36   priv_t * p = (priv_t *) effp->priv;
  37   effp->out_signal.rate = effp->in_signal.rate * p->factor;
  38   return p->factor == 1? SOX_EFF_NULL : SOX_SUCCESS;
  39 }
  40
  41 static int flow(sox_effect_t * effp, const sox_sample_t * ibuf,
  42     sox_sample_t * obuf, size_t * isamp, size_t * osamp)
  43 {
  44   priv_t * p = (priv_t *)effp->priv;
  45   size_t ilen = *isamp, olen = *osamp;
  46   while (sox_true) {
  47     for (; p->pos && olen; p->pos = (p->pos + 1) % p->factor, --olen)
  48       *obuf++ = 0;
  49     if (!ilen || !olen)
  50       break;
  51     *obuf++ = *ibuf++;
  52     --olen, --ilen;
  53     ++p->pos;
  54   }
  55   *isamp -= ilen, *osamp -= olen;
  56   return SOX_SUCCESS;
  57 }
  58
  59 sox_effect_handler_t const * lsx_upsample_effect_fn(void)
  60 {
  61   static sox_effect_handler_t handler = {"upsample", "[factor (2)]",
  62     SOX_EFF_RATE | SOX_EFF_MODIFY, create, start, flow, NULL, NULL, NULL, sizeof(priv_t)};
  63   return &handler;
  64 }