src/cvsd-fmt.c

   1 /* libSoX file format: CVSD (see cvsd.c)        (c) 2007-8 SoX contributors
   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 "cvsd.h"
  19
  20 LSX_FORMAT_HANDLER(cvsd)
  21 {
  22   static char const * const names[] = {"cvsd", "cvs", NULL};
  23   static unsigned const write_encodings[] = {SOX_ENCODING_CVSD, 1, 0, 0};
  24   static sox_format_handler_t const handler = {SOX_LIB_VERSION_CODE,
  25     "Headerless MIL Std 188 113 Continuously Variable Slope Delta modulation",
  26     names, SOX_FILE_MONO,
  27     lsx_cvsdstartread, lsx_cvsdread, lsx_cvsdstopread,
  28     lsx_cvsdstartwrite, lsx_cvsdwrite, lsx_cvsdstopwrite,
  29     lsx_rawseek, write_encodings, NULL, sizeof(cvsd_priv_t)
  30   };
  31   return &handler;
  32 }
  33
  34 /* libSoX file format: CVU   (c) 2008 robs@users.sourceforge.net
  35  * Unfiltered, therefore, on decode, use with either filter -4k or rate 8k */
  36
  37 typedef struct {
  38   double         sample, step, step_mult, step_add;
  39   unsigned       last_n_bits;
  40   unsigned char  byte;
  41   off_t          bit_count;
  42 } priv_t;
  43
  44 static int start(sox_format_t * ft)
  45 {
  46   priv_t *p = (priv_t *) ft->priv;
  47
  48   ft->signal.channels = 1;
  49   lsx_rawstart(ft, sox_true, sox_false, sox_true, SOX_ENCODING_CVSD, 1);
  50   p->last_n_bits = 5; /* 101 */
  51   p->step_mult = exp((-1 / .005 / ft->signal.rate));
  52   p->step_add = (1 - p->step_mult) * (.1 * SOX_SAMPLE_MAX);
  53   lsx_debug("step_mult=%g step_add=%f", p->step_mult, p->step_add);
  54   return SOX_SUCCESS;
  55 }
  56
  57 static void decode(priv_t * p, int bit)
  58 {
  59   p->last_n_bits = ((p->last_n_bits << 1) | bit) & 7;
  60
  61   p->step *= p->step_mult;
  62   if (p->last_n_bits == 0 || p->last_n_bits == 7)
  63     p->step += p->step_add;
  64
  65   if (p->last_n_bits & 1)
  66     p->sample = min(p->step_mult * p->sample + p->step, SOX_SAMPLE_MAX);
  67   else
  68     p->sample = max(p->step_mult * p->sample - p->step, SOX_SAMPLE_MIN);
  69 }
  70
  71 static size_t cvsdread(sox_format_t * ft, sox_sample_t * buf, size_t len)
  72 {
  73   priv_t *p = (priv_t *) ft->priv;
  74   size_t i;
  75
  76   for (i = 0; i < len; ++i) {
  77     if (!(p->bit_count & 7))
  78       if (lsx_read_b_buf(ft, &p->byte, (size_t)1) != 1)
  79         break;
  80     ++p->bit_count;
  81     decode(p, p->byte & 1);
  82     p->byte >>= 1;
  83     *buf++ = floor(p->sample + .5);
  84   }
  85   return i;
  86 }
  87
  88 static size_t cvsdwrite(sox_format_t * ft, sox_sample_t const * buf, size_t len)
  89 {
  90   priv_t *p = (priv_t *) ft->priv;
  91   size_t i;
  92
  93   for (i = 0; i < len; ++i) {
  94     decode(p, *buf++ > p->sample);
  95     p->byte >>= 1;
  96     p->byte |= p->last_n_bits << 7;
  97     if (!(++p->bit_count & 7))
  98       if (lsx_writeb(ft, p->byte) != SOX_SUCCESS)
  99         break;
 100   }
 101   return len;
 102 }
 103
 104 LSX_FORMAT_HANDLER(cvu)
 105 {
 106   static char const * const names[] = {"cvu", NULL};
 107   static unsigned const write_encodings[] = {SOX_ENCODING_CVSD, 1, 0, 0};
 108   static sox_format_handler_t const handler = {SOX_LIB_VERSION_CODE,
 109     "Headerless Continuously Variable Slope Delta modulation (unfiltered)",
 110     names, SOX_FILE_MONO, start, cvsdread, NULL, start, cvsdwrite, NULL,
 111     lsx_rawseek, write_encodings, NULL, sizeof(priv_t)
 112   };
 113   return &handler;
 114 }