plc.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Written by Steve Underwood <[email protected]>
 *
 * Copyright (C) 2004 Steve Underwood
 *
 * All rights reserved.
 *
 * See http://www.asterisk.org for more information about
 * the Asterisk project. Please do not directly contact
 * any of the maintainers of this project for assistance;
 * the project provides a web site, mailing lists and IRC
 * channels for your use.
 *
 * This program is free software, distributed under the terms of
 * the GNU General Public License Version 2. See the LICENSE file
 * at the top of the source tree.
 *
 * This version may be optionally licenced under the GNU LGPL licence.
 *
 * A license has been granted to Digium (via disclaimer) for the use of
 * this code.
 */

/*! \file
 *
 * \brief SpanDSP - a series of DSP components for telephony
 *
 * \author Steve Underwood <[email protected]>
 */

/*** MODULEINFO
   <support_level>core</support_level>
 ***/

#include "asterisk.h"

#include <math.h>

#include "asterisk/config.h"
#include "asterisk/module.h"
#include "asterisk/plc.h"

#if !defined(FALSE)
#define FALSE 0
#endif
#if !defined(TRUE)
#define TRUE (!FALSE)
#endif

#if !defined(INT16_MAX)
#define INT16_MAX (32767)
#define INT16_MIN (-32767-1)
#endif

/* We do a straight line fade to zero volume in 50ms when we are filling in for missing data. */
#define ATTENUATION_INCREMENT       0.0025               /* Attenuation per sample */

#define ms_to_samples(t)       (((t)*DEFAULT_SAMPLE_RATE)/1000)

static inline int16_t fsaturate(double damp)
{
   if (damp > 32767.0)
      return  INT16_MAX;
   if (damp < -32768.0)
      return  INT16_MIN;
   return (int16_t) rint(damp);
}

static void save_history(plc_state_t *s, int16_t *buf, int len)
{
   if (len >= PLC_HISTORY_LEN) {
      /* Just keep the last part of the new data, starting at the beginning of the buffer */
       memcpy(s->history, buf + len - PLC_HISTORY_LEN, sizeof(int16_t) * PLC_HISTORY_LEN);
      s->buf_ptr = 0;
      return;
   }
   if (s->buf_ptr + len > PLC_HISTORY_LEN) {
      /* Wraps around - must break into two sections */
      memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t) * (PLC_HISTORY_LEN - s->buf_ptr));
      len -= (PLC_HISTORY_LEN - s->buf_ptr);
      memcpy(s->history, buf + (PLC_HISTORY_LEN - s->buf_ptr), sizeof(int16_t)*len);
      s->buf_ptr = len;
      return;
   }
   /* Can use just one section */
   memcpy(s->history + s->buf_ptr, buf, sizeof(int16_t)*len);
   s->buf_ptr += len;
}

/*- End of function --------------------------------------------------------*/

static void normalise_history(plc_state_t *s)
{
   int16_t tmp[PLC_HISTORY_LEN];

   if (s->buf_ptr == 0)
      return;
   memcpy(tmp, s->history, sizeof(int16_t)*s->buf_ptr);
   memmove(s->history, s->history + s->buf_ptr, sizeof(int16_t) * (PLC_HISTORY_LEN - s->buf_ptr));
   memcpy(s->history + PLC_HISTORY_LEN - s->buf_ptr, tmp, sizeof(int16_t) * s->buf_ptr);
   s->buf_ptr = 0;
}

/*- End of function --------------------------------------------------------*/

static int __inline__ amdf_pitch(int min_pitch, int max_pitch, int16_t amp[], int len)
{
   int i;
   int j;
   int acc;
   int min_acc;
   int pitch;

   pitch = min_pitch;
   min_acc = INT_MAX;
   for (i = max_pitch; i <= min_pitch; i++) {
      acc = 0;
      for (j = 0; j < len; j++)
         acc += abs(amp[i + j] - amp[j]);
      if (acc < min_acc) {
         min_acc = acc;
         pitch = i;
      }
   }
   return pitch;
}

/*- End of function --------------------------------------------------------*/

int plc_rx(plc_state_t *s, int16_t amp[], int len)
{
   int i;
   int pitch_overlap;
   float old_step;
   float new_step;
   float old_weight;
   float new_weight;
   float gain;

   if (s->missing_samples) {
      /* Although we have a real signal, we need to smooth it to fit well
      with the synthetic signal we used for the previous block */

      /* The start of the real data is overlapped with the next 1/4 cycle
         of the synthetic data. */
      pitch_overlap = s->pitch >> 2;
      if (pitch_overlap > len)
         pitch_overlap = len;
      gain = 1.0 - s->missing_samples*ATTENUATION_INCREMENT;
      if (gain < 0.0)
         gain = 0.0;
      new_step = 1.0/pitch_overlap;
      old_step = new_step*gain;
      new_weight = new_step;
      old_weight = (1.0 - new_step)*gain;
      for (i = 0; i < pitch_overlap; i++) {
         amp[i] = fsaturate(old_weight * s->pitchbuf[s->pitch_offset] + new_weight * amp[i]);
         if (++s->pitch_offset >= s->pitch)
            s->pitch_offset = 0;
         new_weight += new_step;
         old_weight -= old_step;
         if (old_weight < 0.0)
            old_weight = 0.0;
      }
      s->missing_samples = 0;
   }
   save_history(s, amp, len);
   return len;
}

/*- End of function --------------------------------------------------------*/

int plc_fillin(plc_state_t *s, int16_t amp[], int len)
{
   int i;
   int pitch_overlap;
   float old_step;
   float new_step;
   float old_weight;
   float new_weight;
   float gain;
   int orig_len;

   orig_len = len;
   if (s->missing_samples == 0) {
      /* As the gap in real speech starts we need to assess the last known pitch,
      and prepare the synthetic data we will use for fill-in */
      normalise_history(s);
      s->pitch = amdf_pitch(PLC_PITCH_MIN, PLC_PITCH_MAX, s->history + PLC_HISTORY_LEN - CORRELATION_SPAN - PLC_PITCH_MIN, CORRELATION_SPAN);
      /* We overlap a 1/4 wavelength */
      pitch_overlap = s->pitch >> 2;
      /* Cook up a single cycle of pitch, using a single of the real signal with 1/4
      cycle OLA'ed to make the ends join up nicely */
      /* The first 3/4 of the cycle is a simple copy */
      for (i = 0;  i < s->pitch - pitch_overlap;  i++)
         s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i];
      /* The last 1/4 of the cycle is overlapped with the end of the previous cycle */
      new_step = 1.0/pitch_overlap;
      new_weight = new_step;
      for ( ; i < s->pitch; i++) {
         s->pitchbuf[i] = s->history[PLC_HISTORY_LEN - s->pitch + i] * (1.0 - new_weight) + s->history[PLC_HISTORY_LEN - 2 * s->pitch + i]*new_weight;
         new_weight += new_step;
      }
      /* We should now be ready to fill in the gap with repeated, decaying cycles
      of what is in pitchbuf */

      /* We need to OLA the first 1/4 wavelength of the synthetic data, to smooth
      it into the previous real data. To avoid the need to introduce a delay
      in the stream, reverse the last 1/4 wavelength, and OLA with that. */
      gain = 1.0;
      new_step = 1.0 / pitch_overlap;
      old_step = new_step;
      new_weight = new_step;
      old_weight = 1.0 - new_step;
      for (i = 0; i < pitch_overlap; i++) {
         amp[i] = fsaturate(old_weight * s->history[PLC_HISTORY_LEN - 1 - i] + new_weight * s->pitchbuf[i]);
         new_weight += new_step;
         old_weight -= old_step;
         if (old_weight < 0.0)
            old_weight = 0.0;
      }
      s->pitch_offset = i;
   } else {
      gain = 1.0 - s->missing_samples*ATTENUATION_INCREMENT;
      i = 0;
   }
   for ( ; gain > 0.0 && i < len; i++) {
      amp[i] = s->pitchbuf[s->pitch_offset] * gain;
      gain -= ATTENUATION_INCREMENT;
      if (++s->pitch_offset >= s->pitch)
         s->pitch_offset = 0;
   }
   for ( ; i < len; i++)
      amp[i] = 0;
   s->missing_samples += orig_len;
   save_history(s, amp, len);
   return len;
}

/*- End of function --------------------------------------------------------*/

plc_state_t *plc_init(plc_state_t *s)
{
   memset(s, 0, sizeof(*s));
   return s;
}
/*- End of function --------------------------------------------------------*/
/*- End of file ------------------------------------------------------------*/

static int reload_module(void)
{
   struct ast_variable *var;
   struct ast_flags config_flags = { 0 };
   struct ast_config *cfg = ast_config_load("codecs.conf", config_flags);

   if (cfg == CONFIG_STATUS_FILEMISSING || cfg == CONFIG_STATUS_FILEUNCHANGED || cfg == CONFIG_STATUS_FILEINVALID) {
      return 0;
   }

   for (var = ast_variable_browse(cfg, "plc"); var; var = var->next) {
      if (!strcasecmp(var->name, "genericplc")) {
         ast_set2_flag(&ast_options, ast_true(var->value), AST_OPT_FLAG_GENERIC_PLC);
      } else if (!strcasecmp(var->name, "genericplc_on_equal_codecs")) {
         ast_set2_flag(&ast_options, ast_true(var->value), AST_OPT_FLAG_GENERIC_PLC_ON_EQUAL_CODECS);
      }
   }
   ast_config_destroy(cfg);

   /*
    * Force on_equal_codecs to false if generic_plc is false.
    */
   if (!ast_opt_generic_plc) {
      ast_set2_flag(&ast_options, 0, AST_OPT_FLAG_GENERIC_PLC_ON_EQUAL_CODECS);
   }

   return 0;
}

static int load_module(void)
{
   reload_module();

   return AST_MODULE_LOAD_SUCCESS;
}

static int unload_module(void)
{
   return 0;
}

AST_MODULE_INFO(ASTERISK_GPL_KEY, AST_MODFLAG_GLOBAL_SYMBOLS | AST_MODFLAG_LOAD_ORDER, "PLC",
   .support_level = AST_MODULE_SUPPORT_CORE,
   .load = load_module,
   .unload = unload_module,
   .reload = reload_module,
   .load_pri = AST_MODPRI_CORE,
   .requires = "extconfig",
);