plc.c

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/*
 * Asterisk -- An open source telephony toolkit.
 *
 * Written by Steve Underwood <steveu@coppice.org>
 *
 * 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 <steveu@coppice.org>
 */
 
/*** 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",
);