Restructure: Move compandor from common code to 'libcompandor'
This commit is contained in:
parent
737bbe8cce
commit
c1d911d516
|
@ -0,0 +1,6 @@
|
|||
AM_CPPFLAGS = -Wall -Wextra -g $(all_includes)
|
||||
|
||||
noinst_LIBRARIES = libcompandor.a
|
||||
|
||||
libcompandor_a_SOURCES = \
|
||||
compandor.c
|
|
@ -0,0 +1,151 @@
|
|||
/* Compandor to use various networks like C-Netz / NMT / AMPS / TACS
|
||||
*
|
||||
* (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
|
||||
* All Rights Reserved
|
||||
*
|
||||
* This program is free software: you can redistribute it and/or modify
|
||||
* it under the terms of the GNU General Public License as published by
|
||||
* the Free Software Foundation, either version 3 of the License, or
|
||||
* (at your option) any later version.
|
||||
*
|
||||
* This program is distributed in the hope that it will be useful,
|
||||
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
||||
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
||||
* GNU General Public License for more details.
|
||||
*
|
||||
* You should have received a copy of the GNU General Public License
|
||||
* along with this program. If not, see <http://www.gnu.org/licenses/>.
|
||||
*/
|
||||
|
||||
#include <stdio.h>
|
||||
#include <stdint.h>
|
||||
#include <string.h>
|
||||
#include <math.h>
|
||||
#include "../common/sample.h"
|
||||
#include "compandor.h"
|
||||
|
||||
//#define db2level(db) pow(10, (double)db / 20.0)
|
||||
|
||||
/* factor is the gain (raise and fall) after given attack/recovery time */
|
||||
#define COMPRESS_ATTACK_FACTOR 1.83 /* about 1.5 after 12 dB step up */
|
||||
#define COMPRESS_RECOVERY_FACTOR 0.44 /* about 0.75 after 12 dB step down */
|
||||
#define EXPAND_ATTACK_FACTOR 1.145 /* about 0.57 after 6 dB step up */
|
||||
#define EXPAND_RECOVERY_FACTOR 0.753 /* about 1.51 after 6 dB step down */
|
||||
|
||||
/* Minimum level value to keep state */
|
||||
#define ENVELOPE_MIN 0.001
|
||||
|
||||
/* Maximum level, to prevent sqrt_tab to overflow */
|
||||
#define ENVELOPE_MAX 9.990
|
||||
|
||||
static double sqrt_tab[10000];
|
||||
|
||||
/*
|
||||
* Init compandor according to ITU-T G.162 specification
|
||||
*
|
||||
* Hopefully this is correct
|
||||
*
|
||||
*/
|
||||
void init_compandor(compandor_t *state, double samplerate, double attack_ms, double recovery_ms, double unaffected_level)
|
||||
{
|
||||
int i;
|
||||
|
||||
memset(state, 0, sizeof(*state));
|
||||
|
||||
state->c.peak = 1.0;
|
||||
state->c.envelope = 1.0;
|
||||
state->e.peak = 1.0;
|
||||
state->e.envelope = 1.0;
|
||||
state->c.step_up = pow(COMPRESS_ATTACK_FACTOR, 1000.0 / attack_ms / samplerate);
|
||||
state->c.step_down = pow(COMPRESS_RECOVERY_FACTOR, 1000.0 / recovery_ms / samplerate);
|
||||
state->e.step_up = pow(EXPAND_ATTACK_FACTOR, 1000.0 / attack_ms / samplerate);
|
||||
state->e.step_down = pow(EXPAND_RECOVERY_FACTOR, 1000.0 / recovery_ms / samplerate);
|
||||
state->c.unaffected = unaffected_level;
|
||||
state->e.unaffected = unaffected_level;
|
||||
|
||||
// FIXME: make global, not at instance
|
||||
for (i = 0; i < 10000; i++)
|
||||
sqrt_tab[i] = sqrt(i * 0.001);
|
||||
}
|
||||
|
||||
void compress_audio(compandor_t *state, sample_t *samples, int num)
|
||||
{
|
||||
double value, peak, envelope, step_up, step_down, unaffected;
|
||||
int i;
|
||||
|
||||
step_up = state->c.step_up;
|
||||
step_down = state->c.step_down;
|
||||
peak = state->c.peak;
|
||||
envelope = state->c.envelope;
|
||||
unaffected = state->c.unaffected;
|
||||
|
||||
// printf("envelope=%.4f\n", envelope);
|
||||
for (i = 0; i < num; i++) {
|
||||
/* normalize sample value to unaffected level */
|
||||
value = *samples / unaffected;
|
||||
|
||||
/* 'peak' is the level that raises directly with the signal
|
||||
* level, but falls with specified recovery rate. */
|
||||
if (fabs(value) > peak)
|
||||
peak = fabs(value);
|
||||
else
|
||||
peak *= step_down;
|
||||
/* 'evelope' is the level that raises with the specified attack
|
||||
* rate to 'peak', but falls with specified recovery rate. */
|
||||
if (peak > envelope)
|
||||
envelope *= step_up;
|
||||
else
|
||||
envelope = peak;
|
||||
if (envelope < ENVELOPE_MIN)
|
||||
envelope = ENVELOPE_MIN;
|
||||
if (envelope > ENVELOPE_MAX)
|
||||
envelope = ENVELOPE_MAX;
|
||||
|
||||
value = value / sqrt_tab[(int)(envelope / 0.001)];
|
||||
//if (i > 47000.0 && i < 48144)
|
||||
//printf("time=%.4f envelope=%.4fdb, value=%.4f\n", (double)i/48000.0, 20*log10(envelope), value);
|
||||
|
||||
*samples++ = value * unaffected;
|
||||
}
|
||||
//exit(0);
|
||||
|
||||
state->c.envelope = envelope;
|
||||
state->c.peak = peak;
|
||||
}
|
||||
|
||||
void expand_audio(compandor_t *state, sample_t *samples, int num)
|
||||
{
|
||||
double value, peak, envelope, step_up, step_down, unaffected;
|
||||
int i;
|
||||
|
||||
step_up = state->e.step_up;
|
||||
step_down = state->e.step_down;
|
||||
peak = state->e.peak;
|
||||
envelope = state->e.envelope;
|
||||
unaffected = state->e.unaffected;
|
||||
|
||||
for (i = 0; i < num; i++) {
|
||||
/* normalize sample value to 0 DB level */
|
||||
value = *samples / unaffected;
|
||||
|
||||
/* for comments: see compress_audio() */
|
||||
if (fabs(value) > peak)
|
||||
peak = fabs(value);
|
||||
else
|
||||
peak *= step_down;
|
||||
if (peak > envelope)
|
||||
envelope *= step_up;
|
||||
else
|
||||
envelope = peak;
|
||||
if (envelope < ENVELOPE_MIN)
|
||||
envelope = ENVELOPE_MIN;
|
||||
|
||||
value = value * envelope;
|
||||
|
||||
*samples++ = value * unaffected;
|
||||
}
|
||||
|
||||
state->e.envelope = envelope;
|
||||
state->e.peak = peak;
|
||||
}
|
||||
|
|
@ -0,0 +1,22 @@
|
|||
|
||||
typedef struct compandor {
|
||||
struct {
|
||||
double unaffected;
|
||||
double step_up;
|
||||
double step_down;
|
||||
double peak;
|
||||
double envelope;
|
||||
} c;
|
||||
struct {
|
||||
double unaffected;
|
||||
double step_up;
|
||||
double step_down;
|
||||
double peak;
|
||||
double envelope;
|
||||
} e;
|
||||
} compandor_t;
|
||||
|
||||
void init_compandor(compandor_t *state, double samplerate, double attack_ms, double recovery_ms, double unaffected_level);
|
||||
void compress_audio(compandor_t *state, sample_t *samples, int num);
|
||||
void expand_audio(compandor_t *state, sample_t *samples, int num);
|
||||
|
Loading…
Reference in New Issue