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osmocom-analog/src/cnetz/dsp.c

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/* C-Netz audio processing
*
* (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 <stdlib.h>
#include <string.h>
#include <math.h>
#include <errno.h>
#include "../common/debug.h"
#include "../common/timer.h"
#include "cnetz.h"
#include "sysinfo.h"
#include "telegramm.h"
#include "dsp.h"
/* test function to mirror received audio from ratio back to radio */
//#define TEST_SCRABLE
/* test the audio quality after cascading two scramblers (TEST_SCRABLE must be defined) */
//#define TEST_UNSCRABLE
#define PI M_PI
#define BITRATE 5280.0 /* bits per second */
#define BLOCK_BITS 198 /* duration of one time slot including pause at beginning and end */
#ifdef TEST_SCRABLE
jitter_t scrambler_test_jb;
scrambler_t scrambler_test_scrambler1;
scrambler_t scrambler_test_scrambler2;
#endif
static int16_t ramp_up[256], ramp_down[256];
void dsp_init(void)
{
}
static void dsp_init_ramp(cnetz_t *cnetz)
{
double c;
int i;
int16_t deviation = cnetz->fsk_deviation;
PDEBUG(DDSP, DEBUG_DEBUG, "Generating smooth ramp table.\n");
for (i = 0; i < 256; i++) {
c = cos((double)i / 256.0 * PI);
#if 0
if (c < 0)
c = -sqrt(-c);
else
c = sqrt(c);
#endif
ramp_down[i] = (int)(c * (double)deviation);
ramp_up[i] = -ramp_down[i];
}
}
/* Init transceiver instance. */
int dsp_init_sender(cnetz_t *cnetz, int measure_speed, double clock_speed[2], double deviation, double noise)
{
int rc = 0;
double size;
PDEBUG(DDSP, DEBUG_DEBUG, "Init FSK for 'Sender'.\n");
if (measure_speed) {
cnetz->measure_speed = measure_speed;
cant_recover = 1;
}
if (clock_speed[0] > 1000 || clock_speed[0] < -1000 || clock_speed[1] > 1000 || clock_speed[1] < -1000) {
PDEBUG(DDSP, DEBUG_ERROR, "Clock speed %.1f,%.1f ppm out of range! Plese use range between +-1000 ppm!\n", clock_speed[0], clock_speed[1]);
return -EINVAL;
}
PDEBUG(DDSP, DEBUG_INFO, "Using clock speed of %.1f ppm (RX) and %.1f ppm (TX) to correct sound card's clock.\n", clock_speed[0], clock_speed[1]);
cnetz->fsk_bitduration = (double)cnetz->sender.samplerate / ((double)BITRATE / (1.0 + clock_speed[1] / 1000000.0));
cnetz->fsk_tx_bitstep = 1.0 / cnetz->fsk_bitduration;
PDEBUG(DDSP, DEBUG_DEBUG, "Use %.4f samples for one bit duration @ %d.\n", cnetz->fsk_bitduration, cnetz->sender.samplerate);
size = cnetz->fsk_bitduration * (double)BLOCK_BITS * 16.0; /* 16 blocks for distributed frames */
cnetz->fsk_tx_buffer_size = size * 1.1; /* more to compensate clock speed */
cnetz->fsk_tx_buffer = calloc(sizeof(int16_t), cnetz->fsk_tx_buffer_size);
if (!cnetz->fsk_tx_buffer) {
PDEBUG(DDSP, DEBUG_DEBUG, "No memory!\n");
rc = -ENOMEM;
goto error;
}
/* create devation and ramp */
if (deviation > 1.0)
deviation = 1.0;
cnetz->fsk_deviation = (int16_t)(deviation * 32766.9); /* be sure not to overflow -32767 .. 32767 */
dsp_init_ramp(cnetz);
cnetz->fsk_noise = noise;
/* create speech buffer */
cnetz->dsp_speech_buffer = calloc(sizeof(int16_t), cnetz->sender.samplerate); /* buffer is greater than sr/1.1, just to be secure */
if (!cnetz->dsp_speech_buffer) {
PDEBUG(DDSP, DEBUG_DEBUG, "No memory!\n");
rc = -ENOMEM;
goto error;
}
/* reinit the sample rate to shrink/expand audio */
init_samplerate(&cnetz->sender.srstate, (double)cnetz->sender.samplerate / 1.1); /* 66 <-> 60 */
rc = fsk_fm_init(&cnetz->fsk_demod, cnetz, cnetz->sender.samplerate, (double)BITRATE / (1.0 + clock_speed[0] / 1000000.0));
if (rc < 0)
goto error;
/* init scrambler for shrinked audio */
scrambler_setup(&cnetz->scrambler_tx, (double)cnetz->sender.samplerate / 1.1);
scrambler_setup(&cnetz->scrambler_rx, (double)cnetz->sender.samplerate / 1.1);
/* reinit jitter buffer for 8000 kHz */
jitter_destroy(&cnetz->sender.audio);
rc = jitter_create(&cnetz->sender.audio, 8000 / 5);
if (rc < 0)
goto error;
/* init compander, according to C-Netz specs, attack and recovery time
* shall not exceed according to ITU G.162 */
init_compander(&cnetz->cstate, 8000, 5.0, 22.5, 32767);
#ifdef TEST_SCRABLE
rc = jitter_create(&scrambler_test_jb, cnetz->sender.samplerate / 5);
if (rc < 0) {
PDEBUG(DDSP, DEBUG_ERROR, "Failed to init jitter buffer for scrambler test!\n");
exit(0);
}
scrambler_setup(&scrambler_test_scrambler1, cnetz->sender.samplerate);
scrambler_setup(&scrambler_test_scrambler2, cnetz->sender.samplerate);
#endif
return 0;
error:
dsp_cleanup_sender(cnetz);
return rc;
}
void dsp_cleanup_sender(cnetz_t *cnetz)
{
PDEBUG(DDSP, DEBUG_DEBUG, "Cleanup FSK for 'Sender'.\n");
if (cnetz->fsk_tx_buffer)
free(cnetz->fsk_tx_buffer);
if (cnetz->dsp_speech_buffer)
free(cnetz->dsp_speech_buffer);
}
/* receive sample time and calculate speed against system clock
* tx: indicates transmit stream
* result: if set the actual signal speed is used (instead of sample rate) */
void calc_clock_speed(cnetz_t *cnetz, uint64_t samples, int tx, int result)
{
struct clock_speed *cs = &cnetz->clock_speed;
double ti;
double speed_ppm_rx[2], speed_ppm_tx[2];
if (!cnetz->measure_speed)
return;
if (result)
tx += 2;
ti = get_time();
/* skip some time to avoid false mesurement due to filling of buffers */
if (cs->meas_ti == 0.0) {
cs->meas_ti = ti + 1.0;
return;
}
if (cs->meas_ti > ti)
return;
/* start sample counting */
if (cs->start_ti[tx] == 0.0) {
cs->start_ti[tx] = ti;
cs->spl_count[tx] = 0;
return;
}
/* add elapsed time */
cs->last_ti[tx] = ti;
cs->spl_count[tx] += samples;
/* only calculate speed, if one second has elapsed */
if (ti - cs->meas_ti <= 1.0)
return;
cs->meas_ti += 1.0;
if (!cs->spl_count[2] || !cs->spl_count[3])
return;
speed_ppm_rx[0] = ((double)cs->spl_count[0] / (double)cnetz->sender.samplerate) / (cs->last_ti[0] - cs->start_ti[0]) * 1000000.0 - 1000000.0;
speed_ppm_tx[0] = ((double)cs->spl_count[1] / (double)cnetz->sender.samplerate) / (cs->last_ti[1] - cs->start_ti[1]) * 1000000.0 - 1000000.0;
speed_ppm_rx[1] = ((double)cs->spl_count[2] / (double)cnetz->sender.samplerate) / (cs->last_ti[2] - cs->start_ti[2]) * 1000000.0 - 1000000.0;
speed_ppm_tx[1] = ((double)cs->spl_count[3] / (double)cnetz->sender.samplerate) / (cs->last_ti[3] - cs->start_ti[3]) * 1000000.0 - 1000000.0;
PDEBUG(DDSP, DEBUG_NOTICE, "Clock: RX=%.2f TX=%.2f; Signal: TX=%.2f RX=%.2f ppm\n", speed_ppm_rx[0], speed_ppm_tx[0], speed_ppm_rx[1], speed_ppm_tx[1]);
}
static int fsk_nothing_encode(cnetz_t *cnetz)
{
int16_t *spl;
double phase, bitstep, r;
int i, count;
spl = cnetz->fsk_tx_buffer;
phase = cnetz->fsk_tx_phase;
bitstep = cnetz->fsk_tx_bitstep * 256.0;
if (cnetz->fsk_noise) {
r = cnetz->fsk_noise;
/* add 198 bits of noise */
for (i = 0; i < 198; i++) {
do {
*spl++ = (double)((int16_t)(random() & 0xffff)) * r;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
} else {
/* add 198 bits of silence */
for (i = 0; i < 198; i++) {
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
}
/* depending on the number of samples, return the number */
count = ((uintptr_t)spl - (uintptr_t)cnetz->fsk_tx_buffer) / sizeof(*spl);
cnetz->fsk_tx_phase = phase;
cnetz->fsk_tx_buffer_length = count;
return count;
}
/* encode one data block into samples
* input: 184 data bits (including barker code)
* output: samples
* return number of samples */
static int fsk_block_encode(cnetz_t *cnetz, const char *bits)
{
/* alloc samples, add 1 in case there is a rest */
int16_t *spl;
double phase, bitstep, deviation;
int i, count;
char last;
deviation = cnetz->fsk_deviation;
spl = cnetz->fsk_tx_buffer;
phase = cnetz->fsk_tx_phase;
bitstep = cnetz->fsk_tx_bitstep * 256.0;
/* add 7 bits of pause */
for (i = 0; i < 7; i++) {
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
/* add 184 bits */
last = ' ';
for (i = 0; i < 184; i++) {
switch (last) {
case ' ':
if (bits[i] == '1') {
/* ramp up from 0 */
do {
*spl++ = ramp_up[(int)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down from 0 */
do {
*spl++ = ramp_down[(int)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
break;
case '1':
if (bits[i] == '1') {
/* stay up */
do {
*spl++ = deviation;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down */
do {
*spl++ = ramp_down[(int)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
break;
case '0':
if (bits[i] == '1') {
/* ramp up */
do {
*spl++ = ramp_up[(int)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* stay down */
do {
*spl++ = -deviation;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
break;
}
last = bits[i];
}
/* add 7 bits of pause */
if (last == '0') {
/* ramp up to 0 */
do {
*spl++ = ramp_up[(int)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down to 0 */
do {
*spl++ = ramp_down[(int)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
for (i = 1; i < 7; i++) {
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
/* depending on the number of samples, return the number */
count = ((uintptr_t)spl - (uintptr_t)cnetz->fsk_tx_buffer) / sizeof(*spl);
cnetz->fsk_tx_phase = phase;
cnetz->fsk_tx_buffer_length = count;
return count;
}
/* encode one distributed data block into samples
* input: 184 data bits (including barker code)
* output: samples
* if a sample contains 0x8000, it indicates where to insert speech block
* return number of samples */
static int fsk_distributed_encode(cnetz_t *cnetz, const char *bits)
{
/* alloc samples, add 1 in case there is a rest */
int16_t *spl, *marker;
double phase, bitstep, deviation;
int i, j, count;
char last;
deviation = cnetz->fsk_deviation;
spl = cnetz->fsk_tx_buffer;
phase = cnetz->fsk_tx_phase;
bitstep = cnetz->fsk_tx_bitstep * 256.0;
/* add 2 * (1+4+1 + 60) bits of pause / for speech */
for (i = 0; i < 2; i++) {
for (j = 0; j < 6; j++) {
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
marker = spl;
for (j = 0; j < 60; j++) {
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
*marker = -32768; /* indicator for inserting speech */
}
/* add 46 * (1+4+1 + 60) bits */
for (i = 0; i < 46; i++) {
/* unmodulated bit */
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
last = ' ';
for (j = 0; j < 4; j++) {
switch (last) {
case ' ':
if (bits[i * 4 + j] == '1') {
/* ramp up from 0 */
do {
*spl++ = ramp_up[(int)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down from 0 */
do {
*spl++ = ramp_down[(int)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
break;
case '1':
if (bits[i * 4 + j] == '1') {
/* stay up */
do {
*spl++ = deviation;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down */
do {
*spl++ = ramp_down[(int)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
break;
case '0':
if (bits[i * 4 + j] == '1') {
/* ramp up */
do {
*spl++ = ramp_up[(int)phase];
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* stay down */
do {
*spl++ = -deviation;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
break;
}
last = bits[i * 4 + j];
}
/* unmodulated bit */
if (last == '0') {
/* ramp up to 0 */
do {
*spl++ = ramp_up[(int)phase] / 2 - deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
} else {
/* ramp down to 0 */
do {
*spl++ = ramp_down[(int)phase] / 2 + deviation / 2;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
marker = spl;
for (j = 0; j < 60; j++) {
do {
*spl++ = 0;
phase += bitstep;
} while (phase < 256.0);
phase -= 256.0;
}
*marker = -32768; /* indicator for inserting speech */
}
/* depending on the number of samples, return the number */
count = ((uintptr_t)spl - (uintptr_t)cnetz->fsk_tx_buffer) / sizeof(*spl);
cnetz->fsk_tx_phase = phase;
cnetz->fsk_tx_buffer_length = count;
return count;
}
void show_level(double level)
{
char text[42] = " ";
if (level > 1.0)
level = 1.0;
if (level < -1.0)
level = -1.0;
text[20 - (int)(level * 20)] = '*';
printf("%s\n", text);
}
/* decode samples and hut for bit changes
* use deviation to find greatest slope of the signal (bit change)
*/
void sender_receive(sender_t *sender, int16_t *samples, int length)
{
cnetz_t *cnetz = (cnetz_t *) sender;
/* measure rx sample speed */
calc_clock_speed(cnetz, length, 0, 0);
#ifdef TEST_SCRABLE
#ifdef TEST_UNSCRABLE
scrambler(&scrambler_test_scrambler1, samples, length);
#endif
jitter_save(&scrambler_test_jb, samples, length);
return;
#endif
fsk_fm_demod(&cnetz->fsk_demod, samples, length);
return;
}
static int fsk_telegramm(cnetz_t *cnetz, int16_t *samples, int length)
{
int count = 0, pos, copy, i, speech_length, speech_pos;
int16_t *spl, *speech_buffer;
const char *bits;
speech_buffer = cnetz->dsp_speech_buffer;
speech_length = cnetz->dsp_speech_length;
speech_pos = cnetz->dsp_speech_pos;
again:
/* there must be length, otherwise we would skip blocks */
if (!length)
return count;
pos = cnetz->fsk_tx_buffer_pos;
spl = cnetz->fsk_tx_buffer + pos;
/* start new telegramm, so we generate one */
if (pos == 0) {
/* measure actual signal speed */
if (cnetz->sched_ts == 0 && cnetz->sched_r_m == 0)
calc_clock_speed(cnetz, cnetz->sender.samplerate * 24 / 10, 1, 1);
/* switch to speech channel */
if (cnetz->sched_switch_mode && cnetz->sched_r_m == 0) {
if (--cnetz->sched_switch_mode == 0) {
/* OgK / SpK(K) / SpK(V) */
PDEBUG(DDSP, DEBUG_INFO, "Switching channel (mode)\n");
cnetz->dsp_mode = cnetz->sched_dsp_mode;
}
}
switch (cnetz->dsp_mode) {
case DSP_MODE_OGK:
if (((1 << cnetz->sched_ts) & si.ogk_timeslot_mask)) {
if (cnetz->sched_r_m == 0) {
/* set last time slot, so we can match received message from mobile station */
cnetz->last_tx_timeslot = cnetz->sched_ts;
PDEBUG(DDSP, DEBUG_DEBUG, "Transmitting 'Rufblock' at timeslot %d\n", cnetz->sched_ts);
bits = cnetz_encode_telegramm(cnetz);
} else {
PDEBUG(DDSP, DEBUG_DEBUG, "Transmitting 'Meldeblock' at timeslot %d\n", cnetz->sched_ts);
bits = cnetz_encode_telegramm(cnetz);
}
fsk_block_encode(cnetz, bits);
} else {
fsk_nothing_encode(cnetz);
}
break;
case DSP_MODE_SPK_K:
PDEBUG(DDSP, DEBUG_DEBUG, "Transmitting 'Konzentrierte Signalisierung'\n");
bits = cnetz_encode_telegramm(cnetz);
fsk_block_encode(cnetz, bits);
break;
case DSP_MODE_SPK_V:
PDEBUG(DDSP, DEBUG_DEBUG, "Transmitting 'Verteilte Signalisierung'\n");
bits = cnetz_encode_telegramm(cnetz);
fsk_distributed_encode(cnetz, bits);
break;
default:
fsk_nothing_encode(cnetz);
}
if (cnetz->dsp_mode == DSP_MODE_SPK_V) {
/* count sub frame */
cnetz->sched_ts += 8;
} else {
/* count slot */
if (cnetz->sched_r_m == 0)
cnetz->sched_r_m = 1;
else {
cnetz->sched_r_m = 0;
cnetz->sched_ts++;
}
}
if (cnetz->sched_ts == 32)
cnetz->sched_ts = 0;
}
copy = cnetz->fsk_tx_buffer_length - pos;
if (length < copy)
copy = length;
for (i = 0; i < copy; i++) {
if (*spl == -32768) {
/* marker found to insert new chunk of audio */
jitter_load(&cnetz->sender.audio, speech_buffer, 100);
compress_audio(&cnetz->cstate, speech_buffer, 100);
speech_length = samplerate_upsample(&cnetz->sender.srstate, speech_buffer, 100, speech_buffer);
if (cnetz->scrambler)
scrambler(&cnetz->scrambler_tx, speech_buffer, speech_length);
/* pre-emphasis is done by cnetz code, not by common code */
/* pre-emphasis makes bad sound in conjunction with scrambler, so we disable */
if (cnetz->pre_emphasis && !cnetz->scrambler)
pre_emphasis(&cnetz->estate, speech_buffer, speech_length);
speech_pos = 0;
}
/* copy speech as long as we have something left in buffer */
if (speech_pos < speech_length)
*samples++ = speech_buffer[speech_pos++];
else
*samples++ = *spl;
spl++;
}
cnetz->dsp_speech_length = speech_length;
cnetz->dsp_speech_pos = speech_pos;
pos += copy;
count += copy;
length -= copy;
if (pos == cnetz->fsk_tx_buffer_length) {
cnetz->fsk_tx_buffer_pos = 0;
goto again;
}
cnetz->fsk_tx_buffer_pos = pos;
return count;
}
/* Provide stream of audio toward radio unit */
void sender_send(sender_t *sender, int16_t *samples, int length)
{
cnetz_t *cnetz = (cnetz_t *) sender;
int count;
/* measure tx sample speed */
calc_clock_speed(cnetz, length, 1, 0);
#ifdef TEST_SCRABLE
jitter_load(&scrambler_test_jb, samples, length);
scrambler(&scrambler_test_scrambler2, samples, length);
return;
#endif
count = fsk_telegramm(cnetz, samples, length);
if (count < length) {
printf("length=%d < count=%d\n", length, count);
printf("this shall not happen, so please fix!\n");
exit(0);
}
}
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