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/* Loss detection
*
* (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 <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <math.h>
#include "../common/debug.h"
#include "loss.h"
/* initialize detector
*
* interval: number of detector calls for one interval of one second
* threshold: intervals may differ by this factor, to be declared as similar
* 0 to disable, e.g. 1.3 for 30 percent change
*/
void audio_init_loss(loss_t *loss, int interval, double threshold, int seconds)
{
memset(loss, 0, sizeof(*loss));
loss->interval = interval;
loss->threshold = threshold;
loss->interval_num = seconds;
}
/* call this when tones/telegrams are detected */
void audio_reset_loss(loss_t *loss)
{
if (loss->interval_count > 0) {
PDEBUG(DDSP, DEBUG_DEBUG, "Signal is recovered (loss is gone).\n");
loss->interval_count = 0;
}
loss->level = 0;
loss->level_count = 0;
}
#define LOSS_MAX_DIFF 1.2 /* 20 % difference */
/* call this for every interval */
int audio_detect_loss(loss_t *loss, double level)
{
double diff;
/* disabled */
if (loss->threshold == 0.0)
return 0;
/* calculate a total level to detect loss */
loss->level += level;
if (++loss->level_count < loss->interval)
return 0;
/* normalize level */
loss->level = loss->level / loss->level_count;
PDEBUG(DDSP, DEBUG_DEBUG, "Noise level = %.0f%%\n", loss->level * 100);
diff = loss->level / loss->level_last;
if (diff < 1.0)
diff = 1.0 / diff;
loss->level_last = loss->level;
loss->level = 0;
loss->level_count = 0;
if (diff < LOSS_MAX_DIFF && loss->level_last > loss->threshold) {
loss->interval_count++;
PDEBUG(DDSP, DEBUG_DEBUG, "Detected signal loss %d for intervals level change %.0f%% (below %.0f%%).\n", loss->interval_count, diff * 100 - 100, LOSS_MAX_DIFF * 100 - 100);
} else if (loss->interval_count > 0) {
audio_reset_loss(loss);
}
if (loss->interval_count == loss->interval_num)
return 1;
return 0;
}
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