94 lines
2.6 KiB
C
94 lines
2.6 KiB
C
/* Loss detection
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*
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* (C) 2016 by Andreas Eversberg <jolly@eversberg.eu>
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* All Rights Reserved
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*
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* This program is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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#include <stdint.h>
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#include <stdlib.h>
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#include <string.h>
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#include <errno.h>
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#include <math.h>
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#include "../common/debug.h"
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#include "loss.h"
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/* initialize detector
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*
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* interval: number of detector calls for one interval of one second
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* threshold: intervals may differ by this factor, to be declared as similar
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* 0 to disable, e.g. 1.3 for 30 percent change
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*/
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void audio_init_loss(loss_t *loss, int interval, double threshold, int seconds)
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{
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memset(loss, 0, sizeof(*loss));
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loss->interval = interval;
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loss->threshold = threshold;
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loss->interval_num = seconds;
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}
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/* call this when tones/telegrams are detected */
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void audio_reset_loss(loss_t *loss)
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{
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if (loss->interval_count > 0) {
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PDEBUG(DDSP, DEBUG_DEBUG, "Signal is recovered (loss is gone).\n");
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loss->interval_count = 0;
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}
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loss->level = 0;
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loss->level_count = 0;
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}
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#define LOSS_MAX_DIFF 1.1 /* 10 % difference */
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/* call this for every interval */
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int audio_detect_loss(loss_t *loss, double level)
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{
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double diff;
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/* disabled */
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if (loss->threshold == 0.0)
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return 0;
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/* calculate a total level to detect loss */
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loss->level += level;
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if (++loss->level_count < loss->interval)
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return 0;
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/* normalize level */
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loss->level = loss->level / loss->level_count;
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PDEBUG(DDSP, DEBUG_DEBUG, "Noise level = %.0f%%\n", loss->level * 100);
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diff = loss->level / loss->level_last;
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if (diff < 1.0)
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diff = 1.0 / diff;
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loss->level_last = loss->level;
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loss->level = 0;
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loss->level_count = 0;
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if (diff < LOSS_MAX_DIFF && loss->level_last > loss->threshold) {
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loss->interval_count++;
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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);
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} else if (loss->interval_count > 0) {
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audio_reset_loss(loss);
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}
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if (loss->interval_count == loss->interval_num)
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return 1;
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return 0;
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}
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