2016-03-01 17:40:38 +00:00
/* 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 ) {
2016-03-15 18:26:13 +00:00
PDEBUG ( DDSP , DEBUG_DEBUG , " Signal is recovered (loss is gone). \n " ) ;
2016-03-01 17:40:38 +00:00
loss - > interval_count = 0 ;
}
loss - > level = 0 ;
loss - > level_count = 0 ;
}
# define LOSS_MAX_DIFF 1.1 /* 10 % 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 ;
2016-03-15 18:26:13 +00:00
PDEBUG ( DDSP , DEBUG_DEBUG , " Noise level = %.0f%% \n " , loss - > level * 100 ) ;
2016-03-01 17:40:38 +00:00
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 + + ;
2016-03-15 18:26:13 +00:00
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 ) ;
2016-03-01 17:40:38 +00:00
} else if ( loss - > interval_count > 0 ) {
audio_reset_loss ( loss ) ;
}
if ( loss - > interval_count = = loss - > interval_num )
return 1 ;
return 0 ;
}