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Improvement of Goertzel filter. Using Hamming window now. Add test routine.

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This commit is contained in:
Andreas Eversberg
2021-11-28 13:11:19 +01:00
parent d1f6a0f6ce
commit dde4113e61
8 changed files with 108 additions and 24 deletions
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17
src/amps/dsp.c
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@@ -114,7 +114,7 @@
#define TACS_SAT_DEVIATION (1700.0 / TACS_SPEECH_DEVIATION) /* no emphasis (panasonic / TI) */
#define TACS_MAX_DISPLAY (8000.0 / TACS_SPEECH_DEVIATION) /* no emphasis */
#define TACS_BITRATE 8000
#define SAT_DURATION 0.05 /* duration of SAT signal measurement */
#define SAT_BANDWIDTH 30.0 /* distance between two SAT tones, also bandwidth for goertzel filter */
#define SAT_QUALITY 0.85 /* quality needed to detect SAT signal */
#define SAT_PRINT 10 /* print sat measurement every 0.5 seconds */
#define DTX_LEVEL 0.50 /* SAT level needed to mute/unmute */
@@ -133,7 +133,7 @@ static double sat_freq[4] = {
5970.0,
6000.0,
6030.0,
5800.0, /* noise level to check against */
5790.0, /* noise level to check against */
};
static sample_t dsp_sine_sat[65536];
@@ -243,8 +243,11 @@ int dsp_init_sender(amps_t *amps, int tolerant)
amps->fsk_deviation = (!tacs) ? AMPS_FSK_DEVIATION : TACS_FSK_DEVIATION;
dsp_init_ramp(amps);
/* allocate ring buffer for SAT signal detection */
amps->sat_samples = (int)((double)amps->sender.samplerate * SAT_DURATION + 0.5);
/* allocate ring buffer for SAT signal detection
* the bandwidth of the Goertzel filter is the reciprocal of the duration
* we half our bandwidth, so that other supervisory signals will be canceled out completely by goertzel filter
*/
amps->sat_samples = (int)((double)amps->sender.samplerate * (1.0 / (SAT_BANDWIDTH / 2.0)) + 0.5);
spl = calloc(sizeof(*spl), amps->sat_samples);
if (!spl) {
PDEBUG(DDSP, DEBUG_ERROR, "No memory!\n");
@@ -732,7 +735,7 @@ static void sender_receive_frame(amps_t *amps, sample_t *samples, int length)
/* decode SAT and signaling tone */
/* compare supervisory signal against noise floor on 5800 Hz */
/* compare supervisory signal against noise floor at 5790 Hz */
static void sat_decode(amps_t *amps, sample_t *samples, int length)
{
double result[3], sat_quality, sig_quality, sat_level, sig_level;
@@ -742,8 +745,8 @@ static void sat_decode(amps_t *amps, sample_t *samples, int length)
audio_goertzel(&amps->sat_goertzel[4], samples, length, 0, &result[2], 1);
/* normalize sat level and signaling tone level */
sat_level = result[0] / ((!tacs) ? AMPS_SAT_DEVIATION : TACS_SAT_DEVIATION) / 0.63662;
sig_level = result[2] / ((!tacs) ? AMPS_FSK_DEVIATION : TACS_FSK_DEVIATION) / 0.63662;
sat_level = result[0] / ((!tacs) ? AMPS_SAT_DEVIATION : TACS_SAT_DEVIATION);
sig_level = result[2] / ((!tacs) ? AMPS_FSK_DEVIATION : TACS_FSK_DEVIATION);
/* get normalized quality of SAT and signaling tone */
sat_quality = (result[0] - result[1]) / result[0];