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NMT: Fixing audio level of supervisory signal to match 0.3 KHz deviation

This commit is contained in:
Andreas Eversberg 2016-08-02 12:53:07 +02:00
parent 55229a397c
commit f15c0dfea3
1 changed files with 16 additions and 5 deletions
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21
src/nmt/dsp.c
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@ -33,10 +33,18 @@
#define PI M_PI
/* Notes on frequency deviation of supervidory signal:
*
* The FSK deviation at 1500 Hz is 3.5 KHz. If we use a level of 10000
* The supervisory deviation shall be 0.3 KHz: 10000 / 3.5 * 0.3 = 857
* Supervisory is raised by pre-emphasis by factor 2.68 (4015 / 1500),
* so we need to lower it: 857 / 2.68 = 320
*/
/* signaling */
#define COMPANDOR_0DB 32767 /* works quite well */
#define TX_PEAK_FSK 10000.0 /* peak amplitude of signaling FSK */
#define TX_PEAK_SUPER 1000.0 /* peak amplitude of supervisory signal */
#define TX_PEAK_FSK 10000.0 /* peak amplitude of signaling FSK +-3.5 KHz @ 1500 Hz */
#define TX_PEAK_SUPER (TX_PEAK_FSK / 3.5 * 0.3 / 2.68) /* peak amplitude of supervisory signal +-0.3 KHz @ 4015 Hz */
#define BIT_RATE 1200 /* baud rate */
#define STEPS_PER_BIT 10 /* step every 1/12000 sec */
#define DIALTONE_HZ 425.0 /* dial tone frequency */
@ -115,6 +123,9 @@ int dsp_init_sender(nmt_t *nmt)
return -ENOMEM;
}
PDEBUG(DDSP, DEBUG_DEBUG, "Using FSK level of %.0f (3.5 KHz deviation @ 1500 Hz)\n", TX_PEAK_FSK);
PDEBUG(DDSP, DEBUG_DEBUG, "Using Supervisory level of %.0f (0.3 KHz deviation @ 4015 Hz)\n", TX_PEAK_SUPER);
/* generate sines */
for (i = 0; i < nmt->samples_per_bit; i++) {
nmt->fsk_sine[0][0][i] = TX_PEAK_FSK * sin(3.0 * PI * (double)i / (double)nmt->samples_per_bit); /* 1.5 waves */
@ -378,15 +389,15 @@ static void super_decode(nmt_t *nmt, int16_t *samples, int length)
if (quality < 0)
quality = 0;
if (nmt->sender.loopback)
PDEBUG_CHAN(DDSP, DEBUG_NOTICE, "Supervisory level %.2f%% quality %.0f%%\n", result[0] / 0.63662 * 100.0, quality * 100.0);
if (nmt->state == STATE_ACTIVE)
PDEBUG_CHAN(DDSP, DEBUG_NOTICE, "Supervisory level %.0f%% quality %.0f%%\n", result[0] / 0.63662 * 32768.0 / TX_PEAK_SUPER * 100.0, quality * 100.0);
if (quality > 0.5) {
if (nmt->super_detected == 0) {
nmt->super_detect_count++;
if (nmt->super_detect_count == SUPER_DETECT_COUNT) {
nmt->super_detected = 1;
nmt->super_detect_count = 0;
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Supervisory signal detected with level=%.0f%%, quality=%.0f%%.\n", result[0] / 0.63662 * 100.0, quality * 100.0);
PDEBUG_CHAN(DDSP, DEBUG_DEBUG, "Supervisory signal detected with level=%.0f%%, quality=%.0f%%.\n", result[0] / 0.63662 * 32768.0 / TX_PEAK_SUPER * 100.0, quality * 100.0);
nmt_rx_super(nmt, 1, quality);
}
} else