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Fixing compander

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This commit is contained in:
Andreas Eversberg
2016-04-23 14:33:02 +02:00
parent 9de121109d
commit 2a092b8cf7
8 changed files with 233 additions and 57 deletions
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19
src/nmt/dsp.c
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@@ -33,8 +33,9 @@
#define PI M_PI
/* signalling */
#define TX_PEAK_FSK 16384 /* peak amplitude of signalling FSK */
#define TX_PEAK_SUPER 1638 /* peak amplitude of supervisory signal */
#define TX_AUDIO_0dBm0 16384 /* works quite well */
#define TX_PEAK_FSK 16384.0 /* peak amplitude of signalling FSK */
#define TX_PEAK_SUPER 1638.0 /* peak amplitude of supervisory signal */
#define BIT_RATE 1200 /* baud rate */
#define STEPS_PER_BIT 10 /* step every 1/12000 sec */
#define DIALTONE_HZ 425.0 /* dial tone frequency */
@@ -84,7 +85,7 @@ int dsp_init_sender(nmt_t *nmt)
int i;
/* attack (3ms) and recovery time (13.5ms) according to NMT specs */
init_compander(&nmt->cstate, 8000, 3.0, 13.5);
init_compander(&nmt->cstate, 8000, 3.0, 13.5, TX_AUDIO_0dBm0);
if ((nmt->sender.samplerate % (BIT_RATE * STEPS_PER_BIT))) {
PDEBUG(DDSP, DEBUG_ERROR, "Sample rate must be a multiple of %d bits per second.\n", BIT_RATE * STEPS_PER_BIT);
@@ -238,7 +239,8 @@ static void fsk_receive_bit(nmt_t *nmt, int bit, double quality, double level)
/* send telegramm */
frames_elapsed = (double)(nmt->rx_sample_count_current - nmt->rx_sample_count_last) / (double)(nmt->samples_per_bit * 166);
nmt_receive_frame(nmt, nmt->fsk_filter_frame, nmt->fsk_filter_qualitysum / 140.0, nmt->fsk_filter_levelsum / 140.0, frames_elapsed);
/* convert level so that received level at TX_PEAK_FSK results in 1.0 (100%) */
nmt_receive_frame(nmt, nmt->fsk_filter_frame, nmt->fsk_filter_qualitysum / 140.0, nmt->fsk_filter_levelsum / 140.0 * 32768.0 / TX_PEAK_FSK, frames_elapsed);
}
char *show_level(int value)
@@ -339,8 +341,8 @@ static void super_decode(nmt_t *nmt, int16_t *samples, int length)
#if 0
/* normalize levels */
result[0] *= 32768.0 / (double)TX_PEAK_SUPER / 0.63662;
result[1] *= 32768.0 / (double)TX_PEAK_SUPER / 0.63662;
result[0] *= 32768.0 / TX_PEAK_SUPER / 0.63662;
result[1] *= 32768.0 / TX_PEAK_SUPER / 0.63662;
printf("signal=%.4f noise=%.4f\n", result[0], result[1]);
#endif
@@ -412,7 +414,7 @@ void sender_receive(sender_t *sender, int16_t *samples, int length)
spl = nmt->fsk_filter_spl;
for (i = 0; i < length; i++) {
#ifdef DEBUG_MODULATOR
printf("|%s|\n", show_level((int)((samples[i] / (double)TX_PEAK_FSK) * 50)+50));
printf("|%s|\n", show_level((int)((samples[i] / TX_PEAK_FSK) * 50)+50));
#endif
spl[pos++] = samples[i];
if (nmt->fsk_filter_mute) {
@@ -441,7 +443,8 @@ void sender_receive(sender_t *sender, int16_t *samples, int length)
spl = nmt->sender.rxbuf;
pos = nmt->sender.rxbuf_pos;
for (i = 0; i < count; i++) {
spl[pos++] = down[i];
#warning hacking: remove after preemphasis implementation
spl[pos++] = down[i] / 2;
if (pos == 160) {
call_tx_audio(nmt->sender.callref, spl, 160);
pos = 0;