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C-Netz: Calibration/fix processing of tone levels on TX and RX side

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FSK and compander levels are adjusted.

Eliminate offsets between subsequent speech chunks. This is done by
high-pass filter. An offset is not passed to the filter.

Do correct audio processing chain:
 time compress -> compressor -> scrambler / pre-emphasis -> TX
 RX -> de-scrambler / de-emphasis -> expander -> time expand
This commit is contained in:
Andreas Eversberg
2016-05-13 08:56:26 +02:00
parent 5a9c9c7401
commit 46fa72894e
4 changed files with 83 additions and 61 deletions
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51
src/cnetz/fsk_fm_demod.c
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@@ -106,7 +106,6 @@
#include <math.h>
#include "../common/timer.h"
#include "../common/debug.h"
#include "../common/call.h"
#include "cnetz.h"
#include "dsp.h"
#include "telegramm.h"
@@ -156,54 +155,9 @@ int fsk_fm_init(fsk_fm_demod_t *fsk, cnetz_t *cnetz, int samplerate, double bitr
fsk->level_threshold = 655;
/* reduce half of DC after about 3ms */
cnetz->offset_removal_factor = pow(0.5, 1.0 / ((double)samplerate / 333.0));
return 0;
}
/* unshrink audio segment from the duration of 60 bits to 12.5 ms */
static inline void unshrink_speech(cnetz_t *cnetz)
{
int16_t *spl;
int32_t value;
int pos, i, count;
double offset, factor;
/* fix offset between speech blocks */
offset = (double)(speech_buffer[0] - cnetz->offset_last_sample);
factor = cnetz->offset_removal_factor;
for (i = 0; i < speech_count; i++) {
value = (int32_t)speech_buffer[i] - (int)offset;
if (value < -32768.0)
value = -32768.0;
else if (value > 32767)
value = 32767;
speech_buffer[i] = value;
offset = offset * factor;
}
cnetz->offset_last_sample = speech_buffer[speech_count-1];
/* de-emphasis is done by cnetz code, not by common code */
/* de-emphasis makes bad sound in conjunction with scrambler, so we disable */
if (cnetz->de_emphasis && !cnetz->scrambler)
de_emphasis(&cnetz->estate, speech_buffer, speech_count);
if (cnetz->scrambler)
scrambler(&cnetz->scrambler_rx, speech_buffer, speech_count);
count = samplerate_downsample(&cnetz->sender.srstate, speech_buffer, speech_count, speech_buffer);
expand_audio(&cnetz->cstate, speech_buffer, count);
spl = cnetz->sender.rxbuf;
pos = cnetz->sender.rxbuf_pos;
for (i = 0; i < count; i++) {
spl[pos++] = speech_buffer[i];
if (pos == 160) {
call_tx_audio(cnetz->sender.callref, spl, 160);
pos = 0;
}
}
cnetz->sender.rxbuf_pos = pos;
}
/* get levels, sync time and jitter from sync sequence or frame data */
static inline void get_levels(fsk_fm_demod_t *fsk, int *_min, int *_max, int *_avg, int *_probes, int num, double *_time, double *_jitter)
{
@@ -514,15 +468,18 @@ void fsk_fm_demod(fsk_fm_demod_t *fsk, int16_t *samples, int length)
} else
if (t >= 5.5 && t < 65.5) {
/* get audio for the duration of 60 bits */
/* prevent overflow, if speech_size != 0 and SPK_V
* has been restarted. */
if (speech_count <= speech_size)
speech_buffer[speech_count++] = samples[i];
} else
if (t >= 65.5) {
if (speech_count) {
unshrink_speech(fsk->cnetz);
unshrink_speech(fsk->cnetz, speech_buffer, speech_count);
speech_count = 0;
}
}
}
bit_time += bits_per_sample;
if (bit_time >= BITS_PER_SUPERFRAME) {