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B-Netz / NMT: minor changes at signal detection

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This commit is contained in:
Andreas Eversberg
2016-05-01 10:23:45 +02:00
parent 47dbf094d9
commit b73894ac49
3 changed files with 18 additions and 14 deletions
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16
src/nmt/dsp.c
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@@ -303,41 +303,45 @@ static inline void fsk_decode_step(nmt_t *nmt, int pos)
nmt->rx_sample_count += nmt->fsk_filter_step;
level = audio_level(spl, max);
/* limit level to prevent division by zero */
if (level < 0.01)
level = 0.01;
// level = 0.63662 / 2.0;
audio_goertzel(spl, max, pos, nmt->fsk_coeff, result, 2);
/* calculate soft bit from both frequencies */
softbit = (result[1] / level - result[0] / level + 1.0) / 2.0;
//printf("%.3f: %.3f\n", level, softbit);
/* scale it, since both filters overlap by some percent */
#define MIN_QUALITY 0.33
softbit = (softbit - MIN_QUALITY) / (1.0 - MIN_QUALITY - MIN_QUALITY);
if (softbit > 1)
softbit = 1;
if (softbit < 0)
softbit = 0;
#ifdef DEBUG_FILTER
// printf("|%s", show_level(result[0]/level*100));
// printf("|%s| low=%.3f high=%.3f level=%d\n", show_level(result[1]/level*100), result[0]/level, result[1]/level, (int)level);
printf("|%s| softbit=%.3f\n", show_level(softbit * 100), softbit);
#endif
if (softbit > 1)
softbit = 1;
if (softbit < 0)
softbit = 0;
if (softbit > 0.5)
bit = 1;
else
bit = 0;
if (nmt->fsk_filter_bit != bit) {
/* if we have a bit change, reset sample counter to one half bit duration */
#ifdef DEBUG_FILTER
puts("bit change");
#endif
/* if we have a bit change, reset sample counter to one half bit duration */
nmt->fsk_filter_bit = bit;
nmt->fsk_filter_sample = 5;
} else if (--nmt->fsk_filter_sample == 0) {
/* if sample counter bit reaches 0, we reset sample counter to one bit duration */
#ifdef DEBUG_FILTER
puts("sample");
#endif
/* if sample counter bit reaches 0, we reset sample counter to one bit duration */
// quality = result[bit] / level;
if (softbit > 0.5)
quality = softbit * 2.0 - 1.0;