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Always use phase enhancement; silently ignore --phase-enhance if given.

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This commit is contained in:
Oliver Jowett 2016-05-31 11:47:57 +01:00
parent 93c135ea66
commit d419b62a65
8 changed files with 6 additions and 59 deletions
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45
demod_2400.c
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@ -118,33 +118,6 @@ static inline int correlate_check_4(uint16_t *m) {
abs(correlate_phase2(&m[10]));
}
// Work out the best phase offset to use for the given message.
static int best_phase(uint16_t *m) {
int test;
int best = -1;
int bestval = (m[0] + m[1] + m[2] + m[3] + m[4] + m[5]); // minimum correlation quality we will accept
// empirical testing suggests that 4..8 is the best range to test for here
// (testing a wider range runs the danger of picking the wrong phase for
// a message that would otherwise be successfully decoded - the correlation
// functions can match well with a one symbol / half bit offset)
// this is consistent with the peak detection which should produce
// the first data symbol with phase offset 4..8
test = correlate_check_4(&m[0]);
if (test > bestval) { bestval = test; best = 4; }
test = correlate_check_0(&m[1]);
if (test > bestval) { bestval = test; best = 5; }
test = correlate_check_1(&m[1]);
if (test > bestval) { bestval = test; best = 6; }
test = correlate_check_2(&m[1]);
if (test > bestval) { bestval = test; best = 7; }
test = correlate_check_3(&m[1]);
if (test > bestval) { bestval = test; best = 8; }
return best;
}
//
// Given 'mlen' magnitude samples in 'm', sampled at 2.4MHz,
// try to demodulate some Mode S messages.
@ -170,7 +143,7 @@ void demodulate2400(struct mag_buf *mag)
uint16_t *preamble = &m[j];
int high;
uint32_t base_signal, base_noise;
int initial_phase, first_phase, last_phase, try_phase;
int try_phase;
int msglen;
// Look for a message starting at around sample 0 with phase offset 3..7
@ -252,22 +225,10 @@ void demodulate2400(struct mag_buf *mag)
continue;
}
if (Modes.phase_enhance) {
first_phase = 4;
last_phase = 8; // try all phases
} else {
// Crosscorrelate against the first few bits to find a likely phase offset
initial_phase = best_phase(&preamble[19]);
if (initial_phase < 0) {
continue; // nothing satisfactory
}
first_phase = last_phase = initial_phase; // try only the phase we think it is
}
// try all phases
Modes.stats_current.demod_preambles++;
bestmsg = NULL; bestscore = -2; bestphase = -1;
for (try_phase = first_phase; try_phase <= last_phase; ++try_phase) {
for (try_phase = 4; try_phase <= 8; ++try_phase) {
uint16_t *pPtr;
int phase, i, score, bytelen;