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FT8 demod: fix duplicated code (1)

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f4exb
2026-03-13 18:37:09 +01:00
parent 71d6208fe9
commit 81f7d2ff99
4 changed files with 104 additions and 331 deletions
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ft8/ft4.cpp
+4 -86
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@@ -1547,88 +1547,6 @@ std::vector<std::vector<float>> FT4::soft_c2m(const FFTEngine::ffts_t &c103)
return m103;
}
//
// guess the probability that a bit is zero vs one,
// based on strengths of strongest tones that would
// give it those values. for soft LDPC decoding.
//
// returns log-likelihood, zero is positive, one is negative.
//
float FT4::bayes(
FT4Params& params,
float best_zero,
float best_one,
int lli,
Stats &bests,
Stats &all
)
{
float maxlog = 4.97;
float ll = 0;
float pzero = 0.5;
float pone = 0.5;
if (params.use_apriori)
{
pzero = 1.0 - apriori174[lli];
pone = apriori174[lli];
}
//
// Bayes combining rule normalization from:
// http://cs.wellesley.edu/~anderson/writing/naive-bayes.pdf
//
// a = P(zero)P(e0|zero)P(e1|zero)
// b = P(one)P(e0|one)P(e1|one)
// p = a / (a + b)
//
// also see Mark Owen's book Practical Signal Processing,
// Chapter 6.
//
// zero
float a = pzero * bests.problt(best_zero) * (1.0 - all.problt(best_one));
// printf("FT8::bayes: a: %f bp: %f ap: %f \n", a, bests.problt(best_zero), all.problt(best_one));
if (params.bayes_how == 1) {
a *= all.problt(all.mean() + (best_zero - best_one));
}
// one
float b = pone * bests.problt(best_one) * (1.0 - all.problt(best_zero));
// printf("FT8::bayes: b: %f bp: %f ap: %f \n", b, bests.problt(best_one), all.problt(best_zero));
if (params.bayes_how == 1) {
b *= all.problt(all.mean() + (best_one - best_zero));
}
float p;
if (a + b == 0) {
p = 0.5;
} else {
p = a / (a + b);
}
// printf("FT8::bayes: all.mean: %f a: %f b: %f p: %f\n", all.mean(), a, b, p);
if (1 - p == 0.0) {
ll = maxlog;
} else {
ll = log(p / (1 - p));
}
if (ll > maxlog) {
ll = maxlog;
}
if (ll < -maxlog) {
ll = -maxlog;
}
return ll;
}
//
// c103 is 103x4 complex tones, before un-gray-coding.
//
@@ -1720,7 +1638,7 @@ void FT4::soft_decode(const FFTEngine::ffts_t &c103, float ll174[])
}
}
float ll = bayes(params, best_zero, best_one, lli, bests, all);
float ll = FT8::bayes(params, best_zero, best_one, lli, bests, all);
ll174[lli++] = ll;
}
}
@@ -1909,7 +1827,7 @@ void FT4::c_soft_decode(const FFTEngine::ffts_t &c103x, float ll174[])
}
}
float ll = bayes(params, best_zero, best_one, lli, bests, all);
float ll = FT8::bayes(params, best_zero, best_one, lli, bests, all);
ll174[lli++] = ll;
}
}
@@ -2084,7 +2002,7 @@ void FT4::soft_decode_pairs(
float best_zero = bitinfo[si * 2 + i].zero;
float best_one = bitinfo[si * 2 + i].one;
// ll174[lli++] = best_zero > best_one ? 4.99 : -4.99;
float ll = bayes(params, best_zero, best_one, lli, bests, all);
float ll = FT8::bayes(params, best_zero, best_one, lli, bests, all);
ll174[lli++] = ll;
}
}
@@ -2262,7 +2180,7 @@ void FT4::soft_decode_triples(
float best_zero = bitinfo[si * 2 + i].zero;
float best_one = bitinfo[si * 2 + i].one;
// ll174[lli++] = best_zero > best_one ? 4.99 : -4.99;
float ll = bayes(params, best_zero, best_one, lli, bests, all);
float ll = FT8::bayes(params, best_zero, best_one, lli, bests, all);
ll174[lli++] = ll;
}
}