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rtl_sdr_fm: fix mean_power - integer-only implementation

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arancormonk
2025-09-04 10:13:05 -04:00
parent 09bf040810
commit f052271a16
1 changed files with 12 additions and 14 deletions
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26
src/rtl_sdr_fm.cpp
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@@ -1983,26 +1983,24 @@ static int resamp_process_block(struct demod_state *s, const int16_t *in, int in
}
long int mean_power(int16_t *samples, int len, int step)
/* DC-corrected mean power (sqrt-free). Returns squared RMS units. */
/* DC-corrected mean power (sqrt-free). Integer-only implementation. */
{
int i;
int64_t p = 0;
int64_t t = 0;
int64_t s;
double dc, err;
for (i = 0; i < len; i += step) {
s = (int64_t)samples[i];
for (int i = 0; i < len; i += step) {
int64_t s = (int64_t)samples[i];
t += s;
p += s * s;
}
/* correct for dc offset in squares */
dc = (double)(t * step) / (double)len;
err = (double)t * 2.0 * dc - dc * dc * (double)len;
double power = ((double)p - err) / (double)len;
if (power < 0.0) power = 0.0;
return (long int)power;
/* DC-corrected energy ≈ p - (t^2)/len with rounded division */
int64_t dc_corr = 0;
if (len > 0) {
int64_t tt = t * t;
dc_corr = (tt + (len / 2)) / len;
}
int64_t energy = p - dc_corr;
if (energy < 0) energy = 0;
return (long int)(energy / (len > 0 ? len : 1));
}
void full_demod(struct demod_state *d)