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DATV: estimate CNR with average of 20% highest and lowest powers in 1.5 times SR bandwidth

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This commit is contained in:
f4exb 2021-03-14 18:57:31 +01:00
parent 227245eb94
commit 451243b381
1 changed files with 33 additions and 2 deletions
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35
plugins/channelrx/demoddatv/leansdr/sdr.h
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@ -17,6 +17,8 @@
#ifndef LEANSDR_SDR_H
#define LEANSDR_SDR_H
#include <numeric>
#include "leansdr/dsp.h"
#include "leansdr/math.h"
@ -1809,6 +1811,7 @@ struct cnr_fft : runnable
out(_out),
fft(nfft),
avgpower(nullptr),
sorted(nullptr),
data(nullptr),
power(nullptr),
phase(0),
@ -1827,6 +1830,9 @@ struct cnr_fft : runnable
if (avgpower) {
delete[] avgpower;
}
if (sorted) {
delete[] sorted;
}
if (data) {
delete[] data;
}
@ -1859,6 +1865,9 @@ struct cnr_fft : runnable
private:
void do_cnr()
{
if (!sorted) {
sorted = new T[fft.n];
}
if (!data) {
data = new complex<T>[fft.n];
}
@ -1886,7 +1895,8 @@ struct cnr_fft : runnable
avgpower[i] = avgpower[i] * (1 - kavg) + power[i] * kavg;
}
#if 0
#define LEANDVB_SDR_CNR_METHOD 2
#if LEANDVB_SDR_CNR_METHOD == 0
int bwslots = (bandwidth / 4) * fft.n;
if (!bwslots) {
@ -1898,7 +1908,7 @@ struct cnr_fft : runnable
// Measure noise left and right of roll-off zones
float n2 = ( avgslots(icf-bwslots*4, icf-bwslots*3) +
avgslots(icf+bwslots*3, icf+bwslots*4) ) / 2;
#else
#elif LEANDVB_SDR_CNR_METHOD == 1
int cbwslots = bandwidth * cslots_ratio * fft.n;
int nstart = bandwidth * nslots_shift_ratio * fft.n;
int nstop = nstart + bandwidth * nslots_ratio * fft.n;
@ -1912,6 +1922,11 @@ struct cnr_fft : runnable
// Measure noise left and right of roll-off zones
float n2 = (avgslots(icf - nstop, icf - nstart) +
avgslots(icf + nstart, icf + nstop)) / 2;
#elif LEANDVB_SDR_CNR_METHOD == 2
int bw = bandwidth * 0.75 * fft.n;
float c2plusn2 = 0;
float n2 = 0;
minmax(icf - bw, icf + bw, n2, c2plusn2);
#endif
float c2 = c2plusn2 - n2;
float cnr = (c2 > 0 && n2 > 0) ? 10 * log10f(c2 / n2) : -50;
@ -1928,10 +1943,26 @@ struct cnr_fft : runnable
return s / (i1 - i0 + 1);
}
void minmax(int i0, int i1, float& min, float&max)
{
int l = 0;
for (int i = i0; i <= i1; ++i, ++l)
sorted[l] = avgpower[i & (fft.n - 1)];
std::sort(sorted, &sorted[l]);
int m = l/5;
min = std::accumulate<T*>(&sorted[0], &sorted[m], (T) 0) / (m+1);
max = std::accumulate<T*>(&sorted[l-m], &sorted[l], (T) 0) / (m+1);
// fprintf(stderr, "l: %d m: %d min: %f max: %f\n", l, m, min, max);
}
pipereader<complex<T>> in;
pipewriter<float> out;
cfft_engine<T> fft;
T *avgpower;
T *sorted;
complex<T> *data;
T *power;
int phase;