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sdrangel/ft8/ft8stats.h

80 lines
2.9 KiB
C++

///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2024 Edouard Griffiths, F4EXB <f4exb06@gmail.com> //
// //
// This is the code from ft8mon: https://github.com/rtmrtmrtmrtm/ft8mon //
// reformatted and adapted to Qt and SDRangel context //
// //
// This program is free software; you can redistribute it and/or modify //
// it under the terms of the GNU General Public License as published by //
// the Free Software Foundation as version 3 of the License, or //
// (at your option) any later version. //
// //
// This program is distributed in the hope that it will be useful, //
// but WITHOUT ANY WARRANTY; without even the implied warranty of //
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the //
// GNU General Public License V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see <http://www.gnu.org/licenses/>. //
///////////////////////////////////////////////////////////////////////////////////
#ifndef _ft8stats_h_
#define _ft8stats_h_
#include <vector>
#include "export.h"
namespace FT8 {
//
// manage statistics for soft decoding, to help
// decide how likely each symbol is to be correct,
// to drive LDPC decoding.
//
// meaning of the how (problt_how) parameter:
// 0: gaussian
// 1: index into the actual distribution
// 2: do something complex for the tails.
// 3: index into the actual distribution plus gaussian for tails.
// 4: similar to 3.
// 5: laplace
//
class FT8_API Stats
{
public:
std::vector<float> a_;
float sum_;
bool finalized_;
float mean_; // cached
float stddev_; // cached
float b_; // cached
int how_;
public:
Stats(int how, float log_tail, float log_rate);
void add(float x);
void finalize();
float mean();
float stddev();
// fraction of distribution that's less than x.
// assumes normal distribution.
// this is PHI(x), or the CDF at x,
// or the integral from -infinity
// to x of the PDF.
float gaussian_problt(float x);
// https://en.wikipedia.org/wiki/Laplace_distribution
// m and b from page 116 of Mark Owen's Practical Signal Processing.
float laplace_problt(float x);
// look into the actual distribution.
float problt(float x);
private:
float log_tail_;
float log_rate_;
};
} //namespace FT8
#endif // _ft8stats_h_