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