mirror of
https://github.com/f4exb/sdrangel.git
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343 lines
10 KiB
C++
343 lines
10 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2023 Edouard Griffiths, F4EXB. //
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// //
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// This is the code from ft8mon: https://github.com/rtmrtmrtmrtm/ft8mon //
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// written by Robert Morris, AB1HL //
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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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#include <math.h>
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#include <complex>
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#include <string>
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#include <algorithm>
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#include "util/timeutil.h"
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#include "util.h"
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namespace FT8 {
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double now()
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{
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return TimeUtil::nowus() / 1000000.0;
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}
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//
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// Goertzel Algorithm for a Non-integer Frequency Index, Rick Lyons
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// https://www.dsprelated.com/showarticle/495.php
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//
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std::complex<float> goertzel(std::vector<float> v, int rate, int i0, int n, float hz)
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{
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// float radians_per_sample = (hz * 2 * M_PI) / rate;
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// float k = radians_per_sample * n;
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float bin_hz = rate / (float)n;
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float k = hz / bin_hz;
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float alpha = 2 * M_PI * k / n;
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float beta = 2 * M_PI * k * (n - 1.0) / n;
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float two_cos_alpha = 2 * cos(alpha);
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float a = cos(beta);
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float b = -sin(beta);
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float c = sin(alpha) * sin(beta) - cos(alpha) * cos(beta);
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float d = sin(2 * M_PI * k);
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float w1 = 0;
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float w2 = 0;
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for (int i = 0; i < n; i++)
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{
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float w0 = v[i0 + i] + two_cos_alpha * w1 - w2;
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w2 = w1;
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w1 = w0;
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}
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float re = w1 * a + w2 * c;
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float im = w1 * b + w2 * d;
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return std::complex<float>(re, im);
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}
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float vmax(const std::vector<float> &v)
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{
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float mx = 0;
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int got = 0;
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for (int i = 0; i < (int)v.size(); i++)
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{
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if (got == 0 || v[i] > mx)
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{
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got = 1;
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mx = v[i];
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}
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}
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return mx;
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}
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std::vector<float> vreal(const std::vector<std::complex<float>> &a)
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{
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std::vector<float> b(a.size());
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for (int i = 0; i < (int)a.size(); i++)
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{
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b[i] = a[i].real();
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}
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return b;
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}
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std::vector<float> vimag(const std::vector<std::complex<float>> &a)
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{
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std::vector<float> b(a.size());
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for (int i = 0; i < (int)a.size(); i++)
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{
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b[i] = a[i].imag();
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}
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return b;
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}
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// generate 8-FSK, at 25 hz, bin size 6.25 hz,
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// 200 samples/second, 32 samples/symbol.
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// used as reference to detect pairs of symbols.
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// superseded by gfsk().
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std::vector<std::complex<float>> fsk_c(const std::vector<int> &syms)
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{
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int n = syms.size();
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std::vector<std::complex<float>> v(n * 32);
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float theta = 0;
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for (int si = 0; si < n; si++)
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{
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float hz = 25 + syms[si] * 6.25;
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for (int i = 0; i < 32; i++)
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{
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v[si * 32 + i] = std::complex<float>(cos(theta), sin(theta));
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theta += 2 * M_PI / (200 / hz);
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}
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}
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return v;
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}
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// copied from wsjt-x ft2/gfsk_pulse.f90.
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// b is 1.0 for FT4; 2.0 for FT8.
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float gfsk_point(float b, float t)
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{
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float c = M_PI * sqrt(2.0 / log(2.0));
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float x = 0.5 * (erf(c * b * (t + 0.5)) - erf(c * b * (t - 0.5)));
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return x;
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}
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// the smoothing window for gfsk.
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// run the window over impulses of symbol frequencies,
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// each impulse at the center of its symbol time.
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// three symbols wide.
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// most of the pulse is in the center symbol.
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// b is 1.0 for FT4; 2.0 for FT8.
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std::vector<float> gfsk_window(int samples_per_symbol, float b)
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{
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std::vector<float> v(3 * samples_per_symbol);
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float sum = 0;
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for (int i = 0; i < (int)v.size(); i++)
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{
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float x = i / (float)samples_per_symbol;
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x -= 1.5;
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float y = gfsk_point(b, x);
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v[i] = y;
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sum += y;
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}
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for (int i = 0; i < (int)v.size(); i++)
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{
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v[i] /= sum;
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}
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return v;
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}
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// gaussian-smoothed fsk.
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// the gaussian smooths the instantaneous frequencies,
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// so that the transitions between symbols don't
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// cause clicks.
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// gwin is gfsk_window(32, 2.0)
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std::vector<std::complex<float>> gfsk_c(
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const std::vector<int> &symbols,
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float hz0, float hz1,
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float spacing, int rate, int symsamples,
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float phase0,
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const std::vector<float> &gwin
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)
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{
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if (!((gwin.size() % 2) == 0))
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{
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std::vector<std::complex<float>> v(symsamples * symbols.size());
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return v;
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}
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// compute frequency for each symbol.
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// generate a spike in the middle of each symbol time;
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// the gaussian filter will turn it into a waveform.
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std::vector<float> hzv(symsamples * (symbols.size() + 2), 0.0);
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for (int bi = 0; bi < (int)symbols.size(); bi++)
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{
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float base_hz = hz0 + (hz1 - hz0) * (bi / (float)symbols.size());
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float fr = base_hz + (symbols[bi] * spacing);
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int mid = symsamples * (bi + 1) + symsamples / 2;
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// the window has even size, so split the impulse over
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// the two middle samples to be symmetric.
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hzv[mid] = fr * symsamples / 2.0;
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hzv[mid - 1] = fr * symsamples / 2.0;
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}
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// repeat first and last symbols
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for (int i = 0; i < symsamples; i++)
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{
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hzv[i] = hzv[i + symsamples];
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hzv[symsamples * (symbols.size() + 1) + i] = hzv[symsamples * symbols.size() + i];
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}
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// run the per-sample frequency vector through
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// the gaussian filter.
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int half = gwin.size() / 2;
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std::vector<float> o(hzv.size());
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for (int i = 0; i < (int)o.size(); i++)
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{
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float sum = 0;
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for (int j = 0; j < (int)gwin.size(); j++)
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{
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int k = i - half + j;
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if (k >= 0 && k < (int)hzv.size())
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{
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sum += hzv[k] * gwin[j];
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}
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}
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o[i] = sum;
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}
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// drop repeated first and last symbols
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std::vector<float> oo(symsamples * symbols.size());
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for (int i = 0; i < (int)oo.size(); i++)
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{
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oo[i] = o[i + symsamples];
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}
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// now oo[i] contains the frequency for the i'th sample.
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std::vector<std::complex<float>> v(symsamples * symbols.size());
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float theta = phase0;
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for (int i = 0; i < (int)v.size(); i++)
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{
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v[i] = std::complex<float>(cos(theta), sin(theta));
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float hz = oo[i];
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theta += 2 * M_PI / (rate / hz);
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}
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return v;
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}
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// gaussian-smoothed fsk.
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// the gaussian smooths the instantaneous frequencies,
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// so that the transitions between symbols don't
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// cause clicks.
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// gwin is gfsk_window(32, 2.0)
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std::vector<float> gfsk_r(
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const std::vector<int> &symbols,
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float hz0, float hz1,
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float spacing, int rate, int symsamples,
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float phase0,
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const std::vector<float> &gwin
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)
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{
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if (!((gwin.size() % 2) == 0))
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{
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std::vector<float> v(symsamples * symbols.size());
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return v;
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}
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// compute frequency for each symbol.
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// generate a spike in the middle of each symbol time;
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// the gaussian filter will turn it into a waveform.
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std::vector<float> hzv(symsamples * (symbols.size() + 2), 0.0);
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for (int bi = 0; bi < (int)symbols.size(); bi++)
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{
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float base_hz = hz0 + (hz1 - hz0) * (bi / (float)symbols.size());
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float fr = base_hz + (symbols[bi] * spacing);
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int mid = symsamples * (bi + 1) + symsamples / 2;
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// the window has even size, so split the impulse over
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// the two middle samples to be symmetric.
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hzv[mid] = fr * symsamples / 2.0;
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hzv[mid - 1] = fr * symsamples / 2.0;
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}
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// repeat first and last symbols
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for (int i = 0; i < symsamples; i++)
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{
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hzv[i] = hzv[i + symsamples];
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hzv[symsamples * (symbols.size() + 1) + i] = hzv[symsamples * symbols.size() + i];
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}
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// run the per-sample frequency vector through
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// the gaussian filter.
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int half = gwin.size() / 2;
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std::vector<float> o(hzv.size());
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for (int i = 0; i < (int)o.size(); i++)
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{
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float sum = 0;
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for (int j = 0; j < (int)gwin.size(); j++)
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{
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int k = i - half + j;
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if (k >= 0 && k < (int)hzv.size())
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{
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sum += hzv[k] * gwin[j];
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}
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}
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o[i] = sum;
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}
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// drop repeated first and last symbols
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std::vector<float> oo(symsamples * symbols.size());
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for (int i = 0; i < (int)oo.size(); i++)
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{
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oo[i] = o[i + symsamples];
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}
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// now oo[i] contains the frequency for the i'th sample.
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std::vector<float> v(symsamples * symbols.size());
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float theta = phase0;
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for (int i = 0; i < (int)v.size(); i++)
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{
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v[i] = cos(theta);
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float hz = oo[i];
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theta += 2 * M_PI / (rate / hz);
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}
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return v;
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}
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const std::string WHITESPACE = " \n\r\t\f\v";
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std::string ltrim(const std::string &s)
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{
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size_t start = s.find_first_not_of(WHITESPACE);
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return (start == std::string::npos) ? "" : s.substr(start);
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}
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std::string rtrim(const std::string &s)
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{
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size_t end = s.find_last_not_of(WHITESPACE);
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return (end == std::string::npos) ? "" : s.substr(0, end + 1);
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}
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std::string trim(const std::string &s) {
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return rtrim(ltrim(s));
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}
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} // namespace FT8
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