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sdrangel/ft8/fft.cpp

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///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2023 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/>. //
///////////////////////////////////////////////////////////////////////////////////
// #include <assert.h>
#include <fftw3.h>
#include <QDebug>
#include "fft.h"
#include "util.h"
#include "ft8plan.h"
#include "ft8plans.h"
#include "fftbuffers.h"
namespace FT8 {
FFTEngine::FFTEngine()
{
m_fftBuffers = new FFTBuffers();
}
FFTEngine::~FFTEngine()
{
delete m_fftBuffers;
}
//
// do just one FFT on samples[i0..i0+block]
// real inputs, complex outputs.
// output has (block / 2) + 1 points.
//
std::vector<std::complex<float>> FFTEngine::one_fft(
const std::vector<float> &samples,
int i0,
int block
)
{
// assert(i0 >= 0);
// assert(block > 1);
int nsamples = samples.size();
int nbins = (block / 2) + 1;
Plan *p = FT8Plans::GetInstance()->getPlan(block);
fftwf_plan plan = p->fwd_;
// assert((int)samples.size() - i0 >= block);
float *m_in = (float *)samples.data() + i0;
if ((((unsigned long long)m_in) % 16) != 0)
{
// m_in must be on a 16-byte boundary for FFTW.
m_in = m_fftBuffers->getR(p->n_);
// assert(m_in);
for (int i = 0; i < block; i++)
{
if (i0 + i < nsamples)
{
m_in[i] = samples[i0 + i];
}
else
{
m_in[i] = 0;
}
}
}
fftwf_complex *m_out = m_fftBuffers->getC(p->n_);
// assert(m_out);
fftwf_execute_dft_r2c(plan, m_in, m_out);
std::vector<std::complex<float>> out(nbins);
for (int bi = 0; bi < nbins; bi++)
{
float re = m_out[bi][0];
float im = m_out[bi][1];
out[bi] = std::complex<float>(re, im);
}
return out;
}
//
// do a full set of FFTs, one per symbol-time.
// bins[time][frequency]
//
FFTEngine::ffts_t FFTEngine::ffts(const std::vector<float> &samples, int i0, int block)
{
// assert(i0 >= 0);
// assert(block > 1 && (block % 2) == 0);
int nsamples = samples.size();
int nbins = (block / 2) + 1;
int nblocks = (nsamples - i0) / block;
ffts_t bins(nblocks);
for (int si = 0; si < nblocks; si++) {
bins[si].resize(nbins);
}
Plan *p = FT8Plans::GetInstance()->getPlan(block);
fftwf_plan plan = p->fwd_;
// allocate our own b/c using p->m_in and p->m_out isn't thread-safe.
float *m_in = m_fftBuffers->getR(p->n_);
fftwf_complex *m_out = m_fftBuffers->getC(p->n_);
// assert(m_in && m_out);
// float *m_in = p->r_;
// fftw_complex *m_out = p->c_;
for (int si = 0; si < nblocks; si++)
{
int off = i0 + si * block;
for (int i = 0; i < block; i++)
{
if (off + i < nsamples)
{
float x = samples[off + i];
m_in[i] = x;
}
else
{
m_in[i] = 0;
}
}
fftwf_execute_dft_r2c(plan, m_in, m_out);
for (int bi = 0; bi < nbins; bi++)
{
float re = m_out[bi][0];
float im = m_out[bi][1];
std::complex<float> c(re, im);
bins[si][bi] = c;
}
}
return bins;
}
//
// do just one FFT on samples[i0..i0+block]
// real inputs, complex outputs.
// output has block points.
//
std::vector<std::complex<float>> FFTEngine::one_fft_c(
const std::vector<float> &samples,
int i0,
int block
)
{
// assert(i0 >= 0);
// assert(block > 1);
int nsamples = samples.size();
Plan *p = FT8Plans::GetInstance()->getPlan(block);
fftwf_plan plan = p->cfwd_;
fftwf_complex *m_in = m_fftBuffers->getCCI(block);
fftwf_complex *m_out = m_fftBuffers->getCCO(block);
// assert(m_in && m_out);
for (int i = 0; i < block; i++)
{
if (i0 + i < nsamples)
{
m_in[i][0] = samples[i0 + i]; // real
}
else
{
m_in[i][0] = 0;
}
m_in[i][1] = 0; // imaginary
}
fftwf_execute_dft(plan, m_in, m_out);
std::vector<std::complex<float>> out(block);
float norm = 1.0 / sqrt(block);
for (int bi = 0; bi < block; bi++)
{
float re = m_out[bi][0];
float im = m_out[bi][1];
std::complex<float> c(re, im);
c *= norm;
out[bi] = c;
}
return out;
}
std::vector<std::complex<float>> FFTEngine::one_fft_cc(
const std::vector<std::complex<float>> &samples,
int i0,
int block
)
{
// assert(i0 >= 0);
// assert(block > 1);
int nsamples = samples.size();
Plan *p = FT8Plans::GetInstance()->getPlan(block);
fftwf_plan plan = p->cfwd_;
fftwf_complex *m_in = m_fftBuffers->getCCI(block);
fftwf_complex *m_out = m_fftBuffers->getCCO(block);
// assert(m_in && m_out);
for (int i = 0; i < block; i++)
{
if (i0 + i < nsamples)
{
m_in[i][0] = samples[i0 + i].real();
m_in[i][1] = samples[i0 + i].imag();
}
else
{
m_in[i][0] = 0;
m_in[i][1] = 0;
}
}
fftwf_execute_dft(plan, m_in, m_out);
std::vector<std::complex<float>> out(block);
// float norm = 1.0 / sqrt(block);
for (int bi = 0; bi < block; bi++)
{
float re = m_out[bi][0];
float im = m_out[bi][1];
std::complex<float> c(re, im);
// c *= norm;
out[bi] = c;
}
return out;
}
std::vector<std::complex<float>> FFTEngine::one_ifft_cc(
const std::vector<std::complex<float>> &bins
)
{
int block = bins.size();
Plan *p = FT8Plans::GetInstance()->getPlan(block);
fftwf_plan plan = p->crev_;
fftwf_complex *m_in = m_fftBuffers->getCCI(block);
fftwf_complex *m_out = m_fftBuffers->getCCO(block);
// assert(m_in && m_out);
for (int bi = 0; bi < block; bi++)
{
float re = bins[bi].real();
float im = bins[bi].imag();
m_in[bi][0] = re;
m_in[bi][1] = im;
}
fftwf_execute_dft(plan, m_in, m_out);
std::vector<std::complex<float>> out(block);
float norm = 1.0 / sqrt(block);
for (int i = 0; i < block; i++)
{
float re = m_out[i][0];
float im = m_out[i][1];
std::complex<float> c(re, im);
c *= norm;
out[i] = c;
}
return out;
}
std::vector<float> FFTEngine::one_ifft(const std::vector<std::complex<float>> &bins)
{
int nbins = bins.size();
int block = (nbins - 1) * 2;
Plan *p = FT8Plans::GetInstance()->getPlan(block);
fftwf_plan plan = p->rev_;
fftwf_complex *m_in = m_fftBuffers->getC(p->n_);
float *m_out = m_fftBuffers->getR(p->n_);
for (int bi = 0; bi < nbins; bi++)
{
float re = bins[bi].real();
float im = bins[bi].imag();
m_in[bi][0] = re;
m_in[bi][1] = im;
}
fftwf_execute_dft_c2r(plan, m_in, m_out);
std::vector<float> out(block);
for (int i = 0; i < block; i++)
{
out[i] = m_out[i];
}
return out;
}
//
// return the analytic signal for signal x,
// just like scipy.signal.hilbert(), from which
// this code is copied.
//
// the return value is x + iy, where y is the hilbert transform of x.
//
std::vector<std::complex<float>> FFTEngine::analytic(const std::vector<float> &x)
{
ulong n = x.size();
std::vector<std::complex<float>> y = one_fft_c(x, 0, n);
// assert(y.size() == n);
// leave y[0] alone.
// float the first (positive) half of the spectrum.
// zero out the second (negative) half of the spectrum.
// y[n/2] is the nyquist bucket if n is even; leave it alone.
if ((n % 2) == 0)
{
for (ulong i = 1; i < n / 2; i++)
y[i] *= 2;
for (ulong i = n / 2 + 1; i < n; i++)
y[i] = 0;
}
else
{
for (ulong i = 1; i < (n + 1) / 2; i++)
y[i] *= 2;
for (ulong i = (n + 1) / 2; i < n; i++)
y[i] = 0;
}
std::vector<std::complex<float>> z = one_ifft_cc(y);
return z;
}
//
// general-purpose shift x in frequency by hz.
// uses hilbert transform to avoid sidebands.
// but it does wrap around at 0 hz and the nyquist frequency.
//
// note analytic() does an FFT over the whole signal, which
// is expensive, and often re-used, but it turns out it
// isn't a big factor in overall run-time.
//
// like weakutil.py's freq_shift().
//
std::vector<float> FFTEngine::hilbert_shift(const std::vector<float> &x, float hz0, float hz1, int rate)
{
// y = scipy.signal.hilbert(x)
std::vector<std::complex<float>> y = analytic(x);
// assert(y.size() == x.size());
float dt = 1.0 / rate;
int n = x.size();
std::vector<float> ret(n);
for (int i = 0; i < n; i++)
{
// complex "local oscillator" at hz.
float hz = hz0 + (i / (float)n) * (hz1 - hz0);
std::complex<float> lo = std::exp(std::complex<float>(0.0, 2 * M_PI * hz * dt * i));
ret[i] = (lo * y[i]).real();
}
return ret;
}
} // namespace FT8
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