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634 lines
16 KiB
C++
634 lines
16 KiB
C++
// ----------------------------------------------------------------------------
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// fftfilt.cxx -- Fast convolution Overlap-Add filter
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//
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// Filter implemented using overlap-add FFT convolution method
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// h(t) characterized by Windowed-Sinc impulse response
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//
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// Reference:
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// "The Scientist and Engineer's Guide to Digital Signal Processing"
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// by Dr. Steven W. Smith, http://www.dspguide.com
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// Chapters 16, 18 and 21
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//
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// Copyright (C) 2006-2008 Dave Freese, W1HKJ
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//
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// This file is part of fldigi.
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//
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// Fldigi 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, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Fldigi 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 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 fldigi. If not, see <http://www.gnu.org/licenses/>.
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//
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// Augmented with more filter types
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// Copyright (C) 2015-2022 Edouard Griffiths, F4EXB
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// ----------------------------------------------------------------------------
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#include <memory.h>
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#include <algorithm>
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#include <iostream>
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#include <fstream>
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#include <cstdlib>
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#include <cmath>
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#include <typeinfo>
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#include <array>
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#include <stdio.h>
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#include <sys/types.h>
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#include <dsp/misc.h>
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#include <dsp/fftfilt.h>
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//------------------------------------------------------------------------------
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// initialize the filter
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// create forward and reverse FFTs
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//------------------------------------------------------------------------------
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// Only need a single instance of g_fft, used for both forward and reverse
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void fftfilt::init_filter()
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{
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flen2 = flen >> 1;
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fft = new g_fft<float>(flen);
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filter = new cmplx[flen];
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filterOpp = new cmplx[flen];
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data = new cmplx[flen];
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output = new cmplx[flen2];
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ovlbuf = new cmplx[flen2];
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std::fill(filter, filter + flen, cmplx{0, 0});
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std::fill(filterOpp, filterOpp + flen, cmplx{0, 0});
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std::fill(data, data + flen , cmplx{0, 0});
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std::fill(output, output + flen2, cmplx{0, 0});
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std::fill(ovlbuf, ovlbuf + flen2, cmplx{0, 0});
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inptr = 0;
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}
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//------------------------------------------------------------------------------
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// fft filter
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// f1 < f2 ==> band pass filter
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// f1 > f2 ==> band reject filter
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// f1 == 0 ==> low pass filter
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// f2 == 0 ==> high pass filter
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//------------------------------------------------------------------------------
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fftfilt::fftfilt(int len)
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{
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flen = len;
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pass = 0;
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window = 0;
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init_filter();
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}
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fftfilt::fftfilt(float f1, float f2, int len)
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{
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flen = len;
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pass = 0;
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window = 0;
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init_filter();
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create_filter(f1, f2);
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}
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fftfilt::fftfilt(float f2, int len)
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{
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flen = len;
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pass = 0;
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window = 0;
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init_filter();
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create_dsb_filter(f2);
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}
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fftfilt::~fftfilt()
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{
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if (fft) delete fft;
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if (filter) delete [] filter;
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if (filterOpp) delete [] filterOpp;
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if (data) delete [] data;
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if (output) delete [] output;
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if (ovlbuf) delete [] ovlbuf;
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}
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void fftfilt::create_filter(float f1, float f2, FFTWindow::Function wf)
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{
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// initialize the filter to zero
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std::fill(filter, filter + flen, cmplx{0, 0});
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// create the filter shape coefficients by fft
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bool b_lowpass, b_highpass;
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b_lowpass = (f2 != 0);
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b_highpass = (f1 != 0);
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for (int i = 0; i < flen2; i++) {
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filter[i] = 0;
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// lowpass @ f2
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if (b_lowpass)
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filter[i] += fsinc(f2, i, flen2);
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// highighpass @ f1
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if (b_highpass)
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filter[i] -= fsinc(f1, i, flen2);
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}
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// highpass is delta[flen2/2] - h(t)
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if (b_highpass && f2 < f1)
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filter[flen2 / 2] += 1;
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FFTWindow fwin;
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fwin.create(wf, flen2);
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fwin.apply(filter);
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// for (int i = 0; i < flen2; i++)
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// filter[i] *= _blackman(i, flen2);
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fft->ComplexFFT(filter); // filter was expressed in the time domain (impulse response)
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// normalize the output filter for unity gain
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float scale = 0, mag;
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for (int i = 0; i < flen2; i++) {
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mag = abs(filter[i]);
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if (mag > scale) scale = mag;
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}
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if (scale != 0) {
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for (int i = 0; i < flen; i++)
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filter[i] /= scale;
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}
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}
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void fftfilt::create_filter(const std::vector<std::pair<float, float>>& limits, bool pass, FFTWindow::Function wf)
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{
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std::vector<int> canvasNeg(flen2, pass ? 0 : 1); // initialize the negative frequencies filter canvas
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std::vector<int> canvasPos(flen2, pass ? 0 : 1); // initialize the positive frequencies filter canvas
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std::fill(filter, filter + flen, cmplx{0, 0}); // initialize the positive filter to zero
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std::fill(filterOpp, filterOpp + flen, cmplx{0, 0}); // initialize the negative filter to zero
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for (const auto& fs : limits)
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{
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const float& f1 = fs.first + 0.5;
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const float& w = fs.second > 0.0 ? fs.second : 0.0;
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const float& f2 = f1 + w;
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for (int i = 0; i < flen; i++)
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{
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if (pass) // pass
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{
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if ((i >= f1*flen) && (i <= f2*flen))
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{
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if (i < flen2) {
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canvasNeg[flen2-1-i] = 1;
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} else {
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canvasPos[i-flen2] = 1;
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}
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}
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}
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else // reject
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{
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if ((i >= f1*flen) && (i <= f2*flen))
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{
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if (i < flen2) {
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canvasNeg[flen2-1-i] = 0;
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} else {
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canvasPos[i-flen2] = 0;
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}
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}
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}
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}
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}
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std::vector<std::pair<int,int>> indexesNegList;
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std::vector<std::pair<int,int>> indexesPosList;
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int cn = 0;
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int cp = 0;
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int defaultSecond = pass ? 0 : flen2 - 1;
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for (int i = 0; i < flen2; i++)
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{
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if ((canvasNeg[i] == 1) && (cn == 0)) {
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indexesNegList.push_back(std::pair<int,int>{i, defaultSecond});
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}
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if ((canvasNeg[i] == 0) && (cn == 1)) {
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indexesNegList.back().second = i;
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}
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if ((canvasPos[i] == 1) && (cp == 0)) {
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indexesPosList.push_back(std::pair<int,int>{i, defaultSecond});
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}
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if ((canvasPos[i] == 0) && (cp == 1)) {
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indexesPosList.back().second = i;
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}
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cn = canvasNeg[i];
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cp = canvasPos[i];
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}
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for (const auto& indexes : indexesPosList)
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{
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const float f1 = indexes.first / (float) flen;
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const float f2 = indexes.second / (float) flen;
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for (int i = 0; i < flen2; i++)
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{
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if (f2 != 0) {
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filter[i] += fsinc(f2, i, flen2);
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}
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if (f1 != 0) {
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filter[i] -= fsinc(f1, i, flen2);
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}
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}
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if (f2 == 0 && f1 != 0) {
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filter[flen2 / 2] += 1;
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}
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}
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for (const auto& indexes : indexesNegList)
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{
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const float f1 = indexes.first / (float) flen;
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const float f2 = indexes.second / (float) flen;
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for (int i = 0; i < flen2; i++)
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{
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if (f2 != 0) {
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filterOpp[i] += fsinc(f2, i, flen2);
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}
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if (f1 != 0) {
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filterOpp[i] -= fsinc(f1, i, flen2);
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}
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}
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if (f2 == 0 && f1 != 0) {
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filterOpp[flen2 / 2] += 1;
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}
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}
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FFTWindow fwin;
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fwin.create(wf, flen2);
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fwin.apply(filter);
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fwin.apply(filterOpp);
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fft->ComplexFFT(filter); // filter was expressed in the time domain (impulse response)
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fft->ComplexFFT(filterOpp); // filter was expressed in the time domain (impulse response)
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float scalen = 0, scalep = 0, magn, magp; // normalize the output filter for unity gain
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for (int i = 0; i < flen2; i++)
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{
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magp = abs(filter[i]);
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if (magp > scalep) {
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scalep = magp;
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}
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magn = abs(filterOpp[i]);
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if (magn > scalen) {
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scalen = magn;
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}
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}
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if (scalep != 0)
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{
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std::for_each(
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filter,
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filter + flen,
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[scalep](fftfilt::cmplx& s) { s /= scalep; }
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);
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}
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if (scalen != 0)
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{
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std::for_each(
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filterOpp,
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filterOpp + flen,
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[scalen](fftfilt::cmplx& s) { s /= scalen; }
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);
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}
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}
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// Double the size of FFT used for equivalent SSB filter or assume FFT is half the size of the one used for SSB
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void fftfilt::create_dsb_filter(float f2, FFTWindow::Function wf)
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{
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// initialize the filter to zero
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std::fill(filter, filter + flen, cmplx{0, 0});
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for (int i = 0; i < flen2; i++) {
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filter[i] = fsinc(f2, i, flen2);
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// filter[i] *= _blackman(i, flen2);
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}
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FFTWindow fwin;
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fwin.create(wf, flen2);
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fwin.apply(filter);
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fft->ComplexFFT(filter); // filter was expressed in the time domain (impulse response)
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// normalize the output filter for unity gain
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float scale = 0, mag;
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for (int i = 0; i < flen2; i++) {
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mag = abs(filter[i]);
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if (mag > scale) scale = mag;
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}
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if (scale != 0) {
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for (int i = 0; i < flen; i++)
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filter[i] /= scale;
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}
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}
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// Double the size of FFT used for equivalent SSB filter or assume FFT is half the size of the one used for SSB
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// used with runAsym for in band / opposite band asymmetrical filtering. Can be used for vestigial sideband modulation.
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void fftfilt::create_asym_filter(float fopp, float fin, FFTWindow::Function wf)
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{
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// in band
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// initialize the filter to zero
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std::fill(filter, filter + flen, cmplx{0, 0});
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for (int i = 0; i < flen2; i++) {
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filter[i] = fsinc(fin, i, flen2);
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// filter[i] *= _blackman(i, flen2);
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}
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FFTWindow fwin;
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fwin.create(wf, flen2);
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fwin.apply(filter);
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fft->ComplexFFT(filter); // filter was expressed in the time domain (impulse response)
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// normalize the output filter for unity gain
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float scale = 0, mag;
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for (int i = 0; i < flen2; i++) {
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mag = abs(filter[i]);
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if (mag > scale) scale = mag;
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}
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if (scale != 0) {
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for (int i = 0; i < flen; i++)
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filter[i] /= scale;
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}
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// opposite band
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// initialize the filter to zero
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std::fill(filterOpp, filterOpp + flen, cmplx{0, 0});
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for (int i = 0; i < flen2; i++) {
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filterOpp[i] = fsinc(fopp, i, flen2);
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// filterOpp[i] *= _blackman(i, flen2);
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}
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fwin.apply(filterOpp);
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fft->ComplexFFT(filterOpp); // filter was expressed in the time domain (impulse response)
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// normalize the output filter for unity gain
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scale = 0;
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for (int i = 0; i < flen2; i++) {
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mag = abs(filterOpp[i]);
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if (mag > scale) scale = mag;
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}
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if (scale != 0) {
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for (int i = 0; i < flen; i++)
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filterOpp[i] /= scale;
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}
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}
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// This filter is constructed directly from frequency domain response. Run with runFilt.
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void fftfilt::create_rrc_filter(float fb, float a)
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{
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std::fill(filter, filter+flen, 0);
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for (int i = 0; i < flen; i++) {
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filter[i] = frrc(fb, a, i, flen);
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}
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// normalize the output filter for unity gain
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float scale = 0, mag;
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for (int i = 0; i < flen; i++)
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{
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mag = abs(filter[i]);
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if (mag > scale) {
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scale = mag;
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}
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}
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if (scale != 0)
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{
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for (int i = 0; i < flen; i++) {
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filter[i] /= scale;
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}
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}
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}
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// test bypass
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int fftfilt::noFilt(const cmplx & in, cmplx **out)
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{
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data[inptr++] = in;
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if (inptr < flen2)
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return 0;
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inptr = 0;
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*out = data;
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return flen2;
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}
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// Filter with fast convolution (overlap-add algorithm).
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int fftfilt::runFilt(const cmplx & in, cmplx **out)
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{
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data[inptr++] = in;
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if (inptr < flen2)
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return 0;
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inptr = 0;
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fft->ComplexFFT(data);
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for (int i = 0; i < flen; i++)
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data[i] *= filter[i];
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fft->InverseComplexFFT(data);
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for (int i = 0; i < flen2; i++) {
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output[i] = ovlbuf[i] + data[i];
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ovlbuf[i] = data[flen2 + i];
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}
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std::fill(data, data + flen , cmplx{0, 0});
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*out = output;
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return flen2;
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}
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// Second version for single sideband
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int fftfilt::runSSB(const cmplx & in, cmplx **out, bool usb, bool getDC)
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{
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data[inptr++] = in;
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if (inptr < flen2)
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return 0;
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inptr = 0;
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fft->ComplexFFT(data);
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// get or reject DC component
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data[0] = getDC ? data[0]*filter[0] : 0;
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// Discard frequencies for ssb
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if (usb)
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{
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for (int i = 1; i < flen2; i++) {
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data[i] *= filter[i];
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data[flen2 + i] = 0;
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}
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}
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else
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{
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for (int i = 1; i < flen2; i++) {
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data[i] = 0;
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data[flen2 + i] *= filter[flen2 + i];
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}
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}
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// in-place FFT: freqdata overwritten with filtered timedata
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fft->InverseComplexFFT(data);
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// overlap and add
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for (int i = 0; i < flen2; i++) {
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output[i] = ovlbuf[i] + data[i];
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ovlbuf[i] = data[i+flen2];
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}
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std::fill(data, data + flen , cmplx{0, 0});
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*out = output;
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return flen2;
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}
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// Version for double sideband. You have to double the FFT size used for SSB.
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int fftfilt::runDSB(const cmplx & in, cmplx **out, bool getDC)
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{
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data[inptr++] = in;
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if (inptr < flen2)
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return 0;
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inptr = 0;
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fft->ComplexFFT(data);
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for (int i = 0; i < flen2; i++) {
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data[i] *= filter[i];
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data[flen2 + i] *= filter[flen2 + i];
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}
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// get or reject DC component
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data[0] = getDC ? data[0] : 0;
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// in-place FFT: freqdata overwritten with filtered timedata
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fft->InverseComplexFFT(data);
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// overlap and add
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for (int i = 0; i < flen2; i++) {
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output[i] = ovlbuf[i] + data[i];
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ovlbuf[i] = data[i+flen2];
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}
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std::fill(data, data + flen , cmplx{0, 0});
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*out = output;
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return flen2;
|
|
}
|
|
|
|
// Version for asymmetrical sidebands. You have to double the FFT size used for SSB.
|
|
int fftfilt::runAsym(const cmplx & in, cmplx **out, bool usb)
|
|
{
|
|
data[inptr++] = in;
|
|
if (inptr < flen2)
|
|
return 0;
|
|
inptr = 0;
|
|
|
|
fft->ComplexFFT(data);
|
|
|
|
data[0] *= filter[0]; // always keep DC
|
|
|
|
if (usb)
|
|
{
|
|
for (int i = 1; i < flen2; i++)
|
|
{
|
|
data[i] *= filter[i]; // usb
|
|
data[flen2 + i] *= filterOpp[flen2 + i]; // lsb is the opposite
|
|
}
|
|
}
|
|
else
|
|
{
|
|
for (int i = 1; i < flen2; i++)
|
|
{
|
|
data[i] *= filterOpp[i]; // usb is the opposite
|
|
data[flen2 + i] *= filter[flen2 + i]; // lsb
|
|
}
|
|
}
|
|
|
|
// in-place FFT: freqdata overwritten with filtered timedata
|
|
fft->InverseComplexFFT(data);
|
|
|
|
// overlap and add
|
|
for (int i = 0; i < flen2; i++) {
|
|
output[i] = ovlbuf[i] + data[i];
|
|
ovlbuf[i] = data[i+flen2];
|
|
}
|
|
|
|
std::fill(data, data + flen , cmplx{0, 0});
|
|
|
|
*out = output;
|
|
return flen2;
|
|
}
|
|
|
|
/* Sliding FFT from Fldigi */
|
|
|
|
struct sfft::vrot_bins_pair {
|
|
cmplx vrot;
|
|
cmplx bins;
|
|
} ;
|
|
|
|
sfft::sfft(int len)
|
|
{
|
|
vrot_bins = new vrot_bins_pair[len];
|
|
delay = new cmplx[len];
|
|
fftlen = len;
|
|
first = 0;
|
|
last = len - 1;
|
|
ptr = 0;
|
|
double phi = 0.0, tau = 2.0 * M_PI/ len;
|
|
k2 = 1.0;
|
|
for (int i = 0; i < len; i++) {
|
|
vrot_bins[i].vrot = cmplx( K1 * cos (phi), K1 * sin (phi) );
|
|
phi += tau;
|
|
delay[i] = vrot_bins[i].bins = 0.0;
|
|
k2 *= K1;
|
|
}
|
|
}
|
|
|
|
sfft::~sfft()
|
|
{
|
|
delete [] vrot_bins;
|
|
delete [] delay;
|
|
}
|
|
|
|
// Sliding FFT, cmplx input, cmplx output
|
|
// FFT is computed for each value from first to last
|
|
// Values are not stable until more than "len" samples have been processed.
|
|
void sfft::run(const cmplx& input)
|
|
{
|
|
cmplx & de = delay[ptr];
|
|
const cmplx z( input.real() - k2 * de.real(), input.imag() - k2 * de.imag());
|
|
de = input;
|
|
|
|
if (++ptr >= fftlen)
|
|
ptr = 0;
|
|
|
|
for (vrot_bins_pair *itr = vrot_bins + first, *end = vrot_bins + last; itr != end ; ++itr)
|
|
itr->bins = (itr->bins + z) * itr->vrot;
|
|
}
|
|
|
|
// Copies the frequencies to a pointer.
|
|
void sfft::fetch(float *result)
|
|
{
|
|
for (vrot_bins_pair *itr = vrot_bins, *end = vrot_bins + last; itr != end; ++itr, ++result)
|
|
*result = itr->bins.real() * itr->bins.real()
|
|
+ itr->bins.imag() * itr->bins.imag();
|
|
}
|
|
|