2024-06-16 09:31:13 +00:00
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/* fcurve.c
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This file is part of a program that implements a Software-Defined Radio.
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Copyright (C) 2013, 2016 Warren Pratt, NR0V
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Copyright (C) 2024 Edouard Griffiths, F4EXB Adapted to SDRangel
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This program is free software; you can redistribute it and/or
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modify it under the terms of the GNU General Public License
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as published by the Free Software Foundation; either version 2
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of the License, or (at your option) any later version.
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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 for more details.
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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, write to the Free Software
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Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
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The author can be reached by email at
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warren@wpratt.com
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*/
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#include "comm.hpp"
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#include "fcurve.hpp"
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#include "fir.hpp"
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namespace WDSP {
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2024-08-08 07:09:40 +00:00
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void FCurve::fc_impulse (std::vector<float>& impulse, int nc, float f0, float f1, float g0, float, int curve, float samplerate, float scale, int ctfmode, int wintype)
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{
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float* A = new float[nc / 2 + 1]; // (float *) malloc0 ((nc / 2 + 1) * sizeof (float));
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2024-06-16 09:31:13 +00:00
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int i;
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2024-06-25 01:50:48 +00:00
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float fn, f;
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int mid = nc / 2;
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2024-06-25 01:50:48 +00:00
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float g0_lin = pow(10.0, g0 / 20.0);
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if (nc & 1)
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{
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for (i = 0; i <= mid; i++)
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{
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2024-06-25 01:50:48 +00:00
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fn = (float)i / (float)mid;
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2024-06-16 09:31:13 +00:00
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f = fn * samplerate / 2.0;
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switch (curve)
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{
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case 0: // fm pre-emphasis
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if (f0 > 0.0)
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A[i] = scale * (g0_lin * f / f0);
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else
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A[i] = 0.0;
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break;
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case 1: // fm de-emphasis
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if (f > 0.0)
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A[i] = scale * (g0_lin * f0 / f);
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else
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A[i] = 0.0;
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break;
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}
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}
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}
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else
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{
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for (i = 0; i < mid; i++)
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{
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fn = ((float)i + 0.5) / (float)mid;
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f = fn * samplerate / 2.0;
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switch (curve)
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{
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case 0: // fm pre-emphasis
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if (f0 > 0.0)
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A[i] = scale * (g0_lin * f / f0);
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else
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A[i] = 0.0;
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break;
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case 1: // fm de-emphasis
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if (f > 0.0)
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A[i] = scale * (g0_lin * f0 / f);
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else
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A[i] = 0.0;
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break;
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}
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}
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}
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if (ctfmode == 0)
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{
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int k, low, high;
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float lowmag, highmag, flow4, fhigh4;
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if (nc & 1)
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{
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low = (int)(2.0 * f0 / samplerate * mid);
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high = (int)(2.0 * f1 / samplerate * mid + 0.5);
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lowmag = A[low];
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highmag = A[high];
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flow4 = pow((float)low / (float)mid, 4.0);
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fhigh4 = pow((float)high / (float)mid, 4.0);
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k = low;
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while (--k >= 0)
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{
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f = (float)k / (float)mid;
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lowmag *= (f * f * f * f) / flow4;
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if (lowmag < 1.0e-20) lowmag = 1.0e-20;
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A[k] = lowmag;
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}
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k = high;
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while (++k <= mid)
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{
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f = (float)k / (float)mid;
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highmag *= fhigh4 / (f * f * f * f);
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if (highmag < 1.0e-20) highmag = 1.0e-20;
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A[k] = highmag;
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}
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}
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else
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{
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low = (int)(2.0 * f0 / samplerate * mid - 0.5);
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high = (int)(2.0 * f1 / samplerate * mid - 0.5);
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lowmag = A[low];
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highmag = A[high];
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flow4 = pow((float)low / (float)mid, 4.0);
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fhigh4 = pow((float)high / (float)mid, 4.0);
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k = low;
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while (--k >= 0)
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{
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f = (float)k / (float)mid;
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lowmag *= (f * f * f * f) / flow4;
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if (lowmag < 1.0e-20) lowmag = 1.0e-20;
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A[k] = lowmag;
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}
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k = high;
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while (++k < mid)
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{
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f = (float)k / (float)mid;
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highmag *= fhigh4 / (f * f * f * f);
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if (highmag < 1.0e-20) highmag = 1.0e-20;
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A[k] = highmag;
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}
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}
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}
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2024-08-08 07:09:40 +00:00
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2024-06-16 09:31:13 +00:00
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if (nc & 1)
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FIR::fir_fsamp_odd(impulse, nc, A, 1, 1.0, wintype);
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else
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FIR::fir_fsamp(impulse, nc, A, 1, 1.0, wintype);
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// print_impulse ("emph.txt", size + 1, impulse, 1, 0);
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delete[] (A);
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}
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// generate mask for Overlap-Save Filter
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2024-08-09 04:33:00 +00:00
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float* FCurve::fc_mults (std::vector<float>& mults, int size, float f0, float f1, float g0, float g1, int curve, float samplerate, float scale, int ctfmode, int wintype)
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{
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std::vector<float> impulse(2 * (size + 1));
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fc_impulse (impulse, size + 1, f0, f1, g0, g1, curve, samplerate, scale, ctfmode, wintype);
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2024-08-09 04:33:00 +00:00
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FIR::fftcv_mults(mults, 2 * size, impulse.data());
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}
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} // namespace WDSP
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