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Uladzimir Karpenka
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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, 2025 Warren Pratt, NR0V
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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.h"
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double* fc_impulse (int nc, double f0, double f1, double g0, double g1, int curve, double samplerate, double scale, int ctfmode, int wintype)
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{
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// check for previous in the cache
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struct Params
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{
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int nc;
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int curve;
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int ctfmode;
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int wintype;
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double f0;
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double f1;
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double g0;
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double g1;
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double samplerate;
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double scale;
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};
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struct Params params;
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memset(¶ms, 0, sizeof(params));
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params.nc = nc;
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params.curve = curve;
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params.ctfmode = ctfmode;
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params.wintype = wintype;
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params.f0 = f0;
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params.f1 = f1;
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params.g0 = g0;
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params.g1 = g1;
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params.samplerate = samplerate;
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params.scale = scale;
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HASH_T h = fnv1a_hash(¶ms, sizeof(params));
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double* imp = get_impulse_cache_entry(FC_CACHE, h, nc);
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if (imp) return imp;
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//
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double* A = (double *) malloc0 ((nc / 2 + 1) * sizeof (double));
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int i;
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double fn, f;
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double* impulse;
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int mid = nc / 2;
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double 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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fn = (double)i / (double)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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else
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{
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for (i = 0; i < mid; i++)
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{
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fn = ((double)i + 0.5) / (double)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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double 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((double)low / (double)mid, 4.0);
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fhigh4 = pow((double)high / (double)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 = (double)k / (double)mid;
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lowmag *= (f * f * f * f) / flow4;
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if (lowmag < 1.0e-100) lowmag = 1.0e-100;
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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 = (double)k / (double)mid;
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highmag *= fhigh4 / (f * f * f * f);
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if (highmag < 1.0e-100) highmag = 1.0e-100;
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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((double)low / (double)mid, 4.0);
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fhigh4 = pow((double)high / (double)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 = (double)k / (double)mid;
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lowmag *= (f * f * f * f) / flow4;
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if (lowmag < 1.0e-100) lowmag = 1.0e-100;
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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 = (double)k / (double)mid;
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highmag *= fhigh4 / (f * f * f * f);
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if (highmag < 1.0e-100) highmag = 1.0e-100;
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A[k] = highmag;
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}
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}
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}
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if (nc & 1)
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impulse = fir_fsamp_odd(nc, A, 1, 1.0, wintype);
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else
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impulse = fir_fsamp(nc, A, 1, 1.0, wintype);
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// print_impulse ("emph.txt", size + 1, impulse, 1, 0);
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_aligned_free (A);
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// store in cache
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add_impulse_to_cache(FC_CACHE, h, nc, impulse);
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return impulse;
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}
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// generate mask for Overlap-Save Filter
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double* fc_mults (int size, double f0, double f1, double g0, double g1, int curve, double samplerate, double scale, int ctfmode, int wintype)
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{
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double* impulse = fc_impulse (size + 1, f0, f1, g0, g1, curve, samplerate, scale, ctfmode, wintype);
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double* mults = fftcv_mults(2 * size, impulse);
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_aligned_free (impulse);
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return mults;
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}
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