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sdrangel/wdsp/fcurve.cpp
2024-08-10 02:06:19 +02:00

160 lines
5.0 KiB
C++

/* fcurve.c
This file is part of a program that implements a Software-Defined Radio.
Copyright (C) 2013, 2016 Warren Pratt, NR0V
Copyright (C) 2024 Edouard Griffiths, F4EXB Adapted to SDRangel
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; either version 2
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 for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
The author can be reached by email at
warren@wpratt.com
*/
#include "comm.hpp"
#include "fcurve.hpp"
#include "fir.hpp"
namespace WDSP {
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)
{
float* A = new float[nc / 2 + 1]; // (float *) malloc0 ((nc / 2 + 1) * sizeof (float));
int i;
float fn, f;
int mid = nc / 2;
float g0_lin = pow(10.0, g0 / 20.0);
if (nc & 1)
{
for (i = 0; i <= mid; i++)
{
fn = (float)i / (float)mid;
f = fn * samplerate / 2.0;
switch (curve)
{
case 0: // fm pre-emphasis
if (f0 > 0.0)
A[i] = scale * (g0_lin * f / f0);
else
A[i] = 0.0;
break;
case 1: // fm de-emphasis
if (f > 0.0)
A[i] = scale * (g0_lin * f0 / f);
else
A[i] = 0.0;
break;
}
}
}
else
{
for (i = 0; i < mid; i++)
{
fn = ((float)i + 0.5) / (float)mid;
f = fn * samplerate / 2.0;
switch (curve)
{
case 0: // fm pre-emphasis
if (f0 > 0.0)
A[i] = scale * (g0_lin * f / f0);
else
A[i] = 0.0;
break;
case 1: // fm de-emphasis
if (f > 0.0)
A[i] = scale * (g0_lin * f0 / f);
else
A[i] = 0.0;
break;
}
}
}
if (ctfmode == 0)
{
int k, low, high;
float lowmag, highmag, flow4, fhigh4;
if (nc & 1)
{
low = (int)(2.0 * f0 / samplerate * mid);
high = (int)(2.0 * f1 / samplerate * mid + 0.5);
lowmag = A[low];
highmag = A[high];
flow4 = pow((float)low / (float)mid, 4.0);
fhigh4 = pow((float)high / (float)mid, 4.0);
k = low;
while (--k >= 0)
{
f = (float)k / (float)mid;
lowmag *= (f * f * f * f) / flow4;
if (lowmag < 1.0e-20) lowmag = 1.0e-20;
A[k] = lowmag;
}
k = high;
while (++k <= mid)
{
f = (float)k / (float)mid;
highmag *= fhigh4 / (f * f * f * f);
if (highmag < 1.0e-20) highmag = 1.0e-20;
A[k] = highmag;
}
}
else
{
low = (int)(2.0 * f0 / samplerate * mid - 0.5);
high = (int)(2.0 * f1 / samplerate * mid - 0.5);
lowmag = A[low];
highmag = A[high];
flow4 = pow((float)low / (float)mid, 4.0);
fhigh4 = pow((float)high / (float)mid, 4.0);
k = low;
while (--k >= 0)
{
f = (float)k / (float)mid;
lowmag *= (f * f * f * f) / flow4;
if (lowmag < 1.0e-20) lowmag = 1.0e-20;
A[k] = lowmag;
}
k = high;
while (++k < mid)
{
f = (float)k / (float)mid;
highmag *= fhigh4 / (f * f * f * f);
if (highmag < 1.0e-20) highmag = 1.0e-20;
A[k] = highmag;
}
}
}
if (nc & 1)
FIR::fir_fsamp_odd(impulse, nc, A, 1, 1.0, wintype);
else
FIR::fir_fsamp(impulse, nc, A, 1, 1.0, wintype);
// print_impulse ("emph.txt", size + 1, impulse, 1, 0);
delete[] (A);
}
// generate mask for Overlap-Save Filter
void 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)
{
std::vector<float> impulse(2 * (size + 1));
fc_impulse (impulse, size + 1, f0, f1, g0, g1, curve, samplerate, scale, ctfmode, wintype);
FIR::fftcv_mults(mults, 2 * size, impulse.data());
}
} // namespace WDSP