233 lines
6.2 KiB
C++
Executable File
233 lines
6.2 KiB
C++
Executable File
/*
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* High Speed modem to transfer data in a 2,7kHz SSB channel
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* =========================================================
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* Author: DJ0ABR
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*
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* (c) DJ0ABR
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* www.dj0abr.de
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*
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* This program 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 2 of the License, or
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* (at your option) any later version.
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*
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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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*
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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., 675 Mass Ave, Cambridge, MA 02139, USA.
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*
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*/
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#include "hsmodem.h"
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#ifdef _WIN32_
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#include "fftw_lib/fftw3.h"
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#endif
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#ifdef _LINUX_
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#include <fftw3.h>
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#endif
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uint16_t* mean(uint16_t* f);
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#define FFT_AUDIOSAMPLERATE 800
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double *din = NULL; // input data for fft
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fftw_complex *cpout = NULL; // ouput data from fft
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fftw_plan plan = NULL;
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int fftidx = 0;
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int fftcount; // number of output values
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uint16_t fftout[FFT_AUDIOSAMPLERATE / 2 + 1];
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float f_fftout[FFT_AUDIOSAMPLERATE / 2 + 1];
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int downsamp = 0;
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int downphase = 0;
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int rxlevel_deteced = 0;
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int rx_in_sync = 0;
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msresamp_crcf fftdecim = NULL;
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uint16_t *make_waterfall(float fre, int *retlen)
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{
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int fftrdy = 0;
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// data come with 44.1k or 48k sample rate
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// downsample to 800 to get 0-4k in 10 Hz steps
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unsigned int num_written = 0;
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liquid_float_complex in;
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liquid_float_complex out;
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in.real = fre;
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in.imag = 0;
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msresamp_crcf_execute(fftdecim, &in, 1, &out, &num_written);
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if (num_written != 1) return NULL;
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fre = out.real;
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// fre are the float samples
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// fill into the fft input buffer
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din[fftidx++] = fre;
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if(fftidx == FFT_AUDIOSAMPLERATE)
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{
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fftidx = 0;
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// the fft buffer is full, execute the FFT
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fftw_execute(plan);
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for (int j = 0; j < fftcount; j++)
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{
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// calculate absolute value (magnitute without phase)
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float fre = (float)cpout[j][0];
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float fim = (float)cpout[j][1];
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float mag = sqrt((fre * fre) + (fim * fim));
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fftout[j] = (uint16_t)mag;
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f_fftout[j] = mag;
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fftrdy = 1;
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}
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if (rx_in_sync == 0)
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{
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// signal detection
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// measure level at band edges
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float edgelevel = 0;
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for (int e = 0; e < 10; e++)
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edgelevel += f_fftout[e];
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edgelevel /= 10;
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for (int e = 300; e < 320; e++)
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edgelevel += f_fftout[e];
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edgelevel /= 20;
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// measure level at mid band
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float midlevel = 0;
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for (int e = 100; e < 200; e++)
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midlevel += f_fftout[e];
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midlevel /= 100;
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//calc difference in %
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int idiff = (int)((edgelevel * 100) / midlevel);
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//printf("diff:%d %% edge:%10.6f midband:%10.6f\n", idiff,edgelevel, midlevel);
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// idiff SDR Console:
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// no signal ... > 100
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// signal < 20
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static int checks = 0;
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static int lastsig = 0;
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int sig = 0;
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// check if signal detected or not
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if (idiff > 100) sig = 0;
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if (idiff < 30) sig = 1;
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rxlevel_deteced = sig;
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// check if changed since last check
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if (sig != lastsig)
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{
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lastsig = sig;
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checks = 0;
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}
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else
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{
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if (checks <= 3) checks++;
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if (checks == 3)
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{
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if (sig == 1)
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{
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printf("===>>> level detected, reset modem\n");
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trigger_resetmodem = 1;
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}
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}
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}
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}
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}
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if(fftrdy == 1)
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{
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*retlen = fftcount;
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return mean(fftout);
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}
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return NULL;
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}
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// smooth fft output
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const int smoothX = 2; // must be an even number !
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const int smoothY = 10;
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int yidx = 0;
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uint16_t* mean(uint16_t* f)
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{
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static uint16_t fa[FFT_AUDIOSAMPLERATE / 2 + 1];
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if (tuning)
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return f;
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// first smooth X values
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for (int x = 0; x < smoothX / 2; x++)
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fa[x] = f[x];
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for (int x = smoothX / 2; x < fftcount - smoothX / 2; x++)
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{
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fa[x] = 0;
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for (int i = -smoothX/2; i < smoothX/2; i++)
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fa[x] += f[x+i];
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fa[x] /= smoothX;
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}
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for (int x = fftcount - smoothX / 2; x < fftcount; x++)
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fa[x] = f[x];
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// smooth Y values
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static uint16_t yarr[smoothY][FFT_AUDIOSAMPLERATE / 2 + 1];
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for (int i = 0; i < fftcount; i++)
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yarr[yidx][i] = fa[i];
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if (++yidx >= smoothY) yidx = 0;
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memset(fa, 0, FFT_AUDIOSAMPLERATE / 2 + 1);
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for (int i = 0; i < fftcount; i++)
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{
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for (int j = 0; j < smoothY; j++)
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fa[i] += yarr[j][i];
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fa[i] /= smoothY;
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}
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return fa;
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}
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void _init_fft()
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{
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fftcount = FFT_AUDIOSAMPLERATE / 2 + 1; // number of output samples
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// the FFT outputs 400 values from 0 to 4kHz with a resolution of 10 Hz
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_exit_fft();
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din = (double *)fftw_malloc(sizeof(double) * FFT_AUDIOSAMPLERATE);
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cpout = (fftw_complex *)fftw_malloc(sizeof(fftw_complex) * fftcount);
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plan = fftw_plan_dft_r2c_1d(FFT_AUDIOSAMPLERATE, din, cpout, FFTW_MEASURE);
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// create arbitrary pre decimator
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// decimate 44.1k or 48k down to 8000Hz
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// the FFT rate is 800, but we feed it with 8000 Samplerate
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// this results in a new fft every 100ms with a resolution of 10 Hz
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float ratio = 10.0f * (float)FFT_AUDIOSAMPLERATE / (float)physRXcaprate;
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fftdecim = msresamp_crcf_create(ratio, 40.0f);
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}
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void _exit_fft()
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{
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if(plan) fftw_destroy_plan(plan);
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if(din) fftw_free(din);
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if(cpout) fftw_free(cpout);
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plan = NULL;
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din = NULL;
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cpout = NULL;
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if (fftdecim) msresamp_crcf_destroy(fftdecim);
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fftdecim = NULL;
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}
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