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/* -*- c++ -*- */
/*
* Copyright 2008 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio 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 3, or (at your option)
* any later version.
*
* GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
/*
* This is a minimal example demonstrating how to call the Viterbi decoder
* in continuous streaming mode. It accepts data on stdin and writes to
* stdout.
*
*/
#include <gnuradio/fec/viterbi.h>
#include <cmath>
#include <cstdio>
#define MAXCHUNKSIZE 4096
#define MAXENCSIZE MAXCHUNKSIZE * 16
int main()
{
unsigned char data[MAXCHUNKSIZE];
signed char syms[MAXENCSIZE];
int count = 0;
// Initialize metric table
int mettab[2][256];
int amp = 100;
float RATE = 0.5;
float ebn0 = 12.0;
float esn0 = RATE * pow(10.0, ebn0 / 10);
gen_met(mettab, amp, esn0, 0.0, 4);
// Initialize decoder state
struct gr::fec::viterbi_state state0[64];
struct gr::fec::viterbi_state state1[64];
unsigned char viterbi_in[16];
gr::fec::viterbi_chunks_init(state0);
while (!feof(stdin)) {
unsigned int n = fread(syms, 1, MAXENCSIZE, stdin);
unsigned char* out = data;
for (unsigned int i = 0; i < n; i++) {
// FIXME: This implements hard decoding by slicing the input stream
unsigned char sym = syms[i] > 0 ? -amp : amp;
// Write the symbol to the decoder input
viterbi_in[count % 4] = sym;
// Every four symbols, perform the butterfly2 operation
if ((count % 4) == 3) {
gr::fec::viterbi_butterfly2(viterbi_in, mettab, state0, state1);
// Every sixteen symbols, perform the readback operation
if ((count > 64) && (count % 16) == 11) {
gr::fec::viterbi_get_output(state0, out);
fwrite(out++, 1, 1, stdout);
}
}
count++;
}
}
return 0;
}
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