///////////////////////////////////////////////////////////////////////////////////
// Copyright (C) 2016 Edouard Griffiths, F4EXB. //
// //
// 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 as version 3 of the License, or //
// //
// 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 V3 for more details. //
// //
// You should have received a copy of the GNU General Public License //
// along with this program. If not, see . //
///////////////////////////////////////////////////////////////////////////////////
/* descramble.h */
// Functions for processing the radio-header:
// descramble
// deinterleave
// FECdecoder
// (C) 2011 Jonathan Naylor G4KLX
/*
* 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; version 2 of the License.
*
* 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.
*/
// This code was originally written by JOnathan Naylor, G4KLX, as part
// of the "pcrepeatercontroller" project
// More info:
// http://groups.yahoo.com/group/pcrepeatercontroller
// Changes:
// Convert C++ to C
// Version 20111106: initial release
// F4EXB: Convert back to C++ !
#include
#include "descramble.h"
namespace DSDplus
{
const int Descramble::SCRAMBLER_TABLE_BITS[] = {
0,0,0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,
0,0,1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,
1,1,0,1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,
1,1,1,1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,
0,0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,
0,1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,
1,0,1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,
1,1,1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,
0,0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,
1,0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,
0,1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,1,
1,1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,0,
0,1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,
0,0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,0,
1,0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,1,1,
1,1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,0,0,
1,1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,
0,1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,0,1,
0,1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0,1,0,0,0,0,1,0,1,0,1,0,1,1,1,1,
1,0,1,0,0,1,0,1,0,0,0,1,1,0,1,1,1,0,0,0,1,1,1,1,1,1,1,0,0,0,0,1,
1,1,0,1,1,1,1,0,0,1,0,1,1,0,0,1,0,0,1,0,0,0,0,0,0,1,0,0,0,1,0,0,
1,1,0,0,0,1,0,1,1,1,0,1,0,1,1,0,1,1,0,0,0,0,0,1,1,0,0,1,1,0,1,0,
1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0};
int Descramble::traceBack(int * out, int * m_pathMemory0, int * m_pathMemory1,
int * m_pathMemory2, int * m_pathMemory3)
{
enum FEC_STATE
{
S0, S1, S2, S3
} state;
int loop;
int length = 0;
state = S0;
for (loop = 329; loop >= 0; loop--, length++)
{
switch (state)
{
case S0: // if state S0
if (m_pathMemory0[loop])
{
state = S2; // lower path
}
else
{
state = S0; // upper path
}
; // end else - if
out[loop] = 0;
break;
case S1: // if state S1
if (m_pathMemory1[loop])
{
state = S2; // lower path
}
else
{
state = S0; // upper path
}
; // end else - if
out[loop] = 1;
break;
case S2: // if state S2
if (m_pathMemory2[loop])
{
state = S3; // lower path
}
else
{
state = S1; // upper path
}
; // end else - if
out[loop] = 0;
break;
case S3: // if state S3
if (m_pathMemory3[loop])
{
state = S3; // lower path
}
else
{
state = S1; // upper path
}
; // end else - if
out[loop] = 1;
break;
}; // end switch
}; // end for
return (length);
} // end function
void Descramble::viterbiDecode(int n, int *data, int *m_pathMemory0, int *m_pathMemory1,
int *m_pathMemory2, int *m_pathMemory3, int *m_pathMetric)
{
int tempMetric[4];
int metric[8];
int loop;
int m1;
int m2;
metric[0] = (data[1] ^ 0) + (data[0] ^ 0);
metric[1] = (data[1] ^ 1) + (data[0] ^ 1);
metric[2] = (data[1] ^ 1) + (data[0] ^ 0);
metric[3] = (data[1] ^ 0) + (data[0] ^ 1);
metric[4] = (data[1] ^ 1) + (data[0] ^ 1);
metric[5] = (data[1] ^ 0) + (data[0] ^ 0);
metric[6] = (data[1] ^ 0) + (data[0] ^ 1);
metric[7] = (data[1] ^ 1) + (data[0] ^ 0);
// Pres. state = S0, Prev. state = S0 & S2
m1 = metric[0] + m_pathMetric[0];
m2 = metric[4] + m_pathMetric[2];
if (m1 < m2)
{
m_pathMemory0[n] = 0;
tempMetric[0] = m1;
}
else
{
m_pathMemory0[n] = 1;
tempMetric[0] = m2;
}; // end else - if
// Pres. state = S1, Prev. state = S0 & S2
m1 = metric[1] + m_pathMetric[0];
m2 = metric[5] + m_pathMetric[2];
if (m1 < m2)
{
m_pathMemory1[n] = 0;
tempMetric[1] = m1;
}
else
{
m_pathMemory1[n] = 1;
tempMetric[1] = m2;
}; // end else - if
// Pres. state = S2, Prev. state = S2 & S3
m1 = metric[2] + m_pathMetric[1];
m2 = metric[6] + m_pathMetric[3];
if (m1 < m2)
{
m_pathMemory2[n] = 0;
tempMetric[2] = m1;
}
else
{
m_pathMemory2[n] = 1;
tempMetric[2] = m2;
}
// Pres. state = S3, Prev. state = S1 & S3
m1 = metric[3] + m_pathMetric[1];
m2 = metric[7] + m_pathMetric[3];
if (m1 < m2)
{
m_pathMemory3[n] = 0;
tempMetric[3] = m1;
}
else
{
m_pathMemory3[n] = 1;
tempMetric[3] = m2;
}; // end else - if
for (loop = 0; loop < 4; loop++)
{
m_pathMetric[loop] = tempMetric[loop];
}; // end for
} // end function ViterbiDecode
int Descramble::FECdecoder(int * in, int * out)
{
int outLen;
int m_pathMemory0[330];
memset(m_pathMemory0, 0, 330 * sizeof(int));
int m_pathMemory1[330];
memset(m_pathMemory1, 0, 330 * sizeof(int));
int m_pathMemory2[330];
memset(m_pathMemory2, 0, 330 * sizeof(int));
int m_pathMemory3[330];
memset(m_pathMemory3, 0, 330 * sizeof(int));
int m_pathMetric[4];
int loop, loop2;
int n = 0;
for (loop = 0; loop < 4; loop++)
{
m_pathMetric[loop] = 0;
}; // end for
for (loop2 = 0; loop2 < 660; loop2 += 2, n++)
{
int data[2];
if (in[loop2])
{
data[1] = 1;
}
else
{
data[1] = 0;
}; // end else - if
if (in[loop2 + 1])
{
data[0] = 1;
}
else
{
data[0] = 0;
}; // end else - if
viterbiDecode(n, data, m_pathMemory0, m_pathMemory1, m_pathMemory2,
m_pathMemory3, m_pathMetric);
}; // end for
outLen = traceBack(out, m_pathMemory0, m_pathMemory1, m_pathMemory2,
m_pathMemory3);
// Swap endian-ness
// code removed (done converting bits into octets), done in main program
//for (loop=0;loop<330;loop+=8) {
// int temp;
// temp=out[loop];out[loop]=out[loop+7];out[loop+7]=temp;
// temp=out[loop+1];out[loop+1]=out[loop+6];out[loop+6]=temp;
// temp=out[loop+2];out[loop+2]=out[loop+5];out[loop+5]=temp;
// temp=out[loop+3];out[loop+3]=out[loop+4];out[loop+4]=temp;
//}
return (outLen);
} // end function FECdecoder
void Descramble::deinterleave(int * in, int * out)
{
int k = 0;
int loop = 0;
// function starts here
// init vars
k = 0;
for (loop = 0; loop < 660; loop++)
{
out[k] = in[loop];
k += 24;
if (k >= 672)
{
k -= 671;
}
else if (k >= 660)
{
k -= 647;
}; // end elsif - if
}; // end for
} // end function deinterleave
void Descramble::scramble (int * in,int * out)
{
int loop = 0;
int m_count = 0;
for (loop = 0; loop < 660; loop++)
{
out[loop] = in[loop] ^ SCRAMBLER_TABLE_BITS[m_count++];
if (m_count >= SCRAMBLER_TABLE_BITS_LENGTH)
{
m_count = 0U;
}; // end if
}; // end for
}
} // namespace DSDplus