mirror of
https://github.com/f4exb/sdrangel.git
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351 lines
9.7 KiB
C++
351 lines
9.7 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2016 Edouard Griffiths, F4EXB. //
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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 as version 3 of the License, or //
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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 V3 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, see <http://www.gnu.org/licenses/>. //
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///////////////////////////////////////////////////////////////////////////////////
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/* descramble.h */
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// Functions for processing the radio-header:
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// descramble
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// deinterleave
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// FECdecoder
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// (C) 2011 Jonathan Naylor G4KLX
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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; version 2 of the License.
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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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// This code was originally written by JOnathan Naylor, G4KLX, as part
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// of the "pcrepeatercontroller" project
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// More info:
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// http://groups.yahoo.com/group/pcrepeatercontroller
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// Changes:
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// Convert C++ to C
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// Version 20111106: initial release
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// F4EXB: Convert back to C++ !
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#include <string.h>
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#include "descramble.h"
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namespace DSDplus
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{
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const int Descramble::SCRAMBLER_TABLE_BITS[] = {
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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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,
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1,0,0,1,1,1,0,0,1,1,1,1,0,1,1,0};
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int Descramble::traceBack(int * out, int * m_pathMemory0, int * m_pathMemory1,
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int * m_pathMemory2, int * m_pathMemory3)
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{
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enum FEC_STATE
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{
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S0, S1, S2, S3
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} state;
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int loop;
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int length = 0;
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state = S0;
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for (loop = 329; loop >= 0; loop--, length++)
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{
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switch (state)
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{
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case S0: // if state S0
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if (m_pathMemory0[loop])
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{
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state = S2; // lower path
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}
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else
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{
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state = S0; // upper path
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}
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; // end else - if
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out[loop] = 0;
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break;
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case S1: // if state S1
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if (m_pathMemory1[loop])
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{
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state = S2; // lower path
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}
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else
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{
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state = S0; // upper path
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}
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; // end else - if
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out[loop] = 1;
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break;
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case S2: // if state S2
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if (m_pathMemory2[loop])
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{
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state = S3; // lower path
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}
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else
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{
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state = S1; // upper path
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}
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; // end else - if
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out[loop] = 0;
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break;
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case S3: // if state S3
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if (m_pathMemory3[loop])
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{
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state = S3; // lower path
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}
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else
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{
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state = S1; // upper path
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}
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; // end else - if
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out[loop] = 1;
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break;
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}; // end switch
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}; // end for
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return (length);
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} // end function
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void Descramble::viterbiDecode(int n, int *data, int *m_pathMemory0, int *m_pathMemory1,
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int *m_pathMemory2, int *m_pathMemory3, int *m_pathMetric)
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{
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int tempMetric[4];
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int metric[8];
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int loop;
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int m1;
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int m2;
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metric[0] = (data[1] ^ 0) + (data[0] ^ 0);
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metric[1] = (data[1] ^ 1) + (data[0] ^ 1);
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metric[2] = (data[1] ^ 1) + (data[0] ^ 0);
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metric[3] = (data[1] ^ 0) + (data[0] ^ 1);
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metric[4] = (data[1] ^ 1) + (data[0] ^ 1);
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metric[5] = (data[1] ^ 0) + (data[0] ^ 0);
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metric[6] = (data[1] ^ 0) + (data[0] ^ 1);
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metric[7] = (data[1] ^ 1) + (data[0] ^ 0);
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// Pres. state = S0, Prev. state = S0 & S2
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m1 = metric[0] + m_pathMetric[0];
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m2 = metric[4] + m_pathMetric[2];
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if (m1 < m2)
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{
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m_pathMemory0[n] = 0;
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tempMetric[0] = m1;
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}
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else
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{
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m_pathMemory0[n] = 1;
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tempMetric[0] = m2;
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}; // end else - if
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// Pres. state = S1, Prev. state = S0 & S2
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m1 = metric[1] + m_pathMetric[0];
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m2 = metric[5] + m_pathMetric[2];
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if (m1 < m2)
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{
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m_pathMemory1[n] = 0;
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tempMetric[1] = m1;
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}
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else
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{
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m_pathMemory1[n] = 1;
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tempMetric[1] = m2;
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}; // end else - if
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// Pres. state = S2, Prev. state = S2 & S3
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m1 = metric[2] + m_pathMetric[1];
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m2 = metric[6] + m_pathMetric[3];
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if (m1 < m2)
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{
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m_pathMemory2[n] = 0;
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tempMetric[2] = m1;
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}
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else
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{
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m_pathMemory2[n] = 1;
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tempMetric[2] = m2;
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}
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// Pres. state = S3, Prev. state = S1 & S3
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m1 = metric[3] + m_pathMetric[1];
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m2 = metric[7] + m_pathMetric[3];
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if (m1 < m2)
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{
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m_pathMemory3[n] = 0;
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tempMetric[3] = m1;
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}
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else
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{
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m_pathMemory3[n] = 1;
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tempMetric[3] = m2;
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}; // end else - if
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for (loop = 0; loop < 4; loop++)
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{
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m_pathMetric[loop] = tempMetric[loop];
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}; // end for
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} // end function ViterbiDecode
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int Descramble::FECdecoder(int * in, int * out)
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{
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int outLen;
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int m_pathMemory0[330];
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memset(m_pathMemory0, 0, 330 * sizeof(int));
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int m_pathMemory1[330];
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memset(m_pathMemory1, 0, 330 * sizeof(int));
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int m_pathMemory2[330];
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memset(m_pathMemory2, 0, 330 * sizeof(int));
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int m_pathMemory3[330];
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memset(m_pathMemory3, 0, 330 * sizeof(int));
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int m_pathMetric[4];
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int loop, loop2;
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int n = 0;
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for (loop = 0; loop < 4; loop++)
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{
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m_pathMetric[loop] = 0;
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}; // end for
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for (loop2 = 0; loop2 < 660; loop2 += 2, n++)
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{
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int data[2];
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if (in[loop2])
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{
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data[1] = 1;
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}
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else
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{
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data[1] = 0;
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}; // end else - if
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if (in[loop2 + 1])
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{
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data[0] = 1;
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}
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else
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{
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data[0] = 0;
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}; // end else - if
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viterbiDecode(n, data, m_pathMemory0, m_pathMemory1, m_pathMemory2,
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m_pathMemory3, m_pathMetric);
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}; // end for
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outLen = traceBack(out, m_pathMemory0, m_pathMemory1, m_pathMemory2,
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m_pathMemory3);
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// Swap endian-ness
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// code removed (done converting bits into octets), done in main program
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//for (loop=0;loop<330;loop+=8) {
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// int temp;
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// temp=out[loop];out[loop]=out[loop+7];out[loop+7]=temp;
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// temp=out[loop+1];out[loop+1]=out[loop+6];out[loop+6]=temp;
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// temp=out[loop+2];out[loop+2]=out[loop+5];out[loop+5]=temp;
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// temp=out[loop+3];out[loop+3]=out[loop+4];out[loop+4]=temp;
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//}
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return (outLen);
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} // end function FECdecoder
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void Descramble::deinterleave(int * in, int * out)
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{
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int k = 0;
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int loop = 0;
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// function starts here
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// init vars
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k = 0;
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for (loop = 0; loop < 660; loop++)
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{
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out[k] = in[loop];
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k += 24;
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if (k >= 672)
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{
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k -= 671;
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}
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else if (k >= 660)
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{
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k -= 647;
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}; // end elsif - if
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}; // end for
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} // end function deinterleave
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void Descramble::scramble (int * in,int * out)
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{
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int loop = 0;
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int m_count = 0;
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for (loop = 0; loop < 660; loop++)
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{
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out[loop] = in[loop] ^ SCRAMBLER_TABLE_BITS[m_count++];
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if (m_count >= SCRAMBLER_TABLE_BITS_LENGTH)
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{
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m_count = 0U;
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}; // end if
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}; // end for
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}
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} // namespace DSDplus
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