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/* -*- c++ -*- */
/*
* Copyright 2018 Ron Economos.
*
* This 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.
*
* This software 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 software; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
/*
* This file has been adapted from https://github.com/drmpeg/gr-dvbs2rx
*/
#include "bbframe_descramble.h"
#include <algorithm>
namespace dvbs2
{
BBFrameDescrambler::BBFrameDescrambler(dvbs2_framesize_t framesize, dvbs2_code_rate_t rate)
{
if (framesize == FECFRAME_NORMAL)
{
switch (rate)
{
case C1_4:
kbch = 16008;
break;
case C1_3:
kbch = 21408;
break;
case C2_5:
kbch = 25728;
break;
case C1_2:
kbch = 32208;
break;
case C3_5:
kbch = 38688;
break;
case C2_3:
kbch = 43040;
break;
case C3_4:
kbch = 48408;
break;
case C4_5:
kbch = 51648;
break;
case C5_6:
kbch = 53840;
break;
case C8_9:
kbch = 57472;
break;
case C9_10:
kbch = 58192;
break;
default:
kbch = 0;
break;
}
}
else if (framesize == FECFRAME_SHORT)
{
switch (rate)
{
case C1_4:
kbch = 3072;
break;
case C1_3:
kbch = 5232;
break;
case C2_5:
kbch = 6312;
break;
case C1_2:
kbch = 7032;
break;
case C3_5:
kbch = 9552;
break;
case C2_3:
kbch = 10632;
break;
case C3_4:
kbch = 11712;
break;
case C4_5:
kbch = 12432;
break;
case C5_6:
kbch = 13152;
break;
case C8_9:
kbch = 14232;
break;
default:
kbch = 0;
break;
}
}
init();
}
BBFrameDescrambler::~BBFrameDescrambler()
{
}
void BBFrameDescrambler::init()
{
std::fill(bb_derandomise, &bb_derandomise[FRAME_SIZE_NORMAL / 8], 0);
int sr = 0x4A80;
for (int i = 0; i < FRAME_SIZE_NORMAL; i++)
{
int b = ((sr) ^ (sr >> 1)) & 1;
bb_derandomise[i / 8] = b << (7 - (i % 8)) | bb_derandomise[i / 8];
sr >>= 1;
if (b)
sr |= 0x4000;
}
}
int BBFrameDescrambler::work(uint8_t *frame)
{
for (int j = 0; j < (int)kbch / 8; ++j)
frame[j] = frame[j] ^ bb_derandomise[j];
return 0;
}
}
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