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BFM demod: implemented forward error correction in RDS decoder

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This commit is contained in:
f4exb
2015-12-17 04:17:21 +01:00
parent 3c1a9790c0
commit 444f829e29
5 changed files with 90 additions and 5 deletions
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plugins/channel/bfm/rdsdecoder.cpp
+62 -5
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@@ -16,6 +16,7 @@
///////////////////////////////////////////////////////////////////////////////////
#include <QDebug>
#include "boost/format.hpp"
#include "rdsdecoder.h"
const unsigned int RDSDecoder::offset_pos[5] = {0,1,2,3,2};
@@ -31,14 +32,32 @@ RDSDecoder::RDSDecoder()
m_bitCounter = 0;
m_lastseenOffset = 0;
m_wrongBlocksCounter = 0;
m_correctedBlocksCounter = 0;
m_blocksCounter = 0;
m_blockBitCounter = 0;
m_blockNumber = 0;
m_groupAssemblyStarted = false;
m_sync = SYNC;
m_groupGoodBlocksCounter = 0;
m_wrongBlocksCounter = 0;
m_goodBlock = false;
m_error_lut[0x200] = 0b1000000000000000;
m_error_lut[0x300] = 0b1100000000000000;
m_error_lut[0x180] = 0b0110000000000000;
m_error_lut[0x0c0] = 0b0011000000000000;
m_error_lut[0x060] = 0b0001100000000000;
m_error_lut[0x030] = 0b1000110000000000;
m_error_lut[0x018] = 0b1000011000000000;
m_error_lut[0x00c] = 0b1000001100000000;
m_error_lut[0x006] = 0b1000000110000000;
m_error_lut[0x003] = 0b1000000011000000;
m_error_lut[0x2dd] = 0b1000000001100000;
m_error_lut[0x3b2] = 0b1000000000110000;
m_error_lut[0x1d9] = 0b1000000000011000;
m_error_lut[0x230] = 0b1000000000001100;
m_error_lut[0x118] = 0b1000000000000110;
m_error_lut[0x08c] = 0b1000000000000011;
m_error_lut[0x046] = 0b1000000000000001;
}
RDSDecoder::~RDSDecoder()
@@ -130,8 +149,15 @@ bool RDSDecoder::frameSync(bool bit)
}
else
{
m_wrongBlocksCounter++;
m_goodBlock = false;
if (err_corr(block_received_crc, block_calculated_crc, dataword))
{
m_correctedBlocksCounter++;
}
else
{
m_wrongBlocksCounter++;
m_goodBlock = false;
}
}
}
}
@@ -145,8 +171,15 @@ bool RDSDecoder::frameSync(bool bit)
}
else
{
m_wrongBlocksCounter++;
m_goodBlock = false;
if (err_corr(block_received_crc, block_calculated_crc, dataword))
{
m_correctedBlocksCounter++;
}
else
{
m_wrongBlocksCounter++;
m_goodBlock = false;
}
}
}
@@ -199,8 +232,10 @@ bool RDSDecoder::frameSync(bool bit)
}
m_qua = 2.0 * (50 - m_wrongBlocksCounter);
m_corr = 2.0 * m_correctedBlocksCounter;
m_blocksCounter = 0;
m_wrongBlocksCounter = 0;
m_correctedBlocksCounter = 0;
}
}
break;
@@ -258,3 +293,25 @@ unsigned int RDSDecoder::calc_syndrome(unsigned long message, unsigned char mlen
return (reg & ((1<<plen)-1)); // select the bottom plen bits of reg
}
bool RDSDecoder::err_corr(unsigned int received_crc, unsigned int calculated_crc, unsigned int& symbol)
{
unsigned int syn = received_crc ^ calculated_crc;
ui_lut_t::iterator lutIt = m_error_lut.find(syn);
if (lutIt != m_error_lut.end())
{
symbol ^= lutIt->second;
/*
unsigned int syncorr = calc_syndrome(symbol, 16);
std::string recstring = str(boost::format("%03X") % received_crc);
std::string calstring = str(boost::format("%03X") % calculated_crc);
std::string synstring = str(boost::format("%03X") % syn);
std::string corstring = str(boost::format("%03X") % syncorr);
qDebug() << "RDSDecoder::err_corr: " << recstring.c_str() << ":" << calstring.c_str() << ":" << synstring.c_str() << ":" << corstring.c_str();*/
return true;
}
else
{
return false;
}
}