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78 lines
3.9 KiB
C++
78 lines
3.9 KiB
C++
///////////////////////////////////////////////////////////////////////////////////
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// Copyright (C) 2021 Jon Beniston, M7RCE <jon@beniston.com> //
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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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// (at your option) any later version. //
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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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#include <cstdint>
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// DVB-S coder - See ETSI EN 300 421 V1.1.2
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class DVBS {
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static const uint8_t tsSync = 0x47; //!< Transport stream sync byte - should be at start of every TS packet
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static const int interleaveDepth = 12; //!< Interleaving depth
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static const int rsK = 239; //!< Reed-Solomon input length
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static const int rs2T = 16; //!< Reed-Solomon number check/parity symbols
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static const int rsN = rsK + rs2T; //!< Reed-Solomon block length
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public:
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static const int tsPacketLen = 188; //!< Length of transport stream packets
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static const int rsPacketLen = 204; //!< Length of packet after adding RS parity bytes
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static const int m_maxIQSymbols = 204*8; //!< Maximum number of IQ symbols per packet
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enum CodeRate {RATE_1_2, RATE_2_3, RATE_3_4, RATE_5_6, RATE_7_8};
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DVBS();
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~DVBS();
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int encode(const uint8_t *ts, uint8_t *iq);
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void setCodeRate(CodeRate codeRate);
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private:
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uint8_t *m_packet; //!< Buffer to hold input data + partiy bytes
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int m_prbsPacketCount; //!< Counts 0-7
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int m_prbsIdx; //!< Index in to m_prbsLUT
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uint8_t **m_interleaveFIFO; //!< FIFOs for convolutional interleaving
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int *m_interleaveLen; //!< Length of each FIFO
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int *m_interleaveIdx; //!< Write index in to FIFOs
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CodeRate m_codeRate; //!< Convolution coding rate
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unsigned m_delayLine; //!< Delay line for convolution encoder
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int m_punctureState; //!< Puncturing state
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uint8_t m_prevIQ; //!< Saved bit from previous packet
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bool m_prevIQValid; //!< Whether there is a saved bit
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protected:
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static const uint8_t m_prbsLUT[tsPacketLen*8-1]; //!< PRBS lookup table
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static const uint8_t rsPoly[rs2T]; //!< Reed-Solomon generator polynomial
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static const uint8_t m_gfLog[256]; //!< GF(2^8) log lookup table
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static const uint8_t m_gfExp[512]; //!< GF(2^8) exponent lookup table
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static uint8_t gfMul(uint8_t a, uint8_t b); //!< GF(2^8) multiplication
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void scramble(const uint8_t *packetIn, uint8_t *packetOut);
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void reedSolomon(uint8_t *packet);
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void interleave(uint8_t *packet);
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int convolution(const uint8_t *packet, uint8_t *iq);
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};
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