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https://github.com/aicodix/modem.git
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removed payload CRC check: let user decide
This commit is contained in:
Ahmet Inan
parent
c87bfc6e78
commit
5a6e5cd995
3 changed files with 15 additions and 27 deletions
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@ -3,10 +3,10 @@
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Quick start:
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Create file ```uncoded.dat``` with ```42976``` bits of random data:
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Create file ```uncoded.dat``` with ```43008``` bits of random data:
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```
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dd if=/dev/urandom of=uncoded.dat bs=1 count=5372
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dd if=/dev/urandom of=uncoded.dat bs=1 count=5376
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```
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Encode file ```uncoded.dat``` to ```encoded.wav``` [WAV](https://en.wikipedia.org/wiki/WAV) audio file with 8000 Hz sample rate, 16 bits and only 1 (real) channel:
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20
decode.cc
20
decode.cc
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@ -161,7 +161,7 @@ struct Decoder
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static const int filter_len = (((21 * rate) / 8000) & ~3) | 1;
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static const int guard_len = symbol_len / 8;
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static const int code_bits = 64800;
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static const int data_bits = code_bits - 32 - 12 * 16 - 21600;
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static const int data_bits = code_bits - 12 * 16 - 21600;
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static const int code_cols = 432;
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static const int cons_cnt = code_bits / Mod::BITS;
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static const int code_rows = cons_cnt / code_cols;
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@ -185,7 +185,6 @@ struct Decoder
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DSP::BipBuffer<cmplx, buffer_len> input_hist;
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SchmidlCox<value, cmplx, search_pos, symbol_len/2, guard_len> correlator;
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CODE::CRC<uint16_t> crc0;
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CODE::CRC<uint32_t> crc1;
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typedef CODE::GaloisField<16, 0b10000000000101101, uint16_t> GF;
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GF gf;
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CODE::BoseChaudhuriHocquenghemDecoder<24, 1, 65343, GF> bchdec1;
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@ -265,7 +264,7 @@ struct Decoder
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bint[Mod::BITS*i+k] = code[cons_cnt*k+i];
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}
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Decoder(uint8_t *out, DSP::ReadPCM<value> *pcm, int skip_count) :
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pcm(pcm), resample(rate, (rate * 19) / 40, 2), correlator(mls0_seq()), crc0(0xA8F4), crc1(0xD419CC15)
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pcm(pcm), resample(rate, (rate * 19) / 40, 2), correlator(mls0_seq()), crc0(0xA8F4)
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{
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CODE::BoseChaudhuriHocquenghemGenerator<255, 71>::matrix(genmat, true, {
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0b100011101, 0b101110111, 0b111110011, 0b101101001,
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@ -390,7 +389,7 @@ struct Decoder
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for (int i = 0; i < cons_cnt; ++i)
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Mod::soft(bint+Mod::BITS*i, cons[i], precision);
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deinterleave();
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int count = ldpcdec(code, code+data_bits+32+12*16);
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int count = ldpcdec(code, code+data_bits+12*16);
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if (count < 0)
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std::cerr << "payload LDPC decoding did not converge." << std::endl;
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if (1) {
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@ -412,10 +411,10 @@ struct Decoder
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value sigma = std::sqrt(np / (2 * sp));
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precision = 1 / (sigma * sigma);
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}
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for (int i = 0; i < data_bits+32+12*16; ++i)
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for (int i = 0; i < data_bits+12*16; ++i)
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CODE::set_le_bit(out, i, code[i] < 0);
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int ecnt = 0;
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for (int i = 0; i < data_bits+32+12*16; ++i) {
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for (int i = 0; i < data_bits+12*16; ++i) {
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if (!code[i]) {
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if (ecnt < 24) {
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erasures[ecnt++] = i;
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@ -427,18 +426,13 @@ struct Decoder
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}
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if (ecnt)
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std::cerr << "payload LDPC produced " << ecnt << " erasures." << std::endl;
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int ret = bchdec1(out, out+(data_bits+32)/8, erasures, ecnt, data_bits+32);
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int ret = bchdec1(out, out+data_bits/8, erasures, ecnt, data_bits);
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if (ret < 0) {
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std::cerr << "payload BCH error." << std::endl;
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return;
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}
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if (ret)
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std::cerr << "payload BCH corrected " << ret << " errors." << std::endl;
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crc1.reset();
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for (int i = 0; i < (data_bits+32)/8; ++i)
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crc1(out[i]);
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if (crc1())
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std::cerr << "payload CRC error." << std::endl;
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}
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};
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@ -492,7 +486,7 @@ int main(int argc, char **argv)
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std::cerr << "Couldn't open file \"" << output_name << "\" for writing." << std::endl;
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return 1;
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}
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const int data_len = code_len - (32 + 12 * 16 + 21600) / 8;
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const int data_len = code_len - (12 * 16 + 21600) / 8;
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for (int i = 0; i < data_len; ++i)
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output_file.put(output_data[i]);
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delete []output_data;
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18
encode.cc
18
encode.cc
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@ -29,7 +29,7 @@ struct Encoder
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static const int symbol_len = (1280 * rate) / 8000;
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static const int guard_len = symbol_len / 8;
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static const int code_bits = 64800;
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static const int data_bits = code_bits - 32 - 12 * 16 - 21600;
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static const int data_bits = code_bits - 12 * 16 - 21600;
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static const int code_cols = 432;
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static const int cons_cnt = code_bits / Mod::BITS;
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static const int code_rows = cons_cnt / code_cols;
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@ -43,7 +43,6 @@ struct Encoder
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DSP::WritePCM<value> *pcm;
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DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
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CODE::CRC<uint16_t> crc0;
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CODE::CRC<uint32_t> crc1;
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CODE::BoseChaudhuriHocquenghemEncoder<255, 71> bchenc0;
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CODE::BoseChaudhuriHocquenghemEncoder<65535, 65343> bchenc1;
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CODE::LDPCEncoder<DVB_T2_TABLE_A3> ldpcenc;
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@ -150,7 +149,7 @@ struct Encoder
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bint[Mod::BITS*i+k] = code[cons_cnt*k+i];
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}
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Encoder(DSP::WritePCM<value> *pcm, uint8_t *inp, int freq_off, uint64_t call_sign) :
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pcm(pcm), crc0(0xA8F4), crc1(0xD419CC15), bchenc0({
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pcm(pcm), crc0(0xA8F4), bchenc0({
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0b100011101, 0b101110111, 0b111110011, 0b101101001,
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0b110111101, 0b111100111, 0b100101011, 0b111010111,
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0b000010011, 0b101100101, 0b110001011, 0b101100011,
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@ -170,15 +169,10 @@ struct Encoder
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schmidl_cox();
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meta_data((call_sign << 8) | 2);
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pilot_block();
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crc1.reset();
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for (int i = 0; i < data_bits/8; ++i)
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crc1(inp[i]);
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for (int i = 0; i < 4; ++i)
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inp[data_bits/8+i] = (crc1() >> (8*i)) & 255;
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bchenc1(inp, inp+(data_bits+32)/8, data_bits+32);
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for (int i = 0; i < data_bits+32+12*16; ++i)
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bchenc1(inp, inp+data_bits/8, data_bits);
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for (int i = 0; i < data_bits+12*16; ++i)
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code[i] = nrz(CODE::get_le_bit(inp, i));
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ldpcenc(code, code+data_bits+32+12*16);
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ldpcenc(code, code+data_bits+12*16);
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interleave();
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CODE::MLS seq3(mls3_poly), seq4(mls4_poly);
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for (int j = 0; j < code_rows; ++j) {
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@ -258,7 +252,7 @@ int main(int argc, char **argv)
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return 1;
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}
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const int code_len = 64800 / 8;
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const int data_len = code_len - (32 + 12 * 16 + 21600) / 8;
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const int data_len = code_len - (12 * 16 + 21600) / 8;
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uint8_t *input_data = new uint8_t[code_len];
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for (int i = 0; i < data_len; ++i)
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input_data[i] = input_file.get();
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