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https://github.com/aicodix/modem.git
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use the first 32 comb pilots to signal the mode
This commit is contained in:
Ahmet Inan
parent
4430de392b
commit
4b99f82aac
2 changed files with 99 additions and 215 deletions
169
decode.cc
169
decode.cc
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@ -24,17 +24,12 @@ namespace DSP { using std::abs; using std::min; using std::cos; using std::sin;
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#include "fft.hh"
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#include "mls.hh"
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#include "crc.hh"
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#include "osd.hh"
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#include "psk.hh"
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#include "qam.hh"
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#include "polar_tables.hh"
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#include "polar_list_decoder.hh"
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void base37_decoder(char *str, long long int val, int len)
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{
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for (int i = len-1; i >= 0; --i, val /= 37)
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str[i] = " 0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ"[val%37];
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}
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#include "hadamard_encoder.hh"
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#include "hadamard_decoder.hh"
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template <typename value, typename cmplx, int rate>
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struct Decoder
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@ -61,8 +56,6 @@ struct Decoder
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static const int mls0_poly = 0b1100110001;
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static const int mls0_seed = 214;
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static const int mls0_off = - mls0_len / 2;
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static const int mls1_len = 255;
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static const int mls1_off = - mls1_len / 2;
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static const int mls1_poly = 0b100101011;
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static const int buffer_len = 5 * extended_len;
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static const int search_pos = extended_len;
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@ -73,15 +66,15 @@ struct Decoder
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DSP::BipBuffer<cmplx, buffer_len> input_hist;
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DSP::TheilSenEstimator<value, cols_max> tse;
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SchmidlCox<value, cmplx, search_pos, symbol_len, 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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CODE::OrderedStatisticsDecoder<255, 71, 4> osddec;
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CODE::HadamardEncoder<6> hadamardenc;
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CODE::HadamardDecoder<6> hadamarddec;
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CODE::PolarListDecoder<mesg_type, code_max> polardec;
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uint8_t output_data[data_max];
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int8_t genmat[255*71];
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mesg_type mesg[bits_max];
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code_type code[bits_max], perm[bits_max];
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cmplx cons[cons_max], prev[cols_max];
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int8_t mode[32];
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cmplx cons[cons_max], chan[cols_max];
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cmplx fdom[symbol_len], tdom[symbol_len];
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value index[cols_max], phase[cols_max];
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value cfo_rad, sfo_rad;
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@ -196,20 +189,18 @@ struct Decoder
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return input_hist(tmp);
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}
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Decoder(DSP::ReadPCM<value> *pcm, const char *const *output_names, int output_count) :
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pcm(pcm), correlator(mls0_seq()), crc0(0xA8F4), crc1(0x8F6E37A0)
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pcm(pcm), correlator(mls0_seq()), crc1(0x8F6E37A0)
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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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0b110111101, 0b111100111, 0b100101011, 0b111010111,
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0b000010011, 0b101100101, 0b110001011, 0b101100011,
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0b100011011, 0b100111111, 0b110001101, 0b100101101,
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0b101011111, 0b111111001, 0b111000011, 0b100111001,
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0b110101001, 0b000011111, 0b110000111, 0b110110001});
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blockdc.samples(filter_len);
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DSP::Phasor<cmplx> osc;
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const cmplx *buf;
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int output_index = 0;
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int comb_cols = 32;
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int code_cols = 256;
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int comb_dist = 9;
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int comb_off = 4;
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int cons_cols = code_cols + comb_cols;
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int code_off = - cons_cols / 2;
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while (output_index < output_count) {
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do {
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if (!pcm->good())
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@ -223,108 +214,87 @@ struct Decoder
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std::cerr << "coarse cfo: " << cfo_rad * (rate / Const::TwoPi()) << " Hz " << std::endl;
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osc.omega(-cfo_rad);
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i+symbol_pos+symbol_len] * osc();
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for (int i = 0; i < guard_len; ++i)
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osc();
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fwd(fdom, tdom);
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CODE::MLS seq0(mls0_poly, mls0_seed);
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for (int i = 0; i < mls0_len; ++i)
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fdom[bin(i+mls0_off)] *= nrz(seq0());
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for (int i = 0; i < cons_cols; ++i)
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chan[i] = fdom[bin(i+code_off)];
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i+symbol_pos+symbol_len+extended_len] * osc();
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for (int i = 0; i < guard_len; ++i)
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osc();
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fwd(fdom, tdom);
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CODE::MLS seq1(mls1_poly);
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for (int i = 0; i < mls1_len; ++i)
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fdom[bin(i+mls1_off)] *= nrz(seq1());
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int8_t soft[mls1_len];
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uint8_t data[(mls1_len+7)/8];
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for (int i = 0; i < mls1_len; ++i)
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soft[i] = std::min<value>(std::max<value>(
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std::nearbyint(127 * demod_or_erase(
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fdom[bin(i+mls1_off)], fdom[bin(i-1+mls1_off)]).real()),
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-127), 127);
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bool unique = osddec(data, soft, genmat);
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if (!unique) {
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std::cerr << "OSD error." << std::endl;
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continue;
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}
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uint64_t md = 0;
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for (int i = 0; i < 55; ++i)
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md |= (uint64_t)CODE::get_be_bit(data, i) << i;
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uint16_t cs = 0;
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for (int i = 0; i < 16; ++i)
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cs |= (uint16_t)CODE::get_be_bit(data, i+55) << i;
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crc0.reset();
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if (crc0(md<<9) != cs) {
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std::cerr << "header CRC error." << std::endl;
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continue;
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}
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oper_mode = md & 255;
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if (oper_mode && (oper_mode < 23 || oper_mode > 30)) {
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auto clamp = [](int v){ return v < -127 ? -127 : v > 127 ? 127 : v; };
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for (int i = 0; i < comb_cols; ++i)
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mode[i] = clamp(std::nearbyint(127 * demod_or_erase(fdom[bin(i*comb_dist+comb_off+code_off)], chan[i]).real() * nrz(seq1())));
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oper_mode = hadamarddec(mode);
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if (oper_mode < 0 || oper_mode > 8) {
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std::cerr << "operation mode " << oper_mode << " unsupported." << std::endl;
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continue;
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}
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std::cerr << "oper mode: " << oper_mode << std::endl;
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if ((md>>8) == 0 || (md>>8) >= 129961739795077L) {
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std::cerr << "call sign unsupported." << std::endl;
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continue;
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}
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char call_sign[10];
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base37_decoder(call_sign, md>>8, 9);
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call_sign[9] = 0;
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std::cerr << "call sign: " << call_sign << std::endl;
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if (!oper_mode)
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continue;
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int data_bits = 0;
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int cons_rows = 0;
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int comb_cols = 32;
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int code_cols = 256;
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int comb_dist = 9;
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int comb_off = 4;
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switch (oper_mode) {
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case 23:
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case 1:
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mod_bits = 2;
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cons_rows = 8;
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code_order = 12;
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data_bits = 2048;
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frozen_bits = frozen_4096_2080;
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break;
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case 24:
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case 2:
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mod_bits = 2;
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cons_rows = 16;
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code_order = 13;
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data_bits = 4096;
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frozen_bits = frozen_8192_4128;
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break;
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case 25:
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case 3:
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mod_bits = 2;
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cons_rows = 32;
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code_order = 14;
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data_bits = 8192;
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frozen_bits = frozen_16384_8224;
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break;
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case 26:
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case 4:
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mod_bits = 4;
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cons_rows = 4;
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code_order = 12;
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data_bits = 2048;
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frozen_bits = frozen_4096_2080;
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break;
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case 27:
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case 5:
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mod_bits = 4;
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cons_rows = 8;
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code_order = 13;
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data_bits = 4096;
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frozen_bits = frozen_8192_4128;
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break;
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case 28:
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case 6:
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mod_bits = 4;
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cons_rows = 16;
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code_order = 14;
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data_bits = 8192;
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frozen_bits = frozen_16384_8224;
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break;
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case 29:
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case 7:
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mod_bits = 6;
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cons_rows = 6;
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code_order = 13;
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data_bits = 4096;
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frozen_bits = frozen_8192_4128;
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break;
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case 30:
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case 8:
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mod_bits = 6;
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cons_rows = 11;
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code_order = 14;
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@ -335,32 +305,27 @@ struct Decoder
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return;
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}
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int data_bytes = data_bits / 8;
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int cons_cols = code_cols + comb_cols;
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int code_off = - cons_cols / 2;
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for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)
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correlator(buf = next_sample());
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i] * osc();
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for (int i = 0; i < guard_len; ++i)
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osc();
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fwd(fdom, tdom);
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for (int i = 0; i < cons_cols; ++i)
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prev[i] = fdom[bin(i+code_off)];
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std::cerr << "demod ";
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CODE::MLS seq0(mls0_poly);
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for (int j = 0; j < cons_rows; ++j) {
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for (int i = 0; i < extended_len; ++i)
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correlator(buf = next_sample());
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i] * osc();
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for (int i = 0; i < guard_len; ++i)
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osc();
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fwd(fdom, tdom);
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for (int i = 0; i < cons_cols; ++i)
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cons[cons_cols*j+i] = demod_or_erase(fdom[bin(i+code_off)], prev[i]);
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if (j) {
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for (int i = 0; i < extended_len; ++i)
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correlator(buf = next_sample());
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i] * osc();
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for (int i = 0; i < guard_len; ++i)
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osc();
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fwd(fdom, tdom);
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} else {
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for (int i = 0; i < symbol_pos+symbol_len+extended_len; ++i)
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correlator(buf = next_sample());
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seq1.reset();
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hadamardenc(mode, oper_mode);
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}
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for (int i = 0; i < comb_cols; ++i)
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cons[cons_cols*j+comb_dist*i+comb_off] *= nrz(seq0());
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fdom[bin(comb_dist*i+comb_off+code_off)] *= nrz(seq1()) * mode[i];
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for (int i = 0; i < cons_cols; ++i)
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cons[cons_cols*j+i] = demod_or_erase(fdom[bin(i+code_off)], chan[i]);
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for (int i = 0; i < comb_cols; ++i) {
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index[i] = code_off + comb_dist * i + comb_off;
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phase[i] = arg(cons[cons_cols*j+comb_dist*i+comb_off]);
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@ -372,27 +337,9 @@ struct Decoder
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cons[cons_cols*j+i] *= DSP::polar<value>(1, -tse(i+code_off));
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for (int i = 0; i < cons_cols; ++i)
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if (i % comb_dist == comb_off)
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prev[i] = fdom[bin(i+code_off)];
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chan[i] = fdom[bin(i+code_off)];
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else
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prev[i] *= DSP::polar<value>(1, tse(i+code_off));
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for (int i = 0; i < cons_cols; ++i) {
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index[i] = code_off + i;
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if (i % comb_dist == comb_off) {
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phase[i] = arg(cons[cons_cols*j+i]);
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} else {
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code_type tmp[mod_max];
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mod_hard(tmp, cons[cons_cols*j+i]);
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phase[i] = arg(cons[cons_cols*j+i] * conj(mod_map(tmp)));
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}
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}
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tse.compute(index, phase, cons_cols);
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//std::cerr << "Theil-Sen slope = " << tse.slope() << std::endl;
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//std::cerr << "Theil-Sen yint = " << tse.yint() << std::endl;
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for (int i = 0; i < cons_cols; ++i)
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cons[cons_cols*j+i] *= DSP::polar<value>(1, -tse(i+code_off));
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for (int i = 0; i < cons_cols; ++i)
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if (i % comb_dist != comb_off)
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prev[i] *= DSP::polar<value>(1, tse(i+code_off));
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chan[i] *= DSP::polar<value>(1, tse(i+code_off));
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std::cerr << ".";
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}
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std::cerr << " done" << std::endl;
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