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https://github.com/aicodix/modem.git
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do the demodulation online using the first preamble
This commit is contained in:
Ahmet Inan
parent
7b45ee894d
commit
daa47615d3
1 changed files with 145 additions and 130 deletions
275
decode.cc
275
decode.cc
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@ -184,11 +184,10 @@ struct Decoder
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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 = (rows_max + 8) * (symbol_len + guard_len);
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static const int buffer_len = 6 * (symbol_len + guard_len);
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static const int search_pos = buffer_len - 4 * (symbol_len + guard_len);
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DSP::ReadPCM<value> *pcm;
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DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
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DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
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DSP::BlockDC<value, value> blockdc;
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DSP::Hilbert<cmplx, filter_len> hilbert;
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DSP::BipBuffer<cmplx, buffer_len> input_hist;
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@ -202,8 +201,8 @@ struct Decoder
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int8_t genmat[255*71];
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mesg_type mesg[44096], mess[65536];
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code_type code[65536];
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cmplx head[symbol_len], tail[symbol_len], cons[cons_max];
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cmplx fdom[symbol_len], tdom[buffer_len];
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cmplx cons[cons_max], prev[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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const uint32_t *frozen_bits;
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@ -212,6 +211,7 @@ struct Decoder
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int oper_mode;
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int mod_bits;
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int cons_cnt;
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int cons_cols;
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int cons_bits;
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int mesg_bits;
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@ -321,8 +321,11 @@ struct Decoder
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bool real = pcm->channels() == 1;
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blockdc.samples(2*(symbol_len+guard_len));
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DSP::Phasor<cmplx> osc;
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const cmplx *buf;
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bool okay;
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do {
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okay = false;
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do {
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if (!pcm->good())
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return;
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@ -332,141 +335,153 @@ struct Decoder
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tmp = hilbert(blockdc(tmp.real()));
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buf = input_hist(tmp);
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} while (!correlator(buf));
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symbol_pos = correlator.symbol_pos;
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cfo_rad = correlator.cfo_rad;
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std::cerr << "symbol pos: " << symbol_pos << std::endl;
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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+guard_len)] * 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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-128), 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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switch (oper_mode) {
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case 6:
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cons_cols = 432;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 7:
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cons_cols = 400;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 8:
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cons_cols = 400;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 9:
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cons_cols = 360;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 10:
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cons_cols = 512;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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case 11:
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cons_cols = 384;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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case 12:
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cons_cols = 384;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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case 13:
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cons_cols = 256;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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default:
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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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cons_cnt = cons_bits / mod_bits;
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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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okay = true;
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} while (skip_count--);
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symbol_pos = correlator.symbol_pos;
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cfo_rad = correlator.cfo_rad;
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std::cerr << "symbol pos: " << symbol_pos << std::endl;
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std::cerr << "coarse cfo: " << cfo_rad * (rate / Const::TwoPi()) << " Hz " << std::endl;
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DSP::Phasor<cmplx> osc;
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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+guard_len)] * 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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-128), 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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if (!okay)
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return;
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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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return;
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}
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oper_mode = md & 255;
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int cons_cols;
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switch (oper_mode) {
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case 6:
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cons_cols = 432;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 7:
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cons_cols = 400;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 8:
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cons_cols = 400;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 9:
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cons_cols = 360;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64800;
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mesg_bits = 43808;
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frozen_bits = frozen_64800_43072;
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break;
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case 10:
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cons_cols = 512;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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case 11:
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cons_cols = 384;
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mod_bits = 3;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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case 12:
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cons_cols = 384;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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case 13:
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cons_cols = 256;
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mod_bits = 2;
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code_order = 16;
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cons_bits = 64512;
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mesg_bits = 44096;
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frozen_bits = frozen_64512_43072;
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break;
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default:
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std::cerr << "operation mode " << oper_mode << " unsupported." << std::endl;
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return;
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}
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cons_cnt = cons_bits / mod_bits;
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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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return;
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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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int cons_rows = cons_cnt / cons_cols;
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int code_off = - cons_cols / 2;
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osc.omega(-cfo_rad);
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for (int i = 0; i < buffer_len; ++i)
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tdom[i] = buf[i] * osc();
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cmplx *cur = tdom + symbol_pos - (cons_rows + 1) * (symbol_len + guard_len);
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fwd(fdom, cur);
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i+symbol_pos+2*(symbol_len+guard_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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for (int j = 0; j < cons_rows; ++j) {
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for (int i = 0; i < symbol_len+guard_len; ++i) {
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cmplx tmp;
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pcm->read(reinterpret_cast<value *>(&tmp), 1);
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if (real)
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tmp = hilbert(blockdc(tmp.real()));
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buf = input_hist(tmp);
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}
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for (int i = 0; i < symbol_len; ++i)
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tdom[i] = buf[i+symbol_pos+2*(symbol_len+guard_len)] * osc();
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for (int i = 0; i < guard_len; ++i)
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osc();
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for (int i = 0; i < cons_cols; ++i)
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head[bin(i+code_off)] = fdom[bin(i+code_off)];
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fwd(fdom, cur += symbol_len+guard_len);
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prev[i] = fdom[bin(i+code_off)];
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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)], head[bin(i+code_off)]);
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cons[cons_cols*j+i] = demod_or_erase(fdom[bin(i+code_off)], prev[i]);
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}
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if (1) {
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value sum_slope = 0, sum_yint = 0;
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@ -561,7 +576,7 @@ int main(int argc, char **argv)
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return 1;
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}
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int skip_count = 1;
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int skip_count = 0;
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if (argc > 3)
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skip_count = std::atoi(argv[3]);
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