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added extended length constant

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This commit is contained in:
Ahmet Inan 2023-12-14 08:21:34 +01:00
commit e27c8e1e06
1 changed files with 9 additions and 8 deletions
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17
decode.cc
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@ -177,6 +177,7 @@ struct Decoder
static const int symbol_len = (1280 * rate) / 8000;
static const int filter_len = (((21 * rate) / 8000) & ~3) | 1;
static const int guard_len = symbol_len / 8;
static const int extended_len = symbol_len + guard_len;
static const int max_bits = 1360 + 32;
static const int cons_cols = 256;
static const int cons_rows = 4;
@ -188,8 +189,8 @@ struct Decoder
static const int mls1_len = 255;
static const int mls1_off = - mls1_len / 2;
static const int mls1_poly = 0b100101011;
static const int buffer_len = 6 * (symbol_len + guard_len);
static const int search_pos = buffer_len - 4 * (symbol_len + guard_len);
static const int buffer_len = 6 * extended_len;
static const int search_pos = buffer_len - 4 * extended_len;
DSP::ReadPCM<value> *pcm;
DSP::FastFourierTransform<symbol_len, cmplx, -1> fwd;
DSP::BlockDC<value, value> blockdc;
@ -279,7 +280,7 @@ struct Decoder
0b101011111, 0b111111001, 0b111000011, 0b100111001,
0b110101001, 0b000011111, 0b110000111, 0b110110001});
blockdc.samples(2*(symbol_len+guard_len));
blockdc.samples(2*extended_len);
DSP::Phasor<cmplx> osc;
const cmplx *buf;
bool okay;
@ -298,7 +299,7 @@ struct Decoder
osc.omega(-cfo_rad);
for (int i = 0; i < symbol_len; ++i)
tdom[i] = buf[i+symbol_pos+(symbol_len+guard_len)] * osc();
tdom[i] = buf[i+symbol_pos+extended_len] * osc();
fwd(fdom, tdom);
CODE::MLS seq1(mls1_poly);
for (int i = 0; i < mls1_len; ++i)
@ -347,7 +348,7 @@ struct Decoder
if (!okay || !oper_mode)
return;
for (int i = 0; i < symbol_pos+(symbol_len+guard_len); ++i)
for (int i = 0; i < symbol_pos+extended_len; ++i)
buf = next_sample();
for (int i = 0; i < symbol_len; ++i)
tdom[i] = buf[i] * osc();
@ -358,7 +359,7 @@ struct Decoder
prev[i] = fdom[bin(i+code_off)];
std::cerr << "demod ";
for (int j = 0; j < cons_rows; ++j) {
for (int i = 0; i < symbol_len+guard_len; ++i)
for (int i = 0; i < extended_len; ++i)
buf = next_sample();
for (int i = 0; i < symbol_len; ++i)
tdom[i] = buf[i] * osc();
@ -393,8 +394,8 @@ struct Decoder
value avg_yint = sum_yint / cons_rows;
//for (int i = 0; i < cons_cnt; ++i)
// cons[i] *= DSP::polar<value>(1, -(avg_yint+avg_slope*((i%cons_cols)+code_off)));
sfo_rad -= avg_slope * symbol_len / value(symbol_len+guard_len);
cfo_rad += avg_yint / (symbol_len+guard_len);
sfo_rad -= avg_slope * symbol_len / value(extended_len);
cfo_rad += avg_yint / extended_len;
std::cerr << "coarse sfo: " << 1000000 * sfo_rad / Const::TwoPi() << " ppm" << std::endl;
std::cerr << "finer cfo: " << cfo_rad * (rate / Const::TwoPi()) << " Hz " << std::endl;
}