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do not resample

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Ahmet Inan 2021-09-02 19:57:10 +02:00
commit a7d2bc1cbf
1 changed files with 3 additions and 42 deletions
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45
decode.cc
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@ -10,7 +10,6 @@ Copyright 2021 Ahmet Inan <inan@aicodix.de>
#include <cmath>
namespace DSP { using std::abs; using std::min; using std::cos; using std::sin; }
#include "bip_buffer.hh"
#include "resampler.hh"
#include "xorshift.hh"
#include "trigger.hh"
#include "complex.hh"
@ -190,7 +189,6 @@ struct Decoder
DSP::FastFourierTransform<symbol_len, cmplx, 1> bwd;
DSP::BlockDC<value, value> blockdc;
DSP::Hilbert<cmplx, filter_len> hilbert;
DSP::Resampler<value, filter_len, 3> resample;
DSP::BipBuffer<cmplx, buffer_len> input_hist;
SchmidlCox<value, cmplx, search_pos, symbol_len/2, guard_len> correlator;
CODE::CRC<uint16_t> crc0;
@ -202,7 +200,7 @@ struct Decoder
mesg_type mesg[44096], mess[65536];
code_type code[65536];
cmplx head[symbol_len], tail[symbol_len], cons[cons_max];
cmplx fdom[symbol_len], tdom[buffer_len], resam[buffer_len];
cmplx fdom[symbol_len], tdom[buffer_len];
value cfo_rad, sfo_rad;
const uint32_t *frozen_bits;
int code_order;
@ -239,28 +237,6 @@ struct Decoder
fdom[(i+mls0_off/2+symbol_len/2)%(symbol_len/2)] = nrz(seq0());
return fdom;
}
int displacement(const cmplx *sym0, const cmplx *sym1)
{
fwd(head, sym0);
fwd(tail, sym1);
for (int i = 0; i < symbol_len; ++i)
head[i] *= conj(tail[i]);
bwd(tail, head);
int idx = 0;
for (int i = 0; i < symbol_len; ++i)
if (norm(tail[i]) > norm(tail[idx]))
idx = i;
if (idx > symbol_len / 2)
idx -= symbol_len;
return -idx;
}
value frac_cfo(const cmplx *samples)
{
cmplx sum;
for (int i = 0; i < symbol_len/2; ++i)
sum += samples[i] * conj(samples[i+symbol_len/2]);
return arg(sum) / (symbol_len/2);
}
void lengthen()
{
int code_bits = 1 << code_order;
@ -329,7 +305,7 @@ struct Decoder
}
}
Decoder(uint8_t *out, DSP::ReadPCM<value> *pcm, int skip_count) :
pcm(pcm), resample(rate, (rate * 19) / 40, 2), correlator(mls0_seq()), crc0(0xA8F4), crc1(0xD419CC15)
pcm(pcm), correlator(mls0_seq()), crc0(0xA8F4), crc1(0xD419CC15)
{
CODE::BoseChaudhuriHocquenghemGenerator<255, 71>::matrix(genmat, true, {
0b100011101, 0b101110111, 0b111110011, 0b101101001,
@ -475,24 +451,9 @@ struct Decoder
int cons_rows = cons_cnt / cons_cols;
int code_off = - cons_cols / 2;
int dis = displacement(buf+symbol_pos-(cons_rows+1)*(symbol_len+guard_len), buf+symbol_pos+2*(symbol_len+guard_len));
sfo_rad = (dis * Const::TwoPi()) / ((cons_rows+3)*(symbol_len+guard_len));
std::cerr << "coarse sfo: " << 1000000 * sfo_rad / Const::TwoPi() << " ppm" << std::endl;
if (dis) {
value diff = sfo_rad * (rate / Const::TwoPi());
resample(resam, buf, -diff, buffer_len);
symbol_pos = std::nearbyint(correlator.symbol_pos * (1 - sfo_rad / Const::TwoPi()));
std::cerr << "resam pos: " << symbol_pos << std::endl;
} else {
for (int i = 0; i < buffer_len; ++i)
resam[i] = buf[i];
}
cfo_rad = correlator.cfo_rad + correlator.frac_cfo - frac_cfo(resam+symbol_pos);
std::cerr << "finer cfo: " << cfo_rad * (rate / Const::TwoPi()) << " Hz " << std::endl;
osc.omega(-cfo_rad);
for (int i = 0; i < buffer_len; ++i)
tdom[i] = resam[i] * osc();
tdom[i] = buf[i] * osc();
cmplx *cur = tdom + symbol_pos - (cons_rows + 1) * (symbol_len + guard_len);
fwd(fdom, cur);