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added partial_transmit_sequence() helper

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This commit is contained in:
Ahmet Inan 2025-08-08 07:16:03 +02:00
commit 40e14d4fdb
1 changed files with 21 additions and 113 deletions
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134
decode.cc
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@ -223,6 +223,24 @@ struct Decoder : Common
md |= uint64_t(mesg[i].v[best] < 0) << i;
return md;
}
bool partial_transmit_sequence(int offset, int stride)
{
cmplx sum;
for (int i = offset; i < tone_count; i += stride)
if (i % block_length == pilot_off)
sum += demod[i];
if (abs(sum) < pilot_tones / (2 * stride)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
return false;
}
cmplx rot = std::abs(sum.real()) < std::abs(sum.imag()) ? cmplx(0, sum.imag() < 0 ? 1 : -1) : cmplx(sum.real() < 0 ? -1 : 1);
for (int i = offset; i < tone_count; i += stride) {
tone[i] *= rot;
demod[i] *= rot;
}
return true;
}
Decoder(DSP::ReadPCM<value> *pcm, const char *const *output_names, int output_count) : pcm(pcm), correlator(mls0_seq())
{
blockdc.samples(filter_len);
@ -296,119 +314,9 @@ struct Decoder : Common
tone[i] *= nrz(seq1());
for (int i = 0; i < tone_count; ++i)
demod[i] = demod_or_erase(tone[i], chan[i]);
auto rot = [](cmplx p){ return std::abs(p.real()) < std::abs(p.imag()) ? cmplx(0, p.imag() < 0 ? 1 : -1) : cmplx(p.real() < 0 ? -1 : 1); };
cmplx ptsa_sum;
for (int i = 0; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsa_sum += demod[i];
cmplx ptsa_phase = rot(ptsa_sum);
if (abs(ptsa_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 0; i < tone_count; i += 8) {
tone[i] *= ptsa_phase;
demod[i] *= ptsa_phase;
}
cmplx ptsb_sum;
for (int i = 1; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsb_sum += demod[i];
cmplx ptsb_phase = rot(ptsb_sum);
if (abs(ptsb_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 1; i < tone_count; i += 8) {
tone[i] *= ptsb_phase;
demod[i] *= ptsb_phase;
}
cmplx ptsc_sum;
for (int i = 2; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsc_sum += demod[i];
cmplx ptsc_phase = rot(ptsc_sum);
if (abs(ptsc_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 2; i < tone_count; i += 8) {
tone[i] *= ptsc_phase;
demod[i] *= ptsc_phase;
}
cmplx ptsd_sum;
for (int i = 3; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsd_sum += demod[i];
cmplx ptsd_phase = rot(ptsd_sum);
if (abs(ptsd_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 3; i < tone_count; i += 8) {
tone[i] *= ptsd_phase;
demod[i] *= ptsd_phase;
}
cmplx ptse_sum;
for (int i = 4; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptse_sum += demod[i];
cmplx ptse_phase = rot(ptse_sum);
if (abs(ptse_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 4; i < tone_count; i += 8) {
tone[i] *= ptse_phase;
demod[i] *= ptse_phase;
}
cmplx ptsf_sum;
for (int i = 5; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsf_sum += demod[i];
cmplx ptsf_phase = rot(ptsf_sum);
if (abs(ptsf_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 5; i < tone_count; i += 8) {
tone[i] *= ptsf_phase;
demod[i] *= ptsf_phase;
}
cmplx ptsg_sum;
for (int i = 6; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsg_sum += demod[i];
cmplx ptsg_phase = rot(ptsg_sum);
if (abs(ptsg_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 6; i < tone_count; i += 8) {
tone[i] *= ptsg_phase;
demod[i] *= ptsg_phase;
}
cmplx ptsh_sum;
for (int i = 7; i < tone_count; i += 8)
if (i % block_length == pilot_off)
ptsh_sum += demod[i];
cmplx ptsh_phase = rot(ptsh_sum);
if (abs(ptsh_sum) < pilot_tones / (8 * 2)) {
std::cerr << "pilot phase damaged" << std::endl;
oper_mode = -1;
break;
}
for (int i = 7; i < tone_count; i += 8) {
tone[i] *= ptsh_phase;
demod[i] *= ptsh_phase;
}
for (int i = 0; i < 8; ++i)
if (!partial_transmit_sequence(i, 8))
break;
for (int i = 0; i < pilot_tones; ++i) {
index[i] = tone_off + block_length * i + pilot_off;
phase[i] = arg(demod[block_length*i+pilot_off]);