341 lines
No EOL
11 KiB
C++
341 lines
No EOL
11 KiB
C++
#include <cstdlib>
|
|
#include <cstring>
|
|
#include <cstdio>
|
|
#include <cmath>
|
|
|
|
#include "common/wave.h"
|
|
#include "ft8/pack.h"
|
|
#include "ft8/encode.h"
|
|
#include "ft8/pack_v2.h"
|
|
#include "ft8/encode_v2.h"
|
|
#include "ft8/unpack.h"
|
|
|
|
#include "ft8/ldpc.h"
|
|
#include "fft/kiss_fftr.h"
|
|
|
|
|
|
void usage() {
|
|
printf("Decode a 15-second WAV file.\n");
|
|
}
|
|
|
|
|
|
float hann_i(int i, int N) {
|
|
float x = sinf((float)M_PI * i / (N - 1));
|
|
return x*x;
|
|
}
|
|
|
|
|
|
struct Candidate {
|
|
int16_t score;
|
|
uint16_t time_offset;
|
|
uint16_t freq_offset;
|
|
uint8_t time_sub;
|
|
uint8_t freq_sub;
|
|
};
|
|
|
|
|
|
void heapify_down(Candidate * heap, int heap_size) {
|
|
// heapify from the root down
|
|
int current = 0;
|
|
while (true) {
|
|
int largest = current;
|
|
int left = 2 * current + 1;
|
|
int right = left + 1;
|
|
|
|
if (left < heap_size && heap[left].score < heap[largest].score) {
|
|
largest = left;
|
|
}
|
|
if (right < heap_size && heap[right].score < heap[largest].score) {
|
|
largest = right;
|
|
}
|
|
if (largest == current) {
|
|
break;
|
|
}
|
|
|
|
Candidate tmp = heap[largest];
|
|
heap[largest] = heap[current];
|
|
heap[current] = tmp;
|
|
current = largest;
|
|
}
|
|
}
|
|
|
|
|
|
void heapify_up(Candidate * heap, int heap_size) {
|
|
// heapify from the last node up
|
|
int current = heap_size - 1;
|
|
while (current > 0) {
|
|
int parent = (current - 1) / 2;
|
|
if (heap[current].score >= heap[parent].score) {
|
|
break;
|
|
}
|
|
|
|
Candidate tmp = heap[parent];
|
|
heap[parent] = heap[current];
|
|
heap[current] = tmp;
|
|
current = parent;
|
|
}
|
|
}
|
|
|
|
|
|
// Find top N candidates in frequency and time according to their sync strength (looking at Costas symbols)
|
|
// We treat and organize the candidate list as a min-heap (empty initially).
|
|
void find_sync(const uint8_t *power, int num_blocks, int num_bins, const uint8_t *sync_map, int num_candidates, Candidate *heap) {
|
|
int heap_size = 0;
|
|
|
|
for (int alt = 0; alt < 4; ++alt) {
|
|
for (int time_offset = 0; time_offset < num_blocks - NN; ++time_offset) {
|
|
for (int freq_offset = 0; freq_offset < num_bins - 8; ++freq_offset) {
|
|
int score = 0;
|
|
|
|
// Compute score over Costas symbols (0-7, 36-43, 72-79)
|
|
for (int m = 0; m <= 72; m += 36) {
|
|
for (int k = 0; k < 7; ++k) {
|
|
int offset = ((time_offset + k + m) * 4 + alt) * num_bins + freq_offset;
|
|
score += 8 * (int)power[offset + sync_map[k]] -
|
|
power[offset + 0] - power[offset + 1] -
|
|
power[offset + 2] - power[offset + 3] -
|
|
power[offset + 4] - power[offset + 5] -
|
|
power[offset + 6] - power[offset + 7];
|
|
}
|
|
}
|
|
|
|
// If the heap is full AND the current candidate is better than
|
|
// the worst in the heap, we remove the worst and make space
|
|
if (heap_size == num_candidates && score > heap[0].score) {
|
|
heap[0] = heap[heap_size - 1];
|
|
--heap_size;
|
|
|
|
heapify_down(heap, heap_size);
|
|
}
|
|
|
|
// If there's free space in the heap, we add the current candidate
|
|
if (heap_size < num_candidates) {
|
|
heap[heap_size].score = score;
|
|
heap[heap_size].time_offset = time_offset;
|
|
heap[heap_size].freq_offset = freq_offset;
|
|
heap[heap_size].time_sub = alt / 2;
|
|
heap[heap_size].freq_sub = alt % 2;
|
|
++heap_size;
|
|
|
|
heapify_up(heap, heap_size);
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
|
|
// Compute FFT magnitudes (log power) for each timeslot in the signal
|
|
void extract_power(const float * signal, int num_blocks, int num_bins, uint8_t * power) {
|
|
const int block_size = 2 * num_bins; // Average over 2 bins per FSK tone
|
|
const int nfft = 2 * block_size; // We take FFT of two blocks, advancing by one
|
|
|
|
float window[nfft];
|
|
for (int i = 0; i < nfft; ++i) {
|
|
window[i] = hann_i(i, nfft);
|
|
}
|
|
|
|
size_t fft_work_size;
|
|
kiss_fftr_alloc(nfft, 0, 0, &fft_work_size);
|
|
|
|
printf("N_FFT = %d\n", nfft);
|
|
printf("FFT work area = %lu\n", fft_work_size);
|
|
|
|
void * fft_work = malloc(fft_work_size);
|
|
kiss_fftr_cfg fft_cfg = kiss_fftr_alloc(nfft, 0, fft_work, &fft_work_size);
|
|
|
|
int offset = 0;
|
|
float fft_norm = 1.0f / nfft;
|
|
for (int i = 0; i < num_blocks; ++i) {
|
|
// Loop over two possible time offsets (0 and block_size/2)
|
|
for (int time_sub = 0; time_sub <= block_size/2; time_sub += block_size/2) {
|
|
kiss_fft_scalar timedata[nfft];
|
|
kiss_fft_cpx freqdata[nfft/2 + 1];
|
|
float mag_db[nfft/2 + 1];
|
|
|
|
// Extract windowed signal block
|
|
for (int j = 0; j < nfft; ++j) {
|
|
timedata[j] = window[j] * signal[(i * block_size) + (j + time_sub)];
|
|
}
|
|
|
|
kiss_fftr(fft_cfg, timedata, freqdata);
|
|
|
|
// Compute log magnitude in decibels
|
|
for (int j = 0; j < nfft/2 + 1; ++j) {
|
|
float mag2 = fft_norm * (freqdata[j].i * freqdata[j].i + freqdata[j].r * freqdata[j].r);
|
|
mag_db[j] = 10.0f * log10f(1.0E-10f + mag2);
|
|
}
|
|
|
|
// Loop over two possible frequency bin offsets (for averaging)
|
|
for (int freq_sub = 0; freq_sub < 2; ++freq_sub) {
|
|
for (int j = 0; j < num_bins; ++j) {
|
|
float db1 = mag_db[j * 2 + freq_sub];
|
|
float db2 = mag_db[j * 2 + freq_sub + 1];
|
|
float db = (db1 + db2) / 2;
|
|
|
|
// Scale decibels to unsigned 8-bit range
|
|
int scaled = (int)(2 * (db + 100));
|
|
power[offset] = (scaled < 0) ? 0 : ((scaled > 255) ? 255 : scaled);
|
|
++offset;
|
|
}
|
|
}
|
|
}
|
|
}
|
|
|
|
free(fft_work);
|
|
}
|
|
|
|
|
|
uint8_t max2(uint8_t a, uint8_t b) {
|
|
return (a >= b) ? a : b;
|
|
}
|
|
|
|
|
|
uint8_t max4(uint8_t a, uint8_t b, uint8_t cand, uint8_t d) {
|
|
return max2(max2(a, b), max2(cand, d));
|
|
}
|
|
|
|
|
|
// Compute log likelihood log(p(1) / p(0)) of 174 message bits
|
|
// for later use in soft-decision LDPC decoding
|
|
void extract_likelihood(const uint8_t *power, int num_bins, const Candidate & cand, const uint8_t *code_map, float *log174) {
|
|
int offset = (cand.time_offset * 4 + cand.time_sub * 2 + cand.freq_sub) * num_bins + cand.freq_offset;
|
|
|
|
int k = 0;
|
|
// Go over FSK tones and skip Costas sync symbols
|
|
for (int i = 7; i < NN - 7; ++i) {
|
|
if (i == 36) i += 7;
|
|
|
|
// Pointer to 8 bins of the current symbol
|
|
const uint8_t * ps = power + (offset + i * 4 * num_bins);
|
|
uint8_t s2[8];
|
|
|
|
for (int i = 0; i < 8; ++i) {
|
|
s2[i] = ps[code_map[i]];
|
|
}
|
|
|
|
// Extract bit significance (and convert them to float)
|
|
// 8 FSK tones = 3 bits
|
|
log174[k + 0] = (int)max4(s2[4], s2[5], s2[6], s2[7]) - (int)max4(s2[0], s2[1], s2[2], s2[3]);
|
|
log174[k + 1] = (int)max4(s2[2], s2[3], s2[6], s2[7]) - (int)max4(s2[0], s2[1], s2[4], s2[5]);
|
|
log174[k + 2] = (int)max4(s2[1], s2[3], s2[5], s2[7]) - (int)max4(s2[0], s2[2], s2[4], s2[6]);
|
|
// printf("%d %d %d %d %d %d %d %d : %.0f %.0f %.0f\n",
|
|
// ps[0], ps[1], ps[2], ps[3], ps[4], ps[5], ps[6], ps[7],
|
|
// log174[k + 0], log174[k + 1], log174[k + 2]);
|
|
k += 3;
|
|
}
|
|
|
|
// Compute the variance of log174
|
|
float sum = 0;
|
|
float sum2 = 0;
|
|
float inv_n = 1.0f / (3 * ND);
|
|
for (int i = 0; i < 3 * ND; ++i) {
|
|
sum += log174[i];
|
|
sum2 += log174[i] * log174[i];
|
|
}
|
|
float variance = (sum2 - sum * sum * inv_n) * inv_n;
|
|
|
|
// Normalize log174 such that sigma = 2.83 (Why? It's in WSJT-X)
|
|
float norm_factor = 2.83f / sqrtf(variance);
|
|
|
|
for (int i = 0; i < 3 * ND; ++i) {
|
|
log174[i] *= norm_factor;
|
|
//printf("%.1f ", log174[i]);
|
|
}
|
|
//printf("\n");
|
|
}
|
|
|
|
|
|
int main(int argc, char ** argv) {
|
|
// Expect one command-line argument
|
|
if (argc < 2) {
|
|
usage();
|
|
return -1;
|
|
}
|
|
|
|
const char * wav_path = argv[1];
|
|
|
|
int sample_rate = 12000;
|
|
int num_samples = 15 * sample_rate;
|
|
float signal[num_samples];
|
|
|
|
int rc = load_wav(signal, num_samples, sample_rate, wav_path);
|
|
if (rc < 0) {
|
|
return -1;
|
|
}
|
|
|
|
// Costas 7x7 tone pattern
|
|
const uint8_t kCostas_map_v1[] = { 2,5,6,0,4,1,3 };
|
|
const uint8_t kCostas_map_v2[] = { 3,1,4,0,6,5,2 };
|
|
// Gray maps (used only in v2)
|
|
const uint8_t kGray_map_v1[8] = { 0,1,2,3,4,5,6,7 }; // identity map
|
|
const uint8_t kGray_map_v2[8] = { 0,1,3,2,5,6,4,7 };
|
|
|
|
const float fsk_dev = 6.25f;
|
|
|
|
const int num_bins = (int)(sample_rate / (2 * fsk_dev));
|
|
const int block_size = 2 * num_bins;
|
|
const int num_blocks = (num_samples - (block_size/2) - block_size) / block_size;
|
|
uint8_t power[num_blocks * 4 * num_bins]; // [num_blocks][4][num_bins] ~ 200 KB
|
|
|
|
printf("%d blocks, %d bins\n", num_blocks, num_bins);
|
|
|
|
extract_power(signal, num_blocks, num_bins, power);
|
|
|
|
int num_candidates = 250;
|
|
Candidate heap[num_candidates];
|
|
|
|
find_sync(power, num_blocks, num_bins, kCostas_map_v1, num_candidates, heap);
|
|
|
|
for (int idx = 0; idx < num_candidates; ++idx) {
|
|
Candidate &cand = heap[idx];
|
|
|
|
float log174[3 * ND];
|
|
extract_likelihood(power, num_bins, cand, kGray_map_v1, log174);
|
|
|
|
const int num_iters = 20;
|
|
int plain[3 * ND];
|
|
int ok = 0;
|
|
|
|
bp_decode(log174, num_iters, plain, &ok);
|
|
//ldpc_decode(log174, num_iters, plain, &ok);
|
|
//printf("ldpc_decode() = %d\n", ok);
|
|
|
|
if (ok == 87) {
|
|
float freq_hz = (cand.freq_offset + cand.freq_sub / 2.0f) * fsk_dev;
|
|
float time_sec = (cand.time_offset + cand.time_sub / 2.0f) / fsk_dev;
|
|
//printf("%03d: score = %d freq = %.1f time = %.2f\n", idx,
|
|
// cand.score, freq_hz, time_sec);
|
|
|
|
uint8_t a87[11];
|
|
uint8_t mask = 0x80;
|
|
uint8_t position = 0;
|
|
for (int i = 0; i < 11; ++i) {
|
|
a87[i] = 0;
|
|
}
|
|
// Extract payload + CRC (last 87 bits)
|
|
for (int i = 174 - 87; i < 174; ++i) {
|
|
if (plain[i]) {
|
|
a87[position] |= mask;
|
|
}
|
|
mask >>= 1;
|
|
if (!mask) {
|
|
mask = 0x80;
|
|
++position;
|
|
}
|
|
}
|
|
|
|
for (int i = 0; i < 11; ++i) {
|
|
//printf("%02x ", a87[i]);
|
|
}
|
|
//printf("\n");
|
|
|
|
char message[20];
|
|
unpack(a87, message);
|
|
|
|
printf("000000 0 %4.1f %4d ~ %s\n", time_sec, (int)(freq_hz + 0.5f), message);
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
} |