Fixed FFT scaling, moved logging to stderr

This commit is contained in:
Karlis Goba 2018-12-28 20:42:22 +02:00
parent 5de7436d87
commit ccc80ff9e3
2 changed files with 38 additions and 20 deletions

View file

@ -2,11 +2,11 @@
#include <stdio.h>
#define LOG_INFO 0
#define LOG_WARN 1
#define LOG_ERROR 2
#define LOG_FATAL 3
#define LOG_DEBUG 0
#define LOG_INFO 1
#define LOG_WARN 2
#define LOG_ERROR 3
#define LOG_FATAL 4
#define LOG(level, ...) if (level >= LOG_LEVEL) printf(__VA_ARGS__)
#define LOG(level, ...) if (level >= LOG_LEVEL) fprintf(stderr, __VA_ARGS__)

View file

@ -9,16 +9,20 @@
#include "ft8/constants.h"
#include "common/wave.h"
#include "common/debug.h"
#include "fft/kiss_fftr.h"
#define LOG_LEVEL LOG_INFO
const int kMax_candidates = 100;
const int kLDPC_iterations = 20;
const int kMax_decoded_messages = 50;
const int kMax_message_length = 20;
void usage() {
printf("Decode a 15-second WAV file.\n");
fprintf(stderr, "Decode a 15-second WAV file.\n");
}
@ -55,6 +59,7 @@ float blackman_i(int i, int N) {
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
const float fft_norm = 2.0f / nfft;
float window[nfft];
for (int i = 0; i < nfft; ++i) {
@ -64,15 +69,13 @@ void extract_power(const float signal[], int num_blocks, int num_bins, uint8_t p
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);
LOG(LOG_INFO, "N_FFT = %d\n", nfft);
LOG(LOG_INFO, "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);
// Currently bit unsure about the scaling factor of kiss FFT
int offset = 0;
float fft_norm = 1.0f / nfft / sqrtf(nfft);
float max_mag = -100.0f;
for (int i = 0; i < num_blocks; ++i) {
// Loop over two possible time offsets (0 and block_size/2)
@ -90,8 +93,8 @@ void extract_power(const float signal[], int num_blocks, int num_bins, uint8_t p
// 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(1E-10f + mag2);
float mag2 = (freqdata[j].i * freqdata[j].i + freqdata[j].r * freqdata[j].r);
mag_db[j] = 10.0f * log10f(1E-10f + mag2 * fft_norm * fft_norm);
}
// Loop over two possible frequency bin offsets (for averaging)
@ -102,7 +105,7 @@ void extract_power(const float signal[], int num_blocks, int num_bins, uint8_t p
float db = (db1 + db2) / 2;
// Scale decibels to unsigned 8-bit range and clamp the value
int scaled = (int)(2 * (db + 100));
int scaled = (int)(2 * (db + 120));
power[offset] = (scaled < 0) ? 0 : ((scaled > 255) ? 255 : scaled);
++offset;
@ -112,20 +115,34 @@ void extract_power(const float signal[], int num_blocks, int num_bins, uint8_t p
}
}
printf("Max magnitude: %.1f dB\n", max_mag);
LOG(LOG_INFO, "Max magnitude: %.1f dB\n", max_mag);
free(fft_work);
}
void normalize_signal(float *signal, int num_samples) {
float max_amp = 1E-5f;
for (int i = 0; i < num_samples; ++i) {
float amp = fabsf(signal[i]);
if (amp > max_amp) {
max_amp = amp;
}
}
for (int i = 0; i < num_samples; ++i) {
signal[i] /= max_amp;
}
}
void print_tones(const uint8_t *code_map, const float *log174) {
for (int k = 0; k < 3 * FT8_ND; k += 3) {
uint8_t max = 0;
if (log174[k + 0] > 0) max |= 4;
if (log174[k + 1] > 0) max |= 2;
if (log174[k + 2] > 0) max |= 1;
printf("%d", code_map[max]);
LOG(LOG_DEBUG, "%d", code_map[max]);
}
printf("\n");
LOG(LOG_DEBUG, "\n");
}
@ -146,6 +163,7 @@ int main(int argc, char **argv) {
if (rc < 0) {
return -1;
}
normalize_signal(signal, num_samples);
const float fsk_dev = 6.25f; // tone deviation in Hz and symbol rate
@ -154,7 +172,7 @@ int main(int argc, char **argv) {
const int block_size = 2 * num_bins;
const int num_blocks = (num_samples - (block_size/2) - block_size) / block_size;
printf("%d blocks, %d bins\n", num_blocks, num_bins);
LOG(LOG_INFO, "%d blocks, %d bins\n", num_blocks, num_bins);
// Compute FFT over the whole signal and store it
uint8_t power[num_blocks * 4 * num_bins];
@ -220,10 +238,10 @@ int main(int argc, char **argv) {
// Fake WSJT-X-like output for now
int snr = 0; // TODO: compute SNR
printf("000000 %3d %4.1f %4d ~ %s\n", idx, time_sec, (int)(freq_hz + 0.5f), message);
printf("000000 %3d %4.1f %4d ~ %s\n", cand.score, time_sec, (int)(freq_hz + 0.5f), message);
}
}
printf("Decoded %d messages\n", num_decoded);
LOG(LOG_INFO, "Decoded %d messages\n", num_decoded);
return 0;
}