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/*---------------------------------------------------------------------------*\
FILE........: freedv_700d_comprx.c
AUTHOR......: David Rowe
DATE CREATED: July 2022
Complex valued rx to support ctests. Includes a few operations that will
only work if complex Tx and Rx signals are being handled correctly.
\*---------------------------------------------------------------------------*/
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>
#include "codec2_cohpsk.h"
#include "comp_prim.h"
#include "freedv_api.h"
#include "freedv_api_internal.h"
#include "ofdm_internal.h"
int main(int argc, char *argv[]) {
/* with no arguments then run with no test code */
int test_num = 0;
if (argc == 2) {
if (strcmp(argv[1], "tx") == 0) {
test_num = 1;
}
if (strcmp(argv[1], "rx") == 0) {
test_num = 2;
}
}
fprintf(stderr, "%d\n", test_num);
struct freedv *freedv;
freedv = freedv_open(FREEDV_MODE_700D);
assert(freedv != NULL);
/* note API functions to tell us how big our buffers need to be */
short speech_out[freedv_get_n_max_speech_samples(freedv)];
short demod_in[2 * freedv_get_n_max_modem_samples(freedv)];
COMP demod_in_comp[2 * freedv_get_n_max_modem_samples(freedv)];
/* set up small freq offset */
float foff_hz = 25;
COMP phase_ch;
phase_ch.real = 1.0;
phase_ch.imag = 0.0;
/* set complex sine wave interferer at -fc */
COMP interferer_phase = {1.0, 0.0};
COMP interferer_freq;
interferer_freq.real =
cos(2.0 * M_PI * freedv->ofdm->tx_centre / FREEDV_FS_8000);
interferer_freq.imag =
sin(2.0 * M_PI * freedv->ofdm->tx_centre / FREEDV_FS_8000);
interferer_freq = cconj(interferer_freq);
/* log a file of demod input samples for plotting in Octave */
FILE *fdemod = fopen("demod.f32", "wb");
assert(fdemod != NULL);
/* measure demod input power, interferer input power */
float power_d = 0.0;
float power_interferer = 0.0;
int frames = 0, sum_sync = 0, frames_snr = 0;
float sum_snr = 0.0;
size_t nin, nout;
nin = freedv_nin(freedv);
while (fread(demod_in, sizeof(short), 2 * nin, stdin) == 2 * nin) {
for (int i = 0; i < nin; i++) {
demod_in_comp[i].real = (float)demod_in[2 * i];
demod_in_comp[i].imag = (float)demod_in[2 * i + 1];
// demod_in_comp[i].imag = 0;
}
if (test_num == 1) {
/* So Tx is a complex OFDM signal centered at +fc. A small
shift fd followed by Re{} will only work if Tx is complex.
If Tx is real, neg freq components at -fc+fd will be
aliased on top of fc+fd wanted signal by Re{} operation.
This can be tested by setting demod_in_comp[i].imag = 0
above */
fdmdv_freq_shift_coh(demod_in_comp, demod_in_comp, foff_hz,
FREEDV_FS_8000, &phase_ch, nin);
for (int i = 0; i < nin; i++) demod_in_comp[i].imag = 0.0;
}
if (test_num == 2) {
/* a complex sinewave (carrier) at -fc will only be ignored if
Rx is treating signal as complex, otherwise if real a +fc
alias will appear in the middle of our wanted signal at
+fc, this can be tested by setting demod_in_comp[i].imag =
0 below */
for (int i = 0; i < nin; i++) {
COMP a = fcmult(2E4, interferer_phase);
interferer_phase = cmult(interferer_phase, interferer_freq);
power_interferer += a.real * a.real + a.imag * a.imag;
COMP d = demod_in_comp[i];
power_d += d.real * d.real + d.imag * d.imag;
demod_in_comp[i] = cadd(d, a);
// demod_in_comp[i].imag = 0;
}
}
/* useful to take a look at this with Octave */
fwrite(demod_in_comp, sizeof(COMP), nin, fdemod);
nout = freedv_comprx(freedv, speech_out, demod_in_comp);
nin = freedv_nin(freedv); /* call me on every loop! */
fwrite(speech_out, sizeof(short), nout, stdout);
int sync;
float snr_est;
freedv_get_modem_stats(freedv, &sync, &snr_est);
fprintf(stderr, "sync: %d snr_est: %f\n", sync, snr_est);
frames++;
sum_sync += sync;
if (sync) {
sum_snr += snr_est;
frames_snr++;
}
}
fclose(fdemod);
freedv_close(freedv);
if (test_num == 2)
fprintf(stderr, "Demod/Interferer power ratio: %3.2f dB\n",
10 * log10(power_d / power_interferer));
float snr_av = sum_snr / frames_snr;
fprintf(stderr, "frames: %d sum_sync: %d snr_av: %3.2f dB\n", frames,
sum_sync, snr_av);
if (snr_av > 8.0)
return 0;
else
return 1;
}
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