/* Simple test program */
int main(int argc, char **argv) {
if(argc < 3) {
fprintf(stderr, "Error: missing argument.\n");
fprintf(stderr, "Syntax: rds_wav <out.wav> <text>\n");
return EXIT_FAILURE;
}
set_rds_pi(0x1234);
set_rds_ps(argv[2]);
set_rds_rt(argv[2]);
float buffer[LENGTH];
// Set the format of the output file
SNDFILE *outf;
SF_INFO sfinfo;
sfinfo.frames = LENGTH;
sfinfo.samplerate = 228000;
sfinfo.channels = 1;
sfinfo.format = SF_FORMAT_WAV | SF_FORMAT_PCM_16;
sfinfo.sections = 1;
sfinfo.seekable = 0;
// Open the output file
if (! (outf = sf_open(argv[1], SFM_WRITE, &sfinfo))) {
fprintf(stderr, "Error: could not open output file %s.\n", argv[1]) ;
return EXIT_FAILURE;
}
for(int j=0; j<40; j++) {
get_rds_samples(buffer, LENGTH);
if(sf_write_float(outf, buffer, LENGTH) != LENGTH) {
fprintf(stderr, "Error: writing to file %s.\n", argv[1]);
return EXIT_FAILURE;
}
}
if(sf_close(outf) ) {
fprintf(stderr, "Error: closing file %s.\n", argv[1]);
}
return EXIT_SUCCESS;
}
// samples provided by this function are in 0..10: they need to be divided by
// 10 after.
int fm_mpx_get_samples(float *mpx_buffer, struct rds_content_struct* rds_params, struct rds_signal_info* rds_signal, struct fm_mpx_struct * fm_mpx_status) {
get_rds_samples(mpx_buffer, fm_mpx_status->length, rds_params, rds_signal);
if(fm_mpx_status->inf == NULL) return 0; // if there is no audio, stop here
int i;
for(i=0; i<fm_mpx_status->length; i++) {
if(fm_mpx_status->audio_pos >= fm_mpx_status->downsample_factor) {
fm_mpx_status->audio_pos -= fm_mpx_status->downsample_factor;
if(fm_mpx_status->audio_len == 0) {
int j;
for(j=0; j<2; j++) { // one retry
fm_mpx_status->audio_len = sf_read_float(fm_mpx_status->inf, fm_mpx_status->audio_buffer, fm_mpx_status->length);
if (fm_mpx_status->audio_len < 0) {
fprintf(stderr, "Error reading audio\n");
return -1;
}
if(fm_mpx_status->audio_len == 0) {
if( sf_seek(fm_mpx_status->inf, 0, SEEK_SET) < 0 ) {
fprintf(stderr, "Could not rewind in audio file, terminating\n");
return -1;
}
} else {
break;
}
}
fm_mpx_status->audio_index = 0;
} else {
fm_mpx_status->audio_index += fm_mpx_status->channels;
fm_mpx_status->audio_len -= fm_mpx_status->channels;
}
}
// First store the current sample(s) into the FIR filter's ring buffer
if(fm_mpx_status->channels == 0) {
fm_mpx_status->fir_buffer_mono[fm_mpx_status->fir_index] = fm_mpx_status->audio_buffer[fm_mpx_status->audio_index];
} else {
// In stereo operation, generate sum and difference signals
fm_mpx_status->fir_buffer_mono[fm_mpx_status->fir_index] =
fm_mpx_status->audio_buffer[fm_mpx_status->audio_index] + fm_mpx_status->audio_buffer[fm_mpx_status->audio_index + 1];
fm_mpx_status->fir_buffer_stereo[fm_mpx_status->fir_index] =
fm_mpx_status->audio_buffer[fm_mpx_status->audio_index] - fm_mpx_status->audio_buffer[fm_mpx_status->audio_index + 1];
}
fm_mpx_status->fir_index++;
if(fm_mpx_status->fir_index >= FIR_SIZE) fm_mpx_status->fir_index = 0;
// Now apply the FIR low-pass filter
/* As the FIR filter is symmetric, we do not multiply all
the coefficients independently, but two-by-two, thus reducing
the total number of multiplications by a factor of two
*/
float out_mono = 0;
float out_stereo = 0;
int ifbi = fm_mpx_status->fir_index; // ifbi = increasing FIR Buffer Index
int dfbi = fm_mpx_status->fir_index; // dfbi = decreasing FIR Buffer Index
int fi;
for(fi=0; fi<FIR_HALF_SIZE; fi++) { // fi = Filter Index
dfbi--;
if(dfbi < 0) dfbi = FIR_SIZE-1;
out_mono +=
fm_mpx_status->low_pass_fir[fi] *
(fm_mpx_status->fir_buffer_mono[ifbi] + fm_mpx_status->fir_buffer_mono[dfbi]);
if(fm_mpx_status->channels > 1) {
out_stereo +=
fm_mpx_status->low_pass_fir[fi] *
(fm_mpx_status->fir_buffer_stereo[ifbi] + fm_mpx_status->fir_buffer_stereo[dfbi]);
}
ifbi++;
if(ifbi >= FIR_SIZE) ifbi = 0;
}
// End of FIR filter
mpx_buffer[i] =
mpx_buffer[i] + // RDS data samples are currently in mpx_buffer
4.05*out_mono; // Unmodulated monophonic (or stereo-sum) signal
// XXX: YLB Added the stereo pilot tone to all signals mono or stereo.
mpx_buffer[i] += .9*carrier_19[fm_mpx_status->phase_19]; // Stereo pilot tone
fm_mpx_status->phase_19++;
if(fm_mpx_status->phase_19 >= 12) fm_mpx_status->phase_19 = 0;
if(fm_mpx_status->channels>1) {
mpx_buffer[i] += 4.05 * carrier_38[fm_mpx_status->phase_38] * out_stereo; // Stereo difference signal
fm_mpx_status->phase_38++;
if(fm_mpx_status->phase_38 >= 6) fm_mpx_status->phase_38 = 0;
}
fm_mpx_status->audio_pos++;
}
return 0;
}