radio95/fm95
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use real parts, and add a mpx lpf for audio

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KubaPro010
2025-05-01 11:40:45 +02:00
parent 685ce7635f
commit f0245bcc26
2 changed files with 15 additions and 14 deletions
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6
README.md
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@@ -11,7 +11,7 @@ FM95 is a audio processor for FM, it does:
Supports these inputs:
- Audio (via Pulse)
- MPX (via Pulse, basically passthrough, i don't recommend this unless you have something else than rds or sca to modulate)
- MPX (via Pulse, basically passthrough, i don't recommend this unless you have something else than rds or sca to modulate, you could run chimer95 via here)
- RDS (via Pulse, expects unmodulated RDS, stereo, left channel on 57 KHz, right on 66.5, rds95 is recommended here, in modulation this is inphase to the pilot)
- SCA (via Pulse, by default on 67 khz with a 7 khz deviation)
@@ -21,7 +21,7 @@ and one output:
## How to compile?
To compile you need `cmake` and `libpulse-dev`, if you have those then do these commands:
To compile you need `cmake`, `liquid-dsp` and `libpulse-dev`, if you have those then do these commands:
```bash
mkdir build
@@ -34,7 +34,7 @@ Done!
## CPU Usage?
Should run completly fine on a pi 5, fine on a pi 3b (30% cpu)
Should run completly fine on a pi 5, fine on a pi 3b (30% cpu, 45% with lpf)
## Other Apps

23
src/fm95.c
View File

@@ -360,9 +360,11 @@ int main(int argc, char **argv) {
FMModulator sca_mod;
init_fm_modulator(&sca_mod, sca_frequency, sca_deviation, sample_rate);
iirfilt_crcf lpf_l, lpf_r;
lpf_l = iirfilt_crcf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_LOWPASS, LIQUID_IIRDES_SOS, LPF_ORDER, (15000.0f/sample_rate), 0.0f, 1.0f, 40.0f);
lpf_r = iirfilt_crcf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_LOWPASS, LIQUID_IIRDES_SOS, LPF_ORDER, (15000.0f/sample_rate), 0.0f, 1.0f, 40.0f);
iirfilt_rrrf lpf_l, lpf_r;
lpf_l = iirfilt_rrrf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_LOWPASS, LIQUID_IIRDES_SOS, LPF_ORDER, (15000.0f/sample_rate), 0.0f, 1.0f, 40.0f);
lpf_r = iirfilt_rrrf_create_prototype(LIQUID_IIRDES_CHEBY2, LIQUID_IIRDES_LOWPASS, LIQUID_IIRDES_SOS, LPF_ORDER, (15000.0f/sample_rate), 0.0f, 1.0f, 40.0f);
iirfilt_rrrf mpx_lpf = iirfilt_rrrf_create_prototype(LIQUID_IIRDES_BUTTER, LIQUID_IIRDES_LOWPASS, LIQUID_IIRDES_SOS, 2, (polar_stereo ? (46250/sample_rate) : (53000/sample_rate)), 0.0f, 1.0f, 1.0f);
ResistorCapacitor preemp_l, preemp_r;
init_preemphasis(&preemp_l, preemphasis_tau, sample_rate);
@@ -439,12 +441,8 @@ int main(int argc, char **argv) {
float ready_l = apply_preemphasis(&preemp_l, l_in);
float ready_r = apply_preemphasis(&preemp_r, r_in);
complex float temp_l = ready_l + ready_l * I;
iirfilt_crcf_execute(lpf_l, temp_l, &temp_l);
ready_l = creal(temp_l);
complex float temp_r = ready_r + ready_r * I;
iirfilt_crcf_execute(lpf_r, temp_r, &temp_r);
ready_r = creal(temp_r);
iirfilt_rrrf_execute(lpf_l, ready_l, &ready_l);
iirfilt_rrrf_execute(lpf_r, ready_r, &ready_r);
ready_l = process_agc_stereo(&agc, ready_l, ready_r, &ready_r);
ready_l = hard_clip(ready_l*audio_volume, clipper_threshold);
@@ -488,6 +486,8 @@ int main(int argc, char **argv) {
audio = hard_clip(audio, 1.0f-mpx); // Prevent clipping, via clipping the audio signal with relation to the mpx signal
iirfilt_rrrf_execute(mpx_lpf, audio, &audio);
output[i] = (audio+mpx)*master_volume;
if(rds_on || stereo) advance_oscillator(&osc);
}
@@ -499,8 +499,9 @@ int main(int argc, char **argv) {
}
}
printf("Cleaning up...\n");
iirfilt_crcf_destroy(lpf_l);
iirfilt_crcf_destroy(lpf_r);
iirfilt_rrrf_destroy(lpf_l);
iirfilt_rrrf_destroy(lpf_r);
iirfilt_rrrf_destroy(mpx_lpf);
free_PulseInputDevice(&input_device);
if(mpx_on) free_PulseInputDevice(&mpx_device);
if(rds_on) free_PulseInputDevice(&rds_device);