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Code Issues Activity

turn lpf and emphasis into a common rc

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This commit is contained in:
KubaPro010
2025-01-21 14:32:50 +01:00
parent 1fef2f7598
commit 3ac9d67e3d
12 changed files with 40 additions and 45 deletions
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2
.vscode/.server-controller-port.log vendored
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@@ -1,5 +1,5 @@
{
"port": 13452,
"time": 1735989625302,
"time": 1737462229390,
"version": "0.0.3"
}

4
.vscode/settings.json vendored
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@@ -9,6 +9,8 @@
"stdlib.h": "c",
"error.h": "c",
"math.h": "c",
"options.h": "c"
"options.h": "c",
"random": "c",
"__locale": "c"
}
}

24
lib/filters.c
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@@ -1,25 +1,23 @@
#include "filters.h"
void init_emphasis(Emphasis *pe, float tau, float sample_rate) {
pe->prev_sample = 0.0f;
pe->alpha = exp(-1 / (tau * sample_rate));
void init_rc(ResistorCapacitor *rc, float tau, float sample_rate) {
rc->prev_sample = 0.0f;
rc->alpha = exp(-1 / (tau * sample_rate));
}
float apply_pre_emphasis(Emphasis *pe, float sample) {
float audio = sample-pe->alpha*pe->prev_sample;
pe->prev_sample = audio;
float apply_pre_emphasis(ResistorCapacitor *rc, float sample) {
float audio = sample-rc->alpha*rc->prev_sample;
rc->prev_sample = audio;
return audio*2;
}
void init_low_pass_filter(LowPassFilter *lp, float cutoff_frequency, float sample_rate) {
float rc = 1/(M_2PI*cutoff_frequency);
lp->alpha = sample_rate/(sample_rate+rc);
lp->prev_sample = 0.0f;
void init_low_pass_filter(ResistorCapacitor *rc, float cutoff_frequency, float sample_rate) {
init_rc(&rc, (-1 / (sample_rate * log(sample_rate/(sample_rate+(1/(M_2PI*cutoff_frequency)))))), sample_rate);
}
float apply_low_pass_filter(LowPassFilter *lp, float sample) {
float output = lp->alpha*sample+(1-lp->alpha)*lp->prev_sample;
lp->prev_sample = output;
float apply_low_pass_filter(ResistorCapacitor *rc, float sample) {
float output = rc->alpha*sample+(1-rc->alpha)*rc->prev_sample;
rc->prev_sample = output;
return output;
}

15
lib/filters.h
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@@ -11,18 +11,13 @@
typedef struct {
float alpha;
float prev_sample;
} Emphasis;
} ResistorCapacitor;
void init_emphasis(Emphasis *pe, float tau, float sample_rate);
float apply_pre_emphasis(Emphasis *pe, float sample);
void init_rc(ResistorCapacitor *pe, float tau, float sample_rate);
float apply_pre_emphasis(ResistorCapacitor *pe, float sample);
typedef struct {
float alpha;
float prev_sample;
} LowPassFilter;
void init_low_pass_filter(LowPassFilter *lp, float cutoff_frequency, float sample_rate);
float apply_low_pass_filter(LowPassFilter *lp, float sample);
void init_low_pass_filter(ResistorCapacitor *lp, float cutoff_frequency, float sample_rate);
float apply_low_pass_filter(ResistorCapacitor *lp, float sample);
typedef struct {

6
src/crosby_stereo_coder.c
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@@ -122,9 +122,9 @@ int main() {
Oscillator osc;
init_oscillator(&osc, 50000.0, SAMPLE_RATE);
#ifdef PREEMPHASIS
Emphasis preemp_l, preemp_r;
init_emphasis(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_emphasis(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp_l, preemp_r;
init_rc(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_rc(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf_l, lpf_r;

4
src/mono_passthrough.c
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@@ -104,8 +104,8 @@ int main() {
}
#ifdef PREEMPHASIS
Emphasis preemp;
init_emphasis(&preemp, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp;
init_rc(&preemp, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf;

2
src/options.h
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@@ -1,4 +1,4 @@
// #define PREEMPHASIS
#define PREEMPHASIS
// #define LPF
#define buffer_maxlength 12288

6
src/polar_stereo_coder.c
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@@ -121,9 +121,9 @@ int main() {
Oscillator stereo_osc;
init_oscillator(&stereo_osc, 31250.0, SAMPLE_RATE);
#ifdef PREEMPHASIS
Emphasis preemp_l, preemp_r;
init_emphasis(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_emphasis(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp_l, preemp_r;
init_rc(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_rc(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf_l, lpf_r;

4
src/sca_mod.c
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@@ -112,8 +112,8 @@ int main() {
FMModulator mod;
init_fm_modulator(&mod, FREQUENCY, DEVIATION, SAMPLE_RATE);
#ifdef PREEMPHASIS
Emphasis preemp;
init_emphasis(&preemp, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp;
init_rc(&preemp, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf;

6
src/ssb_stereo_coder.c
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@@ -128,9 +128,9 @@ int main() {
DelayLine monoDelay;
init_delay_line(&monoDelay, 99);
#ifdef PREEMPHASIS
Emphasis preemp_l, preemp_r;
init_emphasis(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_emphasis(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp_l, preemp_r;
init_rc(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_rc(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf_l, lpf_r;

6
src/stereo_coder.c
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@@ -122,9 +122,9 @@ int main() {
Oscillator pilot_osc;
init_oscillator(&pilot_osc, 19000.0, SAMPLE_RATE); // Pilot, it's there to indicate stereo and as a refrence signal with the stereo carrier
#ifdef PREEMPHASIS
Emphasis preemp_l, preemp_r;
init_emphasis(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_emphasis(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp_l, preemp_r;
init_rc(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_rc(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf_l, lpf_r;

6
src/stereo_sca_mod.c
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@@ -124,9 +124,9 @@ int main() {
init_fm_modulator(&mod_mono, 67000, 6000, SAMPLE_RATE);
init_fm_modulator(&mod_stereo, 80000, 6000, SAMPLE_RATE);
#ifdef PREEMPHASIS
Emphasis preemp_l, preemp_r;
init_emphasis(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_emphasis(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
ResistorCapacitor preemp_l, preemp_r;
init_rc(&preemp_l, PREEMPHASIS_TAU, SAMPLE_RATE);
init_rc(&preemp_r, PREEMPHASIS_TAU, SAMPLE_RATE);
#endif
#ifdef LPF
LowPassFilter lpf_l, lpf_r;