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add compressor

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This commit is contained in:
KubaPro010
2025-03-01 21:00:56 +01:00
parent 8c9f6464b8
commit b513b98a9a
5 changed files with 278 additions and 15 deletions
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2
.vscode/.server-controller-port.log vendored
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@@ -1,5 +1,5 @@
{
"port": 13452,
"time": 1738344784291,
"time": 1740856477215,
"version": "0.0.3"
}

3
.vscode/settings.json vendored
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@@ -19,5 +19,6 @@
"stdint.h": "c",
"asoundlib.h": "c",
"hilbert.h": "c"
}
},
"C_Cpp.errorSquiggles": "disabled"
}

233
lib/filters.c
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@@ -77,4 +77,237 @@ float hard_clip(float sample, float threshold) {
} else {
return sample; // No clipping
}
}
float voltage_db_to_voltage(float db) {
return powf(10.0f, db / 20.0f);
}
float power_db_to_voltage(float db) {
return powf(10.0f, db / 10.0f);
}
float voltage_to_voltage_db(float linear) {
return 20.0f * log10f(fmaxf(linear, 1e-10f)); // Avoid log(0)
}
float voltage_to_power_db(float linear) {
return 10.0f * log10f(fmaxf(linear, 1e-10f)); // Avoid log(0)
}
void init_compressor(Compressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate) {
compressor->threshold = threshold;
compressor->ratio = ratio;
compressor->knee = knee;
compressor->makeup_gain = makeup_gain;
compressor->attack = attack;
compressor->release = release;
compressor->sample_rate = sample_rate;
compressor->gainReduction = 0.0f;
compressor->rmsEnv = 0.0f;
compressor->rmsTime = rmsTime;
}
float rms_compress(Compressor *compressor, float sample) {
float env;
float rmsAlpha = 1.0f - exp(-1.0f / (compressor->rmsTime * compressor->sample_rate));
compressor->rmsEnv = (1.0f - rmsAlpha) * compressor->rmsEnv + rmsAlpha * (sample * sample);
env = sqrtf(compressor->rmsEnv);
float input_db = voltage_to_voltage_db(env);
float targetGR = 0.0f;
if(input_db > compressor->threshold) {
if(compressor->knee > 0.0f) {
float delta = input_db - compressor->threshold;
if(delta < compressor->knee / 2.0f) {
targetGR = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee;
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * delta;
}
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * (input_db - compressor->threshold);
}
} else {
targetGR = 0.0f;
}
float coeff;
if(targetGR > compressor->gainReduction) {
coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate));
} else {
coeff = expf(-1.0f / (compressor->release * compressor->sample_rate));
}
compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * targetGR;
float gain = voltage_db_to_voltage(compressor->makeup_gain - compressor->gainReduction);
return sample * gain;
}
float peak_compress(Compressor *compressor, float sample) {
float env = fabsf(sample);
float input_db = voltage_to_voltage_db(env);
float targetGR = 0.0f;
if(input_db > compressor->threshold) {
if(compressor->knee > 0.0f) {
float delta = input_db - compressor->threshold;
if(delta < compressor->knee / 2.0f) {
targetGR = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee;
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * delta;
}
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * (input_db - compressor->threshold);
}
} else {
targetGR = 0.0f;
}
float coeff;
if(targetGR > compressor->gainReduction) {
coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate));
} else {
coeff = expf(-1.0f / (compressor->release * compressor->sample_rate));
}
compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * targetGR;
float gain = voltage_db_to_voltage(compressor->makeup_gain - compressor->gainReduction);
return sample * gain;
}
void init_compressor_stereo(StereoCompressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate) {
compressor->threshold = threshold;
compressor->ratio = ratio;
compressor->knee = knee;
compressor->makeup_gain = makeup_gain;
compressor->attack = attack;
compressor->release = release;
compressor->sample_rate = sample_rate;
compressor->gainReduction = 0.0f;
compressor->rmsEnv = 0.0f;
compressor->rmsEnv2 = 0.0f;
compressor->rmsTime = rmsTime;
}
float rms_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) {
float env_l;
float env_r;
float rmsAlpha = 1.0f - exp(-1.0f / (compressor->rmsTime * compressor->sample_rate));
compressor->rmsEnv = (1.0f - rmsAlpha) * compressor->rmsEnv + rmsAlpha * (l * l);
compressor->rmsEnv2 = (1.0f - rmsAlpha) * compressor->rmsEnv + rmsAlpha * (r * r);
env_l = sqrtf(compressor->rmsEnv);
env_r = sqrtf(compressor->rmsEnv2);
float input_db = voltage_to_voltage_db(env_l);
float input_db_r = voltage_to_voltage_db(env_r);
float targetGR = 0.0f;
if(input_db > compressor->threshold) {
if(compressor->knee > 0.0f) {
float delta = input_db - compressor->threshold;
if(delta < compressor->knee / 2.0f) {
targetGR = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee;
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * delta;
}
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * (input_db - compressor->threshold);
}
} else {
targetGR = 0.0f;
}
float targetGR_r = 0.0f;
if(input_db_r > compressor->threshold) {
if(compressor->knee > 0.0f) {
float delta = input_db_r - compressor->threshold;
if(delta < compressor->knee / 2.0f) {
targetGR_r = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee;
} else {
targetGR_r = (1.0f - 1.0f / compressor->ratio) * delta;
}
} else {
targetGR_r = (1.0f - 1.0f / compressor->ratio) * (input_db_r - compressor->threshold);
}
} else {
targetGR_r = 0.0f;
}
float shared_target_gr;
if(targetGR > targetGR_r) {
shared_target_gr = targetGR;
} else {
shared_target_gr = targetGR_r;
}
float coeff;
if(shared_target_gr > compressor->gainReduction) {
coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate));
} else {
coeff = expf(-1.0f / (compressor->release * compressor->sample_rate));
}
compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * shared_target_gr;
float gain = voltage_db_to_voltage(compressor->makeup_gain - compressor->gainReduction);
*output_r = r * gain;
return l * gain;
}
float peak_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) {
float env_l = fabsf(l);
float env_r = fabsf(r);
float input_db = voltage_to_voltage_db(env_l);
float input_db_r = voltage_to_voltage_db(env_r);
float targetGR = 0.0f;
if(input_db > compressor->threshold) {
if(compressor->knee > 0.0f) {
float delta = input_db - compressor->threshold;
if(delta < compressor->knee / 2.0f) {
targetGR = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee;
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * delta;
}
} else {
targetGR = (1.0f - 1.0f / compressor->ratio) * (input_db - compressor->threshold);
}
} else {
targetGR = 0.0f;
}
float targetGR_r = 0.0f;
if(input_db_r > compressor->threshold) {
if(compressor->knee > 0.0f) {
float delta = input_db_r - compressor->threshold;
if(delta < compressor->knee / 2.0f) {
targetGR_r = (1.0f - 1.0f / compressor->ratio) * (delta * delta) / compressor->knee;
} else {
targetGR_r = (1.0f - 1.0f / compressor->ratio) * delta;
}
} else {
targetGR_r = (1.0f - 1.0f / compressor->ratio) * (input_db_r - compressor->threshold);
}
} else {
targetGR_r = 0.0f;
}
float shared_target_gr;
if(targetGR > targetGR_r) {
shared_target_gr = targetGR;
} else {
shared_target_gr = targetGR_r;
}
float coeff;
if(shared_target_gr > compressor->gainReduction) {
coeff = expf(-1.0f / (compressor->attack * compressor->sample_rate));
} else {
coeff = expf(-1.0f / (compressor->release * compressor->sample_rate));
}
compressor->gainReduction = coeff * compressor->gainReduction + (1.0f - coeff) * shared_target_gr;
float gain = voltage_db_to_voltage(compressor->makeup_gain - compressor->gainReduction);
*output_r = r * gain;
return l * gain;
}

44
lib/filters.h
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@@ -25,16 +25,40 @@ void init_hpf(BiquadFilter* filter, float cutoffFreq, float qFactor, float sampl
float apply_frequency_filter(BiquadFilter* filter, float input);
float hard_clip(float sample, float threshold);
float voltage_db_to_voltage(float db);
float power_db_to_voltage(float db);
float voltage_to_voltage_db(float linear);
float voltage_to_power_db(float linear);
typedef struct {
float *buffer;
int write_idx; // Write position
int read_idx; // Read position
int size; // Total buffer size
int delay; // Delay in samples
} DelayLine;
float threshold;
float ratio;
float knee;
float makeup_gain;
float attack;
float release;
float sample_rate;
float gainReduction;
float rmsEnv;
float rmsTime;
} Compressor;
void init_compressor(Compressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate);
float peak_compress(Compressor *compressor, float sample);
float rms_compress(Compressor *compressor, float sample);
void init_delay_line(DelayLine *delay_line, int max_delay);
void set_delay_line(DelayLine *delay_line, int new_delay);
float delay_line(DelayLine *delay_line, float in);
void exit_delay_line(DelayLine *delay_line);
typedef struct {
float threshold;
float ratio;
float knee;
float makeup_gain;
float attack;
float release;
float sample_rate;
float gainReduction;
float rmsEnv;
float rmsEnv2;
float rmsTime;
} StereoCompressor;
void init_compressor_stereo(StereoCompressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate);
float peak_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r);
float rms_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r);

11
src/fm95.c
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@@ -34,7 +34,7 @@
#include <pulse/error.h>
#define MASTER_VOLUME 1.0f // Volume of everything combined, for calibration
#define AUDIO_VOLUME 2.0f // Audio volume, before clipper
#define AUDIO_VOLUME 1.0f // Audio volume, before clipper
#define MONO_VOLUME 0.45f // L+R Signal
#define PILOT_VOLUME 0.09f // 19 KHz Pilot
#define STEREO_VOLUME 0.45f // L-R signal, should be same as MONO
@@ -373,6 +373,9 @@ int main(int argc, char **argv) {
BiquadFilter lpf_l, lpf_r;
init_lpf(&lpf_l, LPF_CUTOFF, 1.25f, SAMPLE_RATE);
init_lpf(&lpf_r, LPF_CUTOFF, 1.25f, SAMPLE_RATE);
StereoCompressor comp;
init_compressor_stereo(&comp, -2.0f, 15.0f, 2.0f, 0.0f, 0.015f, 0.25f, 0.01f, SAMPLE_RATE);
// #endregion
signal(SIGINT, stop);
@@ -413,8 +416,10 @@ int main(int argc, char **argv) {
float current_mpx_in = mpx_in[i];
float current_sca_in = sca_in[i];
float ready_l = apply_frequency_filter(&lpf_l, l_in);
float ready_r = apply_frequency_filter(&lpf_r, r_in);
float ready_r;
float ready_l = peak_compress_stereo(&comp, l_in, r_in, &ready_r);
ready_l = apply_frequency_filter(&lpf_l, l_in);
ready_r = apply_frequency_filter(&lpf_r, r_in);
ready_l = apply_preemphasis(&preemp_l, ready_l)*2;
ready_r = apply_preemphasis(&preemp_r, ready_r)*2;
ready_l = hard_clip(ready_l*audio_volume, clipper_threshold);