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the good old simple compressor

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KubaPro010
2025-03-02 10:19:26 +01:00
parent 7761b7ee03
commit 42998e668c
3 changed files with 26 additions and 164 deletions
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153
lib/filters.c
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@@ -121,144 +121,31 @@ float voltage_to_power_db(float linear) {
return 10.0f * log10f(fmaxf(linear, 1e-10f)); // Avoid log(0)
}
static float compute_gain_reduction(float input_db, float threshold, float ratio, float knee) {
float gain_reduction = 0.0f;
if (knee > 0.0f && input_db > (threshold - knee / 2.0f) && input_db < (threshold + knee / 2.0f)) {
float knee_range = input_db - (threshold - knee / 2.0f);
float knee_factor = knee_range * knee_range / (2.0f * knee);
gain_reduction = (ratio - 1.0f) * knee_factor / ratio;
} else if (input_db > threshold) {
gain_reduction = (threshold - input_db) * (1.0f - 1.0f / ratio);
}
return gain_reduction;
}
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;
void init_compressor(Compressor *compressor, float attack, float release) {
compressor->attack = attack;
compressor->release = release;
compressor->sample_rate = sample_rate;
compressor->gainReduction = 0.0f;
compressor->rmsEnv = 0.0f;
compressor->rmsTime = rmsTime;
compressor->max = 0.0f;
}
float peak_compress(Compressor *compressor, float sample) {
float input_level_db = voltage_to_voltage_db(fabsf(sample));
float desired_gain_reduction = compute_gain_reduction(input_level_db,
compressor->threshold,
compressor->ratio,
compressor->knee);
float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack));
float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release));
float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef;
compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction);
float gain = voltage_db_to_voltage(compressor->gainReduction + compressor->makeup_gain);
return sample * gain;
float sample_abs = fabsf(sample);
if(sample_abs > compressor->max) {
compressor->max += (sample_abs - compressor->max) / * compressor->attack;
} else {
compressor->max *= compressor->release;
}
return sample/(compressor->max+0.01);
}
float rms_compress(Compressor *compressor, float sample) {
float rms_coef = expf(-1.0f / (compressor->sample_rate * compressor->rmsTime));
float squared_input = sample * sample;
compressor->rmsEnv = squared_input + rms_coef * (compressor->rmsEnv - squared_input);
float input_level_db = voltage_to_voltage_db(sqrtf(fmaxf(compressor->rmsEnv, 1e-9f)));
float desired_gain_reduction = compute_gain_reduction(input_level_db,
compressor->threshold,
compressor->ratio,
compressor->knee);
float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack));
float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release));
float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef;
compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction);
float gain = voltage_db_to_voltage(compressor->gainReduction + compressor->makeup_gain);
return sample * gain;
float peak_compress_stereo(Compressor *compressor, float l, float r, float *output_r) {
float l_abs = fabsf(l);
float r_abs = fabsf(r);
float max = (l_abs > r_abs) ? l_abs : r_abs;
if(max > compressor->max) {
compressor->max += (max - compressor->max) / compressor->attack;
} else {
compressor->max *= compressor->release;
}
*output_r = r/(compressor->max+0.01);
return l/(compressor->max+0.01);
}
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 peak_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) {
float max_level = fmaxf(fabsf(l), fabsf(r));
float input_level_db = voltage_to_voltage_db(max_level);
float desired_gain_reduction = compute_gain_reduction(input_level_db,
compressor->threshold,
compressor->ratio,
compressor->knee);
float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack));
float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release));
float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef;
compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction);
float gain = voltage_db_to_voltage(compressor->gainReduction + compressor->makeup_gain);
*output_r = r * gain;
return l * gain;
}
float rms_compress_stereo(StereoCompressor *compressor, float l, float r, float *output_r) {
float rms_coef = expf(-1.0f / (compressor->sample_rate * compressor->rmsTime));
float squared_input1 = l * l;
float squared_input2 = r * r;
compressor->rmsEnv = squared_input1 + rms_coef * (compressor->rmsEnv - squared_input1);
compressor->rmsEnv2 = squared_input2 + rms_coef * (compressor->rmsEnv2 - squared_input2);
float max_rms = fmaxf(compressor->rmsEnv, compressor->rmsEnv2);
float input_level_db = voltage_to_voltage_db(sqrtf(fmaxf(max_rms, 1e-9f)));
float desired_gain_reduction = compute_gain_reduction(input_level_db,
compressor->threshold,
compressor->ratio,
compressor->knee);
float attack_coef = expf(-1.0f / (compressor->sample_rate * compressor->attack));
float release_coef = expf(-1.0f / (compressor->sample_rate * compressor->release));
float coef = (fabsf(desired_gain_reduction) > fabsf(compressor->gainReduction)) ? attack_coef : release_coef;
compressor->gainReduction = desired_gain_reduction + coef * (compressor->gainReduction - desired_gain_reduction);
float gain = voltage_db_to_voltage(compressor->gainReduction + compressor->makeup_gain);
*output_r = r * gain;
return l * gain;
}

30
lib/filters.h
View File

@@ -32,34 +32,10 @@ float voltage_to_voltage_db(float linear);
float voltage_to_power_db(float linear);
typedef struct {
float threshold;
float ratio;
float knee;
float makeup_gain;
float attack;
float release;
float sample_rate;
float gainReduction;
float rmsEnv;
float rmsTime;
float max;
} Compressor;
void init_compressor(Compressor *compressor, float threshold, float ratio, float knee, float makeup_gain, float attack, float release, float rmsTime, float sample_rate);
void init_compressor(Compressor *compressor, float attack, float release);
float peak_compress(Compressor *compressor, float sample);
float rms_compress(Compressor *compressor, float sample);
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);
float peak_compress_stereo(Compressor *compressor, float l, float r, float *output_r);

7
src/fm95.c
View File

@@ -375,9 +375,8 @@ int main(int argc, char **argv) {
init_lpf(&lpf_l, LPF_CUTOFF, 1.25f, SAMPLE_RATE);
init_lpf(&lpf_r, LPF_CUTOFF, 1.25f, SAMPLE_RATE);
StereoCompressor comp;
// THRESH RATIO KNE MAKE ATT REL RMS
init_compressor_stereo(&comp, -24.0f, 4.0f, 2.0f, 24.0f, 0.025f, 0.4f, 0.04f, SAMPLE_RATE);
Compressor comp;
init_compressor(&comp, 0.9995f, 0.8f);
// #endregion
signal(SIGINT, stop);
@@ -419,7 +418,7 @@ int main(int argc, char **argv) {
float current_sca_in = sca_in[i];
float ready_r;
float ready_l = rms_compress_stereo(&comp, l_in, r_in, &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)*4;