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Code Issues Activity

get rid of lpf as it barely works, swh-plugin's lowpass_iir_1891 works better

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KubaPro010
2025-03-09 09:35:10 +01:00
parent 2c18edc6a8
commit 0a99e3364c
4 changed files with 3 additions and 46 deletions
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21
lib/filters.c
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@@ -10,27 +10,6 @@ float apply_preemphasis(ResistorCapacitor *filter, float sample) {
return out;
}
void init_lpf(BiquadFilter* filter, float cutoffFreq, float qFactor, float sampleRate) {
float cutoffNorm = cutoffFreq / sampleRate;
float K = tanf(M_PI * cutoffNorm);
float norm = 1.0f/(1.0f+K/qFactor+K*K);
filter->a0 = K*K*norm;
filter->a1 = 2.0f*K*K*norm;
filter->a2 = K*K*norm;
filter->b1 = 2.0f*(K*K-1.0f)*norm;
filter->b2 = (1.0f-K/qFactor+K*K)*norm;
filter->z1 = 0.0f;
filter->z2 = 0.0f;
}
float apply_biquad(BiquadFilter* filter, float input) {
float out = input*filter->a0+filter->z1;
filter->z1 = input*filter->a1+filter->z2-filter->b1*out;
filter->z2 = input*filter->a2-filter->b2*out;
return out;
}
float hard_clip(float sample, float threshold) {
if (sample > threshold) {

9
lib/filters.h
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@@ -14,15 +14,6 @@ typedef struct
void init_preemphasis(ResistorCapacitor *filter, float tau, float sample_rate);
float apply_preemphasis(ResistorCapacitor *filter, float sample);
typedef struct {
// https://www.earlevel.com/main/2012/11/26/biquad-c-source-code/
float a0, a1, a2;
float b1, b2;
float z1, z2;
} BiquadFilter;
void init_lpf(BiquadFilter* filter, float cutoffFreq, float qFactor, float sampleRate);
float apply_biquad(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);