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KubaPro010
2025-03-27 18:43:49 +01:00
parent 04b6935519
commit 34071c1967
2 changed files with 9 additions and 8 deletions
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15
lib/filters.c
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@@ -18,23 +18,24 @@ float hard_clip(float sample, float threshold) {
void init_lpf(FIR *filter, float cutoff, int sample_rate) { void init_lpf(FIR *filter, float cutoff, int sample_rate) {
float a = tanf(M_PI*cutoff/sample_rate); float a = tanf(M_PI*cutoff/sample_rate);
float a2 = a*a; float a2 = a*a;
float r; float r, e;
for(int i = 0; i < FIR_ORDER; i++) { for(int i = 0; i < FIR_ORDER; i++) {
r = sinf(M_PI*(2.0f*i+1.0f)/(4.0f*FIR_ORDER)); r = sinf(M_PI*(2.0f*i+1.0f)/(4.0f*FIR_ORDER));
sample_rate = a2+2.0f*a*r+1.0f; e = a2+2.0f*a*r+1.0f;
filter->A[i] = a2 / sample_rate; filter->A[i] = a2 / e;
filter->d1[i] = 2.0f*(1.0f-a2)/sample_rate; filter->d1[i] = 2.0f*(1.0f-a2)/e;
filter->d2[i] = -(a2 - 2.0f * a * r + 1.0f) / sample_rate; filter->d2[i] = -(a2 - 2.0f * a * r + 1.0f) / e;
} }
} }
float process_lpf(FIR *filter, float x) { float process_lpf(FIR *filter, float x) {
float output;
for(int i = 0; i < FIR_ORDER; i++) { for(int i = 0; i < FIR_ORDER; i++) {
filter->w0[i] = filter->d1[i]*filter->w1[i] + filter->d2[i]*filter->w2[i] + x; filter->w0[i] = filter->d1[i]*filter->w1[i] + filter->d2[i]*filter->w2[i] + x;
x = filter->A[i] * (filter->w0[i] + 2.0f * filter->w1[i] + filter->w2[i]); output = filter->A[i] * (filter->w0[i] + 2.0f * filter->w1[i] + filter->w2[i]);
filter->w2[i] = filter->w1[i]; filter->w2[i] = filter->w1[i];
filter->w1[i] = filter->w0[i]; filter->w1[i] = filter->w0[i];
} }
return x; return output;
} }

2
lib/filters.h
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@@ -5,7 +5,7 @@
#include "constants.h" #include "constants.h"
#include "oscillator.h" #include "oscillator.h"
#define FIR_ORDER 10 #define FIR_ORDER 21
typedef struct typedef struct
{ {