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Code Issues Activity

remove lpf and add normalization to the preemp

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This commit is contained in:
kuba
2025-03-26 19:26:40 +01:00
parent 6a83a18cf4
commit 2e36f34b4a
5 changed files with 9 additions and 30 deletions
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lib/filters.c
+3 -14
View File
@@ -2,26 +2,15 @@
void init_preemphasis(ResistorCapacitor *filter, float tau, float sample_rate) {
filter->prev_sample = 0.0f;
filter->alpha = exp(-1 / (tau*sample_rate));
filter->alpha = expf(-1 / (tau*sample_rate));
filter->gain = 1.0f / (1.0f - filter->alpha);
}
float apply_preemphasis(ResistorCapacitor *filter, float sample) {
float out = sample-filter->alpha*filter->prev_sample;
float out = (sample - filter->alpha * filter->prev_sample) * filter->gain;
filter->prev_sample = sample;
return out;
}
float hard_clip(float sample, float threshold) {
return fmaxf(-threshold, fminf(threshold, sample));
}
void init_rc_lpf(ResistorCapacitor *filter, float cutoff, float sample_rate) {
filter->prev_sample = 0.0f;
float dt = 1.0f/sample_rate;
float rc = 1.0f/(cutoff*M_2PI);
filter->alpha = dt/(rc+dt);
}
float apply_rc_lpf(ResistorCapacitor *filter, float sample) {
float out = filter->prev_sample+(filter->alpha*(sample-filter->prev_sample));
filter->prev_sample = sample;
return out;
}
lib/filters.h
+2 -6
View File
@@ -5,18 +5,14 @@
#include "constants.h"
#include "oscillator.h"
#define FILTER_LEN 51
typedef struct
{
float alpha;
float prev_sample;
float gain;
} ResistorCapacitor;
void init_preemphasis(ResistorCapacitor *filter, float tau, float sample_rate);
float apply_preemphasis(ResistorCapacitor *filter, float sample);
float hard_clip(float sample, float threshold);
void init_rc_lpf(ResistorCapacitor *filter, float cutoff, float sample_rate);
float apply_rc_lpf(ResistorCapacitor *filter, float sample);
float hard_clip(float sample, float threshold);