radio95/fm95
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Code Issues Activity

man github.dev is better than that, but tilt doesn't work

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This commit is contained in:
Kuba
2025-08-08 23:04:51 +02:00
committed by GitHub
parent 1ec3ee9466
commit 883d2f86dc
2 changed files with 14 additions and 13 deletions
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22
filter/iir.c
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@@ -15,22 +15,22 @@ inline float apply_preemphasis(ResistorCapacitor *filter, float sample) {
return out;
}
void tilt_init(TiltCorrectionFilter* filter, float alpha) {
// Allow correction_strength > 1.0 for aggressive correction
filter->alpha = 0.9999f; // Fixed time constant for DC tracking
filter->gain = alpha; // Separate gain parameter
filter->dc_estimate = 0.0f;
void tilt_init(TiltCorrectionFilter* filter, float correction_strength) {
filter->alpha = 0.9999f;
filter->gain = correction_strength; // Can be > 1.0
filter->x_prev = 0.0f;
filter->y_prev = 0.0f;
}
float tilt(TiltCorrectionFilter* filter, float input) {
// Track the baseline/DC level
filter->dc_estimate = filter->alpha * filter->dc_estimate + (1.0f - filter->alpha) * input;
// High-pass filter
float hp_out = filter->alpha * (filter->y_prev + input - filter->x_prev);
// Calculate the deviation from baseline
float deviation = input - filter->dc_estimate;
// Apply gain and add back to original
float output = input + filter->gain * hp_out;
// Apply correction gain and add back to baseline
float output = filter->dc_estimate + deviation * filter->gain;
filter->x_prev = input;
filter->y_prev = hp_out;
return output;
}

3
filter/iir.h
View File

@@ -15,7 +15,8 @@ float apply_preemphasis(ResistorCapacitor *filter, float sample);
typedef struct {
float alpha;
float dc_estimate;
float x_prev;
float y_prev;
float gain;
} TiltCorrectionFilter;