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Update iir.c

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This commit is contained in:
Kuba
2025-08-08 22:20:29 +02:00
committed by GitHub
parent 9602d26966
commit 3a8a96bf13
1 changed files with 3 additions and 8 deletions
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11
filter/iir.c
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@@ -15,19 +15,14 @@ inline float apply_preemphasis(ResistorCapacitor *filter, float sample) {
return out; return out;
} }
void tilt_init(TiltCorrectionFilter* filter, float cutoff_freq, float sample_rate) { void tilt_init(TiltCorrectionFilter* filter, float alpha) {
// High-pass filter: H(z) = (1 - z^-1) / (1 - α*z^-1) filter->alpha = alpha; // 0.95 to 0.99 typically
float dt = 1.0f / sample_rate;
float tau = 1.0f / (2.0f * M_PI * cutoff_freq);
float alpha = tau / (tau + dt);
filter->alpha = alpha;
filter->x_prev = 0.0f; filter->x_prev = 0.0f;
filter->y_prev = 0.0f; filter->y_prev = 0.0f;
} }
float tilt(TiltCorrectionFilter* filter, float input) { float tilt(TiltCorrectionFilter* filter, float input) {
// High-pass filter: y[n] = α*y[n-1] + (x[n] - x[n-1]) // High-pass: y[n] = α*y[n-1] + (x[n] - x[n-1])
float output = filter->alpha * filter->y_prev + (input - filter->x_prev); float output = filter->alpha * filter->y_prev + (input - filter->x_prev);
filter->x_prev = input; filter->x_prev = input;