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16 lines
577 B
C
16 lines
577 B
C
#include "iir.h"
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void init_preemphasis(ResistorCapacitor *filter, float tau, float sample_rate, float ref_freq) {
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float dt = 1.0f / sample_rate;
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filter->alpha = tau / (tau + dt);
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float omega = M_2PI * ref_freq / sample_rate;
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filter->gain = 1.0f / sqrtf(1.0f + filter->alpha * filter->alpha - 2.0f * filter->alpha * cosf(omega));
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filter->prev_sample = 0.0f;
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}
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inline float apply_preemphasis(ResistorCapacitor *filter, float sample) {
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float out = (sample - filter->alpha * filter->prev_sample) * filter->gain;
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filter->prev_sample = sample;
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return out;
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} |