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Appli/Core/Inc/fx_equalizer.h

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+#ifndef FX_EQUALIZER_H
+#define FX_EQUALIZER_H
+
+#include <stdbool.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define FX_EQ_NUM_BANDS 10U
+
+typedef struct
+{
+    float freq_hz;   /* frequence centrale de la bande */
+    float gain_db;   /* -24.0 a +24.0 dB */
+    float q;         /* facteur de qualite, typiquement 0.5 a 5.0 */
+} FxEqBand;
+
+typedef struct
+{
+    bool     enabled;
+    FxEqBand bands[FX_EQ_NUM_BANDS];
+} FxEqualizerParams;
+
+typedef struct
+{
+    /* coefficients biquad mis en cache, recalcules seulement si les parametres changent */
+    float b0, b1, b2, a1, a2;
+    /* dernieres valeurs de parametres utilisees pour calculer les coefficients ci-dessus */
+    float last_freq_hz;
+    float last_gain_db;
+    float last_q;
+} FxEqBandState;
+
+typedef struct
+{
+    FxEqBandState band_state[FX_EQ_NUM_BANDS];
+    /* etat du filtre (direct form 1), par bande */
+    float x1[FX_EQ_NUM_BANDS];
+    float x2[FX_EQ_NUM_BANDS];
+    float y1[FX_EQ_NUM_BANDS];
+    float y2[FX_EQ_NUM_BANDS];
+} FxEqualizerState;
+
+void  FxEqualizer_Init(FxEqualizerState *state, FxEqualizerParams *params);
+float FxEqualizer_Process(FxEqualizerState *state, const FxEqualizerParams *params, float input);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* FX_EQUALIZER_H */