ajout effets audio

Appli/Core/Src/fx_overdrive.c

@@ -0,0 +1,39 @@
+#include "fx_overdrive.h"
+#include <math.h>
+
+void FxOverdrive_Init(FxOverdriveState *state, FxOverdriveParams *params)
+{
+    state->tone_lp_state = 0.0f;
+
+    params->enabled = false;
+    params->drive   = 0.4f;
+    params->tone    = 0.6f;
+    params->level   = 0.7f;
+}
+
+float FxOverdrive_Process(FxOverdriveState *state, const FxOverdriveParams *params, float input)
+{
+    if (!params->enabled)
+    {
+        return input;
+    }
+
+    float driven = input * (1.0f + params->drive * 20.0f);
+
+    /* Ecretage asymetrique (exponentiel) : plus caracteristique/agressif qu'un tanh symetrique. */
+    float shaped;
+    if (driven >= 0.0f)
+    {
+        shaped = 1.0f - expf(-driven);
+    }
+    else
+    {
+        shaped = -1.0f + expf(driven);
+    }
+
+    /* Filtre passe-bas une pole pour la tonalite : coefficient = tone (0..1). */
+    float coeff = 0.05f + params->tone * 0.9f;
+    state->tone_lp_state += coeff * (shaped - state->tone_lp_state);
+
+    return state->tone_lp_state * params->level;
+}