Ajout octaver

Appli/Core/Src/fx_octaver.c

@@ -0,0 +1,141 @@
+#include "fx_octaver.h"
+#include <math.h>
+
+#define FX_OCTAVER_BUFFER_MASK    (FX_OCTAVER_BUFFER_SIZE - 1U)
+#define FX_OCTAVER_ENV_TABLE_SIZE 256U
+
+/* Rapport de vitesse de lecture pour chaque voix : lire le buffer plus vite que
+ * l'ecriture multiplie la frequence (octave au-dessus), plus lentement la divise
+ * (octave en-dessous). */
+static const float fx_octaver_ratios[FX_OCTAVER_NUM_VOICES] =
+{
+    0.25f, /* -2 octaves */
+    0.5f,  /* -1 octave  */
+    2.0f,  /* +1 octave  */
+    4.0f   /* +2 octaves */
+};
+
+/* Fenetre de Hann tabulee (evite un cosf() par grain et par echantillon). */
+static float fx_octaver_env_table[FX_OCTAVER_ENV_TABLE_SIZE + 1U];
+static bool  fx_octaver_env_table_ready = false;
+
+static void FxOctaver_BuildEnvTable(void)
+{
+    if (fx_octaver_env_table_ready)
+    {
+        return;
+    }
+    for (uint32_t i = 0; i <= FX_OCTAVER_ENV_TABLE_SIZE; i++)
+    {
+        float phase = (float)i / (float)FX_OCTAVER_ENV_TABLE_SIZE;
+        fx_octaver_env_table[i] = 0.5f - 0.5f * cosf(2.0f * (float)M_PI * phase);
+    }
+    fx_octaver_env_table_ready = true;
+}
+
+static inline float FxOctaver_EnvLookup(float phase)
+{
+    float pos = phase * (float)FX_OCTAVER_ENV_TABLE_SIZE;
+    uint32_t i0 = (uint32_t)pos;
+    if (i0 >= FX_OCTAVER_ENV_TABLE_SIZE)
+    {
+        i0 = FX_OCTAVER_ENV_TABLE_SIZE - 1U;
+    }
+    float frac = pos - (float)i0;
+    return fx_octaver_env_table[i0] * (1.0f - frac) + fx_octaver_env_table[i0 + 1U] * frac;
+}
+
+static inline float FxOctaver_ReadInterpolated(const float *buffer, uint32_t write_idx, float delay)
+{
+    float read_pos = (float)write_idx - delay;
+    while (read_pos < 0.0f)
+    {
+        read_pos += (float)FX_OCTAVER_BUFFER_SIZE;
+    }
+    uint32_t i0 = (uint32_t)read_pos & FX_OCTAVER_BUFFER_MASK;
+    uint32_t i1 = (i0 + 1U) & FX_OCTAVER_BUFFER_MASK;
+    float frac = read_pos - (float)(uint32_t)read_pos;
+    return buffer[i0] * (1.0f - frac) + buffer[i1] * frac;
+}
+
+/* Lecteur de grains a deux pointeurs en fondu croise : chaque pointeur avance
+ * (ou recule) dans le buffer a une vitesse "ratio" differente de celle de
+ * l'ecriture, ce qui change la hauteur percue. Les deux grains sont toujours
+ * en opposition de phase exacte (decales d'un demi-grain a l'origine, et le
+ * meme increment est applique aux deux avant chaque repli) : la fenetre de
+ * Hann du second grain vaut donc toujours 1 moins celle du premier, ce qui
+ * garantit un niveau de sortie constant pendant le fondu et evite un second
+ * calcul de fenetre. */
+static float FxOctaver_ProcessVoice(FxOctaverVoiceState *vs, const float *buffer, uint32_t write_idx, float ratio)
+{
+    float step = 1.0f - ratio;
+
+    for (uint32_t g = 0; g < 2U; g++)
+    {
+        vs->delay[g] += step;
+        if (vs->delay[g] >= (float)FX_OCTAVER_GRAIN_SIZE)
+        {
+            vs->delay[g] -= (float)FX_OCTAVER_GRAIN_SIZE;
+        }
+        else if (vs->delay[g] < 0.0f)
+        {
+            vs->delay[g] += (float)FX_OCTAVER_GRAIN_SIZE;
+        }
+    }
+
+    float phase0 = vs->delay[0] / (float)FX_OCTAVER_GRAIN_SIZE;
+    float env0 = FxOctaver_EnvLookup(phase0);
+    float env1 = 1.0f - env0;
+
+    float sample0 = FxOctaver_ReadInterpolated(buffer, write_idx, vs->delay[0]);
+    float sample1 = FxOctaver_ReadInterpolated(buffer, write_idx, vs->delay[1]);
+
+    return env0 * sample0 + env1 * sample1;
+}
+
+void FxOctaver_Init(FxOctaverState *state, FxOctaverParams *params)
+{
+    params->enabled     = false;
+    params->level_down2 = 0.0f;
+    params->level_down1 = 0.0f;
+    params->level_dry   = 1.0f;
+    params->level_up1   = 0.0f;
+    params->level_up2   = 0.0f;
+
+    for (uint32_t i = 0; i < FX_OCTAVER_BUFFER_SIZE; i++)
+    {
+        state->buffer[i] = 0.0f;
+    }
+    state->write_idx = 0U;
+
+    for (uint32_t v = 0; v < FX_OCTAVER_NUM_VOICES; v++)
+    {
+        state->voices[v].delay[0] = 0.0f;
+        state->voices[v].delay[1] = (float)FX_OCTAVER_GRAIN_SIZE * 0.5f;
+    }
+
+    FxOctaver_BuildEnvTable();
+}
+
+float FxOctaver_Process(FxOctaverState *state, const FxOctaverParams *params, float input)
+{
+    if (!params->enabled)
+    {
+        return input;
+    }
+
+    state->buffer[state->write_idx & FX_OCTAVER_BUFFER_MASK] = input;
+
+    float down2 = FxOctaver_ProcessVoice(&state->voices[0], state->buffer, state->write_idx, fx_octaver_ratios[0]);
+    float down1 = FxOctaver_ProcessVoice(&state->voices[1], state->buffer, state->write_idx, fx_octaver_ratios[1]);
+    float up1   = FxOctaver_ProcessVoice(&state->voices[2], state->buffer, state->write_idx, fx_octaver_ratios[2]);
+    float up2   = FxOctaver_ProcessVoice(&state->voices[3], state->buffer, state->write_idx, fx_octaver_ratios[3]);
+
+    state->write_idx++;
+
+    return input * params->level_dry
+         + down2 * params->level_down2
+         + down1 * params->level_down1
+         + up1   * params->level_up1
+         + up2   * params->level_up2;
+}