Next try for a Chorus (modulated delay).

Fixed distortion due to too high loudness (volume) inside mdaEPiano.

MicroMDAEPiano.ino

@@ -228,18 +228,22 @@ void setup()
   Serial.print(audio_block_time_us);
   Serial.println(F("ms)"));
 
-  if (!modchorus_r.begin(r_delayline, CHORUS_DELAY_LENGTH, NUM_CHORUS)) {
+  if (!modchorus_r.begin(r_delayline, CHORUS_DELAY_LENGTH)) {
     Serial.println(F("AudioModulatedEffectChorus - right channel begin failed"));
     while (1);
   }
-  if (!modchorus_l.begin(l_delayline, CHORUS_DELAY_LENGTH, NUM_CHORUS)) {
+  if (!modchorus_l.begin(l_delayline, CHORUS_DELAY_LENGTH)) {
     Serial.println(F("AudioModulatedEffectChorus - left channel begin failed"));
     while (1);
   }
 
+  // chorus modulation fixed
   mod_sine1.amplitude(1.0);
   mod_sine1.frequency(5.0);
   mod_sine1.phase(0);
+  // chorus level fixed
+  mixer_r.gain(2, 1.0);
+  mixer_l.gain(2, 1.0);
 
   AudioInterrupts();
 

config.h

@@ -61,7 +61,6 @@
 #define SAMPLE_RATE 44100
 #define REDUCE_LOUDNESS 0
 #define USE_XFADE_DATA 1
-#define NUM_CHORUS 2
 
 //*************************************************************************************************
 //* DEBUG OUTPUT SETTINGS
@@ -237,6 +236,10 @@
 #define ENC_CHORUS_DELAY_MAX 20
 #define ENC_CHORUS_DELAY_DEFAULT 15
 //
+#define ENC_CHORUS_INTENSITY_MIN 0
+#define ENC_CHORUS_INTENSITY_MAX 100
+#define ENC_CHORUS_INTENSITY_DEFAULT 50
+//
 #define ENC_CHORUS_LEVEL_MIN 0
 #define ENC_CHORUS_LEVEL_MAX 99
 #define ENC_CHORUS_LEVEL_DEFAULT 50
@@ -326,6 +329,7 @@ struct config_t {
   uint8_t reverb_level;
   uint8_t chorus_frequency;
   uint8_t chorus_delay;
+  uint8_t chorus_intensity;
   uint8_t chorus_level;
   uint8_t bass_lr_level;
   uint8_t bass_mono_level;

effect_modulated_chorus.cpp

@@ -22,6 +22,7 @@
 */
 
 #include <Arduino.h>
+#include "limits.h"
 #include "effect_modulated_chorus.h"
 
 /******************************************************************/
@@ -32,13 +33,11 @@
 // 140219 - correct storage class (not static)
 // 190527 - adding modulation input (by Holger Wirtz)
 
-boolean AudioModulatedEffectChorus::begin(short *delayline, int d_length, int n_chorus)
+boolean AudioModulatedEffectChorus::begin(short *delayline, int d_length)
 {
 #if 0
   Serial.print("AudioModulatedEffectChorus.begin(Chorus delay line length = ");
   Serial.print(d_length);
-  Serial.print(", n_chorus = ");
-  Serial.print(n_chorus);
   Serial.println(")");
 #endif
 
@@ -52,78 +51,102 @@ boolean AudioModulatedEffectChorus::begin(short *delayline, int d_length, int n_
   if (d_length < 10) {
     return (false);
   }
-  if (n_chorus < 1) {
-    return (false);
-  }
 
   l_delayline = delayline;
-  delay_length = d_length / 2;
-  num_chorus = n_chorus;
+  delay_length = d_length;
+  delay_length_half = d_length / 2;
 
   return (true);
 }
 
-void AudioModulatedEffectChorus::voices(int n_chorus)
-{
-  num_chorus = n_chorus;
-}
-
 //int last_idx = 0;
 void AudioModulatedEffectChorus::update(void)
 {
   audio_block_t *block;
   audio_block_t *modulation;
   short *bp;
-  int sum;
-  int c_idx;
-
-  if (l_delayline == NULL)return;
+  short *mp;
+  float mod_idx;
+  int x1;
+  int x2;
+  int y1;
+  int y2;
+
+  if (l_delayline == NULL)
+    return;
 
-  // do passthru
-  // It stores the unmodified data in the delay line so that
-  // it isn't as likely to click
-  if (num_chorus <= 1) {
-    // Just passthrough
+  /*
     block = receiveWritable(0);
-    if (block) {
+    if (block)
+    {
       bp = block->data;
-      for (int i = 0; i < AUDIO_BLOCK_SAMPLES; i++) {
+      uint32_t tmp = delay_length / (num_chorus - 1) - 1;
+      for (int i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
+      {
         l_circ_idx++;
-        if (l_circ_idx >= delay_length) {
+        if (l_circ_idx >= delay_length)
+        {
           l_circ_idx = 0;
         }
-        l_delayline[l_circ_idx] = *bp++;
+        l_delayline[l_circ_idx] = *bp;
+        sum = 0;
+        c_idx = l_circ_idx;
+        for (int k = 0; k < num_chorus; k++)
+        {
+          sum += l_delayline[c_idx];
+          if (num_chorus > 1)c_idx -= tmp;
+          if (c_idx < 0)
+          {
+            c_idx += delay_length;
+          }
+        }
+        bp++ = sum / num_chorus;
       }
+      // transmit the block
       transmit(block, 0);
       release(block);
     }
-    return;
-  }
-
-  //          L E F T  C H A N N E L
+  */
 
   block = receiveWritable(0);
   modulation = receiveReadOnly(1);
 
-  if (block) {
+  if (block && modulation)
+  {
     bp = block->data;
-    uint32_t tmp = delay_length / (num_chorus - 1) - 1;
-    for (int i = 0; i < AUDIO_BLOCK_SAMPLES; i++) {
-      l_circ_idx++;
-      if (l_circ_idx >= delay_length) {
+    mp = modulation->data;
+
+    for (int i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
+    {
+      if (l_circ_idx >= delay_length)
         l_circ_idx = 0;
+      l_delayline[l_circ_idx] = *bp; // write signal into circular buffer
+
+      mod_idx = float(*mp) / SHRT_MAX * delay_length_half + l_circ_idx; // calculate index with modulation as a float
+
+      if (mod_idx > delay_length)
+        mod_idx = mod_idx - delay_length;
+      else if (mod_idx < 0)
+        mod_idx = delay_length + mod_idx;
+
+      // linear interpolation
+      x1 = int(mod_idx);
+      y1 = *(block->data + x1);
+      if (x1 + 1 > delay_length)
+      {
+        x2 = 0;
+        y2 = *block->data;
       }
-      l_delayline[l_circ_idx] = *bp;
-      sum = 0;
-      c_idx = l_circ_idx;
-      for (int k = 0; k < num_chorus; k++) {
-        sum += l_delayline[c_idx];
-        if (num_chorus > 1)c_idx -= tmp;
-        if (c_idx < 0) {
-          c_idx += delay_length;
-        }
+      else
+      {
+        x2 = x1 + 1;
+        y2 = *(block->data + x2);
       }
-      *bp++ = sum / num_chorus;
+      *bp = (*bp >> 1) + (int((float(y2 - y1) / (x2 - x1) * (mod_idx - x1) + y1) + 0.5) >> 1); // mix original signal 1:1 with modulated signal
+
+      bp++;
+      mp++;
+      l_circ_idx++;
     }
 
     // transmit the block

effect_modulated_chorus.h

@@ -41,20 +41,19 @@ class AudioModulatedEffectChorus :
 {
   public:
     AudioModulatedEffectChorus(void):
-      AudioStream(2, inputQueueArray), num_chorus(2)
+      AudioStream(2, inputQueueArray)
     { }
 
-    boolean begin(short *delayline, int delay_length, int n_chorus);
+    boolean begin(short *delayline, int delay_length);
     virtual void update(void);
-    void voices(int n_chorus);
 
   private:
     audio_block_t *inputQueueArray[2];
 
     short *l_delayline;
     short l_circ_idx;
-    int num_chorus;
     int delay_length;
+    int delay_length_half;
 };
 
 #endif

mdaEPiano.cpp

@@ -252,7 +252,8 @@ void mdaEPiano::setOverdrive(float value)
 
 void mdaEPiano::setLoudness(float value)
 {
-  volume = value * 0.32258; // 0.00002 * 127^2
+  //volume = value * 0.32258; // 0.00002 * 127^2
+  volume = value * 0.2; // 0.00002 * 127^2
 }
 
 void mdaEPiano::setParameter(int32_t index, float value)