From b6180721d847bdc6ea18ec24a6ebcafc2af0e538 Mon Sep 17 00:00:00 2001
From: Holger Wirtz <wirtz@parasitstudio.de>
Date: Mon, 17 Jun 2019 11:42:18 +0200
Subject: [PATCH] Fixed rounding of floats for working with negative numbers.

---
 config.h                   |  2 +-
 effect_modulated_delay.cpp | 38 ++++++++++++--------------------------
 2 files changed, 13 insertions(+), 27 deletions(-)

diff --git a/config.h b/config.h
index 2b80ebc..ebf74a8 100644
--- a/config.h
+++ b/config.h
@@ -57,7 +57,7 @@
 #define USE_XFADE_DATA 1
 // CHORUS parameters
 #define INTERPOLATION_WINDOW_SIZE 21 // use only odd numbers!!!
-#define INTERPOLATE_MODE 11
+//#define INTERPOLATE_MODE 11
 #define CHORUS_WAVEFORM WAVEFORM_SINE // WAVEFORM_SINE WAVEFORM_TRIANGLE WAVEFORM_SAWTOOTH WAVEFORM_SAWTOOTH_REVERSE
 #define CHORUS_DELAY_LENGTH_SAMPLES (15*AUDIO_BLOCK_SAMPLES) // one AUDIO_BLOCK_SAMPLES = 2.902ms; you need doubled length, e.g. delay point is 20ms, so you need up to 40ms delay!
 
diff --git a/effect_modulated_delay.cpp b/effect_modulated_delay.cpp
index 6d738c1..c0e06f1 100644
--- a/effect_modulated_delay.cpp
+++ b/effect_modulated_delay.cpp
@@ -87,7 +87,8 @@ void AudioEffectModulatedDelay::update(void)
 
   if (block && modulation)
   {
-    float _tmp;
+    float mod_number;
+    float mod_fraction;
 
     for (uint16_t i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
     {
@@ -99,11 +100,12 @@ void AudioEffectModulatedDelay::update(void)
       // Calculate modulation index as a float, for interpolation later.
       // The index is located around the half of the delay length multiplied by the current amount of the modulator
       mod_idx = float(*mp) / SHRT_MAX * float(_delay_length >> 1);
+      mod_fraction = modff(mod_idx, &mod_number);
 
 #ifdef INTERPOLATE_MODE
       // Generate a an array with the size of INTERPOLATION_WINDOW_SIZE of x/y values around mod_idx for interpolation
       uint8_t c;
-      int16_t c_mod_idx = _circ_idx - int(mod_idx + 0.5); // This is the pointer to the value in the circular buffer at the current modulation index
+      int16_t c_mod_idx = _circ_idx - int(round(mod_idx)); // This is the pointer to the value in the circular buffer at the current modulation index
       for (j = ~(INTERPOLATION_WINDOW_SIZE >> 1) | 0x01, c = 0; j <= INTERPOLATION_WINDOW_SIZE >> 1; j++, c++) // only another way to say: from -INTERPOLATION_WINDOW_SIZE/2 to INTERPOLATION_WINDOW_SIZE/2
       {
         int16_t jc_mod_idx = (c_mod_idx + j) % _delay_length; // The modulation index pointer plus the value of the current window pointer
@@ -113,39 +115,23 @@ void AudioEffectModulatedDelay::update(void)
           y[c] = float(_delayline[jc_mod_idx]);
         x[c] = float(j);
       }
-      *bp = int(s.value(modff(mod_idx, &_tmp)) + 0.5);
+      *bp = int(round(s.value(mod_fraction)));
 #else
       // Simple interpolation
-      int16_t c_mod_idx = (_circ_idx - int(mod_idx + 0.5)) % _delay_length;
-      float fraction = modff(mod_idx, &_tmp);
+      int16_t c_mod_idx = (_circ_idx - int(round(mod_idx))) % _delay_length;
       float value1, value2;
+
       if (c_mod_idx < 0)
       {
-        if (fraction < 0.5)
-        {
-          value1 = _delayline[_delay_length + c_mod_idx - 1];
-          value2 = _delayline[_delay_length + c_mod_idx];
-        }
-        else
-        {
-          value1 = _delayline[_delay_length + c_mod_idx];
-          value2 = _delayline[_delay_length + c_mod_idx + 1];
-        }
+        value1 = _delayline[_delay_length + c_mod_idx];
+        value2 = _delayline[_delay_length + c_mod_idx - 1];
       }
       else
       {
-        if (fraction < 0.5)
-        {
-          value1 = _delayline[c_mod_idx - 1];
-          value2 = _delayline[c_mod_idx];
-        }
-        else
-        {
-          value1 = _delayline[c_mod_idx];
-          value2 = _delayline[c_mod_idx + 1];
-        }
+        value1 = _delayline[c_mod_idx];
+        value2 = _delayline[c_mod_idx - 1];
       }
-      *bp = int ((fraction * value1) + ((1.0 - fraction) * value2) + 0.5);
+      *bp = mod_fraction * value1 + (1.0 - mod_fraction) * value2;
 #endif
 
       bp++; // next audio data