From ef104f6909f3d3250ea401f13e6362094efc1bf1 Mon Sep 17 00:00:00 2001
From: Holger Wirtz <wirtz@parasitstudio.de>
Date: Fri, 25 Oct 2019 13:03:31 +0200
Subject: [PATCH] Trying a faster way to mix stereo to mono. Garbage collection
 at config.h.

---
 config.h               | 24 +++++++++---------------
 effect_stereo_mono.cpp | 10 ++++++++++
 2 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/config.h b/config.h
index f973320..1051744 100644
--- a/config.h
+++ b/config.h
@@ -44,12 +44,16 @@
 //* DEVICE SETTINGS
 //*************************************************************************************************
 
-// MIDI
+//*************************************************************************************************
+//* MIDI HARDWARE SETTINGS
+//*************************************************************************************************
 //#define MIDI_DEVICE_DIN Serial1
 #define MIDI_DEVICE_USB 1
 #define MIDI_DEVICE_USB_HOST 1
 
-// AUDIO
+//*************************************************************************************************
+//* AUDIO HARDWARE SETTINGS
+//*************************************************************************************************
 // If nothing is defined Teensy internal DAC is used as audio output device!
 // Left and right channel audio signal is presented on pins A21 and A22.
 #define AUDIO_DEVICE_USB
@@ -61,9 +65,8 @@
 #define PT8211_AUDIO
 
 //*************************************************************************************************
-//* MIDI SETTINGS
+//* MIDI SOFTWARE SETTINGS
 //*************************************************************************************************
-
 #define DEFAULT_MIDI_CHANNEL MIDI_CHANNEL_OMNI
 #define MIDI_MERGE_THRU 1
 #define SYSEXBANK_DEFAULT 0
@@ -82,7 +85,7 @@
 //#define USE_REVERB 1
 
 //*************************************************************************************************
-//* AUDIO SETTINGS
+//* AUDIO SOFTWARE SETTINGS
 //*************************************************************************************************
 // https://rechneronline.de/funktionsgraphen/
 #ifndef TEENSY_AUDIO_BOARD
@@ -141,7 +144,6 @@
 #endif 
 
 #define CONTROL_RATE_MS 50
-
 #define BACK_FROM_VOLUME_MS 1000
 
 //*************************************************************************************************
@@ -156,7 +158,6 @@
 //*************************************************************************************************
 //* HARDWARE SETTINGS
 //*************************************************************************************************
-
 #if defined(__IMXRT1062__) //Teensy-4.0
 #define TEENSY4
 #endif
@@ -248,9 +249,8 @@
 
 // Some optimizations
 #define USE_TEENSY_DSP 1
-#define SUM_UP_AS_INT 1
 
-/* HELPER MACROS */
+// HELPER MACROS
 #define TIME_MS2SAMPLES(x) floor(uint32_t(x) * AUDIO_SAMPLE_RATE / 1000)
 #define SAMPLES2TIME_MS(x) float(uint32_t(x) * 1000 / AUDIO_SAMPLE_RATE)
 // Modulated delay options
@@ -367,12 +367,6 @@ struct config_t {
   uint8_t engine;
 };
 
-// struct for smoothing value changes
-struct value_change_t {
-  float diff;
-  uint16_t steps;
-};
-
 inline float mapfloat(float val, float in_min, float in_max, float out_min, float out_max)
 {
   return (val - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
diff --git a/effect_stereo_mono.cpp b/effect_stereo_mono.cpp
index 6ceae55..8eb9067 100644
--- a/effect_stereo_mono.cpp
+++ b/effect_stereo_mono.cpp
@@ -45,6 +45,7 @@ void AudioEffectStereoMono::update(void)
   {
     if (block[0] && block[1])
     {
+#ifdef USE_OLD_STEREO_TO_MONO
       int16_t *bp[2] = { block[0]->data, block[1]->data };
 
       for (uint16_t i = 0; i < AUDIO_BLOCK_SAMPLES; i++)
@@ -54,6 +55,15 @@ void AudioEffectStereoMono::update(void)
         bp[0]++;
         bp[1]++;
       }
+#else
+      // device every channel by 2 
+      arm_shift_q15(block[0]->data, -1, block[0]->data, AUDIO_BLOCK_SAMPLES);
+      arm_shift_q15(block[1]->data, -1, block[1]->data, AUDIO_BLOCK_SAMPLES);
+      // add channel 2 to channel 1
+      arm_add_q15(block[0]->data, block[1]->data, block[0]->data, AUDIO_BLOCK_SAMPLES);
+      // copy channel 1 to channel 2
+      arm_copy_q15(block[0]->data, block[1]->data, AUDIO_BLOCK_SAMPLES);
+#endif
     }
   }