AR: trying to improve coexistence with HUB75

Hub75 is very memory hungry. So we try to make a bit more RAM available
* use 16bit samples when compiling with HUB75 support --> 3KB saved
* avoid using aPLL (HUB75 needs it)
* move audio buffers from BSS (always allocated) to heap (only allocated when FFTtask runs) --> 10Kb saved
* suspend live preview for 6 seconds when out-of-memory

usermods/audioreactive/audio_source.h

@@ -37,7 +37,8 @@
 #define SRate_t int
 #endif
 
-constexpr i2s_port_t AR_I2S_PORT = I2S_NUM_0;       // I2S port to use (do not change ! I2S_NUM_1 possible but this has limitation -> no MCLK routing, no ADC support)
+constexpr i2s_port_t AR_I2S_PORT = I2S_NUM_0;       // I2S port to use (do not change!  I2S_NUM_1 possible but this has 
+                                                    // strong limitations -> no MCLK routing, no ADC support, no PDM support
 
 //#include <driver/i2s_std.h>
 //#include <driver/i2s_pdm.h>
@@ -73,6 +74,11 @@ constexpr i2s_port_t AR_I2S_PORT = I2S_NUM_0;       // I2S port to use (do not c
 // data type requested from the I2S driver - currently we always use 32bit
 //#define I2S_USE_16BIT_SAMPLES   // (experimental) define this to request 16bit - more efficient but possibly less compatible
 
+#if defined(WLED_ENABLE_HUB75MATRIX) && defined(CONFIG_IDF_TARGET_ESP32)
+  // this is bitter, but necessary to survive
+  #define I2S_USE_16BIT_SAMPLES
+#endif
+
 #ifdef I2S_USE_16BIT_SAMPLES
 #define I2S_SAMPLE_RESOLUTION I2S_BITS_PER_SAMPLE_16BIT
 #define I2S_datatype int16_t
@@ -301,6 +307,9 @@ class I2SSource : public AudioSource {
       #if defined(ARDUINO_ARCH_ESP32) && !defined(CONFIG_IDF_TARGET_ESP32S3) && !defined(CONFIG_IDF_TARGET_ESP32S2) && !defined(CONFIG_IDF_TARGET_ESP32C3)
       if (ESP.getChipRevision() == 0) _config.use_apll = false; // APLL is broken on ESP32 revision 0
       #endif
+      #if defined(WLED_ENABLE_HUB75MATRIX)
+        _config.use_apll = false; // APLL needed for HUB75 DMA driver ?
+      #endif
 #endif
 
       if (_i2sMaster == false) {