start/stop DAC and other small changes in order to reduce click noise…

… at beginning / end of audio playback

src/AudioOutputI2S.cpp

@@ -26,6 +26,10 @@
 #endif
 #include "AudioOutputI2S.h"
 
+
+#define WAIT_SAMPLES_BEFORE_DAC_EN 100
+
+
 #if defined(ESP32) || defined(ESP8266)
 AudioOutputI2S::AudioOutputI2S(int port, int output_mode, int dma_buf_count, int use_apll)
 {
@@ -47,6 +51,7 @@ AudioOutputI2S::AudioOutputI2S(int port, int output_mode, int dma_buf_count, int
   wclkPin = 25;
   doutPin = 22;
   SetGain(1.0);
+  dac_sample_count=0;
 }
 
 bool AudioOutputI2S::SetPinout()
@@ -148,6 +153,7 @@ bool AudioOutputI2S::SetOutputModeMono(bool mono)
 
 bool AudioOutputI2S::begin(bool txDAC)
 {
+
   #ifdef ESP32
     if (!i2sOn)
     {
@@ -198,14 +204,16 @@ bool AudioOutputI2S::begin(bool txDAC)
       if (output_mode == INTERNAL_DAC || output_mode == INTERNAL_PDM)
       {
         i2s_set_pin((i2s_port_t)portNo, NULL);
-        i2s_set_dac_mode(I2S_DAC_CHANNEL_BOTH_EN);
+        // i2s_set_dac_mode(I2S_DAC_CHANNEL_BOTH_EN);
       }
       else
       {
         SetPinout();
       }
-      i2s_zero_dma_buffer((i2s_port_t)portNo);
-    }
+      // i2s_zero_dma_buffer((i2s_port_t)portNo);
+    } 
+	else dac_sample_count=0;  // just reset counter for DAC enable!
+
   #elif defined(ESP8266)
     (void)dma_buf_count;
     (void)use_apll;
@@ -259,6 +267,9 @@ bool AudioOutputI2S::ConsumeSample(int16_t sample[2])
   }
   #ifdef ESP32
     uint32_t s32;
+
+	if (++dac_sample_count==WAIT_SAMPLES_BEFORE_DAC_EN)  i2s_set_dac_mode(I2S_DAC_CHANNEL_BOTH_EN);
+
     if (output_mode == INTERNAL_DAC)
     {
       int16_t l = Amplify(ms[LEFTCHANNEL]) + 0x8000;
@@ -302,10 +313,12 @@ bool AudioOutputI2S::stop()
     return false;
 
   #ifdef ESP32
-    i2s_zero_dma_buffer((i2s_port_t)portNo);
+    // i2s_zero_dma_buffer((i2s_port_t)portNo);
+    i2s_set_dac_mode(I2S_DAC_CHANNEL_DISABLE);
   #elif defined(ARDUINO_ARCH_RP2040)
     I2S.end();
   #endif
-  i2sOn = false;
+   // i2sOn = false;  // removed to avoid re-installation of I2S-driver
+                      // when next file is played (not sure about side effects ...)
   return true;
 }

src/AudioOutputI2S.h

@@ -53,6 +53,7 @@ class AudioOutputI2S : public AudioOutput
     bool mono;
     bool i2sOn;
     int dma_buf_count;
+	int dac_sample_count;
     int use_apll;
     // We can restore the old values and free up these pins when in NoDAC mode
     uint32_t orig_bck;