PWM decimation

Author: pschatzmann

src/AudioConfig.h

@@ -809,6 +809,11 @@ using WiFiServerSecure = BearSSL::WiFiServerSecure;
 #  define ANALOG_MAX_SAMPLE_RATE 44100
 #endif
 
+#ifndef PWM_MAX_SAMPLE_RATE
+#  define PWM_MAX_SAMPLE_RATE 8000
+#endif
+
+
 #ifndef URL_CLIENT_TIMEOUT
 #  define URL_CLIENT_TIMEOUT 60000;
 #  define URL_HANDSHAKE_TIMEOUT 120000

src/AudioTools/AudioCodecs/AudioEncoded.h

@@ -93,6 +93,7 @@ class EncodedAudioOutput : public ModifyingOutput {
     }
   }
 
+
   void setOutput(Print &outputStream) { setOutput(&outputStream); }
 
   /// Defines the output
@@ -266,18 +267,18 @@ class EncodedAudioStream : public ReformatBaseStream {
   }
 
   EncodedAudioStream(AudioOutput *outputStream, AudioDecoder *decoder) {
-    setOutput(*outputStream);
     setDecoder(decoder);
+    setOutput(*outputStream);
   }
 
   EncodedAudioStream(Print *outputStream, AudioDecoder *decoder) {
-    setOutput(*outputStream);
     setDecoder(decoder);
+    setOutput(*outputStream);
   }
 
   EncodedAudioStream(Print *outputStream, AudioEncoder *encoder) {
-    setOutput(*outputStream);
     setEncoder(encoder);
+    setOutput(*outputStream);
   }
 
   EncodedAudioStream(AudioDecoder *decoder) { setDecoder(decoder); }

src/AudioTools/AudioCodecs/CodecMP3Helix.h

@@ -70,7 +70,8 @@ class MP3DecoderHelix : public AudioDecoder  {
         }
 
         /// Defines the output Stream
-        virtual void setOutput(Print &outStream){
+        void setOutput(Print &outStream) override {
+            AudioDecoder::setOutput(outStream);
             if (mp3!=nullptr) mp3->setOutput(outStream);
         }
 

src/AudioTools/CoreAudio/AudioPWM/AudioPWM.h

@@ -34,7 +34,7 @@ class PWMAudioOutput : public AudioOutput {
   PWMConfig config() { return audio_config; }
 
   /// updates the sample rate dynamically
-  virtual void setAudioInfo(AudioInfo info) {
+  void setAudioInfo(AudioInfo info) override {
     TRACEI();
     AudioOutput::cfg = info;
     PWMConfig cfg = audio_config;
@@ -43,9 +43,9 @@ class PWMAudioOutput : public AudioOutput {
       cfg.sample_rate = info.sample_rate;
       cfg.bits_per_sample = info.bits_per_sample;
       cfg.channels = info.channels;
-      cfg.logInfo();
       end();
       begin(cfg);
+      cfg.logInfo();
     }
   }
 
@@ -59,8 +59,7 @@ class PWMAudioOutput : public AudioOutput {
   bool begin(PWMConfig config) {
     TRACED();
     this->audio_config = config;
-    AudioOutput::setAudioInfo(audio_config);
-    return pwm.begin(audio_config);
+    return begin();
   }
 
   bool begin() {

src/AudioTools/CoreAudio/AudioPWM/PWMAudioAVR.h

@@ -73,6 +73,8 @@ class PWMDriverAVR : public DriverPWMBase {
   /// Setup LED PWM
   void setupPWM() {
     TRACED();
+    audio_config.pwm_frequency = 62500;
+
     if (audio_config.channels > 2) {
       LOGW("Max 2 channels supported - you requested %d",
            audio_config.channels);

src/AudioTools/CoreAudio/AudioPWM/PWMAudioBase.h

@@ -37,18 +37,23 @@ struct PWMConfig : public AudioInfo {
     bits_per_sample = 16;
   }
 
-  // basic pwm information
+  /// size of an inidividual buffer
   uint16_t buffer_size = PWM_BUFFER_SIZE;
+  /// number of buffers
   uint8_t buffers = PWM_BUFFER_COUNT;
 
-  // additinal info which might not be used by all processors
-  uint32_t pwm_frequency = PWM_AUDIO_FREQUENCY;  // audable range is from 20 to
-                                                 // 20,000Hz (not used by ESP32)
-  uint8_t resolution = 8;  // Only used by ESP32: must be between 8 and 11 ->
-                           // drives pwm frequency
-  uint8_t timer_id = 0;    // Only used by ESP32 must be between 0 and 3
+  /// additinal info which might not be used by all processors
+  uint32_t pwm_frequency = 0;  // audable range is from 20 to
+  /// Only used by ESP32: must be between 8 and 11 ->  drives pwm frequency                                              // 20,000Hz (not used by ESP32)
+  uint8_t resolution = 8;  
+  /// Timer used: Only used by ESP32 must be between 0 and 3                         
+  uint8_t timer_id = 0;    
+
+  /// max sample sample rate that still produces good audio
+  uint32_t max_sample_rate = PWM_MAX_SAMPLE_RATE;
 
 #ifndef __AVR__
+  /// GPIO of starting pin
   uint16_t start_pin = PIN_PWM_START;
 
   /// support assignament of int array
@@ -116,7 +121,8 @@ class DriverPWMBase {
 
   // restart with prior definitions
   bool begin(PWMConfig cfg) {
-    TRACED();
+    TRACEI();
+
     decimation_factor = 0;
     audio_config = cfg;
     decimate.setChannels(cfg.channels);
@@ -140,9 +146,9 @@ class DriverPWMBase {
     // initialize if necessary
     if (!isTimerStarted() || !cfg.equals(actual_info)) {
       audio_config.logConfig();
+      actual_info = cfg;
       setupPWM();
       setupTimer();
-      actual_info = cfg;
     }
 
     // reset class variables
@@ -323,19 +329,19 @@ class DriverPWMBase {
   }
 
   /// Provides the max working sample rate
-  virtual int maxSampleRate() { return 48000; }
+  virtual int maxSampleRate() { return audio_config.max_sample_rate; }
 
   /// The requested sampling rate is too hight: we only process half of the
   /// samples so we can half the sampling rate
   virtual bool isDecimateActive() {
-    return audio_config.sample_rate >= ANALOG_MAX_SAMPLE_RATE;
+    return audio_config.sample_rate >= audio_config.max_sample_rate;
   }
 
   /// Decimation factor to reduce the sample rate
   virtual int decimation() { 
     if (decimation_factor == 0){
       for (int j = 1; j < 20; j++){
-          if (audio_config.sample_rate / j <= ANALOG_MAX_SAMPLE_RATE){
+          if (audio_config.sample_rate / j <= audio_config.max_sample_rate){
             decimation_factor = j;
             LOGI("Decimation factor: %d" ,j);
             return j;

src/AudioTools/CoreAudio/AudioPWM/PWMAudioESP32.h

@@ -59,16 +59,18 @@ class PWMDriverESP32 : public DriverPWMBase {
   virtual void startTimer() {
     if (!timer) {
       TRACEI();
-      audio_config = audioInfo();
-      timer.begin(pwm_callback, audio_config.sample_rate, HZ);
+      timer.begin(pwm_callback, effectiveOutputSampleRate(), HZ);
+      actual_timer_frequency = effectiveOutputSampleRate();
       is_timer_started = true;
     }
   }
 
   /// Setup LED PWM
   virtual void setupPWM() {
     // frequency is driven by selected resolution
-    audio_config.pwm_frequency = frequency(audio_config.resolution) * 1000;
+    if (audio_config.pwm_frequency == 0){
+      audio_config.pwm_frequency = frequency(audio_config.resolution) * 1000;
+    }
 
     pins.resize(audio_config.channels);
     for (int j = 0; j < audio_config.channels; j++) {
@@ -102,6 +104,11 @@ class PWMDriverESP32 : public DriverPWMBase {
   virtual void setupTimer() {
     timer.setCallbackParameter(this);
     timer.setIsSave(false);
+
+    if (actual_timer_frequency != effectiveOutputSampleRate()){
+      timer.end();
+      startTimer();
+    }
   }
 
   /// write a pwm value to the indicated channel. The max value depends on the
@@ -117,6 +124,7 @@ class PWMDriverESP32 : public DriverPWMBase {
  protected:
   Vector<PinInfo> pins;
   TimerAlarmRepeating timer;
+  uint32_t actual_timer_frequency = 0;
 
   /// provides the max value for the indicated resulution
   int maxUnsignedValue(int resolution) { return pow(2, resolution); }

src/AudioTools/CoreAudio/AudioPWM/PWMAudioMBED.h

@@ -65,6 +65,10 @@ class PWMDriverMBED : public DriverPWMBase {
   /// Setup PWM Pins
   virtual void setupPWM() {
     TRACED();
+    if (audio_config.pwm_frequency == 0){
+      audio_config.pwm_frequency = PWM_AUDIO_FREQUENCY;
+    }
+
     unsigned long period =
         1000000l / audio_config.pwm_frequency;  // -> 30.517578125 microseconds
     pins.resize(audio_config.channels);

src/AudioTools/CoreAudio/AudioPWM/PWMAudioRP2040.h

@@ -99,6 +99,9 @@ class PWMDriverRP2040 : public DriverPWMBase {
   // defines the pwm_config which will be used to drive the pins
   pwm_config setupPWMConfig() {
     TRACED();
+    if (audio_config.pwm_frequency == 0){
+      audio_config.pwm_frequency = PWM_AUDIO_FREQUENCY;
+    }
     // setup pwm frequency
     pwm_config pico_pwm_config = pwm_get_default_config();
     int wrap_value = maxOutputValue();  // amplitude of square wave (pwm values

src/AudioTools/CoreAudio/AudioPWM/PWMAudioRenesas.h

@@ -78,6 +78,10 @@ class PWMDriverRenesas : public DriverPWMBase {
   /// Setup PWM Pins
   virtual void setupPWM() {
     TRACED();
+    if (audio_config.pwm_frequency == 0){
+      audio_config.pwm_frequency = PWM_AUDIO_FREQUENCY;
+    }
+
     pins.resize(audio_config.channels);
     for (int j = 0; j < audio_config.channels; j++) {
       LOGD("Processing channel %d", j);
@@ -113,7 +117,7 @@ class PWMDriverRenesas : public DriverPWMBase {
     }
   }
 
-  int maxSampleRate() override { return ANALOG_MAX_SAMPLE_RATE; }
+  int maxSampleRate() override { return audio_config.max_sample_rate; }
 
   int decimation() override {
     for (int j = 1; j < 5; j++) {