DynamicMemoryStream post processing

Author: pschatzmann

examples/examples-audiokit/streams-audiokit-ram-audiokit/streams-audiokit-ram-audiokit.ino

@@ -29,6 +29,12 @@ void record_start(bool pinStatus, int pin, void* ref){
 
 void record_end(bool pinStatus, int pin, void* ref){
   Serial.println("Playing...");
+
+  // Remove popping noise, from button: we delete 6 segments at the beginning and end 
+  // and on the resulting audio we slowly raise the volume on the first segment
+  // end decrease it on the last segment
+  recording.postProcessSmoothTransition<int16_t>(channels, 6, 0.01);
+
   copier.begin(kit, recording);  // start playback
 }
 

src/AudioTools/AudioStreams.h

@@ -338,6 +338,7 @@ class DynamicMemoryStream : public AudioStreamX {
   };
 
   DynamicMemoryStream() = default;
+  
   DynamicMemoryStream(bool isLoop, int defaultBufferSize=DEFAULT_BUFFER_SIZE ) {
     this->default_buffer_size = defaultBufferSize;
     is_loop = isLoop;
@@ -460,6 +461,37 @@ class DynamicMemoryStream : public AudioStreamX {
     return audio_list;
   }
 
+  /// @brief  Post processing after the recording. We add a smooth transition at the beginning and at the end
+  /// @tparam T 
+  /// @param factor 
+  template<typename T>
+  void postProcessSmoothTransition(int channels, int remove, float factor = 0.01){
+      if (remove>0){
+        for (int j=0;j<remove;j++){
+          DataNode* node = nullptr;
+          audio_list.pop_front(node);
+          if (node!=nullptr) delete node;
+          node = nullptr;
+          audio_list.pop_back(node);
+          if (node!=nullptr) delete node;
+        }
+      }
+
+      // Remove popping noise
+      SmoothTransition<T> clean_start(channels, true, false, factor);
+      auto first = *list().begin();   
+      if (first!=nullptr){ 
+        clean_start.convert(first->data,first->len);
+      }
+
+      SmoothTransition<T> clean_end(channels, false, true, factor);
+      auto last = * (--(list().end()));
+      if (last!=nullptr){
+        clean_end.convert(last->data,last->len);  
+      }  
+  }
+
+
 protected:
   List<DataNode*> audio_list;
   List<DataNode*>::Iterator it = audio_list.end();

src/AudioTools/Converter.h

@@ -941,7 +941,7 @@ class SmoothTransition : public BaseConverter<T> {
                 if (factor>=0.8){
                     break;
                 } else {
-                    values[j]*=factor;
+                    values[j]=factor*values[j];
                 }
                 factor += inc;
             }
@@ -953,7 +953,7 @@ class SmoothTransition : public BaseConverter<T> {
                 if (factor>=0.8){
                     break;
                 } else {
-                    values[j]*=factor;
+                    values[j]=factor*values[j];
                 }
             }
         }