Add invert phase DSP filter

openrtx/include/dsp.h

@@ -54,6 +54,15 @@ void dsp_pwmCompensate(audio_sample_t *buffer, size_t length);
  */
 void dsp_dcRemoval(audio_sample_t *buffer, size_t length);
 
+/*
+ * Inverts the phase of the audio buffer passed as paramenter.
+ * The buffer will be processed in place to save memory.
+ *
+ * @param buffer: the buffer to be used as both source and destination.
+ * @param length: the length of the input buffer.
+ */
+void dsp_invertPhase(audio_sample_t *buffer, uint16_t length);
+
 #ifdef __cplusplus
 }
 

openrtx/src/dsp.cpp

@@ -57,9 +57,11 @@ void dsp_applyFIR(audio_sample_t *buffer,
                   uint16_t length,
                   std::array<float, order> taps)
 {
-    for(int i = length - 1; i >= 0; i--) {
+    for(int i = length - 1; i >= 0; i--)
+    {
         float acc = 0.0f;
-        for(uint16_t j = 0; j < order; j++) {
+        for(uint16_t j = 0; j < order; j++)
+        {
             if (i >= j)
                 acc += buffer[i - j] * taps[j];
         }