Implement all-pass filter

1 files changed, 24 insertions, 0 deletions

diff --git a/src/DSP/AllPassFilter.cpp b/src/DSP/AllPassFilter.cpp
new file mode 100644
index 0000000..e90bff7
--- /dev/null
+++ b/src/DSP/AllPassFilter.cpp
@@ -0,0 +1,24 @@
+#include "AllPassFilter.h"
+
+void AllPassFilter::prepare(double sampleRate, int samplesPerBlock) {
+  int maxDelayTimeMs = 100;
+  int maxDelaySamples = static_cast<int>(sampleRate * maxDelayTimeMs / 1000.0);
+
+  delayBuffer.resize(maxDelaySamples, 0.0f);
+  delayInSamples = static_cast<int>(sampleRate * 0.02);
+  delayBufferWritePos = 0;
+}
+
+void AllPassFilter::process(float* sample) {
+  int delayBufferLength = (int)delayBuffer.size();
+  int delayReadPos =
+      (delayBufferWritePos - delayInSamples + delayBufferLength) %
+      delayBufferLength;
+  float xn = *sample;
+  float delayedSample = delayBuffer[delayReadPos];
+  float yn = -gain * xn + delayedSample;  
+
+  delayBuffer[delayBufferWritePos] = xn + gain * yn;
+  *sample = yn;
+  delayBufferWritePos = (delayBufferWritePos + 1) % delayBufferLength;
+}