1 files changed, 27 insertions, 0 deletions
diff --git a/intern/audaspace/FX/AUD_LowpassCalculator.cpp b/intern/audaspace/FX/AUD_LowpassCalculator.cpp
new file mode 100644
index 00000000000..57452f09038
--- /dev/null
+++ b/intern/audaspace/FX/AUD_LowpassCalculator.cpp
@@ -0,0 +1,27 @@
+#include "AUD_LowpassCalculator.h"
+
+#include <cmath>
+
+#ifndef M_PI
+#define M_PI 3.14159265358979323846
+#endif
+
+AUD_LowpassCalculator::AUD_LowpassCalculator(float frequency, float Q) :
+	m_frequency(frequency),
+	m_Q(Q)
+{
+}
+
+void AUD_LowpassCalculator::recalculateCoefficients(AUD_SampleRate rate, std::vector<float> &b, std::vector<float> &a)
+{
+	float w0 = 2 * M_PI * m_frequency / rate;
+	float alpha = sin(w0) / (2 * m_Q);
+	float norm = 1 + alpha;
+	float c = cos(w0);
+	a.push_back(1);
+	a.push_back(-2 * c / norm);
+	a.push_back((1 - alpha) / norm);
+	b.push_back((1 - c) / (2 * norm));
+	b.push_back((1 - c) / norm);
+	b.push_back(b[0]);
+}