1 files changed, 38 insertions, 0 deletions
diff --git a/portaudio/qa/loopback/src/biquad_filter.h b/portaudio/qa/loopback/src/biquad_filter.h
new file mode 100755
index 0000000..0895aba
--- /dev/null
+++ b/portaudio/qa/loopback/src/biquad_filter.h
@@ -0,0 +1,38 @@
+#ifndef _BIQUADFILTER_H
+#define _BIQUADFILTER_H
+
+
+/**
+ * Unit_BiquadFilter implements a second order IIR filter.
+ *
+ * @author (C) 2002 Phil Burk, SoftSynth.com, All Rights Reserved
+ */
+
+#define BIQUAD_MIN_RATIO     (0.000001)
+#define BIQUAD_MIN_Q         (0.00001)
+
+typedef struct BiquadFilter_s
+{
+    double      xn1;    // storage for delayed signals
+    double      xn2;
+    double      yn1;
+    double      yn2;
+
+    double      a0;     // coefficients
+    double      a1;
+    double      a2;
+
+    double      b1;
+    double      b2;
+
+    double      cos_omega;
+    double      sin_omega;
+    double      alpha;
+} BiquadFilter;
+
+void BiquadFilter_SetupHighPass( BiquadFilter *filter, double ratio, double Q );
+void BiquadFilter_SetupNotch( BiquadFilter *filter, double ratio, double Q );
+
+void BiquadFilter_Filter( BiquadFilter *filter, float *inputs, float *outputs, int numSamples );
+
+#endif