Diff: biquad.h

Revision:

3:abd20f34fd68

Parent:

2:9a9b643fcc66

--- a/biquad.h	Wed Feb 15 18:12:50 2012 +0000
+++ b/biquad.h	Thu Feb 16 00:07:57 2012 +0000
@@ -1,8 +1,9 @@
 /*
  *  biquad.h
  *
- *  Original source material from Robert Bristow Johnson at 
+ *  Original source material from Robert Bristow-Johnson at 
  *  http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt
+ *  and Nigel Redmon at http://www.earlevel.com/ 
  *  
  *  Derived from public domain C implementation by Tom St. Denis
  *
@@ -25,6 +26,12 @@
 #define M_PI        3.14159265358979323846
 #endif
 
+/* formulation types */
+typedef enum {
+    DIRECT_FORM_I = 0,
+    TRANSPOSED_DIRECT_FORM_II
+} BIQUAD_FORMULATION_TYPE;
+
 /* filter types */
 typedef enum {
     LPF, /* low pass filter */
@@ -41,17 +48,29 @@
 
 public:
     Biquad(BIQUAD_FILTER_TYPE type, 
-        T dbGain,  /* gain of filter */
+        T dbGain,  /* peak gain of filter */
         T freq,  /* center frequency */
         T srate,  /* sampling rate */
-        T bandwidth); /* bandwidth in octaves */
+        T Q, /* Q */
+        BIQUAD_FORMULATION_TYPE form = DIRECT_FORM_I);                       
         
-    void Reset(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T bandwidth, bool clearHistory = false);
+    void Reset(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T Q, bool clearHistory = false, BIQUAD_FORMULATION_TYPE form = DIRECT_FORM_I);
+    
+    void CalcCoefficientsDirectI(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T Q);
+    
+    void CalcCoefficientsTransposedDirectII(BIQUAD_FILTER_TYPE type, T dbGain, T freq, T srate, T Q);
     
     T Calculate(T sample);
     
-    T a0, a1, a2, a3, a4;
+    BIQUAD_FORMULATION_TYPE form;    
+    
+    // used for DIRECT_FORM_1
+    T a0_I, a1_I, a2_I, a3_I, a4_I; 
     T x1, x2, y1, y2;
+    
+    // used for TRANSPOSED_DIRECT_FORM_II
+    T a0_II, a1_II, a2_II, b1_II, b2_II;    
+    T z1, z2;        
 
 };