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changeset 247:a98a8fe967c0

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* Add decimation filter for 8x decimation
author Chris Cannam <c.cannam@qmul.ac.uk>
date Thu, 10 Jan 2008 15:14:11 +0000
parents 0105e9b916a9
children fd68f25b9949
files dsp/rateconversion/Decimator.cpp dsp/rateconversion/Decimator.h
diffstat 2 files changed, 39 insertions(+), 5 deletions(-) [+]
line wrap: on
line diff
--- a/dsp/rateconversion/Decimator.cpp	Thu Jan 10 15:13:48 2008 +0000
+++ b/dsp/rateconversion/Decimator.cpp	Thu Jan 10 15:14:11 2008 +0000
@@ -10,6 +10,8 @@
 
 #include "Decimator.h"
 
+#include <iostream>
+
 //////////////////////////////////////////////////////////////////////
 // Construction/Destruction
 //////////////////////////////////////////////////////////////////////
@@ -37,7 +39,32 @@
 
     decBuffer = new double[ m_inputLength ];
 
-    if( m_decFactor == 4 )
+    // If adding new factors here, add them to
+    // getHighestSupportedFactor in the header as well
+
+    if(m_decFactor == 8)
+    {
+        //////////////////////////////////////////////////
+        b[0] = 0.060111378492136;
+        b[1] = -0.257323420830598;
+        b[2] = 0.420583503165928;
+        b[3] = -0.222750785197418;
+        b[4] = -0.222750785197418;
+        b[5] = 0.420583503165928;
+        b[6] = -0.257323420830598;
+        b[7] = 0.060111378492136;
+
+        a[0] = 1;
+        a[1] = -5.667654878577432;
+        a[2] = 14.062452278088417;
+        a[3] = -19.737303840697738;
+        a[4] = 16.889698874608641;
+        a[5] = -8.796600612325928;
+        a[6] = 2.577553446979888;
+        a[7] = -0.326903916815751;
+        //////////////////////////////////////////////////
+    }
+    else if( m_decFactor == 4 )
     {
 	//////////////////////////////////////////////////
 	b[ 0 ] = 0.10133306904918619;
@@ -82,6 +109,10 @@
     }
     else
     {
+        if ( m_decFactor != 1 ) {
+            std::cerr << "WARNING: Decimator::initialise: unsupported decimation factor " << m_decFactor << ", no antialiasing filter will be used" << std::endl;
+        }
+
 	//////////////////////////////////////////////////
 	b[ 0 ] = 1;
 	b[ 1 ] = 0;
@@ -117,7 +148,7 @@
     o1=o2=o3=o4=o5=o6=o7=0;
 }
 
-void Decimator::doAntiAlias(double *src, double *dst, unsigned int length)
+void Decimator::doAntiAlias(const double *src, double *dst, unsigned int length)
 {
 
     for( unsigned int i = 0; i < length; i++ )
@@ -139,7 +170,7 @@
 
 }
 
-void Decimator::process(double *src, double *dst)
+void Decimator::process(const double *src, double *dst)
 {
     if( m_decFactor != 1 )
     {
--- a/dsp/rateconversion/Decimator.h	Thu Jan 10 15:13:48 2008 +0000
+++ b/dsp/rateconversion/Decimator.h	Thu Jan 10 15:14:11 2008 +0000
@@ -13,12 +13,15 @@
 class Decimator  
 {
 public:
-    void process( double* src, double* dst );
-    void doAntiAlias( double* src, double* dst, unsigned int length );
+    void process( const double* src, double* dst );
+    void doAntiAlias( const double* src, double* dst, unsigned int length );
 
     Decimator( unsigned int inLength, unsigned int decFactor );
     virtual ~Decimator();
 
+    int getFactor() const { return m_decFactor; }
+    static int getHighestSupportedFactor() { return 8; }
+
 private:
     void resetFilter();
     void deInitialise();