comparison dsp/rateconversion/Decimator.cpp @ 22:f7edcd9138bd

* Add decimation filter for 8x decimation

     This file copyright 2005-2006 Christian Landone.
     All rights reserved.
 */
 
 #include "Decimator.h"
+
+#include <iostream>
 
 //////////////////////////////////////////////////////////////////////
 // Construction/Destruction
 //////////////////////////////////////////////////////////////////////
 

     m_decFactor = decFactor;
     m_outputLength = m_inputLength / m_decFactor;
 
     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;
 	b[ 1 ] = -0.2447523353702363;
 	b[ 2 ] = 0.33622528590120965;

 	a[ 6 ] = 0.23659265908013868;
 	a[ 7 ] = 0.032352924250533946;
     }
     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;
 	b[ 2 ] = 0;
 	b[ 3 ] = 0;

     Input = Output = 0;
 
     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++ )
     {
 	Input = (double)src[ i ];

 	dst[ i ] = Output;
     }
 
 }
 
-void Decimator::process(double *src, double *dst)
+void Decimator::process(const double *src, double *dst)
 {
     if( m_decFactor != 1 )
     {
 	doAntiAlias( src, decBuffer, m_inputLength );
     }