diff --git a/CMakeLists.txt b/CMakeLists.txt
index 2acfbbd9b..36d90c533 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -212,6 +212,7 @@ set(sdrbase_HEADERS
     sdrbase/dsp/interpolator.h
     sdrbase/dsp/hbfiltertraits.h
     sdrbase/dsp/inthalfbandfilter.h
+    sdrbase/dsp/inthalfbandfilterdb.h
     sdrbase/dsp/kissfft.h
     sdrbase/dsp/kissengine.h
     sdrbase/dsp/lowpass.h
diff --git a/sdrbase/dsp/inthalfbandfilter.h b/sdrbase/dsp/inthalfbandfilter.h
index 3a45ba65f..b362bd6a9 100644
--- a/sdrbase/dsp/inthalfbandfilter.h
+++ b/sdrbase/dsp/inthalfbandfilter.h
@@ -1,3 +1,20 @@
+///////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2016 F4EXB                                                      //
+// written by Edouard Griffiths                                                  //
+//                                                                               //
+// This program is free software; you can redistribute it and/or modify          //
+// it under the terms of the GNU General Public License as published by          //
+// the Free Software Foundation as version 3 of the License, or                  //
+//                                                                               //
+// This program is distributed in the hope that it will be useful,               //
+// but WITHOUT ANY WARRANTY; without even the implied warranty of                //
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                  //
+// GNU General Public License V3 for more details.                               //
+//                                                                               //
+// You should have received a copy of the GNU General Public License             //
+// along with this program. If not, see <http://www.gnu.org/licenses/>.          //
+///////////////////////////////////////////////////////////////////////////////////
+
 #ifndef INCLUDE_INTHALFBANDFILTER_H
 #define INCLUDE_INTHALFBANDFILTER_H
 
@@ -86,51 +103,6 @@ public:
         }
     }
 
-    // upsample by 2, return center part of original spectrum - double buffer variant
-    bool workInterpolateCenterDB(Sample* sampleIn, Sample *SampleOut)
-    {
-        switch(m_state)
-        {
-            case 0:
-                // insert sample into ring-buffer
-                m_samplesDB[m_ptrDB][0] = 0;
-                m_samplesDB[m_ptrDB][1] = 0;
-                m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
-                m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
-
-                // save result
-                doFIRDB(SampleOut);
-
-                // advance write-pointer
-                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-                // next state
-                m_state = 1;
-
-                // tell caller we didn't consume the sample
-                return false;
-
-            default:
-                // insert sample into ring-buffer
-                m_samplesDB[m_ptrDB][0] = sampleIn->real();
-                m_samplesDB[m_ptrDB][1] = sampleIn->imag();
-                m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
-                m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
-
-                // save result
-                doFIRDB(SampleOut);
-
-                // advance write-pointer
-                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-                // next state
-                m_state = 0;
-
-                // tell caller we consumed the sample
-                return true;
-        }
-    }
-
 	bool workDecimateCenter(qint32 *x, qint32 *y)
 	{
 		// insert sample into ring-buffer
@@ -356,99 +328,6 @@ public:
         }
     }
 
-    // upsample by 2, from lower half of original spectrum - double buffer variant
-    bool workInterpolateLowerHalfDB(Sample* sampleIn, Sample *sampleOut)
-    {
-        Sample s;
-
-        switch(m_state)
-        {
-        case 0:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = 0;
-            m_samplesDB[m_ptrDB][1] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(s.imag());
-            sampleOut->setImag(-s.real());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 1;
-
-            // tell caller we didn't consume the sample
-            return false;
-
-        case 1:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(-s.real());
-            sampleOut->setImag(-s.imag());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 2;
-
-            // tell caller we consumed the sample
-            return true;
-
-        case 2:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = 0;
-            m_samplesDB[m_ptrDB][1] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(-s.imag());
-            sampleOut->setImag(s.real());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 3;
-
-            // tell caller we didn't consume the sample
-            return false;
-
-        default:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(s.real());
-            sampleOut->setImag(s.imag());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 0;
-
-            // tell caller we consumed the sample
-            return true;
-        }
-    }
-
 	// downsample by 2, return upper half of original spectrum
 	bool workDecimateUpperHalf(Sample* sample)
 	{
@@ -603,99 +482,6 @@ public:
         }
     }
 
-    // upsample by 2, move original spectrum to upper half - double buffer variant
-    bool workInterpolateUpperHalfDB(Sample* sampleIn, Sample *sampleOut)
-    {
-        Sample s;
-
-        switch(m_state)
-        {
-        case 0:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = 0;
-            m_samplesDB[m_ptrDB][1] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(-s.imag());
-            sampleOut->setImag(s.real());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 1;
-
-            // tell caller we didn't consume the sample
-            return false;
-
-        case 1:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(-s.real());
-            sampleOut->setImag(-s.imag());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 2;
-
-            // tell caller we consumed the sample
-            return true;
-
-        case 2:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = 0;
-            m_samplesDB[m_ptrDB][1] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(s.imag());
-            sampleOut->setImag(-s.real());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 3;
-
-            // tell caller we didn't consume the sample
-            return false;
-
-        default:
-            // insert sample into ring-buffer
-            m_samplesDB[m_ptrDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
-            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
-            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
-
-            // save result
-            doFIRDB(&s);
-            sampleOut->setReal(s.real());
-            sampleOut->setImag(s.imag());
-
-            // advance write-pointer
-            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
-
-            // next state
-            m_state = 0;
-
-            // tell caller we consumed the sample
-            return true;
-        }
-    }
-
     void myDecimate(const Sample* sample1, Sample* sample2)
     {
         m_samples[m_ptr][0] = sample1->real();
@@ -726,42 +512,14 @@ public:
 
 protected:
 	qint32 m_samples[HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1][2];     // Valgrind optim (from qint16)
-	qint32 m_samplesDB[2*(HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1)][2]; // double buffer technique
 	qint16 m_ptr;
-	int m_ptrDB;
-	int m_sizeDB;
 	int m_state;
 
-    void doFIRDB(Sample* sample)
-    {
-        int a = m_ptrDB + m_sizeDB; // tip pointer
-        int b = m_ptrDB + 1; // tail pointer
-        qint32 iAcc = 0;
-        qint32 qAcc = 0;
-
-        for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
-        {
-            iAcc += (m_samplesDB[a][0] + m_samplesDB[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
-            qAcc += (m_samplesDB[a][1] + m_samplesDB[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
-            a -= 2;
-            b += 2;
-        }
-
-        iAcc += ((qint32)m_samplesDB[b-1][0]) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
-        qAcc += ((qint32)m_samplesDB[b-1][1]) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
-
-        sample->setReal(iAcc >> HBFIRFilterTraits<HBFilterOrder>::hbShift -1);
-        sample->setImag(qAcc >> HBFIRFilterTraits<HBFilterOrder>::hbShift -1);
-    }
-
 	void doFIR(Sample* sample)
 	{
 		// init read-pointer
-//		int a = HBFIRFilterTraits<HBFilterOrder>::hbMod[m_ptr + 2 + 1]; // 0 + 1
-//		int b = HBFIRFilterTraits<HBFilterOrder>::hbMod[m_ptr + 2 - 2]; //-1 - 1
-		// ancient way:
-		int a = (m_ptr + 1) % (HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1);
-		int b = (m_ptr + (HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1)) % (HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1);
+		int a = HBFIRFilterTraits<HBFilterOrder>::hbMod[m_ptr + 2 + 1]; // 0 + 1
+		int b = HBFIRFilterTraits<HBFilterOrder>::hbMod[m_ptr + 2 - 2]; //-1 - 1
 
 		// go through samples in buffer
 		qint32 iAcc = 0;
@@ -776,16 +534,11 @@ protected:
 			qAcc += (m_samples[a][1] + m_samples[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
 
 			// update read-pointer
-//			a = HBFIRFilterTraits<HBFilterOrder>::hbMod[a + 2 + 2];
-//			b = HBFIRFilterTraits<HBFilterOrder>::hbMod[b + 2 - 2];
-			// ancient way:
-			a = (a + 2) % (HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1);
-			b = (b + (HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1)) % (HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1);
+			a = HBFIRFilterTraits<HBFilterOrder>::hbMod[a + 2 + 2];
+			b = HBFIRFilterTraits<HBFilterOrder>::hbMod[b + 2 - 2];
 		}
 
-//		a = HBFIRFilterTraits<HBFilterOrder>::hbMod[a + 2 - 1];
-		// ancient way:
-		a = (a + HBFIRFilterTraits<HBFilterOrder>::hbOrder) % (HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1);
+		a = HBFIRFilterTraits<HBFilterOrder>::hbMod[a + 2 - 1];
 
 		iAcc += ((qint32)m_samples[a][0] + 1) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
 		qAcc += ((qint32)m_samples[a][1] + 1) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
@@ -837,22 +590,13 @@ protected:
 template<uint32_t HBFilterOrder>
 IntHalfbandFilter<HBFilterOrder>::IntHalfbandFilter()
 {
-    m_sizeDB = HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1;
-
     for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder + 1; i++)
     {
         m_samples[i][0] = 0;
         m_samples[i][1] = 0;
-
-        if (i < m_sizeDB)
-        {
-            m_samplesDB[i][0] = 0;
-            m_samplesDB[i][1] = 0;
-        }
     }
 
     m_ptr = 0;
-    m_ptrDB = 0;
 
     m_state = 0;
 }
diff --git a/sdrbase/dsp/inthalfbandfilterdb.h b/sdrbase/dsp/inthalfbandfilterdb.h
new file mode 100644
index 000000000..751d7eca5
--- /dev/null
+++ b/sdrbase/dsp/inthalfbandfilterdb.h
@@ -0,0 +1,594 @@
+///////////////////////////////////////////////////////////////////////////////////
+// Copyright (C) 2016 F4EXB                                                      //
+// written by Edouard Griffiths                                                  //
+//                                                                               //
+// Integer half-band FIR based interpolator and decimator                        //
+// This is the double buffer variant                                             //
+//                                                                               //
+// This program is free software; you can redistribute it and/or modify          //
+// it under the terms of the GNU General Public License as published by          //
+// the Free Software Foundation as version 3 of the License, or                  //
+//                                                                               //
+// This program is distributed in the hope that it will be useful,               //
+// but WITHOUT ANY WARRANTY; without even the implied warranty of                //
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the                  //
+// GNU General Public License V3 for more details.                               //
+//                                                                               //
+// You should have received a copy of the GNU General Public License             //
+// along with this program. If not, see <http://www.gnu.org/licenses/>.          //
+///////////////////////////////////////////////////////////////////////////////////
+
+#ifndef INCLUDE_INTHALFBANDFILTER_DB_H
+#define INCLUDE_INTHALFBANDFILTER_DB_H
+
+#include <stdint.h>
+#include "dsp/dsptypes.h"
+#include "dsp/hbfiltertraits.h"
+#include "util/export.h"
+
+template<uint32_t HBFilterOrder>
+class SDRANGEL_API IntHalfbandFilterDB {
+public:
+    IntHalfbandFilterDB();
+
+	// downsample by 2, return center part of original spectrum
+	bool workDecimateCenter(Sample* sample)
+	{
+		// insert sample into ring-buffer
+	    m_samplesDB[m_ptrDB][0] = sample->real();
+	    m_samplesDB[m_ptrDB][1] = sample->imag();
+	    m_samplesDB[m_ptrDB + m_sizeDB][0] = sample->real();
+	    m_samplesDB[m_ptrDB + m_sizeDB][1] = sample->imag();
+
+		switch(m_state)
+		{
+			case 0:
+				// advance write-pointer
+			    m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 1;
+
+				// tell caller we don't have a new sample
+				return false;
+
+			default:
+				// save result
+				doFIR(sample);
+
+				// advance write-pointer
+				m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 0;
+
+				// tell caller we have a new sample
+				return true;
+		}
+	}
+
+    // upsample by 2, return center part of original spectrum - double buffer variant
+    bool workInterpolateCenter(Sample* sampleIn, Sample *SampleOut)
+    {
+        switch(m_state)
+        {
+            case 0:
+                // insert sample into ring-buffer
+                m_samplesDB[m_ptrDB][0] = 0;
+                m_samplesDB[m_ptrDB][1] = 0;
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
+
+                // save result
+                doFIR(SampleOut);
+
+                // advance write-pointer
+                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+                // next state
+                m_state = 1;
+
+                // tell caller we didn't consume the sample
+                return false;
+
+            default:
+                // insert sample into ring-buffer
+                m_samplesDB[m_ptrDB][0] = sampleIn->real();
+                m_samplesDB[m_ptrDB][1] = sampleIn->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
+
+                // save result
+                doFIR(SampleOut);
+
+                // advance write-pointer
+                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+                // next state
+                m_state = 0;
+
+                // tell caller we consumed the sample
+                return true;
+        }
+    }
+
+	bool workDecimateCenter(qint32 *x, qint32 *y)
+	{
+		// insert sample into ring-buffer
+	    m_samplesDB[m_ptrDB][0] = *x;
+	    m_samplesDB[m_ptrDB][1] = *y;
+	    m_samplesDB[m_ptrDB + m_sizeDB][0] = *x;
+	    m_samplesDB[m_ptrDB + m_sizeDB][1] = *y;
+
+		switch(m_state)
+		{
+			case 0:
+				// advance write-pointer
+			    m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 1;
+
+				// tell caller we don't have a new sample
+				return false;
+
+			default:
+				// save result
+				doFIR(x, y);
+
+				// advance write-pointer
+				m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 0;
+
+				// tell caller we have a new sample
+				return true;
+		}
+	}
+
+	// downsample by 2, return lower half of original spectrum
+	bool workDecimateLowerHalf(Sample* sample)
+	{
+		switch(m_state)
+		{
+			case 0:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = -sample->imag();
+			    m_samplesDB[m_ptrDB][1] = sample->real();
+			    m_samplesDB[m_ptrDB + m_sizeDB][0] = -sample->imag();
+			    m_samplesDB[m_ptrDB + m_sizeDB][1] = sample->real();
+
+				// advance write-pointer
+			    m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 1;
+
+				// tell caller we don't have a new sample
+				return false;
+
+			case 1:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = -sample->real();
+			    m_samplesDB[m_ptrDB][1] = -sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = -sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = -sample->imag();
+
+				// save result
+				doFIR(sample);
+
+				// advance write-pointer
+				m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 2;
+
+				// tell caller we have a new sample
+				return true;
+
+			case 2:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = sample->imag();
+			    m_samplesDB[m_ptrDB][1] = -sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = -sample->real();
+
+				// advance write-pointer
+                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 3;
+
+				// tell caller we don't have a new sample
+				return false;
+
+			default:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = sample->real();
+			    m_samplesDB[m_ptrDB][1] = sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = sample->imag();
+
+				// save result
+				doFIR(sample);
+
+				// advance write-pointer
+				m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 0;
+
+				// tell caller we have a new sample
+				return true;
+		}
+	}
+
+    // upsample by 2, from lower half of original spectrum - double buffer variant
+    bool workInterpolateLowerHalf(Sample* sampleIn, Sample *sampleOut)
+    {
+        Sample s;
+
+        switch(m_state)
+        {
+        case 0:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = 0;
+            m_samplesDB[m_ptrDB][1] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(s.imag());
+            sampleOut->setImag(-s.real());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 1;
+
+            // tell caller we didn't consume the sample
+            return false;
+
+        case 1:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(-s.real());
+            sampleOut->setImag(-s.imag());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 2;
+
+            // tell caller we consumed the sample
+            return true;
+
+        case 2:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = 0;
+            m_samplesDB[m_ptrDB][1] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(-s.imag());
+            sampleOut->setImag(s.real());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 3;
+
+            // tell caller we didn't consume the sample
+            return false;
+
+        default:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(s.real());
+            sampleOut->setImag(s.imag());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 0;
+
+            // tell caller we consumed the sample
+            return true;
+        }
+    }
+
+	// downsample by 2, return upper half of original spectrum
+	bool workDecimateUpperHalf(Sample* sample)
+	{
+		switch(m_state)
+		{
+			case 0:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = sample->imag();
+			    m_samplesDB[m_ptrDB][1] = -sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = -sample->real();
+
+				// advance write-pointer
+                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 1;
+
+				// tell caller we don't have a new sample
+				return false;
+
+			case 1:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = -sample->real();
+			    m_samplesDB[m_ptrDB][1] = -sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = -sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = -sample->imag();
+
+				// save result
+				doFIR(sample);
+
+				// advance write-pointer
+				m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 2;
+
+				// tell caller we have a new sample
+				return true;
+
+			case 2:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = -sample->imag();
+			    m_samplesDB[m_ptrDB][1] = sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = -sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = sample->real();
+
+				// advance write-pointer
+                m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 3;
+
+				// tell caller we don't have a new sample
+				return false;
+
+			default:
+				// insert sample into ring-buffer
+			    m_samplesDB[m_ptrDB][0] = sample->real();
+			    m_samplesDB[m_ptrDB][1] = sample->imag();
+                m_samplesDB[m_ptrDB + m_sizeDB][0] = sample->real();
+                m_samplesDB[m_ptrDB + m_sizeDB][1] = sample->imag();
+
+				// save result
+				doFIR(sample);
+
+				// advance write-pointer
+				m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+				// next state
+				m_state = 0;
+
+				// tell caller we have a new sample
+				return true;
+		}
+	}
+
+    // upsample by 2, move original spectrum to upper half - double buffer variant
+    bool workInterpolateUpperHalf(Sample* sampleIn, Sample *sampleOut)
+    {
+        Sample s;
+
+        switch(m_state)
+        {
+        case 0:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = 0;
+            m_samplesDB[m_ptrDB][1] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(-s.imag());
+            sampleOut->setImag(s.real());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 1;
+
+            // tell caller we didn't consume the sample
+            return false;
+
+        case 1:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(-s.real());
+            sampleOut->setImag(-s.imag());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 2;
+
+            // tell caller we consumed the sample
+            return true;
+
+        case 2:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = 0;
+            m_samplesDB[m_ptrDB][1] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = 0;
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = 0;
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(s.imag());
+            sampleOut->setImag(-s.real());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 3;
+
+            // tell caller we didn't consume the sample
+            return false;
+
+        default:
+            // insert sample into ring-buffer
+            m_samplesDB[m_ptrDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB][1] = sampleIn->imag();
+            m_samplesDB[m_ptrDB + m_sizeDB][0] = sampleIn->real();
+            m_samplesDB[m_ptrDB + m_sizeDB][1] = sampleIn->imag();
+
+            // save result
+            doFIR(&s);
+            sampleOut->setReal(s.real());
+            sampleOut->setImag(s.imag());
+
+            // advance write-pointer
+            m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+            // next state
+            m_state = 0;
+
+            // tell caller we consumed the sample
+            return true;
+        }
+    }
+
+    void myDecimate(const Sample* sample1, Sample* sample2)
+    {
+        m_samplesDB[m_ptrDB][0] = sample1->real();
+        m_samplesDB[m_ptrDB][1] = sample1->imag();
+        m_samplesDB[m_ptrDB + m_sizeDB][0] = sample1->real();
+        m_samplesDB[m_ptrDB + m_sizeDB][1] = sample1->imag();
+
+        m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+        m_samplesDB[m_ptrDB][0] = sample2->real();
+        m_samplesDB[m_ptrDB][1] = sample2->imag();
+        m_samplesDB[m_ptrDB + m_sizeDB][0] = sample2->real();
+        m_samplesDB[m_ptrDB + m_sizeDB][1] = sample2->imag();
+
+        doFIR(sample2);
+
+        m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+    }
+
+    void myDecimate(qint32 x1, qint32 y1, qint32 *x2, qint32 *y2)
+    {
+        m_samplesDB[m_ptrDB][0] = x1;
+        m_samplesDB[m_ptrDB][1] = y1;
+        m_samplesDB[m_ptrDB + m_sizeDB][0] = x1;
+        m_samplesDB[m_ptrDB + m_sizeDB][1] = y1;
+
+        m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+
+        m_samplesDB[m_ptrDB][0] = *x2;
+        m_samplesDB[m_ptrDB][1] = *y2;
+        m_samplesDB[m_ptrDB + m_sizeDB][0] = *x2;
+        m_samplesDB[m_ptrDB + m_sizeDB][1] = *y2;
+
+        doFIR(x2, y2);
+
+        m_ptrDB = (m_ptrDB + 1) % m_sizeDB;
+    }
+
+protected:
+	qint32 m_samplesDB[2*(HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1)][2]; // double buffer technique
+	int m_ptrDB;
+	int m_sizeDB;
+	int m_state;
+
+    void doFIR(Sample* sample)
+    {
+        int a = m_ptrDB + m_sizeDB; // tip pointer
+        int b = m_ptrDB + 1; // tail pointer
+        qint32 iAcc = 0;
+        qint32 qAcc = 0;
+
+        for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
+        {
+            iAcc += (m_samplesDB[a][0] + m_samplesDB[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
+            qAcc += (m_samplesDB[a][1] + m_samplesDB[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
+            a -= 2;
+            b += 2;
+        }
+
+        iAcc += ((qint32)m_samplesDB[b-1][0]) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
+        qAcc += ((qint32)m_samplesDB[b-1][1]) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
+
+        sample->setReal(iAcc >> HBFIRFilterTraits<HBFilterOrder>::hbShift -1);
+        sample->setImag(qAcc >> HBFIRFilterTraits<HBFilterOrder>::hbShift -1);
+    }
+
+    void doFIR(qint32 *x, qint32 *y)
+    {
+        int a = m_ptrDB + m_sizeDB; // tip pointer
+        int b = m_ptrDB + 1; // tail pointer
+        qint32 iAcc = 0;
+        qint32 qAcc = 0;
+
+        for (int i = 0; i < HBFIRFilterTraits<HBFilterOrder>::hbOrder / 4; i++)
+        {
+            iAcc += (m_samplesDB[a][0] + m_samplesDB[b][0]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
+            qAcc += (m_samplesDB[a][1] + m_samplesDB[b][1]) * HBFIRFilterTraits<HBFilterOrder>::hbCoeffs[i];
+            a -= 2;
+            b += 2;
+        }
+
+        iAcc += ((qint32)m_samplesDB[b-1][0]) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
+        qAcc += ((qint32)m_samplesDB[b-1][1]) << (HBFIRFilterTraits<HBFilterOrder>::hbShift - 1);
+
+        *x = iAcc >> (HBFIRFilterTraits<HBFilterOrder>::hbShift -1); // HB_SHIFT incorrect do not loose the gained bit
+        *y = qAcc >> (HBFIRFilterTraits<HBFilterOrder>::hbShift -1);
+    }
+};
+
+template<uint32_t HBFilterOrder>
+IntHalfbandFilterDB<HBFilterOrder>::IntHalfbandFilterDB()
+{
+    m_sizeDB = HBFIRFilterTraits<HBFilterOrder>::hbOrder - 1;
+
+    for (int i = 0; i < m_sizeDB; i++)
+    {
+        m_samplesDB[i][0] = 0;
+        m_samplesDB[i][1] = 0;
+    }
+
+    m_ptrDB = 0;
+    m_state = 0;
+}
+
+#endif // INCLUDE_INTHALFBANDFILTER_DB_H
diff --git a/sdrbase/dsp/upchannelizer.cpp b/sdrbase/dsp/upchannelizer.cpp
index 1d463185c..709ba7d37 100644
--- a/sdrbase/dsp/upchannelizer.cpp
+++ b/sdrbase/dsp/upchannelizer.cpp
@@ -202,20 +202,20 @@ void UpChannelizer::applyConfiguration()
 }
 
 UpChannelizer::FilterStage::FilterStage(Mode mode) :
-    m_filter(new IntHalfbandFilter<UPCHANNELIZER_HB_FILTER_ORDER>),
+    m_filter(new IntHalfbandFilterDB<UPCHANNELIZER_HB_FILTER_ORDER>),
     m_workFunction(0)
 {
     switch(mode) {
         case ModeCenter:
-            m_workFunction = &IntHalfbandFilter<UPCHANNELIZER_HB_FILTER_ORDER>::workInterpolateCenterDB;
+            m_workFunction = &IntHalfbandFilterDB<UPCHANNELIZER_HB_FILTER_ORDER>::workInterpolateCenter;
             break;
 
         case ModeLowerHalf:
-            m_workFunction = &IntHalfbandFilter<UPCHANNELIZER_HB_FILTER_ORDER>::workInterpolateLowerHalfDB;
+            m_workFunction = &IntHalfbandFilterDB<UPCHANNELIZER_HB_FILTER_ORDER>::workInterpolateLowerHalf;
             break;
 
         case ModeUpperHalf:
-            m_workFunction = &IntHalfbandFilter<UPCHANNELIZER_HB_FILTER_ORDER>::workInterpolateUpperHalfDB;
+            m_workFunction = &IntHalfbandFilterDB<UPCHANNELIZER_HB_FILTER_ORDER>::workInterpolateUpperHalf;
             break;
     }
 }
diff --git a/sdrbase/dsp/upchannelizer.h b/sdrbase/dsp/upchannelizer.h
index d773ecab3..a4a6410cb 100644
--- a/sdrbase/dsp/upchannelizer.h
+++ b/sdrbase/dsp/upchannelizer.h
@@ -23,7 +23,7 @@
 #include <QMutex>
 #include "util/export.h"
 #include "util/message.h"
-#include "dsp/inthalfbandfilter.h"
+#include "dsp/inthalfbandfilterdb.h"
 
 #define UPCHANNELIZER_HB_FILTER_ORDER 96
 
@@ -69,8 +69,8 @@ protected:
             ModeUpperHalf
         };
 
-        typedef bool (IntHalfbandFilter<UPCHANNELIZER_HB_FILTER_ORDER>::*WorkFunction)(Sample* sIn, Sample *sOut);
-        IntHalfbandFilter<UPCHANNELIZER_HB_FILTER_ORDER>* m_filter;
+        typedef bool (IntHalfbandFilterDB<UPCHANNELIZER_HB_FILTER_ORDER>::*WorkFunction)(Sample* sIn, Sample *sOut);
+        IntHalfbandFilterDB<UPCHANNELIZER_HB_FILTER_ORDER>* m_filter;
         WorkFunction m_workFunction;
 
         FilterStage(Mode mode);