Add Filtering and defines

Add FIR passband Filtering
Add defines to swithc features on and off

ambed/cfirfilter.cpp

@@ -0,0 +1,74 @@
+//
+//  cfirfilter.cpp
+//  ambed
+//
+//  Created by Jean-Luc Deltombe (LX3JL) on 26/04/2017.
+//  Copyright © 2015 Jean-Luc Deltombe (LX3JL). All rights reserved.
+//
+// ----------------------------------------------------------------------------
+//    This file is part of ambed.
+//
+//    xlxd 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, either version 3 of the License, or
+//    (at your option) any later version.
+//
+//    xlxd 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 for more details.
+//
+//    You should have received a copy of the GNU General Public License
+//    along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
+// ----------------------------------------------------------------------------
+// FIRFilter by Geoffrey Merck F4FXL / KC3FRA
+
+#include "cfirfilter.h"
+#include <string.h>
+
+CFIRFilter::CFIRFilter(const float* taps, int tapsLength)
+{
+    m_taps = new float[tapsLength];
+    m_buffer = new float[tapsLength];
+
+    ::memcpy(m_taps, taps, tapsLength * sizeof(float));
+    ::memset(m_buffer, 0, tapsLength * sizeof(float));
+    m_currentBufferPostion = 0;
+}
+
+CFIRFilter::~CFIRFilter()
+{
+    delete[] m_taps;
+    delete[] m_buffer;
+}
+
+inline float CFIRFilter::Process(float inputSample)
+{
+    // Buffer latest sample
+    m_buffer[m_currentBufferPostion] = inputSample;
+
+    float outputSample = 0.0f;
+    for(int i = 0; i < m_tapsLength; i++)
+    {
+        outputSample += m_taps[i] * m_buffer[(m_currentBufferPostion + i) % m_tapsLength];
+    }
+
+    m_currentBufferPostion = (m_currentBufferPostion + 1) % m_tapsLength;
+
+    return outputSample;
+}
+
+void CFIRFilter::Process(uint8* voice, int length)
+{
+    for(int i = 0; i < length; i++)
+    {
+        //Get the sample
+        float input = (float)(short)MAKEWORD(voice[i+1], voice[i]);
+        
+        float output = Process(input);
+
+        //write processed sample back
+        voice[i] = HIBYTE((short)output);
+        voice[i+1] = LOBYTE((short)output);
+    }
+}

ambed/cfirfilter.h

@@ -0,0 +1,52 @@
+//
+//  cfirfilter.h
+//  ambed
+//
+//  Created by Jean-Luc Deltombe (LX3JL) on 26/04/2017.
+//  Copyright © 2015 Jean-Luc Deltombe (LX3JL). All rights reserved.
+//
+// ----------------------------------------------------------------------------
+//    This file is part of ambed.
+//
+//    xlxd 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, either version 3 of the License, or
+//    (at your option) any later version.
+//
+//    xlxd 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 for more details.
+//
+//    You should have received a copy of the GNU General Public License
+//    along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
+// ----------------------------------------------------------------------------
+// FIRFilter by Geoffrey Merck F4FXL / KC3FRA
+
+#ifndef cfirfilter_h
+#define cfirfilter_h
+
+#include "main.h"
+
+class CFIRFilter
+{
+public :
+    //Constructor
+    CFIRFilter(const float* taps, int tapsLength);
+
+    // Destructor
+    ~CFIRFilter();
+
+    // Processing
+    float Process(float inputSample);
+    void Process(uint8* voice, int length);
+
+private:
+    float* m_taps;
+    int m_tapsLength;
+    float* m_buffer;
+    int m_currentBufferPostion;
+};
+
+#endif //cfirfilter_h
+

ambed/cusb3xxxinterface.cpp

@@ -152,8 +152,15 @@ void CUsb3xxxInterface::Task(void)
             {
                 Queue = Channel->GetVoiceQueue();
                 CVoicePacket *clone = new CVoicePacket(VoicePacket);
+#if USE_BANDPASSFILTER
+                //Aply band pass before AGC to avoidd amplifying signals we do not want
+                Channel->ApplyFilter(*clone);
+#endif
+#if USE_AGC == 1
                 Channel->ApplyAGC(*clone);
-                //clone->ApplyGain(Channel->GetSpeechGain());
+#else
+                clone->ApplyGain(Channel->GetSpeechGain());
+#endif
                 Queue->push(clone);
                 Channel->ReleaseVoiceQueue();
             }

ambed/cvocodecchannel.cpp

@@ -31,7 +31,6 @@
 // constructor
 
 CVocodecChannel::CVocodecChannel(CVocodecInterface *InterfaceIn, int iChIn, CVocodecInterface *InterfaceOut, int iChOut, int iSpeechGain)
-: m_AGC((float)iSpeechGain)
 {
     m_bOpen = false;
     m_InterfaceIn = InterfaceIn;
@@ -39,6 +38,12 @@ CVocodecChannel::CVocodecChannel(CVocodecInterface *InterfaceIn, int iChIn, CVoc
     m_InterfaceOut = InterfaceOut;
     m_iChannelOut = iChOut;
     m_iSpeechGain = iSpeechGain;
+#if USE_AGC == 1
+    m_AGC = new CAGC((float)iSpeechGain);
+#endif
+#if USE_BANDPASSFILTER == 1
+    m_filter = new CFIRFilter(FILTER_TAPS, FILTER_TAPS_LENGTH);
+#endif
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////
@@ -47,6 +52,12 @@ CVocodecChannel::CVocodecChannel(CVocodecInterface *InterfaceIn, int iChIn, CVoc
 CVocodecChannel::~CVocodecChannel()
 {
     PurgeAllQueues();
+#if USE_AGC == 1
+    delete m_AGC;
+#endif
+#if USE_BANDPASSFILTER == 1
+    delete m_filter;
+#endif
 }
 
 ////////////////////////////////////////////////////////////////////////////////////////
@@ -92,11 +103,20 @@ uint8 CVocodecChannel::GetCodecOut(void) const
     return m_InterfaceOut->GetChannelCodec(m_iChannelOut);
 }
 
+#if USE_AGC == 1
 void CVocodecChannel::ApplyAGC(CVoicePacket& voicePacket)
 {
-    m_AGC.Apply(voicePacket.GetVoice(), voicePacket.GetVoiceSize());
+    m_AGC->Apply(voicePacket.GetVoice(), voicePacket.GetVoiceSize());
     //std::cout << "Gain : " << m_AGC.GetGain() << "\n";
 }
+#endif
+
+#if USE_BANDPASSFILTER == 1
+void CVocodecChannel::ApplyFilter(CVoicePacket& voicePacket)
+{
+    m_filter->Process(voicePacket.GetVoice(), voicePacket.GetVoiceSize());
+}
+#endif
 
 ////////////////////////////////////////////////////////////////////////////////////////
 // queues helpers

ambed/cvocodecchannel.h

@@ -27,7 +27,12 @@
 #define cvocodecchannel_h
 
 #include "cpacketqueue.h"
+#if USE_AGC == 1
 #include "cagc.h"
+#endif
+#if USE_BANDPASSFILTER == 1
+#include "cfirfilter.h"
+#endif
 #include "cvoicepacket.h"
 
 ////////////////////////////////////////////////////////////////////////////////////////
@@ -57,7 +62,12 @@ public:
     int   GetSpeechGain(void) const         { return m_iSpeechGain; }
     
     //Processing
+#if USE_AGC == 1
     void ApplyAGC(CVoicePacket& voicePacket);
+#endif
+#if USE_BANDPASSFILTER
+    void ApplyFilter(CVoicePacket& voicePacket);
+#endif
     
     // interfaces
     bool IsInterfaceIn(const CVocodecInterface *interface)      { return (interface == m_InterfaceIn); }
@@ -98,7 +108,12 @@ protected:
     int                 m_iSpeechGain;
     
 private:
-    CAGC m_AGC;
+#if USE_AGC == 1
+    CAGC* m_AGC;
+#endif
+#if USE_BANDPASSFILTER == 1
+    CFIRFilter* m_filter;
+#endif
 };
 
 ////////////////////////////////////////////////////////////////////////////////////////

ambed/main.h

@@ -70,8 +70,12 @@
 #define CODEC_AMBE2PLUS                 2
 
 // Transcoding speech gains
-#define CODECGAIN_AMBEPLUS              -3//-10                                  // in dB
+#define CODECGAIN_AMBEPLUS              -10                                  // in dB
-#define CODECGAIN_AMBE2PLUS             +3//+10                                 // in dB
+#define CODECGAIN_AMBE2PLUS             +10                                 // in dB
+
+// Transcoding Tweaks
+#define USE_AGC                         0
+#define USE_BANDPASSFILTER              1
 
 // Timeouts -----------------------------------------------------
 #define STREAM_ACTIVITY_TIMEOUT         3                                   // in seconds
@@ -98,6 +102,42 @@ typedef unsigned int            uint;
 #define LOWORD(dw)				((uint16)(uint32)(dw & 0x0000FFFF))
 #define HIWORD(dw)				((uint16)((((uint32)(dw)) >> 16) & 0xFFFF))
 
+////////////////////////////////////////////////////////////////////////////////////////
+// FIR Filter coefficients computed to be the closest to the recommended filter in 
+// Documentation
+//
+// Following GNU Octave script was used
+/*
+pkg load signal;
+fsamp = 8000;
+fcuts = [200 300 3000 3400];
+mags = [0 1 0];
+devs = [0.2 1 0.2];
+
+[n,Wn,beta,ftype] = kaiserord(fcuts,mags,devs,fsamp);
+n = n + rem(n,2);
+hh = fir1(n,Wn,ftype,kaiser(n+1,beta),'noscale');
+
+freqz(hh);
+[H,f] = freqz(hh,1,1024,fsamp);
+plot(f,abs(H))
+disp(hh);
+grid
+*/
+
+#if USE_BANDPASSFILTER == 1
+
+const float FILTER_TAPS[] {
+-0.0153779f,  0.0114832f, -0.0060703f, -0.0221526f, 0.0085472f, -0.0449400f,
+-0.0068112f, -0.0307485f, -0.0548559f, -0.0022596f, -0.0879344f, -0.0166698f,
+-0.0533627f, -0.1015552f,  0.0424673f, -0.2116654f,  0.1267453f,  0.7375000f,
+0.1267453f, -0.2116654f,  0.0424673f, -0.1015552f, -0.0533627f, -0.0166698f,
+-0.0879344f, -0.0022596f, -0.0548559f, -0.0307485f, -0.0068112f, -0.0449400f,
+0.0085472f, -0.0221526f, -0.0060703f,  0.0114832f, -0.0153779f };
+#define FILTER_TAPS_LENGTH          35
+
+#endif
+
 ////////////////////////////////////////////////////////////////////////////////////////
 // global objects