diff --git a/ambed/cfirfilter.cpp b/ambed/cfirfilter.cpp
new file mode 100644
index 0000000..602e01c
--- /dev/null
+++ b/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 .
+// ----------------------------------------------------------------------------
+// FIRFilter by Geoffrey Merck F4FXL / KC3FRA
+
+#include "cfirfilter.h"
+#include
+
+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);
+ }
+}
diff --git a/ambed/cfirfilter.h b/ambed/cfirfilter.h
new file mode 100644
index 0000000..aa1dafd
--- /dev/null
+++ b/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 .
+// ----------------------------------------------------------------------------
+// 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
+
diff --git a/ambed/cusb3xxxinterface.cpp b/ambed/cusb3xxxinterface.cpp
index 210b01f..49c1269 100644
--- a/ambed/cusb3xxxinterface.cpp
+++ b/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();
}
diff --git a/ambed/cvocodecchannel.cpp b/ambed/cvocodecchannel.cpp
index 382c04d..8ce57f8 100644
--- a/ambed/cvocodecchannel.cpp
+++ b/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
diff --git a/ambed/cvocodecchannel.h b/ambed/cvocodecchannel.h
index 58fdfe5..735fa00 100644
--- a/ambed/cvocodecchannel.h
+++ b/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
};
////////////////////////////////////////////////////////////////////////////////////////
diff --git a/ambed/main.h b/ambed/main.h
index bcfb1f7..ef60a2b 100644
--- a/ambed/main.h
+++ b/ambed/main.h
@@ -68,8 +68,12 @@
#define CODEC_AMBE2PLUS 2
// Transcoding speech gains
-#define CODECGAIN_AMBEPLUS -3//-10 // in dB
-#define CODECGAIN_AMBE2PLUS +3//+10 // in dB
+#define CODECGAIN_AMBEPLUS -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
@@ -96,6 +100,42 @@ 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