Add AGC

ambed/cagc.cpp

@@ -0,0 +1,82 @@
+//
+//  cagc.cpp
+//  ambed
+//
+//  Created by Jean-Luc Deltombe (LX3JL) on 28/04/2017.
+//  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/>.
+// ----------------------------------------------------------------------------
+// Geoffrey Merck F4FXL / KC3FRA AGC code borrowed from Liquid DSP
+// Only took the parts we need qnd recoeded it to be close the XLX coding style
+// https://github.com/jgaeddert/liquid-dsp/blob/master/src/agc/src/agc.c
+
+#include "main.h"
+#include <math.h>
+#include "cagc.h"
+
+
+////////////////////////////////////////////////////////////////////////////////////////
+// constructor
+
+CAGC::CAGC(float initialLeveldB)
+{
+    // set internal gain appropriately
+    m_g = powf(10.0f, -initialLeveldB/20.0f);
+
+    // ensure resulting gain is not arbitrarily low
+    if (m_g < 1e-16f)
+        m_g = 1e-16f;
+
+    m_scale = 1.0f;
+    m_bandwidth = 1e-2f;
+    m_y2_prime = 1.0f;
+}
+
+void CAGC::Apply(uint8 * voice, int size)
+{
+    for (int i = 0; i < size; i+=2)
+    {
+        //Get the sample
+        float _x = (float)(short)MAKEWORD(voice[i+1], voice[i]);
+
+        //apply AGC
+        // apply gain to input sample
+        float _y = _x * m_g;
+
+        // compute output signal energy
+        float y2 = _y * _y;
+
+        // smooth energy estimate using single-pole low-pass filter
+        m_y2_prime = (1.0f - m_alpha) * m_y2_prime + m_alpha*y2;
+
+        // update gain according to output energy
+        if (m_y2_prime > 1e-6f)
+            m_g *= exp( -0.5f * m_alpha * log(m_y2_prime) );
+
+        // clamp to 120 dB gain
+        if (m_g > 1e6f)
+            m_g = 1e6f;
+
+        // apply output scale
+        _y *= m_scale;
+
+        //write processed sample back to it
+        voice[i] = HIBYTE((short)_y);
+        voice[i+1] = LOBYTE((short)_y);
+    }    
+}

ambed/cagc.h

@@ -0,0 +1,56 @@
+//
+//  cagc.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/>.
+// ----------------------------------------------------------------------------
+// Geoffrey Merck F4FXL / KC3FRA AGC code borrowed from Liquid DSP
+// Only took the parts we need qnd recoeded it to be close the XLX coding style
+// https://github.com/jgaeddert/liquid-dsp/blob/master/src/agc/src/agc.c
+
+#ifndef cagc_h
+#define cagc_h
+
+#include "main.h"
+
+class CAGC
+{
+public:
+    //Constructor
+    CAGC(float initialLeveldB);
+
+    //methods
+    void Apply(uint8 * voice, int size);
+    float GetGain(){ return m_scale; }//gets current gain (linear)
+
+private:
+    // gain variables
+    float m_g;            // current gain value
+    float m_scale;        // output scale value
+
+    // gain control loop filter parameters
+    float m_bandwidth;    // bandwidth-time constant
+    float m_alpha;        // feed-back gain
+
+    // signal level estimate
+    float m_y2_prime;     // filtered output signal energy estimate
+};
+
+#endif /* cgc_h */

ambed/cusb3xxxinterface.cpp

@@ -152,7 +152,10 @@ void CUsb3xxxInterface::Task(void)
             {
                 Queue = Channel->GetVoiceQueue();
                 CVoicePacket *clone = new CVoicePacket(VoicePacket);
-                clone->ApplyGain(Channel->GetSpeechGain());
+                CAGC agc = Channel->GetAGC();
+                agc.Apply(clone->GetVoice(), clone->GetVoiceSize());
+                std::cout << "Gain : " << agc.GetGain();
+                //clone->ApplyGain(Channel->GetSpeechGain());
                 Queue->push(clone);
                 Channel->ReleaseVoiceQueue();
             }

ambed/cvocodecchannel.cpp

@@ -27,11 +27,11 @@
 #include "cvocodecchannel.h"
 #include "cvocodecinterface.h"
 
-
 ////////////////////////////////////////////////////////////////////////////////////////
 // constructor
 
 CVocodecChannel::CVocodecChannel(CVocodecInterface *InterfaceIn, int iChIn, CVocodecInterface *InterfaceOut, int iChOut, int iSpeechGain)
+: m_AGC((float)iSpeechGain)
 {
     m_bOpen = false;
     m_InterfaceIn = InterfaceIn;

ambed/cvocodecchannel.h

@@ -27,6 +27,7 @@
 #define cvocodecchannel_h
 
 #include "cpacketqueue.h"
+#include "cagc.h"
 
 ////////////////////////////////////////////////////////////////////////////////////////
 // class
@@ -53,6 +54,7 @@ public:
     int   GetChannelIn(void) const          { return m_iChannelIn; }
     int   GetChannelOut(void) const         { return m_iChannelOut; }
     int   GetSpeechGain(void) const         { return m_iSpeechGain; }
+    CAGC& GetAGC()                          { return m_AGC; };
     
     // interfaces
     bool IsInterfaceIn(const CVocodecInterface *interface)      { return (interface == m_InterfaceIn); }
@@ -92,6 +94,8 @@ protected:
     // settings
     int                 m_iSpeechGain;
     
+private:
+    CAGC m_AGC;
 };
 
 ////////////////////////////////////////////////////////////////////////////////////////