diff --git a/MMDVMHost.vcxproj b/MMDVMHost.vcxproj
index c6a4cb1..e63859c 100644
--- a/MMDVMHost.vcxproj
+++ b/MMDVMHost.vcxproj
@@ -192,6 +192,7 @@
     <ClInclude Include="NetworkInfo.h" />
     <ClInclude Include="Nextion.h" />
     <ClInclude Include="NullDisplay.h" />
+    <ClInclude Include="NXDNAudio.h" />
     <ClInclude Include="NXDNControl.h" />
     <ClInclude Include="NXDNConvolution.h" />
     <ClInclude Include="NXDNCRC.h" />
@@ -274,6 +275,7 @@
     <ClCompile Include="NetworkInfo.cpp" />
     <ClCompile Include="Nextion.cpp" />
     <ClCompile Include="NullDisplay.cpp" />
+    <ClCompile Include="NXDNAudio.cpp" />
     <ClCompile Include="NXDNControl.cpp" />
     <ClCompile Include="NXDNConvolution.cpp" />
     <ClCompile Include="NXDNCRC.cpp" />
diff --git a/MMDVMHost.vcxproj.filters b/MMDVMHost.vcxproj.filters
index 4a097f1..c276fc7 100644
--- a/MMDVMHost.vcxproj.filters
+++ b/MMDVMHost.vcxproj.filters
@@ -260,6 +260,9 @@
     <ClInclude Include="NXDNLayer3.h">
       <Filter>Header Files</Filter>
     </ClInclude>
+    <ClInclude Include="NXDNAudio.h">
+      <Filter>Header Files</Filter>
+    </ClInclude>
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="BPTC19696.cpp">
@@ -487,5 +490,8 @@
     <ClCompile Include="NXDNLayer3.cpp">
       <Filter>Source Files</Filter>
     </ClCompile>
+    <ClCompile Include="NXDNAudio.cpp">
+      <Filter>Source Files</Filter>
+    </ClCompile>
   </ItemGroup>
 </Project>
\ No newline at end of file
diff --git a/Makefile b/Makefile
index 868cdc8..ae0175b 100644
--- a/Makefile
+++ b/Makefile
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o Nextion.o \
-		NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o \
-		P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o \
-		SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o \
-		YSFFICH.o YSFNetwork.o YSFPayload.o
+		NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o \
+		NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/Makefile.Pi b/Makefile.Pi
index d80cbd9..3ef9513 100644
--- a/Makefile.Pi
+++ b/Makefile.Pi
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o Nextion.o \
-		NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o \
-		P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o \
-		SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o \
-		YSFFICH.o YSFNetwork.o YSFPayload.o
+		NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o \
+		NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/Makefile.Pi.Adafruit b/Makefile.Pi.Adafruit
index 92602be..ec80427 100644
--- a/Makefile.Pi.Adafruit
+++ b/Makefile.Pi.Adafruit
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o HD44780.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o \
-		Nextion.o NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o \
-		P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o \
-		SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o \
-		YSFFICH.o YSFNetwork.o YSFPayload.o
+		Nextion.o NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o \
+		NXDNSACCH.o NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/Makefile.Pi.HD44780 b/Makefile.Pi.HD44780
index 54a8f38..e35f8d3 100644
--- a/Makefile.Pi.HD44780
+++ b/Makefile.Pi.HD44780
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o HD44780.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o \
-		Nextion.o NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o \
-		P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o \
-		SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o \
-		YSFFICH.o YSFNetwork.o YSFPayload.o
+		Nextion.o NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o \
+		NXDNSACCH.o NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/Makefile.Pi.OLED b/Makefile.Pi.OLED
index 4a6ab3b..df8349a 100644
--- a/Makefile.Pi.OLED
+++ b/Makefile.Pi.OLED
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o OLED.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o \
-		Nextion.o NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o \
-		P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o \
-		SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o \
-		YSFFICH.o YSFNetwork.o YSFPayload.o
+		Nextion.o NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o \
+		NXDNSACCH.o NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/Makefile.Pi.PCF8574 b/Makefile.Pi.PCF8574
index ab82b1a..4fbc2a8 100644
--- a/Makefile.Pi.PCF8574
+++ b/Makefile.Pi.PCF8574
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o HD44780.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o \
-		Nextion.o NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o \
-		P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o \
-		SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o \
-		YSFFICH.o YSFNetwork.o YSFPayload.o
+		Nextion.o NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o \
+		NXDNSACCH.o NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/Makefile.Solaris b/Makefile.Solaris
index a641db2..8f58787 100644
--- a/Makefile.Solaris
+++ b/Makefile.Solaris
@@ -10,10 +10,10 @@ OBJECTS = \
 		AMBEFEC.o BCH.o BPTC19696.o Conf.o CRC.o Display.o DMRControl.o DMRCSBK.o DMRData.o DMRDataHeader.o DMREMB.o DMREmbeddedData.o DMRFullLC.o \
 		DMRLookup.o DMRLC.o DMRNetwork.o DMRShortLC.o DMRSlot.o DMRSlotType.o DMRAccessControl.o DMRTrellis.o DStarControl.o DStarHeader.o DStarNetwork.o \
 		DStarSlowData.o Golay2087.o Golay24128.o Hamming.o LCDproc.o Log.o MMDVMHost.o Modem.o ModemSerialPort.o Mutex.o NetworkInfo.o Nextion.o \
-		NullDisplay.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o NXDNUDCH.o P25Audio.o \
-		P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o RSSIInterpolator.o SerialController.o \
-		SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o YSFConvolution.o YSFFICH.o YSFNetwork.o \
-		YSFPayload.o
+		NullDisplay.o NXDNAudio.o NXDNControl.o NXDNConvolution.o NXDNCRC.o NXDNFACCH1.o NXDNLayer3.o NXDNLICH.o NXDNLookup.o NXDNNetwork.o NXDNSACCH.o \
+		NXDNUDCH.o P25Audio.o P25Control.o P25Data.o P25LowSpeedData.o P25Network.o P25NID.o P25Trellis.o P25Utils.o QR1676.o RS129.o RS241213.o \
+		RSSIInterpolator.o SerialController.o SerialPort.o SHA256.o StopWatch.o Sync.o TFTSerial.o Thread.o Timer.o UDPSocket.o UMP.o Utils.o YSFControl.o \
+		YSFConvolution.o YSFFICH.o YSFNetwork.o YSFPayload.o
 
 all:		MMDVMHost
 
diff --git a/NXDNAudio.cpp b/NXDNAudio.cpp
new file mode 100644
index 0000000..c71d9a3
--- /dev/null
+++ b/NXDNAudio.cpp
@@ -0,0 +1,60 @@
+/*
+*   Copyright (C) 2018 by Jonathan Naylor G4KLX
+*
+*   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; either version 2 of the License, or
+*   (at your option) any later version.
+*
+*   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 for more details.
+*
+*   You should have received a copy of the GNU General Public License
+*   along with this program; if not, write to the Free Software
+*   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#include "NXDNAudio.h"
+
+#include <cstdio>
+#include <cassert>
+
+CNXDNAudio::CNXDNAudio()
+{
+}
+
+CNXDNAudio::~CNXDNAudio()
+{
+}
+
+void CNXDNAudio::decode(const unsigned char* in, unsigned char* out) const
+{
+	assert(in != NULL);
+	assert(out != NULL);
+
+	decode(in, out, 0U);
+	decode(in, out, 49U);
+}
+
+void CNXDNAudio::encode(const unsigned char* in, unsigned char* out) const
+{
+	assert(in != NULL);
+	assert(out != NULL);
+
+	encode(in, out, 0U);
+	encode(in, out, 49U);
+}
+
+void CNXDNAudio::decode(const unsigned char* in, unsigned char* out, unsigned int offset) const
+{
+	assert(in != NULL);
+	assert(out != NULL);
+}
+
+void CNXDNAudio::encode(const unsigned char* in, unsigned char* out, unsigned int offset) const
+{
+	assert(in != NULL);
+	assert(out != NULL);
+}
diff --git a/NXDNAudio.h b/NXDNAudio.h
new file mode 100644
index 0000000..fd778c7
--- /dev/null
+++ b/NXDNAudio.h
@@ -0,0 +1,37 @@
+/*
+*   Copyright (C) 2018 by Jonathan Naylor G4KLX
+*
+*   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; either version 2 of the License, or
+*   (at your option) any later version.
+*
+*   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 for more details.
+*
+*   You should have received a copy of the GNU General Public License
+*   along with this program; if not, write to the Free Software
+*   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
+*/
+
+#if !defined(NXDNAudio_H)
+#define	NXDNAudio_H
+
+class CNXDNAudio {
+public:
+	CNXDNAudio();
+	~CNXDNAudio();
+
+	void encode(const unsigned char* in, unsigned char* out) const;
+
+	void decode(const unsigned char* in, unsigned char* out) const;
+
+private:
+	void encode(const unsigned char* in, unsigned char* out, unsigned int offset) const;
+
+	void decode(const unsigned char* in, unsigned char* out, unsigned int offset) const;
+};
+
+#endif