Tested with mobile devices (VOLTE) : 
Samsung S6 Edge, iPhone, Samsung Note4, Samsung S6


INSTALL

1. install the AMR library debs 

libopencore-amrnb-dev - Adaptive Multi Rate speech codec - development files
libopencore-amrnb0 - Adaptive Multi Rate speech codec - shared library
libopencore-amrnb0-dbg - Adaptive Multi Rate speech codec - debugging symbols

apt-get install libopencore-amrnb-dev libopencore-amrnb0 libopencore-amrnb0-dbg

This was tested on Debian 8

2. copy these two files in the current directory (mod_amr)

cp ./usr/include/opencore-amrnb/interf_enc.h .
cp ./usr/include/opencore-amrnb/interf_dec.h .

3. run make, make install
