traud / asterisk-gsm-efr

Asterisk 13 transcoding module: GSM-EFR

Asterisk patch for GSM-EFR

Asterisk already supports Full Rate (GSM-FR). This patch adds Enhanced Full Rate (GSM-EFR).

Installing the patch

At least Asterisk 13 is required. These changes were last tested with Asterisk 13.22 (and Asterisk 16.0). If you use a newer version and the patch fails, please, report!

cd /usr/src/
wget downloads.asterisk.org/pub/telephony/asterisk/asterisk-13-current.tar.gz
tar zxf ./asterisk*
cd ./asterisk*
sudo apt --no-install-recommends --assume-yes install autoconf automake build-essential pkg-config libedit-dev libjansson-dev libsqlite3-dev uuid-dev libxslt1-dev xmlstarlet

Install library:

If you do not want transcoding but pass-through only (because of license issues) please, skip this step. To support transcoding, you’ll need to install OpenCORE AMR, for example in Debian/Ubuntu:

sudo apt --assume-yes install libopencore-amrnb-dev

The patch relies on my AMR patch. Therefore, you have to apply one of those patches as well:

wget github.com/traud/asterisk-amr/archive/master.zip
unzip -qq master.zip
rm master.zip
cp --verbose --recursive ./asterisk-amr*/* ./
patch -p0 <./build_tools.patch
wget github.com/traud/asterisk-gsm-efr/archive/master.zip
unzip -qq master.zip
rm master.zip
cp --verbose --recursive ./asterisk-gsm-efr*/* ./
patch -p0 <./codec_gsm_efr.patch

Run the bootstrap script to re-generate configure:

./bootstrap.sh

Configure your patched Asterisk:

./configure

Compile and install:

make
sudo make install

Testing

You can test GSM-EFR with the VoIP/SIP client in Google Android (AOSP): All apps → Phone → Options → Settings → Calls → Calling accounts → SIP accounts. I recommend Google Nexus devices because some manufactures do not include that client. Even with those manufactures who include the client, some do not test the built-in VoIP/SIP correctly. Therefore, you might experience degraded voice quality. GSM-EFR is the highest AMR mode actually. A paper for ICASSP 2010 compared several narrow-band codecs. Therefore, please, consider AMR.

Thanks goes to

• teams of the Android Open Source Project (AOSP), OpenCORE AMR, Debian Multimedia, and Ubuntu for providing the library.
• Asterisk team: Thanks to their efforts and architecture the module was written in one working day.
• Юрий Остапчук provided the starting point with his code for FreeSWITCH.