Grab the latest rasbian distro, put it on an sdcard, expand file system, update locale, change hostname.

Acquire root for this session, unless you want to type sudo before every command...

sudo -i

Update and Upgrade:

apt-get update

apt-get upgrade

Install Dependencies:

sudo apt-get install libncurses-dev libsdl1.2-dev libsdl-image1.2-dev libavcodec-dev libswscale-dev nasm pkg-config libx264-dev libxext-dev libxfixes-dev zlib1g-dev

Change to source directory and download ffmpeg:

cd /usr/src

git clone https://github.com/FFmpeg/FFmpeg.git

Change Directory to ffmpeg:

cd FFmpeg

Configure FFmpeg:

./configure --enable-nonfree --enable-gpl --enable-libx264 --enable-x11grab --enable-zlib

Create Installer:

make

Install:

make install

Change to source directory and download asterisk:

cd /usr/src

wget http://downloads.asterisk.org/pub/telephony/certified-asterisk/certified-asterisk-11.6-current.tar.gz

Untar asterisk (assuming there is no other files in /usr/src starting with "cert"

tar -zxvf cert*

Change directory to newly untarred asterisk and then to the channels directory:

cd cert*/chan*

Open the Makefile (nano, vi, vim, etc) and add "chan_oss.so: _ASTCFLAGS+=-DHAVE_VIDEO_CONSOLE" below "chan_usbradio.so: _ASTCFLAGS+=-DNDEBUG" and above "h323/Makefile.ast:"

Go back to the root of asterisk source:

cd ..

Run menu select and ensure that you disable chan_alsa and enable chan_oss under the channel drivers menu option:

make menuselect

Enter the channels directory and edit vgrabbers.c, remove all references of X11; we don't need the X11 screen grabber and it appears to be broken. I've spent too much time trying to get it to complie correctly.

Configure asterisk and check for all dependencies if this does not complete you need to go back and install all missing dependencies as listed by configure. If all is well you will see an asterisk logo at the end of the output.

./configure

Make the installer, this can take 5-10 minutes on a pi 2, again if you hit errors go back and resolve until resolved, you should see an asterisk logo if all goes well:

make

If all went well its time to install:

make install