Phone System

Asterisk

Building Asterisk from source
Asterisk needs to be built from source so that it can be patched to enable Presence Subscriptions. A non-root build environment needs to be configured, and the Source RPM downloaded.
The CentOS Wiki provides general instructions.

As root

yum install rpm-build
useradd rpmbuild
su rpmbuild

As rpmbuild - create the build environment

cd
mkdir -p ~/rpmbuild/{BUILD,RPMS,SOURCES,SPECS,SRPMS}
echo '%_topdir %(echo $HOME)/rpmbuild' > ~/.rpmmacros

Fetch the src.rpm - use the current version

wget http://yum.freepbxdistro.org/pbx/SRPMS/asterisk/11/asterisk11-11.13.0-1.shmz65.1.31.src.rpm

Extract the rpm - this will likely show a list of packages that need to be created

rpmbuild --rebuild asterisk11-11.13.0-1.shmz65.1.31.src.rpm

Extract and patch the source - this gives us something to test the ASTERISK-13145 patch on

cd rpmbuild/SPECS/
rpmbuild -bp --without misdn asterisk11.spec 

Test the patch downloaded from the ASTERISK-13145

cd ../BUILD/asterisk-11.13.0/
patch --dry-run -p1 < ../../../gareth-11.13.0.patch

If the patch is ok, then copy it to the SOURCE directory, and add it to the SPEC file - it needs to bee added under the list of Patch1, Patch2, etc, and also under the %patch1, $patch2, etc.
For example, in Asterisk 11.13, it was added as Patch13, and %patch13 needed flags "-p1 -F2"
The Release field also has to be updated, in this case "1%{dist}.1.31_13145%{?_without_optimizations:_debug}"

cp ../../../gareth-11.13.0.patch ../../SOURCES/
cd ../../SPECS/
vim asterisk11.spec

And build

rpmbuild -bb --without misdn asterisk11.spec 

To install, you need to be root. List all the asterisk RPMs already installed, and the upgrade them (The oldpackage flag may be needed if rpm thinks the compiled version is older).

cd /home/rpmbuild/rpmbuild/RPMS/x86_64
rpm -qa | grep asterisk11 | sort

rpm -Uvh --oldpackage <rpm>

Converting WAV to PCM:
Asterisk can't play mu-law files, so they need to be converted to PCM

ORIG=<ulaw file>
PCM=$(echo "$ORIG" | sed 's/ulaw/pcm/')
sox "$ORIG" -r 8000 -c 1 -e signed $PCM

CentOS
RPM Command: 15 Examples to Install, Uninstall, Upgrade, Query RPM Packages
http://wiki.centos.org/HowTos/RebuildSRPM