I had 7.5 yr of multimedia and codec development experince in g711, g729a/b,vad/cng/dtx,g722,.
I had recently completed a sip based video door phone project.
I had used asterix pbx as server for call management and routing for various sip phone such as linphone based on osip as signalling protocol framework, which are freely available online and ported to ARM based product and laptop.