open source voip software for ubuntu linux

Hello,

Can anyone recommend a simple open source voip software in linux for pc-to-pc voice calls.
One requirement i that it should be simple with bare minimal functionality since I will be using as a part of a university project and so I don't want any additional features such as buddylist, GUI, etc.
Even a command line interface will also be fine since I am only interested to test different associated codecs/network characteristics.
The code should be simple with bare minimal libraries so that can be compiled easily.
I am aware of some open-source software such as WengoPhone but it seems that they have lot of associated features supporting different input devices with sophisticated GUI.
I require only PC-to-PC call functionality and I will be using within a LAN.
It will be very helpful if anyone can suggest any software!

Thanks!

You might want to consider Twinkle. It reasonably minimalist (no video) but not totally so. It's available on Debian so I assume it's available for Ubuntu as well.

ciao,
jdk

PJSUA any good? Manual of pjsua - Command Line SIP User Agent/Softphone

You can look into mumble, it's supposed to be a really good voip client, and I THINK it's open source.