MicroSIP is a freeware app that allows you to easily make high-quality VoIP calls (person-to-person or on regular telephones) via open SIP protocol.
Make free domestic and international (rates apply) calls right from the comfort of your home or office computer. MicroSIP provides you with an uncomplicated solution for keeping in touch with friends, family, and colleagues near and far. It won't take up a bunch of space or resources with its small footprint (>2.5MB) and RAM usage (>5MB) - written in C and C++ with minimal possible system resource usage.
MicroSIP is specifically designed with usability in mind, perfect for those who plan to use it daily - keeping it user-friendly allows you to focus on call content and not on configuring and setup or, worse, dropped calls. And during your session, you will enjoy crystal clear voice quality because MicroSIP supports some of the best voice codecs: speex@8,16,32kHz, iLBC@8kHz, GSM@8kHz, G.711@8kHz (PCMU and PCMA), G.722@16kHz, G.729@8kHz, SILK@8,12,16,24kHz, and Linear PCM@8,16,44kHz.
Functionality - voice, messaging, presence, video h264 and h263+
Compatibility - strongly conform to SIP standards
Privacy - configurable encryption TLS / SRTP for control and media
Portability - stores setting in ini file
Multilanguage - included localization files for Brazilian, Bulgarian, Chinese, Dutch, Estonian, Finnish, French, German, Hebrew, Hungarian, Italian, Korean, Norwegian, Polish, Russian, Spanish, Swedish, and Ukrainian.