MicroSIP Lite is a open source portable SIP softphone based on PJSIP stack for Windows OS. It allows doing high quality VoIP calls (person-to-person or on regular telephones) via open SIP protocol. From cloud of SIP providers you can choose best for you, register account and use it with MicroSIP. You'll get free person-to-person calls and cheap international calls. Features include written in C and C++ with minimal possible system resources usage, user friendly in daily usage, voice, messaging, presence, and video h264 and h263+, conform to SIP standards, stores setting in ini file, and configurable encryption TLS / SRTP for control and media.
What's new in this version:
Version 3.3.21 has fixed freezing on incoming call.