Liblinphone is a high-level open source library that integrates all the SIP voice/video and instant messaging features into a single easy-to-use API.
This is the VoIP SDK engine on which Linphone applications are based.
Liblinphone combines our media processing and streaming toolkit (Mediastreamer2) with our user-agent library for SIP signaling (belle-sip).
Liblinphone has support for a variety of languages, each one has its own reference documentation:
C C++ Swift Java C# (coming soon) Python (coming soon) Liblinphone is distributed under GPLv3.