Install libpj2 by entering the following commands in the terminal:
sudo apt update sudo apt install libpj2
PJ Project - PJProject core libraries
PJSIP (a.k.a PJProject) is a multimedia communication library written in C language implementing standard based protocols such as SIP, SDP, RTP, STUN, TURN, and ICE. It combines signaling protocol (SIP) with rich multimedia framework and NAT traversal functionality into high level API that is portable and suitable for almost any type of systems ranging from desktops, embedded systems, to mobile handsets. . This package includes the PJ Project core libraries.