WebRTC client SDK for mobile (iOS + Android)

We need a WebRTC client SDK that can be implemented in 3rd party projects. Needed functionalities:

WebRTC facing side:
- register to a SIP server (kamailio/opensips)
- establish a chat session using SIP MESSAGE (send and receive MESSAGE)
- receive audio call
- receive video call
- enable/disable video during a session (during an ongoing call session re-INVITE and disable or enable video)


WebRTC signaling plane:
- SIP over WebSecureSocket (will connect to a sip server as Kamailio/Opensips/FreeSWITCH)

WebRTC media plane
- codecs: 711, opus, VP8, VP9, H.264
- DTLS/ICE/SRTP


API facing side:
- provide an easy and comprehensive API for quick integration into 3rd party projects