1.15.4 Audio and video calling

The portal allows users to make both ONNET, i.e. calls to other RCS clients, and OFFNET - to non RCS numbers, calls.

The media engine is based on the WebRTC which is integrated in a browser and therefore a user does not have to download any additional plugin.

At the moment, the following browsers support WebRTC:

• Chrome

• Firefox

• Edge

If a browser does not support WebRTC the portal will work just the calling functions will be blocked.

Voipswitch’s softswitch and its OTT/RCS mobile clients fully support the WebRTC technology requirements which include:

• ICE framework
• support for secure RTP with DTLS key exchange
• support for the OPUS codec in the Voicemail and IVR scenarios
• support for the OPUS codec by the mobile clients
• support for VP8 video codec

Onnet calls

ONNET calls can be initiated directly from Chat after selecting an RCS user.

Onnet calls are fully encrypted on the whole path between the browser and the B client which can be another browser or our OTT/RCS mobile client.

Calls from browser are received on the mobile apps with the same codec i.e. OPUS for audio and vp8 for video. The codecs dynamically adjust their bandwidth usage in response to changing network quality

With ICE more than 95% calls are established with media going in peer to peer mode which greatly improves the quality.

Offnet calls

OFFNET calls can be initiated directly from Contacts after selecting the call icon which opens the dialpad.

The WebRTC implementation in browsers requires that audio is encrypted (sRTP). As the offnet traffic is sent to carrriers which expect RTP, the traffic has to be decoded beforehand. VoipSwitch's transcoding application server provides a facility for encrypting/decrypting calls as well as encoding/decoding from for example OPUS to g729 or any other codec commonly used in interconnections.