The SIP and SDP stacks (~1 Mo) are entirely written in javascript and the network transport uses WebSockets as per rfc7118. The live demo doesn't require any installation and can be used to connect to any SIP server using UDP, TCP or TLS transports.

Short but not exhaustive list of supported features:

• Works on Chrome, Firefox, IE, Safari, Opera and Bowser
• Audio / Video call
• Screen/Desktop sharing from Chrome to any SIP client
• Instant messaging
• Presence
• Call Hold / Resume
• Explicit Call transfer
• Multi-line and multi-account
• Dual-tone multi-frequency signaling (DTMF) using SIP INFO
• Click-to-Call
• SIP TelePresence (Video Group chat)
• 3GPP IMS standards

View details »

The API is designed with love to make it easy to develop rich and robust HTML5 applications in few lines of code.
No need to know how SIP work to start writing your code. Using this API, it will be a piece of cake to write HTML5 VoIP applications.
Below, a very compact code showing how to initialize the engine, start the stack and make video call from bob to alice in less than 15 lines:

                        SIPml.init(
                                function(e){
                                    var stack =  new SIPml.Stack({realm: 'example.org', impi: 'bob', impu: 'sip:bob@example.org', password: 'mysecret',
                                        events_listener: { events: 'started', listener: function(e){
                                                    var callSession = stack.newSession('call-audiovideo', {
                                                            video_local: document.getElementById('video-local'), // <video id="video-local" .../>
                                                            video_remote: document.getElementById('video-remote'), // <video id="video-remote" .../>
                                                            audio_remote: document.getElementById('audio-remote') // <audio id="audio-remote" .../>
                                                        });
                                                    callSession.call('alice');
                                                } 
                                            }
                                    });
                                    stack.start();
                                }
                        );