Edit in JSFiddle

/*
 * Check out the full guide at
 *   http://sipjs.com/guides/make-call/
 *
 * This sample uses
 *   http://sipjs.com/download/sip-0.9.0.min.js
 *
 * Login with your developer account to receive calls at
 *   http://sipjs.com/demo-phone
 */

var options = {
      media: {
        local: {
          video: document.getElementById('localVideo')
        },
        remote: {
          video: document.getElementById('remoteVideo'),
          // This is necessary to do an audio/video call as opposed to just a video call
          audio: document.getElementById('remoteVideo')
        }
      },
      ua: {
      	uri: 'test@example.com',
 			  authorizationUser: 'test',
    		password: 'password',
      }
    };
var simple = new SIP.WebRTC.Simple(options);

simple.on('ringing', function() {
	simple.answer();
});
<video id="remoteVideo"></video>
<video id="localVideo" muted="muted"></video>
<!-- sip.js is included by JsFiddle as External Resources -->
video {
    border: 1px solid lightgrey;
}