test SIP.js renegotiation: https://github.com/onsip/SIP.js/issues/168#issuecomment-101303791

gistfile1.html

<script src="dist/sip.js"></script>

<video id="videoElement"></video>

<h1>Firefox</h1>
<p>
ua = new SIP.UA({traceSip: true, uri: 'firefox@sipjs.onsip.com'}).on('invite', function (session) { window.session = session; session.accept(videoElement); });
</p>

<p>
session = ua.invite('chrome@sipjs.onsip.com', videoElement);
</p>

<h1>Chrome</h1>
<p>
ua = new SIP.UA({traceSip: true, uri: 'chrome@sipjs.onsip.com'}).on('invite', function (session) { window.session = session; session.accept(videoElement); });
</p>

<p>
session = ua.invite('firefox@sipjs.onsip.com', videoElement);
</p>

<h1>General</h1>
<p>
session.hold();
</p>

<p>
session.unhold();
</p>