What's the difference between WebRTC and Jingle. I am going to build Android based voice calling app using XMPP ejabberd server. So, which one of these will be best choice for voice calling on Android?
XMPP is a messaging protocol. Jingle the subprotocol that XMPP uses for establishing voice-over-ip calls or transfer files. WebRTC is a Javascript API (there is also a library implementing that API).
You can use Jingle as a signaling protocol to establish a peer-to-perconnection between two XMPP clients using the WebRTC API. This shows an example in Javascript that works in Chrome and Firefox (and Microsoft Edge if you only want audio).