Voice call on an XMPP Chat app

What’s the best and easiest way to integrate voice calling in an Android chat app using Openfire at its back end? I know there are many options - jingle, rayo, asterisk, etc. I’m asking for the easiest way. Workflow is like this:

  1. two JIDs are text chatting with each other.

  2. One of them (any one) presses the call button - and initiates a voice all to the other JID.

  3. Call is answered and voice communication happens

  4. Call is ended by any one of the JIDs

  5. Return back to text chat window

Any bright ideas?