There is no video call option in Spark out of the box. You will have to find some other solution. You may search for Red5 plugin for Spark, but it can be hard to setup.
it is how open stuff works!, you can use redfire plugin if you are using the lates version. it is very easy to configure. for me openfire server is equalent to Micorosft’s instead of paying $$$ you will have a full source code if you are good enough programmer to change it. it is like freedom!