I am looking for sample or a quickstart to implement video chat feature on iOS platform.
Try to start with this: https://backendless.com/developing-an-ios-video-recorder-and-player-in-5-minutes/
The api is almost identical to make it a real time chat. Also, take a look at the examples included into the kID SDK.
You can download SDK - https://backendless.com/downloads/ and try VideoChat example
Have you thinked of trying a simple chat instead of a video one? I’ve tried both and finally chosen the simple one.
QuickBox has a lot of iOS chat code samples in case you need any: http://quickblox.com/developers/SimpleSample-chat_users-ios